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Full text of "The Born Einstein Letters"

THE BORN - EINSTEIN LETTERS 



The correspondence between 
MAX& HEDWIG BORN and 
ALBERT EINSTEIN 
1916/1955 



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Commentaries MAX BORN 
Translation IRENE BORN 
Introduction WERNER HEISENBERG 
Foreword BERTRAND RUSSELL 



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' "You believe in the God who plays dice, 
and I in complete law and order in a world 
which I, in a wildly speculative way, am 
trying to capture.' Thus Einstein, writing 
to Max Born in 1944, summed up two 
utterly contrasted attitudes to science 
which were never reconciled throughout 
this long series of letters. Born, in holding 
that the basis of the material world was 
the purely random behaviour of the 
constituent particles of atoms, shared the 
majority viewpoint among quantum 
scientists; yet Einstein persisted in 
thinking that every event must have its 
cause, and searched constantly for a 
deeper explanation which might bring 
order into the seemingly chaotic sub- 
atomic world. Their conflicting views 
provide the intellectual stimulus of 
much of this correspondence. 

But at a time when politicians were 
realizing the terrifying power of atomic 
physics to provide weapons of unforeseen 
destructiveness neither Born nor Einstein 
could turn their backs on the social 
implications of the new science. At first 
their letters share atone of concern; in 
the end, when the atomic bomb has been 
used and the innocence of science has 
been left far behind, they can only regret 
'the evil which our once-so-beautiful 
science has brought upon the world'. 
The wider effects of war dominate many 
of the letters, for both Born and Einstein 
werefd'rced to flee from Germany during 
the Hitler regime, and the scars of the 
experience lasted so long with Einstein 
that he never felt able to return. 

In spite of their scientific differences 
Born and Einstein sustained a rare and 
close friendship for more than forty years, 
until Einstein's death in 1955 (Max Born 
was to live until 1970). For long periods 
these letters were the only link between 
them. Whether they are commiserating 
over the plight of German Jews in exile, 
or delighting in the plays and poems of 
Bern's wife Hedwig, or exchanging sharp 
and often witty comments about their 
scientific colleagues, the two men reveal 
throughout the essential warmth and 
generosity of their personalities. As 
Bertrand Russell writes in his foreword: 
'In an age of mediocrity and moral pygmies, 
their lives shine with an intense beauty. 
Something of this is reflected in their 
correspondence, and the world is richer 
for its publication'. 



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Drawing of Albert Einstein by Wolgang Born, 1924 



The 
BORN-EINSTEIN 

Letters 

Correspondence between Albert Einstein 

and Max and Hedwig Born 

from 1916 to 1955 

with commentaries by 

MAX BORN 



Translated by Irene Bom 



MACMILLAN 



The Born Letters © igyi G. V. R. Born, I. Newton- John, M. Pryce 

The Einstein Letters © ig^i Estate of Albert Einstein 

Commentaries © igyi G. V. R. Bom 

Translation © 197 J I. Neviton-John 

All rights reserved. No part of this publication may be 

reproduced or transmitted, in any form or by any means, 

without permission. 

First published igyi 

Published by 

THE MACMILLAN PRESS LTD 

London and Basingstoke 

Associated companies in New York Melbourne 

Toronto Dublin Johannesburg and Madras 

Printed in Great Britain by 

ROBERT MACLEHOSE AND GO LTD 

The University Press, Glasgow 



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Foreword 

hy Bertrand Russell 



The correspondence of Albert Einstein and Max Born will 
provoke the greatest interest, both among men of science and a far 
wider pubUc. Not only are they among the most eminent scientists of 
our century, but they had wide interests and an uncommon aware- 
ness of the social responsibility of the scientist. 

These letters, which clearly were not written for publication, 
record their hopes and anxieties in war and peace, their private 
thoughts about the progress of their work and that of colleagues, and 
much that will prove invaluable source material in the history of 
science. 

Something of the nobility of their lives is also revealed. I have 
deeply valued their friendship over many years. Both men were 
brilliant, humble and completely without fear in their pubhc 
utterances. In an age of mediocrity and moral pygmies, their lives 
shine with an intense beauty. Something of this is reflected in their 
correspondence, and the world is the richer for its publication. 



/ December ig68 



Introduction 

by Werner Heisenberg 



The relativity and quantum theories, the theoretical foundation of 
modern physics, are generally held to be abstract systems of ideas, 
inaccessible to the layman, which no longer show much evidence of 
their human origin. It is, however, the human aspect of the develop- 
ing science, more than anything else, which this correspondence 
between Albert Einstein and Max Born renders intelligible. 
Einstein and Born were both in the front rank of those who contri- 
buted towards the formation of modern physics. In the year 191 6, at 
the beginning of the correspondence, Einstein had just completed 
his papers about the general theory of relativity, and was con- 
centrating his efforts on the then still very puzzling quantum 
phenomena. During the years which followed Born, together with 
his pupils in Gottingen, took a number of decisive steps which led 
to an understanding of these very phenomena. Nothing demonstrates 
more clearly the exceptional difficulties which stood in the way of a 
clearer understanding of atomic phenomena - in spite of the con- 
siderable amount of experimental data already obtained - than the 
fact that these two scientists, who on the human level were on such 
intimate terms, failed to agree about the final interpretation of the 
quantum theory. 

But their correspondence does not merely bear witness to the 
dramatic argument about the correct interpretation of atomic 
phenomena. It also shows the way in which human, political and 
ideological problems are intermingled in this discussion, and for this 
reason the contemporary history of the years 191 6 to 1954 plays an 
important part in these letters. Einstein and Born, both interested in 
the social structures around them, actively participated in the history 
of their time, suffering and hoping, and many people who have 



vu 



INTRODUCTION 



suffered in different ways and hoped for other things during this 
epoch will find it instructive to have a look at the world of those days 
through the eyes of these two eminent scientists. 

In the year 1916 Einstein and Born were both in Berlin. Einstein 
had a research appointment at the Prussian Academy of Sciences; 
Born was Professor Extraordinarius for theoretical physics at the 
University of Berlin, but was then on wartime service as scientific 
collaborator of the Artillery-Testing Commission in BerUn. Soon 
after the end of the war Bom became Professor Ordinarius for 
theoretical physics at the University of Berlin; Einstein undertook 
extended lecture tours to many universities in America, Asia and 
Europe. 

The working methods of these two scientists were rather different. 
Einstein basically worked alone. However, he liked to talk to other 
physicists about his problems; now and again he called upon 
individual young collaborators, predominantly mathematicians, to 
help with difficult mathematical investigations. But Einstein did 
not teach according to the usual custom at universities; rather, one 
gained the impression that, even in most of the papers he published 
in collaboration with other people, the inspiration and direction 
were his. 

Born, on the other hand, founded a school of theoretical physics 
in Gottingen. He held the normal courses of lectures, organised 
seminars, and soon succeeded in collecting a fairly large band of 
excellent younger physicists about him, with whom he tried to 
penetrate the unknown territory of the quantum theory. Gottingen 
was then one of the world's most important centres of modern 
physics. In the small university town the mathematical tradition 
had been carried on for more than a century by some of the most 
illustrious of names: Gauss, Riemann, Felix KJein and Hilbert 
all taught in Gottingen. Gottingen thus offered most of the prere- 
quisites for the search for the mathematical laws describing the 
atomic phenomena. James Franck, the experimental physicist, 
awakened the interest of young physicists in the curious behaviour of 
atoms exposed to radiation by his experiments there into electronic 
coUisions. Born and his pupils were striving for insight into the 
fundamental laws of nature underlying these experiments. In this 
way a lively intellectual atmosphere was generated, where 
conversation revolved more frequently around the behaviour of 
electrons within the atom than the events of the day or political 



vui 



INTRODUCTION 



questions. Born and his wife Hedwig, whose letters to Einstein 
constitute a considerable portion of this correspondence, looked 
after this group of young physicists, in both the scientific and the 
human sense. Bern's house was always open for social gatherings 
with young people, and anyone who happened to meet this group 
of youngsters, in the university, or on the ski-slopes of the Harz 
Mountains, may well have wondered how the academic staff 
succeeded in focusing interest so exclusively on such a difficult and 
abstract science. It was part of Germany's great tragedy that the 
revolution of 1933 put a sudden and violent end to this scientific life. 
Born and Franck had to leave Germany. Born found a new sphere of 
activity in England, Franck in America. 

In 1923 Einstein returned to Berhn from his great round-the-world 
trip. He participated regularly in the colloquia where the 6lite of 
Berlin physicists, among them Planck, v. Laue and Nernst, gathered 
to discuss topical research problems. Einstein's contributions to these 
discussions in the colloquia, and his private conversations with 
individual scientists which often took place in his private apartment, 
may well have been the most important part of his educational 
activity at that time. But what limited effectiveness he was still able 
to achieve within a small circle was soon curtailed by political 
developments and their consequences, which were less easily evaded 
in a large city like Berlin than in the friendly little university town of 
Gottingen. Einstein predicted the political catastrophe very early on. 
He therefore assumed new responsibilities in California, and after 
1933 found his ultimate sphere of activity in Princeton, which 
developed into one of the most important American research centres 
during the following decades. 

Relativity theory and quantum theory were the central scientific 
themes of the time. As there were no differences of opinion between 
Einstein and Born about the theory of relativity and the corresponding 
formulation of space and time, the most interesting discussions are 
concerned with the interpretation of the quantum theory. Einstein 
agreed with Born that the mathematical formulation of quantum 
mechanics, developed in Gottingen and consolidated further in 
Cambridge and Copenhagen, correctly described the phenomena 
within the atom. He may also have been willing to admit, for the 
time being at least, that the statistical interpretation of Schroedinger's 
wave function, as formulated by Born, would have to be accepted as a 
working hypothesis. But Einstein did not want to acknowledge that 



IX 



INTRODUCTION 

quantum mechanics represented a final, and even less a complete 
description of these phenomena. The conviction that the world 
could be completely divided into an objective and a subjective 
sphere, and the hypothesis that one should be able to "^ake Pr^^JJ 
statements about the objective side of it, formed a Part of his W 
philosophical attitude. But quantum mechanics could not satisfy 
diese claims, and it does not seem likely that science will ever find 
ts way back to Einstein's postulates. The whole tnckiness of this 
central problem is shown clearly in Born's commentaries on the 
individual letters, which also give us much information about the 
socill and political circumstances connected with the development of 
physics at that time. All scientific work is, of course, based consciou^ 
or subconsciously on some philosophical attitude ; on a Particular 
thought structure which serves as a solid foundation for further 
development. Without a definite attitude of this kind, the concepts 
and associations of ideas produced would be unlikeb^ to attain the 
degree of clarity and lucidity essential for scientific work. Most 
sclLists are willing to accept new empirical data and to recognise 
new results, provided they fit into their philosophical frame- 
work. But in the course of scientific progress it can happen that 
a new range of empirical data can be completely understood on^ 
wheTthe enormous effort is made to enlarge this framework and to 
change the very structure of the thought processes. In the case of 
quantum mechanics, Einstein was apparently no longer willing to 
Tke this step, or perhaps no longer able to do so. The letters between 
Einstdn and Born, and Born's subsequently added commentaries 
movingly demonstrate the degree to which the work of the scientist, 
XcSts subject matter seems to be so far removed from all things 
human, is fundamentally determined by philosophical and human 

^"fiut'^this correspondence should not only be rated an extremely 
valuable document in relation to the history of modern science ; it also 
bears witness to a human attitude which, in a world full of political 
disaster, tries with the best of intentions to help wherever possible, 
anTwhich considers love for one's fellow men to be fundamentally 
of far greater importance than any political ideology. 

W. Heisenberg 



Acknowledgments 



I am greatly obliged to Einstein's executor Dr Otto Nathan in New 
York for permission to use Einstein's letters. I also thank Miss Helen 
Dukas, Einstein's former secretary, for preparing and sending copies 
of these letters to Europe. Mrs Franca Pauli very kindly allowed me 
to use letters of her late husband Professor Wolfgang Pauli, for which 
I am very grateful. I would further like to thank Professor Armin 
Hermann in Stuttgart for his valuable help in reading the proofs. 
I am very grateful to Earl Russell for his warm-hearted preface and 
Professor Werner Heisenberg for his perceptive, sympathetic fore- 
word, I thank my daughter Mrs Irene Newton-John for her excellent 
translation of the original letters. I would like to thank Mrs Hedwig 
Geib for her careful typing of this manuscript, which was often 
illegible. Finally I would like to thank my son Professor Gustav V. R 
Born in London for the efforts he made in dealing with the problems 
which arose in the course of publication. 

Max Born. 

The publishers thank Paul Atkins for his careful work in editing the 
letters and commentaries. 



XI 




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{Photograph by Karsch) 



Plate J. Albert Einstein, late 1940's 




Plate 4. Max AND Hedwig Born, iq^sfS 



{Photograph by Alananne Foche) 



The Born-Einstein Letters 



Einstein's famous paper^ containing the fundamentals of his theory 
of relativity appeared in 1905. The same volume of Annalen der 
Physik contained two more epoch-making papers by him on the 
hypothesis of the light quantum* and the statistical theory of Brow- 
nian movement.^ At that time I was a student in Gottingen and 
attended a seminar conducted by the mathematicians David Hilbert 
and Hermann Minkowsky. They dealt with the electrodynamics and 
optics of moving bodies - the subject that was Einstein's point of 
departure for the theory of relativity. We studied papers by H. A. 
Lorentz, Henri Poincare, G. F. Fitzgerald, Larmor and others, but 
Einstein was not mentioned. I found these problems so fascinating 
that I decided to concentrate on theoretical physics. However, I had 
to postpone any deeper investigation into electrodynamics for other 
reasons.*-^-* After graduating in 1906 I took up the threads again 
and attended lectures by Larmor in Cambridge, England, on more 
recent developments in the Maxwellian theory of electromagnetism, 
and by J. J. Thomson on the experimental progress of the theory of 
electrons. Again Einstein's name was not mentioned. 

When I later (i 907-1 908) tried to develop my experimental skills 
at the Institute presided over by Lummer and Pringsheim in my 
home town of Breslau, I joined an active group of young physicists, 
including Rudolf Ladenburg, Fritz Reiche and Stanislaus Loria. 
We studied the more recent physics Uterature and reported on what 
we had read. When I mentioned Minkowsky's contributions to the 
seminars in Gottingen, which already contained the germ of his 
four-dimensionzd representation of the electromagnetic field, published 
in 1907-8, Reiche and Loria told me about Einstein's paper and 
suggested that I should study it. This I did, and was immediately 
deeply impressed. We were all aware that a genius of the first order 
had emerged. But nobody knew anything about his personality or 
his life, except that he was a civil servant at the Swiss Patent Office in 
Berne. Then Ladenburg decided to look him up during a hoUday 
trip, and his account was the first I heard of Einstein the man. Even 
then he was as he appeared later: completely unpretentious, simple 
and modest in his habits, kind and friendly, yet witty and humorous. 
Ladenburg was enthusiastic and made us curious about the great 
unknown. 

But some time passed before I met him. This was in 1909 at the con- 



BORN-EINSTEIN LETTERS 

ference of natural scientists in Salzburg. As I have described this 
incident and the years following, during which our friendship 
developed, on various occasions,'-'-* I shaU not repeat it here. I 
shall recount only the events which brought us together. In 19 13 
Einstein was appointed as successor to J. H. van't HofFin a research 
post at the BerUn Academy of Sciences, and he was made an ordinary 
member of the mathematical physics division. One year later, 
shortly after the outbreak of the first world war, I became Extra- 
ordinarius for theoretical physics at the University of BerUn, a position 
which was created in order to reUeve Planck of teaching duties. 
Nothing much came of this, as I was called up for military service 
shortiy afterwards (summer 1915). After a short training course as an 
aircraft wireless operator at the Doberitz Camp, I was sent to the 
artillery inspectorate in BerUn as a scientific assistant. The otface 
building in Spichernstrasse was quite close to Einstein's flat at Haber- 
landstrasse 5. Thus it happened tiiat I was able to visit him and talk 

with him frequently, .^ „ , , ,-.• n 

We understood each otiier not only scienufically, but also pohtically 
and in our attitude towards human relationships. I cannot say with 
certainty whether any'correspondence existed between Einstein and 
myself during the preceding years, for nothing has been preserved. 
But I find it hard to beUeve that, when I was working witii Theodor 
von Karman on the furtiier development of Einstein's tiieory of 
speciHc heat of soUd bodies (1912). I did not write to Einstein about 
it Presumably I did not keep any letters at tiiat time. The first letter 
from Einstein to my wife and myself dates from the year 1916, and 
no letters from us to Einstein exist before 1920. The commentary I 
wrote in 1965 therefore depends entirely on my memory for this 
period The firstitem which has been preserved is apostcard addressed 
to me which deals with scientific matters. It was obviously sent from 
Einstein's flat in Wilmersdorf to mine in TepUtzerstrasse, 
Grunewald. 

J Sunday 

sy February, igi6 

Dear Born 

This morning I received the corrected proofs of your paper for 
Physikalische Z<Atschrift, which I read with a certain embarrass- 
ment but at the same time with a feeUng of happiness at being 



BORN-EINSTEIN LETTERS 

completely understood and acknowledged by one of the best of 
my colleagues. But, quite apart from the material contents, it 
was the spirit of positive benevolence radiating from the paper 
which delighted me - it is a sentiment which all too rarely 
flourishes in its pure form under the cold light of the scholar's 
lamp. 

I thank you with all my heart for this happiness which you 
have allowed me to share. 
With kind regards 
Yours 

A. Einstein 



The article which Einstein was so pleased with was on his theory of 
gravitation and general relativity;* I would not write very differently 
about this subject to-day. Since then it has become fashionable to regard 
the relativity aspect of Einstein's general theory as of secondary importance 
and to consider the new law of gravitation as the essential part. I cannot 
share this point of view, which is represented particularly by my Russian 
friend and former collaborator, V. Fock. Einstein's starting point was the 
empirical fact of the equality of inertial and gravitational mass. It follows 
that an observer enclosed inside a box is unable to distinguish whether 
the acceleration of a body inside the box is caused by an external gravi- 
tational field or by the acceleration of the box itself in the opposite 
direction. The existence and the size of a gravitational field inside a small 
space can thus be assumed only in relation to a certain (accelerated) 
system of reference. This was the historical basis of the theory, and it is 
still today, in my opinion, the rational approach. I used it in my book 
Die Relativitatstheorie Einsteinsj'-'^ which was first published in 1920, and 
also retained it in the recendy published new edition. I believe that this is 
justified, both in regard to Einstein's own intention and objectively. 

The following letter to my wife can be understood only if the friendly 
intercourse between Einstein's house and ours is appreciated. My wife 
described this in an article which appeared in the journal Weltwoche a 
few years ago.' It explains the references to the poem and the TIemish 
sow'. The book he mentions is probably one by Max Brod. 



BORN-EINSTEIN LETTERS 



BORN-EINSTEIN LETTERS 



8 September, igi6 

Dear Mrs Born 

Your poem gave me much pleasure, mainly because it is an 
indication of your happy state of mind, but also because it 
shows that you are on the best of terms with both the Muse of 
Parnassus and the 'Flemish sow'. The latter, though, is not really 
needed to make a few cosy evening hours spent in your and 
Max's den appear to me in the most alluring colours ! 

I read the book with great interest. It is certainly enter- 
tainingly written by a man who knows the depths of the human 
soul. Incidentally, I believe that I met him in Prague. I think 
he belongs to a small circle there of philosophical and Zionist 
enthusiasts, which was loosely grouped around the university 
philosophers, a medieval-like band of unwordly people whom 
you got to know by reading the book. 
Best regards to you both 
Yours 

Einstein 

The two papers you wanted are enclosed. The book I will 
return personally. 



Einstein's next letter is again addressed to my wife, but its subject matter 
concerns mc just as much. Presumably I was absent on a lengthy official 
trip. 



8 February, igi8 

Dear Mrs Born 

Your detailed letter with its comforting expression of sympathy 
and confidence gave me much pleasure. My answer will take 
the form of a monologue, thereby completely eliminating the 
ugly chasm between 'you' and 'I'. 



. 



Laue wants to come here. Some time ago he had the chance 
of obtaining a sort of research post here, free from teaching 
duties, through a private award. His effort to get to Berlin then 
was, according to him, based on his dislike of teaching activities. 
Now that this plan will apparently not come off, he is thinking 
of an exchange of posts with your husband. Primary motive, 
therefore: 'BerUn'. Motivation: ambition (of the v«fe?). 
Planck knows about this, the Ministry probably not. I have not 
yet talked about it with Planck. I suppose his efforts are directed 
towards becoming Planck's successor. The poor fish. Nervous 
subtlety. To strive for an aim which is in direct contradiction 
with his natural desire for a quiet life, free from complicated 
human relationships. In this connection please read Andersen's 
pretty little fairytale about the snails. Seen objectively, the 
chance of Laue's plan being successful depends on two 
conditions : 

1 . Sufficient income for Laue from your post, 

2. Your husband's inclination to exchange jobs. 

Just assuming that i. is fulfilled, there remains the question 
of whether you should agree; this is, of course, the question 
which worries you already. My opinion is : 

Accept unconditionally. 

I have no need to assure you how fond I am of you both and how 
glad I am to have you as friends and kindred spirits in this . . . 
desert. But one should not refuse such an ideal post, where one is 
completely independent. There is a wider and freer sphere of 
activity than here, and it gives your husband a better chance to 
display his powers. And most important of all: to be near to 
Planck is a joy. But when Planck eventually retires, you cannot 
be certain, even if you remain there, that your husband will 
succeed to his position. If, on the other hand, it were to be 
someone else, it would be rather less pleasant. One has to be 
prepared for every eventuality. You should not expose yourselves 
to this unless it is necessary. 

Look after yourself, and let my example be a warning to you. 
For me the 'sudden jerk upwards' is no longer possible. 

Sincerest greetings to you, to your children, and to your, I 
hope, soon-to-return lord and master. 
Yours 

Eirutein 



BORN-EINSTEIN LETTERS 

I do not believe that Einstein would later have persisted in attributing 
the motive of ambition to Laue. He probably did not yet know Laue 
well at that time. Later, he acknowledged him not only as a physicist but 
also as an upright and thoroughly honourable human being, as is shown 
in a later letter (No. 8i). To me Laue maintained that his efforts to get to 
Berlin were due less to his dislike of teaching than to his wish to be near 
his admired and much loved teacher, Planck. 

The next letter is without an address, but was presumably sent between 
our two flats in Berlin. 



24 June, igi8 

Dear Born 

Tomorrow we must be off to our summer holiday resort at 
Ahrenshoop (at a Mrs Nieman's, nee Ronow). These lines come 
as a solemn farewell. A Danaean present too. With Haber's 
help I have managed to obtain a travel permit to Finland for 
Nordstrom (from the General Staff). Now he wants to return to 
Holland, but unfortunately I am no longer in a position to attend 
to it. I would ask you to settle the matter, please. It is urgent, as 
Mrs Nordstrom is soon to give birth to her child, in Holland if 
possible. 

With best wishes for a happy time to you and your little band. 
Yours 

Einstein 

I hope the 40 M have arrived — I sent it off in an ordinary letter. 



The Finnish physicist Nordstrom had developed, almost simultaneously 
with Einstein's first publications about the general theory of relativity, 
a rival relativistic theory of gravitation, which contained only one scalar 
potential, as with Newton. According to Einstein, however, the ten 
components of a symmetrical tensor determine the gravitational field. 
Nordstrom' s ideas were shrewd and ingenious. I found out later that he 
had been my strongest competitor for the Berlin Extraordinary 
Professorship. 



BORN-EINSTEIN LETTERS 

Einstein's next letter, clearly from Ahrenshoop, and undated, shows that I 
did attempt to do something for Nordstrom. Whether I was successful I 
cannot remember; I also know nothing of Nordstrom's subsequent fate. 
In Einstein's letter the words 'must' and 'Frische' (holiday resort) were 
underlined. Presimaably he was in some doubt as to whether he would 
'refresh himself' in Ahrenshoop. He was clearly following the wishes of 
his second wife, his cousin Elsa, for she had nursed him during a serious 
illness and had probably saved him from death. 



5 



[undated^ 



Dear Bom 

It is very kind of you to look after the Nordstroms. Just write 
to the General Staff that Nordstrom has already been granted 
a permit for the outward journey, at Haber's request. Then the 
return journey will be readily allowed. As I wrote to you before, 
he has to be back at the beginning of August. 

It is wonderful here, no telephone, no duties, absolute peace. 
I simply can't imagine now how you can bear life in the big city. 
And the weather is wonderful too. I lie on the beach like a 
crocodile and let myself be roasted by the sun, I never see a 
newspaper and don't give a damn for what is called the world. 

What you tell me about the inertia in a crystal lattice is very 
satisfactory. It can only be a matter of electrical energy, since 
the potential energy of the other assumed forces does not enter 
into the inertia, according to the fundamental laws of mechanics. 
I look forward very much to your explanation of this. 

I am reading Kant's Prolegomena here, among other things, 
and am beginning to comprehend the enormous suggestive 
power that emanated from the fellow, and still does. Once you 
concede to him merely the existence of synthetic a priori 
judgements, you are trapped. I have to water down the 'a 
priori' to 'conventional', so as not to have to contradict him, 
but even then the details do not fit. Anyway it is very nice to 
read, even if it is not as good as his predecessor Hume's work. 
Hume also had a far sounder instinct. 

When I am back again, we will all sit down cosily together 
so that you can gently reintroduce me to the bustle of human 



BORN-EINSTEIN LETTERS 

activity, of which I take no notice at the moment. In the 
meantime, I hope that you and your wife are again in good 
health. We are well, and the small harem eat well and are 
thriving. 

Best wishes 
Yours 

Einstein 



So he liked Ahrenshoop after all, and it did him good. The remark about 
inertia in crystal lattices refers to the result of my investigations into 
electromagnetic fields in crystals, which I have published in several books 
and papers. These investigations were a further development of P. P. 
Ewald's fundamental work on dispersion in crystal lattices, but made use 
of a different method which Hilbert had suggested in one of his lectures. 
My result was new: it automatically followed that the electromagnetic 
reciprocal action of the lattice particle's charges contributed to the inertia 
(electromagnetic mass). Einstein's remark that only electrical energy 
would be involved was, however, absolutely correct. 
The letter then contains Einstein's attitude towards the philosophy of 
Kant: it amounts to a rejection. In those days he was a complete empiricist 
and a follower of David Hume. Later on this changed. Speculation and 
guesswork without much empirical foundation played an increasingly 
important role in his thinking. 

I have no idea what his closing remark about the 'small harem' (I cannot 
make it out as anything else) means. Probably it refers to his wife and 
stepdaughters. 

A picture postcard from Ahrenshoop follows. 



^ Ahrenshoop 

2 August, igi8 

Dear Bom 

The closer our journey home approaches, the more I am 
plagued by conscience and the fear of a scolding for being 



BORN-EINSTEIN LETTERS 

lazy about writing. But what can a fellow write who lazes about 
all day, who sees no-one and who at the very most wanders about 
for half an hour in bare feet? If only we could introduce this 
last deUghtful habit (voluntarily) in Berlin! The clover leaf 
amused me very much. One can see that it represents three 
incorrigible hobby-horse riders in brotherly unity; two are 
introspective, one stares unconcernedly into space. The other day 
I read that the population of Europe has grown from 1 13 million 
to almost 400 million during the last century ... a terrible thought, 
which could almost make one reconciled to war! 
To a happy reunion ! 
Yours 

Einstein 



I can't remember what the clover leaves represented. 

The observation about population increase and war is remarkable. 

He added the following to a postcard from Arosa in Switzerland with a 
picture of the Silser Lake that Mrs Elsa Einstein sent. 



7 



ig January, igig 



BrilUant landscape and satisfied citizens, who have nothing to 
fear. This is how it looks. But God knows, I prefer people with 
anxieties, whose tomorrow is threatened by uncertainty. How 
will it all end ? One cannot tear one's thoughts away firom Berlin ; 
so changed and still changing. I believe some good will come 
of it in another sense, once it is calm again. The young who have 
lived through it all will not quickly become philistines. 
Hearty best wishes 
Yours 

Einstein 



That trip abroad was probably Einstein's first after the war. His thoughts 
were still of a Berlin shaken by revolution. The card's brief message shows 



BORN-EINSTEIN LETTERS 

what hopes he had of the new regime, the Republic under Ebert. He 
deeply detested Prussianism with its arrogant militarism, and he believed 
it now to be finally defeated and that everything could improve. I 
believed the same at that time, and this was one bond in our friendship. 
We were completely wrong - it got very much worse. Subsequent letters 
contain reminders of this time of hope. 

After a certain amount of to-ing and fro-ing, the exchange of chairs be- 
tween myself and Laue was finally agreed.We succeeded in acquiring an 
attractive house with a garden in Frankfurt, in Cronstettenstrasse. Ein- 
stein's first letter addressed to us there follows. 



8 



Berlin 
4 June, igig 



Dear Bom 

I already have a bad enough conscience because I have not 
answered your wife's extremely kind letter, and now your 
delightful letter arrives instead of a scolding. I am glad that 
you have made such a splendid nest for yourselves there, in your 
little house and garden. It is wicked of you, though, to take on 
such a burden of responsibility. Do you want to become a 
torment to your students and a reproach to your colleagues? 
Will you even keep your literary promises, e.g. to Sommerfeld ? 
That is going too far. If Shakespeare had lived under present- 
day conditions he may well have altered his lines: 'At lovers' 
perjuries, They say, Jove laughs', which is a little hard, to: 
'At the forgotten promise of a report'. 

And then you tell me that, according to friend Oppenheim, I 
am supposed to have made heaven only knows what wonderful 
discovery. But there is no truth in it. The modest suggestion I 
made to him about this affair, which I told you about at Lake 
Grunewald, has become dangerously swollen in his exuberant 
imagination ! The quantum theory gives me a feeling very much 
like yours. One really ought to be ashamed of its success, 
because it has been obtained in accordance with the Jesuit 
maxim: 'Let not thy left hand know what thy right hand doeth'. 
I do not see the political situation as pessimistically as you. 



ID 



BORN-EINSTEIN LETTERS 

Conditions are hard, but they will never be enforced. They are 
more to satisfy the enemy's eye than his stomach. Ludendorf 
was undoubtedly much worse than the Parisians. The French 
are motivated by fear. Ludendorf, however, had the desires of a 
Napoleon. The hardships resulting from the errors of the French 
are alleviated by a slovenliness which never fails, as in my one- 
time fatherland, Austria.* Eventually, Germany's dangerousness 
will go up in smoke, together with the unity of her opponents, 
accompanied no doubt by a certain hysteresis. May a hard- 
bitten x-brother and determinist be allowed to say, with tears 
in his eyes, that he has lost his faith in humanity ? The impulsive 
behaviour of contemporary man in political matters is enough to 
keep one's faith in determinism alive. 

I am convinced that in the next few years things will be less 
hard than in those we have recently lived through. 

With sincere regards to you and your wife, also from my wife. 
Yours 

Einstein 

Haber's adaptation of your theory to monovalent metals is 
puzzling. 



The Uterary promise concerned my promise to Sommerfeld (Professor of 
Theoretical Physics in Munich) to write an article about atomic theory of 
the soUd state for the volume 'Physics' in the Enzyklopddie der Mathemattk. 
This lengthy treatise later appeared as a book. 

Friend Oppenheim was the son of an important Frankfurt businessman 
(a jeweller), who had founded and endowed the Chair of Theoretical 
Physics occupied first by Laue and later by myself. Oppenheim junior 
was interested in philosophy, particularly the philosophical ideas contained 
in Einstein's theory of relativity. He was probably alludmg to the begin- 
nings of 'a unified field theory', which was intended to combme gravitation 
and electromagnetism and which occupied Einstein throughout his hfe. 
The poUtical remarks show that at that time I took a more pessimistic 
view of the situation than Einstein. The expression 'hard-bitten x-brother 
and determinist' (we used to say 'to x' when calculating with unknown 
values oix, as is normal in mathematics) was probably correct then, lor 
my non-determinist views only arose some years later. 

* Einstein probably meant his time in Prague as Professor at the German 
University; Bohemia was a part of Austria at that time. 

II 



BORN-EINSTEIN LETTERS 



I cannot remember now what Haber's application of my theory to mono- 
valent metals meant. 



y Sunday 

I September, igig 

Dear Mrs Bom 

I have a terribly bad conscience about both of you, but par- 
ticularly you, because I so infrequently settle down to write to 
you. Let me say straight away, so that I won't forget, that I will 
do my best to squeeze some funds out of the K. W. Institute 
[Kaiser- Wilhelm Institute] for your husband, if possible, and 
if we ever have some to give away. I will visit you soon enough 
in your comfortable nest - provided you have no-one billeted on 
you -just you wait ! 

That business with Oppenheim has gone wrong. My aca- 
demic remuneration does not depend on his purse but on that 
of Mr Koppel. I had no idea that your husband's chair was 
founded by Oppenheim - I only know of the observatory there. 
The relationship between Oppenheim (junior) (I have only 
seen old man O. on one single occasion) and us is of a strictly 
private nature and is due to Mr O. junior's philosophical 
hobby-horse. There is just one problem - 1 promised to come and 
stay both with you and with Mr O. junior, if I came to Frankfurt ; 
the solution is beyond my powers, but no doubt it will turn out 
all right in the end. It is nothing like as bad as the answer 
AlthofF gave to someone who had just been passed over for 
someone else for a professorship he had been promised. He said, 
cheerfully and rudely, 'Well, did you believe you were the only 
one to whom I have promised the professorship?'! Yesterday 
Stem came to see me. He is delighted with Frankfurt and with 
the Institute. I quite liked Rausch, though Strindberg's Traum- 
spiel is incomparably better. 

Mr Bieberach's love and veneration for himself and his 
Muse is quite delicious. May God preserve him, for it is the best 
way to be. Years ago, when people lived their lives in greater 
isolation, eccentrics like him were quite the rule amongst 
university professors, because they did not come into personal 

12 



BORN-EINSTEIN LETTERS 

contact with anyone of their own stature in their subject, and 
apart from their subject nothing existed for them. 

Politically, I am more on your husband's side than on yours. 
I believe in the growth potential of the League of Nations, and I 
believe further that the hardships connected with its formation 
will disappear after a while. Even now the conflict of interests of 
the Allies is so considerable that much is being modified (the 
constitutional incident concerning Austria; the intervention 
of the Allies in Silesia). In my opinion, the greatest danger to 
future development would be a withdrawal by the Americans; 
one can only hope that Wilson will be able to prevent it. 

I don't believe that human beings as such can really change 
but I am convinced that it is possible, and indeed necessary, to 
put an end to anarchy in international relations, even if it were 
to mean sacrificing the independence of various countries. 

Now to philosophy. What you call 'Max's materialism' is 
simply the causal way of looking at things. This way of looking 
at things always answers only the question 'Why?', but never 
the question 'To what end ?'. No utility principle and no natural 
selection will make us get over that. However, if someone asks 
'To what purpose should we help one another, make life easier 
for each other, make beautiful music or have inspired thoughts ?', 
he would have to be told: 'If you don't feel it, no-one can 
explain it to you.' Without this primary feeling we are nothing 
and had better not live at all. If someone wanted to make a 
basic investigation to prove that these things help to preserve 
and further human existence, then the question 'To what end?' 
would loom even larger, and an answer on a 'scientific' basis 
would be an even more hopeless task. So if we want to proceed 
in a scientific manner at any cost, we can try to reduce our 
aims to as few as possible and derive the others from them. But 
this will leave you cold. 

I do not agree with the pessimistic assessment of cognition. 
To have a clear view of relationships is one of the most beautiful 
things in life; you could only deny that in a very gloomy, 
nihilistic mood. But you should not quote the Bible to prove 
your point. In Luther's translation it says in many places : 'And 
he knew her; and she bore him a son; his name was. . . .' One 
can assume that the Tree of Knowledge refers to this. Therefore, 
it probably has very little in common with epistemology in our 



13 



BORN-EINSTEIN LETTERS 

sense; or maybe the old fathers fancied themselves in tiiis 
ambiguity? But that is not really like these lovers of speculation 
and argument. 

Thank you very much for the lovely photographs. The one 
of your husband is wonderful: its subject is not so bad, either. 
He has not been here yet; I look forward greatly to seeing him. 
I have spent these last few days very pleasantly sailing, but 
unfortunately have contracted another ailment (stomach) on 
naval service, and I have to spend a few days in bed once more. 
Thus the indistinct writing. 

With kindest regards to you both. 
Yours 

Einstein 



Althoff was for many years an official concerned with university admini- 
stration at the Ministry of Education, where he earned great merit in 
building up the universities. He was well known and feared for his lack of 
consideration and rudeness. 

Otto Stern was a young physicist from Silesia who became my assistant. 
Our Institute possessed a workshop and an able technician called Schmidt. 
Stem made very good use of this to carry out his experiments, later to 
become famous, into a peculiar effect of the quantum, the so-called 
quantisation of direction. Up to that time, this effect had been only 
indirectly deduced from spectroscopic observations; Stern undertook to 
prove it directly by using atomic radiation in a high vacuum. He was 
supported in this by Walter Gerlach, assistant at the Institute of Experi- 
mental Physics (whose head was Prof Wachsmuth). Stem later received 
the Nobel Prize for these investigations. At his suggestion I also experi- 
mented successfully at that time; with my assistant, Elisabeth Bormann, 
I made a direct measurement of the length of the free paths of atoms with 
the aid of atomic radiation. 
I cannot remember what kind of play Rausch vfas. 

The Bieberbach affair was as follows: The Faculty of Natural Sciences 
had a beautifully bound book, in which each new professor was required to 
write a short autobiographical note. When it was given to me by the Dean, 
the mathematician Schoenflies, I naturally read some of the cameo- 
biographies, and also showed them to my wife. She discovered a rather 
comic one - the young mathematician Bieberbach's, which was full of 
vanity. She copied some of the finest passages for Einstein. 
Einstein's explanation to my wife of the nature of scientific research 
reveals the basis of his philosophy in a concise and clear way that is hard 

14 



BORN-EINSTEIN LETTERS 

to find elsewhere. It led to a discussion of the Biblical concept 'cognition' 
which continued for some time between my wife and Einstein. In contrast 
to Einstein, who interpreted the tasting of the forbidden fruit from the 
tree of knowledge as sexual experience, she insisted that it meant spiritual 
enlightenment. For the first chapter of Genesis says : 'And God blessed 
them [man and wife], and God sjiid unto them, Be fruitful, and multiply'. 
And later it says: 'And out of the ground made the Lord God to grow every 
tree . . . the Tree of Life also in the midst of the garden, and the Tree of 
Knowledge of good and evil . . . But of the fruit of the tree which is in the 
midst of the garden, God hath said Ye shall not eat of it.' In the third 
chapter the serpent says to Eve : 'For Gk)d doth know that in the day ye 
eat thereof, then your eyes shall be opened, and ye shall be as gods, 
knowing good and evil.' 

The next letter shows that Einstein ceded this point to her, but not its 
consequences. 



10 



t6 October, igig 



Dear Bom 

You are a splendid fellow! Have forwarded your pamphlet 
with expressions of agreement plus a few quibbles to the lucky 
recipient. 

Your wife was right about the Tree of Knowledge. I clearly 
rated my ancestors more primitive than they were. But we 
won't allow her to reduce - 'cognition' like that. What better 
concept is there? Also, she should not grumble about loneliness 
in company when she has such a splendid fellow with her. It 
all comes from feeling cold. Perhaps the cold will also make you 
lose your temper about that business with the Ministry - that 
would be a good thing. The letters from your wife, incidentally, 
are masterpieces - and that is no flattery. 
Best wishes to you both. 
Yours 

Einstein 



In the original of the letter, the formal German 'Sie' (you) was 
crossed out and the more familiar 'Du' substituted. Several more similar 



15 



BORN-EINSTEIN LETTERS 

alterations occur later, in each instance the more intimate form of 'you' 

being substituted. 

I have forgotten which pamphlet earned me the epithet of a 'splendid 

fellow'. I only remember that I often supported him and his work. 

On the 'cognition' question Einstein freely admits that my wife was right - 

but only in relation to the Tree of Knowledge in the Garden of Eden. 

He remained adamant about the value of 'cognition' in the sense of 

knowledge : 'What better concept is there ?' 

Although I knew that Einstein had a good opinion of me, the offer in the 
first few lines of the next letter, which acknowledged the 'Du' used 
previously, gave me great pleasure. 



II 



g November, igig 



Dear Bom 

From now on we shall use 'Du', if you agree. I have received 
your manuscript. But I cannot help thinking that it is too long 
for the Transactions according to the new rules. I will talk 
to Planck about it. Your application for the K. W. Institute 
will soon be dealt with; just have a little patience. 

In regard to the Toeplitz affair, I can't make a noise again 
just yet, or my bark may prove ineffective in worse cases. 
Antisemitism must be seen as a real thing, based on true 
hereditary qualities, even if for us Jews it is often unpleasant. I 
could well imagine that / myself would choose a Jew as 
my companion, given the choice. On the other hand I 
would consider it reasonable for the Jews themselves to 
collect the money to support Jewish research workers outside 
the universities and to provide them with teaching 
opportunities. 

We look forward very much to seeing your wife. Meanwhile 
I want to apologise to her because, as she has shown, I have not 
yet eaten enough of the fruit of the Tree of Knowledge, 
though in my profession I am obliged to feed regularly on it. 
Many thanks for the pears - your productiveness really extends 
to every imaginable delight. 

i6 



BORN-EINSTEIN LETTERS 

I hope you are not too cold; we are amazingly well organised 
in this respect. 

More soon. For the present, kind regards 
Yours 

Einstein 



Although I was very conscious of Einstein's superiority to myself, it was 
quite easy to address him with the informal 'Du'. He was so simple and 
natural, so entirely without conceit, that the brotherly form of address 
seemed almost inevitable. Of course I was aware of the honour of being on 
such a familiar footing with him. Our friendship was never shaken, even 
though we had some sharp scientific arguments later on (some of which 
are in subsequent letters). 

I cannot remember which manuscript was referred to. 
The Toeplitz affair was probably a snub sustained by my old friend and 
fellow student. Otto Toeplitz, in connection with some appointment or 
other, which he put down to antisemitism. 

Toeplitz was a brilliant mathematician; he made a considerable contri- 
bution to the theory of the square forms of an infinite number of variables 
(in the so-called Hilbert Space), which is currently used in quantum 
mechanics. An important contribution was a long article in Enzjklopddie 
der Mathematik, written in collaboration with another friend and fellow- 
student, Ernst Hellinger. 

Einstein's remarks about antisemitism show that he was very conscious 
of the contrast between Jews and Northern Europeans, and that he took 
the existence of mutual antipathy very much for granted. He often argued 
the case in favour of the suggestion that Jews ought not to press their 
claims in an attempt to obtain the more desirable positions, particularly 
academic ones, but should create jobs for themselves, to be filled from their 
own ranks. I was, as far as I can remember, not altogether of the same 
opinion; my family was amongst those who strove for complete assimi- 
lation and who regarded antisemitic expressions and measures as unjusti- 
fied humiliations. History has shown that Einstein was the more profound, 
although he was then still a long way from recognising the magnitude 
of the threat of antisemitism, and of the shocking crimes resulting 
from it. 



17 



BORN-EINSTEIN LETTERS 



12 



Monday 
g December, igig 



Dear Bom 

Your excellent article in Frankfurter Z^itung gave me much 
pleasure. But now you, as well as I, will be persecuted by the 
press and other rabble, although you to a lesser extent. It is so 
bad for me that I can hardly come up for air, let alone work 
properly. 

That article by Drill is comic, because he introduces into 
philosophy the democratic method of appeaUng to and 
haranguing the masses. Let the man continue to beat his drum; 
it would be a pity to waste time on a reply. Save your temper, 
and let the fellow run around and chatter. His proof of a priori 
causality is truly amazing. 

During the few days I spent with Schlick in Rostock for the 
University's jubilee celebrations, I heard some vile political 
mischief-making and saw some really delightful examples of 
small-state poUtics. What made it so ludicrous was the fact 
that they all knew each other so thoroughly as human beings 
that, when one struck a lofty tone, it was jdways accompanied 
by ridiculous dissonances. The only hall available for the 
celebration was the theatre, which gave it an air of comedy. It 
was charming to see the representatives of the old and the new 
Government sitting together in the two proscenium boxes. 
The new government was, of course, treated to every conceivable 
jibe by the academic dignitaries, while the ex-Grand Duke was 
given a seemingly endless ovation. No revolution can help 
against such inbred servility. Schlick has a good head on him; 
we must try to get him a professorship. He is in desperate need 
of it because of the devaluation of property. However, it will be 
difficult, as he does not belong to the philosophical established 
church of the Kantians. 

Planck's misfortune moves me very deeply. I could not hold 
back the tears when I visited him after my return from Rostock. 
He behaves remarkably bravely and properly, but one can see 
that he is eaten up by grief. 

Your wife's letters are charming, so original and to the point. 
I hope that our friend Oppenheim will soon find the midwife 

i8 



BORN-EINSTEIN LETTERS 

he is looking for; if not, the happy event will have to be post- 
poned for a while. My friend Haber, who turned to me in his 
misery after you moved away, suffers from a similar kind of 
malignant pregnancy. He has such forceful methods for trying 
to wrest truth from nature. For material doubts, he falls back 
on his intuition. He is a kind of raving barbarian, but very 
interesting all the same. 

Your confused Lorenz has ordered me categorically to 
attend an extremely superfluous lecture in Frankfurt; he is one 
of the quaintest birds occupying a professorial chair. Unfortun- 
ately I have other worries. My mother, who is mortally ill, is 
coming to stay with us - sooner or later I must try to accommo- 
date my children with my divorced wife in Germany. Difficulties 
and anxieties at every turn. 

The behaviour of the AlUes is beginning to appear disgusting 
even by my standards. It seems that my hopes for the League of 
Nations will not be realised. Nevertheless, France seems to be 
suffering severely in spite of the coal imports, as can be seen from 
its recent restrictions on railway passenger traffic. Here all fixed 
and movable property is being bought up by foreigners, to the 
point of our becoming an Anglo-American colony. Just as well 
that we do not have to sell our brains, or make an emergency 
sacrifice of them to the state. I hope you are all well and not 
suffering too much from the cold. 
Best wishes 
Yours 

Einstein 



I saw the article in the Frankfurter recently but now I am unable to find it 
again. I remember that after so many years I was still greatly amused by 
my peppery criticism of those hide-bound philosophers. I can only vaguely 
remember Drill, whose article Einstein found comic, as a typically rabid 
opponent of Einstein. Schlick, on the other hand, was an important 
philosopher. Later on he went to Vienna and was the founder of a school 
of philosophy known today as logical positivism. 

Einstein's description of the celebrations at Rostock University is typical 
ofhim. 

I assume that by Planck's misfortune he meant the death of his daughter 
shortly after the birth of her first child. She had a twin sister who was very 
like her, who took on the care of the child and later married her sister's 



19 



BORN-EINSTEIN LETTERS 

husband. Then a terrible thing happened, for she too died under identical 
circumstances after the birth of her first child. 

Einstein's characterisation of Fritz Haber is quite accurate. During the 
war he and I broke off our relationship. He wanted me to join his war 
gas team, which I bluntly refused to do. Later on we became reconciled 
and I made more frequent visits to his institute in Dahlem to get experi- 
mental data from my friend Franck for my work on the calculation of 
chemical heat variations from lattice energies. Haber was keenly interested 
in this, and developed a way of representing my method of calculation 
graphically. This theory later entered the literature of physical chemistry 
as the Born-Haber cyclic process. Thus I had the opportunity to get to 
know the 'raving barbarian', as Einstein called him. On one occasion, 
for example, we were having a lively discussion in his room, but were 
constantly interrupted by assistants, post-graduate students or technicians 
who wanted something from the head of the institute. In the end, someone 
opened the door without having knocked first and the furious Haber 
seized a glass inkpot and flung it in the direction of the door, where it 
broke into pieces, spattering ink over the wall and the door. At the door, 
however, stood Haber's wife. She vanished, terrified, and we continued 
with our work as if nothing had happened. 

The 'confused Lorenz' was Professor of Physical Chemistry at Frankfurt. 
He was indeed a little vague, but all the same very able in his field. I 
received much encouragement from him, in my attempt to explain the 
anomalies of ionic mobility of small ions with the help of dipolar experi- 
ments, for example, and in the experiments concerning the mechanical 
effects of dipoles carried out by my pupil Lertes.* 

The final paragraph of this letter shows that Einstein was no longer able 
to maintain his political hopes, which he had so often set against my 
pessimism. But he tried hard to be fair about the difficulties of France. I 
believe that none of us at that time recognised the real danger resulting 
from the Allies' harsh treatment of Germany, namely, the injury to her 
national pride. This led to the development of the myth of 'the stab in the 
back', to secret rearmament, and ultimately to the rise of National 
Socialism. 



13 



Monday 
sy January, igso 



Dear Bom 

First of all, the matter of our young colleague Dehlinger, whom 
you have written about to Berliner. We are now getting a lot of 
money for astronomical research which I have entirely under 



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BORN-EINSTEIN LETTERS 

my own control. Would he like to work in astrophysics? I 
could appoint him for the time being at a salary of approximately 
6,000 M a year, possibly more if the present adverse conditions 
require it. He would then work with Freundlich. Photometric 
investigations on star spectra. If, however, he prefers a post in 
technology, I have other connections who could try to find 
something for him. It is difficult nowadays to make a living by 
scientific work alone. Let me have further details as soon as 
possible. 

We are also having a sad time just now, because my mother is 
at home in a hopeless condition and suffering unspeakably. It 
could be many months before she is released. Else is doing a great 
deal; it is not easy for her. All this has diminished still further 
my already faltering desire to achieve great things. Now you are 
quite different. Your little clan has its own difficulties to deal with, 
and you, dear Mrs Born, make yourself interesting in a most 
reprehensible way. (Whimsical poems and witty letters only 
are permitted.) And you. Max, are giving lectures on relativity 
to save the institute from penury, and writing papers as if you 
were a single young man living in splendid isolation in his own 
specially heated apartment, with none of the worries of a pater- 
familias nagging you. How do you do it ? 

Haber is complaining bitterly about Fajans. You have des- 
cribed the latter very well. He is quite unaware of the number 
of arbitrary assumptions he makes, and vastly overestimates the 
value of consistent results. You are right in sticking uncompro- 
misingly to your sound method. I myself do not believe that the 
solution to the quanta has to be found by giving up the con- 
tinuum. Similarly, it could be assumed that one could arrive at 
general relativity by giving up the coordinate system. In 
principle, the continuum could possibly be dispensed with. 
But how could the relative movement of n points be described 
without the continuum ? 

PauU's objection is directed not only against Weyl's, but also 
against anyone else's continuum theory. Even against one which 
treated the electron as a singularity. I believe now, as before, 
that one has to look for redundancy in determination by using 
differential equations so that the solutions themselves no longer 
have the character of a continuum. But how ? 

The political situation is developing consistently in favour of 



21 



BORN-EINSTEIN LETTERS 



the Bolsheviks. It seems that the Russians' considerable external 
achievements are gathering an irresistible momentum in 
relation to the increasingly untenable position of the West; 
particularly our position. But before this can happen, streams 
of blood will have to flow; the forces of reaction are also 
growing more violent all the time. Nicolai is being attacked 
and insulted so much that he is no longer able to lecture, not 
even in the Charite. Once again I have had to intercede 
for him in public (one could write a new comedie called: 'The 
friend against his will'). France is really playing a rather sorry 
role in all this (all the same it is to their credit that they have 
rid themselves of the Tiger [Georges Clemenceau]). Victory is 
very hard to bear. Erzberger's trial is comic; those with clean 
hands (and pockets) may stone him, if they exist! By the way, I 
must confess to you that the Bolsheviks do not seem so bad to me, 
however laughable their theories. It would be really interesting 
just to have a look at the thing at close quarters. At any rate, 
their message seems to be very effective, for the weapons the 
Allies used to destroy the German Army melt away in Russia 
like snow in the spring sun. Those fellows have gifted poli- 
ticians at the top. I recently read a brochure by Radek - one 
has to hand it to him, the man knows his business. 

You think I should let my voice be heard in England? I 
would do, if I really had something worthwhile to say. But I 
can see that the people there are deeply involved in their own 
problems. What could they possibly do to banish want? They, 
and the Americans, are sending emergency supplies. But little 
can be done in the face of this mass suffering. 

The peace treaty certainly goes too far. But since its fulfilment 
is quite impossible, it is better that its demands are objectively 
impossible to fulfil, rather than just intolerable. One has to 
acknowledge that the citizens on the other side had to have 
something in black and white as a reward for the courage of the 
French. To rise against the treaty would only make sense if one 
believed in its real significance, which I do not. By the way, I 
am going to England in the spring, to have a medal pressed into 
my hand and to have a closer look at the other side of this 
tomfoolery. Spengler has not spared me either. Sometimes one 
agrees to his suggestions in the evening, and then smiles about 
them next morning. One can see that the whole of his mono- 



22 



BORN-EINSTEIN LETTERS 

mania had its origin in schoolteacher mathematics. Euclid 
versus Descartes is brought into everything, although, one must 
admit, ingeniously. These things are amusing; if someone 
should say the exact opposite tomorrow with sufficient spirit, it 
is amusing once more, but the devil only knows what the truth is. 

That business about causality causes me a lot of trouble, too. 
Can the quantum absorption and emission of light ever be 
understood in the sense of the complete causality requirement, 
or would a statistical residue remain ? I must admit that there I 
lack the courage of my convictions. But I would be very unhappy 
to renounce complete causality. I do not understand Stern's 
interpretation because I cannot make real sense of his statement 
that nature is 'intelligible'. (The question whether strict 
causality exists or not has a definite meaning, even though 
there can probably never be a definite answer to it.) Sommer- 
feld's book is good, although I must say frankly that, for heaven 
only knows what subconscious reason, this person does not ring 
true to me. 

I am pleased that your letters to the Ministry have served 
their purpose. That speaks well for those people; after all you 
did not mince your words. It has really got much better. Just 
imagine what would have happened before, had you written 
like that. Now the dictatorial omnipotence of you Ordinarii 
will be brought to a horrible end, or so I heard the other day. 
Just you wait ! 

For you, Mrs Born, I have an interesting suggestion. As soon 
as your children are up and about again, start learning how to 
experiment in the laboratory. This is such wonderful work if 
one has the time to devote oneself to it. I mean it quite seriously. 
Even assuming that a year or more would have to be spent in 
studying, it would be very much worth while. And once you 
are involved in it, it is a splendid way of working together. You 
do need something to stretch your mind. What do you think of it ? 
Best wishes to you all 
Yours 

Einstein 



Dehlinger was a gifted young physicist from Vienna, who had developed 
a formula for the dispersion of light in the infrared for simple diatomic 



23 



BORN-EINSTEIN LETTERS 

lattices, using my papers on the lattice theory of crystals as his point of 
departure. I know nothing of his subsequent fate. Arnold Berliner was 
then known to every natural scientist as the founder and editor of the 
journal Die Naturwissenschaften (The Natural Sciences) . He was an electrical 
engineer by profession and occupied an important position at the A. E. G. 
(General Electric Co.). Through his journal he exerted considerable 
influence in scientific research circles. Extended correspondence with his 
authors gave him a deep insight into their psychology, which he summar- 
ised as 'Mimosa-like porcupines'. He lived to see the rise of Hitler, was 
unable to go abroad because of his age, and took his own life. 
After his brief reference to the great suffering of his mother and to the 
small troubles in our house (my wife and children had gone down with 
measles), Einstein mentions my lectures on relativity in Frankfurt. In 
those days the inflation of the German currency had already gone so far 
that the Institute's budget was not sufficient. We needed money for the 
experiments into the quantisation of direction that Otto Stern, assisted by 
Walter Gerlach from the Institute for Experimental Physics under 
Wachsmuth, had just begun at the Institute. I myself weis also doing 
some experimental work with beams of silver atoms. It occurred to me to 
exploit the popular interest in Einstein's theory of relativity for this 
purpose by organising lectures on the subject and charging an entrance 
fee for the benefit of the Institute. There was a wave of enthusiasm for 
Einstein's theory at the time, following Sir Arthur Eddington's announce- 
ment to the Royal Society that Einstein's prediction about the deflection 
by the sun of light beams from the stars had been confirmed by a British 
expedition under his leadership. The lectures were well patronised and I 
later wrote a book based on them. 

The remarks concerning the physical chemists Fajans and Haber refer 
to problems which are no longer of interest. 

Einstein's statements about the quanta are more important. They 
contain the early basis for his subsequent position on quantum mechanics. 
He insists unconditionally on retaining a continuum theory, that is, 
differential equations, and on obtaining quantum phenomena (discon- 
tinuities) by redundancy in determination (more equations than unknowns) . 
In this letter Einstein's political views are particularly informative. He 
believed at that time, like many others, that the Bolshevik revolution 
would mean deliverance from the principal evils of our time : militarism, 
bureaucratic oppression, and plutocracy; and he hoped for an improve- 
ment in conditions from the Communists, 'however comic their theories'. 
I do not know if he had read much of Marx, Engels and Lenin's works. 
Similarly he was not very familiar with political and economic writers 
of a bourgeois leaning. At any rate, his hope for the Russian revolution 
was based on his dislike, one could almost say hatred, of the ruling powers 



24 



BORN-EINSTEIN LETTERS 

in the West, than on a rational conviction of the correctness of Communist 
ideology. I emphasise this point because Communist writers often repre- 
sent him as a supporter, or at least a precursor, of their doctrines.* 
The theme of the Russian revolution frequently recurs in later letters. In 
any C£ise, Einstein did not go to Russia but to America when he had to 
leave Germany. He also, as far as I know, never visited Russia. 
My wife never took seriously his suggestion to learn to experiment. That 
kind of activity does not appeal to her. 

The next letter must have been written in answer to the news from us that 
I had obtained a chair in Gottingen. Peter Debye had been there during 
the war as successor to my former teacher, Woldemar Voigt. During my 
time as a private lecturer there were two professors ordinarius in the 
department of physics, E. Riecke in experimental physics and W. Voigt 
in theoretical physics. To attract Debye to Gottingen, an additional 
extraordinariat was founded in 1914. Voigt took this so that Debye 
could become Professor Ordinarius. After Riecke's death a professorship 
extraordinarius was arranged for Robert Pohl. After the end of the war, 
Debye decided to accept an appointment in Zurich. I was offered his 
position in 1920. Einstein's reply to my question as to what we should 
do was as follows. 



14 



5 March, igso 



Dear Bom 

It is difficult to know what advice to give. Theoretical physics 
will flourish wherever j)iom happen to be; there is no other Born 
to be found in Germany today. Therefore the question is really: 
where do you find it more pleasant? Now when I put myself 
in your position, I think I would rather remain in Frankfurt. 
For I would find it intolerable to be assigned to a small circle 
of self-important and, for the most part, unfeeling (and narrow- 
minded) academics (no other social intercourse available). 
Just remember what Hilbert had to endure with these people. 
Something else must be taken into consideration. If Max should 
be faced with the necessity of earning something on the side, a 
possibility one cannot altogether rule out under the present 

• For example, in his book Albert Einstein (Berlin, 1953), Friedrich Herneck 
begins with the words: 'Albert Einstein, one of the greatest Germans after Karl 
Marx . . . '. Einstein would have found that laughable. 



25 



BORN-EINSTEIN LETTERS 

unstable economic conditions, it would be incomparably 
better to live in Frankfurt than Gottingen. On the other hand, 
life in Gottingen may well be more pleasant for the housewife 
than in Frankfurt, and better for the children; but this I cannot 
judge, as I do not know enough about conditions in Frankfurt. 

And after all, it is not so important where one settles. The 
best thing is to follow your instinct without too much reflection. 
And besides, as a person without roots anywhere, I do not feel 
qualified to give advice. My father's ashes lie in Milan. I 
buried my mother here only a few days ago. I myself have 
journeyed to and fro continuously - a stranger everywhere. My 
children are in Switzerland under conditions which make it 
a troublesome undertaking for me when I want to see them. A 
person like me has as his ideal to be at home anywhere with his 
near and dear ones ; he has no right to advise you in this matter. 

I was very interested in your observations about ion mobility; 
I believe the concept is right. In my spare time I always brood 
about the problem of the quanta from the point of view of 
relativity. I do not think the theory can work without the 
continuum. But I do not seem to be able to give tangible form 
to my pet idea, which is to understand the structure of the quanta 
by redundancy in determination, using differential equations. 

Hoping that this letter will find all four of you in good health 
and spirits, I remain, with best wishes 
Yours 

Einstein 



We finally decided in favour of Gottingen. I went to Berlin to negotiate 
with the Ministry of Education, and explained to Ministerial Councillor 
Wende that I felt unable to take on both the theoretical and the experi- 
mental physics departments, but that I would be prepared to go to 
Gottingen if a second chair were to be given to an experimental physicist 
closely connected with me. Wende said that there was no position avail- 
able, that the budget for the current year had already been allocated, and 
that it was extremely unlikely that a new professorship would be approved 
for the next financial year. To prove this, he gave me a great thick book 
which contained the budget estimates of the Ministry, and left the room. 
I studied the pages dealing with physics in Gottingen very carefully, and 
discovered the following: There were two professorships extraordinarius 
for experimental physics, one for Voigt, and the other for Pohl. One bore 

26 



i ; 



BORN-EINSTEIN LETTERS 

the remark: 'To be abolished on the death of the occupant'. Now Voigt 
had just died; but this remark was not placed, as it should have been, 
underneath the column dealing with his position, but below that of Pohl's 
- who was very much alive. This meant that Voigt's position was available. 
When Wende returned I gleefully pointed out the facts to him. But he 
shrugged his shoulders and said that it was obviously a clerical error: 
Voigt's position had only been provided for during his lifetime. However, I 
insisted so forcefully on the letter of the text, that Wende eventually said 
that he could not take the responsibility and would have to consult his 
superiors. The Minister, Professor Becker, and the Ministerial Director, 
Professor Richter, entered the room. When I had explained the position 
to them, they laughed, and Becker said: 'Well, as the revolution is still 
with us one can get away with that sort of thing. We will stand by the 
wording. Please give us some suggestions for the second professor.' So I 
accepted the chair; however, I did not become a full professor, but a 
professor extraordinarius, like the soon-to-be-appointed experimentalist. 
In the following year all three of us, Pohl, the new man and I, were pro- 
moted to full professorships. 

The choice of the 'new one' caused me a few headaches. I followed my 
instinct for the essential requirements of the position, and proposed my 
old friend James Franck. I very much admired his experiments into the 
excitation of atomic line spectra by electronic collision carried out in 
collaboration with Gustav Hertz; they confirmed the fundamental and 
revolutionary assumptions of Bohr's atomic theory, and were therefore one 
of the foundations of quantum physics. That I had made the right choice 
was shown not only by the award of the Nobel Prize for 1925 to Franck and 
Hertz, but also by the flowering of experimental physics in Gottingen 
during the next twelve years (i 921- 1933). This was all therefore basically 
due to a clerical error. 

The letter ends with two remarks about physics. The first of these refers to 
a paper of mine; the second, and more important, contains Einstein's 
ideas about the nature of the quanta. My work on ion mobility had been 
encouraged by the Frankfurt physical chemist R. Lorentz. This work was on 
the fact that ions in aqueous solution, particularly monovalent ones, 
exhibit a strange abnormality of movement : one would think that the 
small ions must be the fastest, the large ones the slowest, but the opposite is 
the case. The chemists explained this by the somewhat vague notion of 
hydration. I was able to define this idea more closely using Debye's 
theory, according to which the water molecules are dipoles. An ion 
moving about amongst them causes them to rotate, the more forcefully 
the smaller its radius. I developed this into a general theory which 
can be termed hydrodynamics, by analogy with the modern magneto- 
hydrodynamics. Also, one of my pupils, Lertes, was able to demonstrate 



27 



BORN-EINSTEIN LETTERS 

experimentally one of the simple effects (the rotation of a sphere, filled 

with water, in a rotating electric field) . 

Einstein was occupied for many years with the idea of explaining quanta 

within the normal framework of differential equations supplemented 

in such a way as to contain a redundancy in determination. We frequently 

talked about it. Although nothing ever came of it, he believed so strongly 

in the value of the idea that he clung to it even after the discovery of 

quantum mechanics. His rejection of the latter was probably connected 

with this. 

What makes this letter of special value to me is the light it throws upon 

Einstein's life and personality. 

A postcard from Berlin follows. 



15 



[Undated] 



Dear Bom 

By the same post I am sending you my last copy of the paper 
you asked for. It got smudged in Teubner's printing works. I 
am very pleased about your little book on relativity. Forgive 
me for not having written in spite of all your kind messages. 
That rogue of a postman is to blame. What is happening about 
Gottingen ? Debye's paper is very good. 
Best wishes 
Yours 

Einstein 

Best wishes to your wife. I will not be able to return to 
Frankfurt for some time. I hope we can meet here before 
that. 



My book on relativity arose out of the lectures I mentioned before which 
I had delivered in Frankfurt. Einstein himself read the proofs and was 
satisfied with my method of presentation. Three editions were published, 
one after another. Now in 1962, after 44 years, it has been re-issued in a 
modernised English language paperback edition, and a similar German 
one appeared in 1964. 

s8 



BORN-EINSTEIN LETTERS 



The following postcard from Kristiania is addressed to my wife, and 
contains condolences on the death of her mother. She died at our house 
in Frankfurt from the so-called 'Asian flu' which was raging all over 
Europe at the time. Underneath Einstein's message there are a few lines 
from his step-daughter Use. 



16 



Kristiania 
18 April, igso 



Dear Mrs Bom 

The news of the bitter experience you had to go through has 
touched me deeply. I know what it means to see one's mother 
suffer the agony of death and be unable to help. There is no 
consolation. All of us have this heavy burden to bear, for it is 
inseparably bound up with life. However, there is one thing: 
to unite in friendship, and to help one another to carry the 
burden. We do, after all, share so many happy experiences that 
we have no need to give way to pointless brooding. The old, 
who have died, live on in the young ones. Don't you feel this 
now in your bereavement when you look at your children? I 
am here with Use, giving a few lectures to the students - a lively, 
congenial crowd. Also the wonderful scenery and a truly 
formidable heatwave, which one would not have suspected up 
here. 

Kindest regards to you and Max 
Yours 

Einstein 

Dear Mrs Born, I want to tell you that I also feel with you in 
your grief, and think of you with warmest sympathy. 
Yours 

Ilse Einstein 



The first of my letters to have been preserved is addressed not to Einstein 
himself but to his wife; it requires no commentary, nor does the letter 
from me to Einstein himself which follows it. 



29 



BORN-EINSTEIN LETTERS 



17 



Frankfurt a.M. 
21 June, igso 



Dear Mrs Einstein • • cu • 

I have sent your kind letter on to my wife in Leipzig, bhe is 
staying there with her father. The last few weeks have been 
very sad; I cannot describe it all to you in detail. Hedi collapsed 
in the end, as a result of all the excitement, pain and over- 
exertion. In spite of this she went to Leipzig, but had to stay in 
bed and recuperate there. Apparently she is getting better now. 
Just now a card arrived from Albert in Kristiania with the sort 
of kind words only he can find; Miss Use also added a few 

words. 

I want to ask a favour of you. You know that I have written a 
largish popular book about the theory of relativity. This will 
also contain a short description of Albert's life and personality. 
Could you possibly get the proofs from Dr Berliner, and read 
through the biographical summary? It was written with great 
sincerity, but I am not sure if the tone is right. There could also 
be some factual errors. I would be most grateful for your un- 
sparing criticism, and for any suggestions for alterations, I want, 
above all, to avoid any suggestion of burning incense before the 
idol. Albert does not need it anyway. Please let me have your 
opinion as soon as possible. 

Yet another favour. The galley proofs, corrected for the 
second time, will be sent off to Albert within the next few days. 
I am or course very much concerned that he should read or at 
least look through the book before it is printed, and that he 
should make suggestions for alterations. He is probably hard to 
get at right now, and I will have to have the proofs back from 
him very soon, because the printing must not be delayed. 
Please make sure that he receives the proofs by the fastest 
possible means, that he reads them as quickly as possible and 
returns them to me by express post. I am most grateful to you 
for selecting and giving us a picture of Albert for the book. 

My little ones are sweet, darling little things, and surround me 
with sunshine. 

The question 'Gottingen, yes or no?' worries us a great deal. 



30 



BORN-EINSTEIN LETTERS 

We are still undecided. If you know what we should do, please 
let us into the secret. 

With kind regards, also to your daughter 
Yours 

M. Born 



18 



Institute for Theoretical Physics 

University of Frankfurt a.M. 

Robert Mayer Str. 2 

16 July, ig20 

Dear Einstein 

We will in all probability go to Gottingen, that is, if Franck is 
offered the chair and accepts; the faculty has put him forward. 
Now the question of my successor becomes urgent. Schonflies 
wanted to write to you and to ask for your expert opinion. I 
would, of course, like to have Stern. But Wachsmuth does not; 
he said to me, 'I think very highly of Stern, but he has such an 
analytical Jewish intellect,' At least it is open antisemitism. But 
Schonflies and Lorenz want to help me. Wachsmuth has 
proposed Kossel, which is very crafty of him; for nothing can 
be said against him, except perhaps that he knows no mathe- 
matics, but that is hardly a fault. Stern has raised the standard 
of our little Institute and really deserves recognition. I do not 
need to explain his value to you, of course. Then Lenz and 
Reiche are under consideration, and perhaps outsiders as well. 
Embarras de richesse! I have asked Laue to give his opinion; 
perhaps it would be best if you were to talk to him about it, so 
that your verdicts do not clash. 

I am being very lazy at the moment and hardly do any work; 
the only experiments I pursue with any eagerness are those on 
the free path lengths of silver atoms. My assistant is very good at 
her job. We have now constructed the apparatus, but the 
measurements will unfortunately not be started before the holi- 
days. We depart for Sulden in the Southern Tyrol (Italy) on 
August 6th; I am looking forward impatiently to getting away 
from it all completely again, and seeing beautiful things. My 
wife has recovered a little from the hard time after the death of 
her mother. We often take trips out, which does her good. To- 
morrow we are going to the Rhine, where she has never been 



31 



BORN-EINSTEIN LETTERS 

before. The children are well. Unfortunately the decision about 
Gottingen drags on endlessly; we have not yet found a flat there. 
My wife will go there next week and try to find accommodation. 
Are you coming to Southern Germany at all? We would so 
much like to see you and talk to you. 

With best wishes to your dear wife and to the young ladies 
Yours 

Max Born 



The following letter, the first of my wife's to Einstein to be preserved, is 
particularly warm and profound and was perhaps the stimulus for his 
keeping our letters from that time onwards. 



19 



Frankfurt 
31 July, igso 



Dear Mr Einstein 

Max has asked me to thank you very much for your letter; 
your judgment is especially important to him, because 
Wachsmuth is agitating against Stern on antisemitic grounds. 
Epstein, as a Jew and a Pole, will therefore be even more 
strongly rejected. Max is working very hard; his experiment 
(atomic diameter of. . . . ?) is under way at last, and he stays at 
the Institute until eight o'clock at night making measurements. 
We are very happy that you will be coming to Nauheim, and I 
hope that you will stay with us for a few days. I am now - after 
my mother's death - so much in need of those true relationships 
of the spirit which are left to me. The further the hour of her 
death Hes behind us, the stronger is my longing for the departed; 
the darker and more incomprehensible seems the enigma of 
death. The ending of such a strong personality and the sudden 
extinction of life is such a tormenting problem that one wonders 
how one is able to live without being constantly troubled by it. 
But it teaches one to live more consciously, to feel more deeply 
and strongly and to hold on to what one possesses. If one did not 
do this, one could sink without hope into the bitter and pessi- 
mistic attitude of mind of Widman's Maikdfer-Komodie; do you 



32 



BORN-EINSTEIN LETTERS 

know it ? Its images constantly haunted my imagination in the 
first bitterness of my grief. One lives under the illusion that it is 
forever May, and that the whole world is constantly filled with 
young, juicy and delicious greenery, put there just for one's own 
use, and then all of a sudden and incredibly fast it happens, and 
one finds oneself lame and weary of life in the mud of a rain- 
soaked road. So I thought, well, I am now in the mud, but I 
can see that it is still May, after all, and I must not allow myself 
to be pulled down. 

We have now decided for Gottingen, but we have as yet no 
prospect of accommodation there and may possibly remain here 
for the winter as the Ministry is still dawdling. 

Something else: Max wants to stay in Nauheim for two days 
so that he will be able to spend the evenings with his colleagues. 
Would you like to do that as well ? Or would you rather travel 
there from here each day (one hour's journey) ? Shall we book a 
room for you in any case and, if so, for how many days ? But 
you must stay with us before and afterwards, whatever happens. 
If you do not, God help you ! We are going to Sulden, Sulden- 
hotel, Tyrol (Italy), on August 6th, via Munich, Merano and 
Bolzano, complete with passports and lire. Your wife was going 
to write to me when your are due to go to Southern Germany; 
how is she, and how are your daughters ? 
With best wishes to you all 
Yours sincerely 

Max and Hedi Bom 



The next letter from my wife initiated a discussion between her and Einstein 
about 'publicity', his attitude to attack or glorification. The first of these 
letters shows that we, and Hedi particularly, were not in agreement with 
him about his reaction to that kind of irritation. We still believed in the 
'secluded temple of science', as Hedi said. From this beginning a real 
conflict developed, as the following letters show. 



33 



BORN-EINSTEIN LETTERS 



20 



Cronstettenstr. g 
8 September, igso 



Dear Mr Einstein 

When are you coming to Nauheim, and on which days are we 
going to have you to ourselves? We will tell no-one of your 
presence and, if you prefer, you can remain incognito. Paulchen 
Oppenheimer seems to be away still. Please send us a postcard 
about your plans. 

We are extremely sorry to hear about the unpleasant rows 
that are worrying you. You must have suffered very much 
from them, for otherwise you would not have allowed yourself 
to be goaded into that rather unfortunate reply in the news- 
papers. Those who know you are sad and suffer with you, 
because they can see that you have taken this infamous mischief- 
making very much to heart. Those who do not know you get a 
false picture of you. That hurts too. In the meanwhile I hope 
you are like old Diogenes again and smile about the beasts 
thrashing about in your barrel. That people can still 
disappoint and irritate you to the point where it affects your 
peace of mind just does not fit my image of you, which I 
keep on the private altar of my heart. You could not have 
withdrawn from the rough and tumble of ordinary life to the 
'secluded temple of science' (see your talk to Planck) had 
you been able to find the same illusions, the same happiness and 
peace in your fellow-man as in your temple. So if the filthy 
waters of the world are now lapping at the steps of your temple, 
shut the door and laugh. Just say, 'After all, I have not entered 
the temple in vain.' Don't get angry. Go on being the holy 
one in the temple - and stay in Germany! There is filth every- 
where - but not another female preacher as enthusiastic and 
self-opinionated as your affectionate friend 
Hedi Bom 

P.S, Now look here! If you or Elsa, to whom best wishes by the 
way, don't get in touch with us soon, I'll join the anti-relativity 
league, or set up in competition with you. 

You simply must read The Home and the World by Rabindranath 
Tagore - the finest novel I've read for a long time. 



34 



BORN-EINSTEIN LETTERS 



21 



g September, igzo 



Dear Boms 

Don't be too hard on me. Everyone has to sacrifice at the altar 
of stupidity from time to time, to please the Deity and the human 
race. And this I have done thoroughly with my article. This is 
shown by the exceedingly appreciative letters from all my dear 
friends. A witty acquaintance said the other day : 'With Einstein 
all is for the sake of publicity; the Weyland G.m.b.H. is his 
latest and most cunning trick'. This is true, or at least partly so. 
Like the man in the fairytale who turned everything he touched 
into gold - so with me everything turns into a fuss in the news- 
papers : suum cuique. 

In the first moment of attack I probably thought of flight. 
But soon my insight and the phlegm returned. Today I think 
only of buying a sailing boat and a country cottage close to 
water. Somewhere near Berlin. 

I'll arrive at your place around the i8th, if you can put up 
with me. However, if I am expected to live in Nauheim for the 
duration of the scientific meeting, would you please see to it, dear 
Born, that we are staying close together. I shall not book any- 
thing from here, as you can judge better what is the best thing 
to do. But I would also like to stay with you for a little while, if 
possible, so that I can have a chat with my charming correspon- 
dent. Writing does not seem to be as effective, because of the 
annoying blotchiness of my ink. Else is also coming, but will 
stay with the Oppenheims. 

We will have to be in Stuttgart on the 28th, where I am going 
to lecture in aid of a public observatory. Afterwards, we are going 
to Swabia, where my boys have been asked to meet me. 
With kindest regards 
Yours 

Einstein 



The important meeting of the Association of German doctors and natural 
scientists took place in Nauheim in September 1920. Einstein lived with 
us in our house on Cronstetterstrassc; we travelled to Nauheim each 



35 



BORN-EINSTEIN LETTERS 



morning and returned in the evening. Nauheim was the scene of an angry 
encounter between Einstein and his opponents, whose motives were by 
no means purely scientific but strongly mixed with antisemitism." In the 
physics section, Philipp Lenard directed some sharp, malicious attacks 
against Einstein, which were undisguisedly antisemitic. Einstein was 
provoked into making a caustic reply and I seem to remember that I sup- 
ported him. Einstein returns to this incident in a later letter (26), where 
he regrets that he allowed himself to lose his temper and reply in anger. 
From then on Lenard carried out a systematic persecution of Einstein. 
He invented the difference between 'German' and 'Jewish' physics. He 
and another important physicist, Johannes Stark, who both later received 
the Nobel Prize, became leading scientific administrators under the Nazis 
and were responsible for the removal of all Jewish scholars. It was in 
Nauheim on this occasion that the outlines of the great danger of anti- 
semitism to German science first appeared. 



22 



Frankfurt a.M. 
2 October, igso 



Dear Einstein 

To judge by your card, Hechingen must be a charming, sleepy 
little place; just right to calm down the agitation which, to our 
regret, you were forced to endure here and in Nauheim. We 
do not want to disturb your slumbering consciousness with 
effusive letters; sometimes it is a good thing if one's friends are 
removed from one's consciousness, and I have the feeling that 
now is the time for us to disappear. After all, there is really 
nothing more obtrusive than 'suffering with someone' ; it is an 
encroachment on a friend's life, a baring of the soul, of which one 
is ashamed afterwards. 

But before we disappear from sight, like Punch, we have two 
other requests, and I would like to charge you, dear Mrs Elsa, 
to remind your husband of them from time to time. i. That your 
husband should write to Mrs HofF, Giintersburg AUee 57. This 
would not really be a waste of time, as there are few people like 
her. 2. My husband feels an inclination to slay the golden calf 
in America and to earn enough through lecturing to build a 
small house in Gottingen to his own requirements. Should you, 
by any chance, have the opportunity to recommend someone to 



36 



BORN-EINSTEIN LETTERS 

lecture over there, please suggest Max. He would be able to go 
there in February, March and April, and appease his longing 
for Broadway at the same time (I can't understand this love of 
his, but forgive him for it.) 

And now without further ado your Punch and Judy bow 
out, 

Max and Hedi Bom, 

until you happen to remember them in their toy chest once again. 



Why I am supposed to have 'longed for Broadway' is incomprehensible 
to me. Anyway, the journey to America did not materialise then. 

The following letter concerns the problem of publicity that I have already 
referred to. In Nauheim, Einstein's enemies had reproached him with 
self-advertising, and with allowing his fame to be broadcast. We had 
already discussed this with Einstein during our talks every evening, after 
returning from Nauheim. We found that he was far too accommodating 
towards journalists, possibly because his wife was understandably pleased 
about his popularity. 

Soon a new incident required urgent attention. An author and journalist, 
who had called on Einstein and had won his and especially Elsa's sympathy 
as a poor Jew, wanted to write and publish a book called Conversations with 
Einstein. We advised Einstein not to allow it, but without success. Following 
is my wife's spirited reaction to this piece of news ; the letter was written 
in Leipzig, where she was visiting her parents, and thus without my 
knowledge. The letter is very long and detailed; I have abbreviated it 
considerably. 



23 Leipzig 

7 October, IQ20 

Dear Mr Einstein 

Today, a friendly but serious word with you. I would much 
prefer not to have to disturb you during your week's holiday, 
but it is a matter of great consequence which has troubled your 
friends ever since Nauheim : 

You must withdraw your permission to X for the publication of 
the book Conversations with Einstein, and what's more at once, 
and by registered letter. And, whatever happens, it must under 



37 



BORN-EINSTEIN LETTERS 

no circumstances be published abroad. I wish I had the eloquence 
of an angel, so that I could make the consequences clear to you. 
Quite by chance ... [a book by X] fell into my hands here; 
the level of this book disgusts me so much that I wrote the enclo- 
sed somewhat malicious comments, which I swear I am going 
to publish unless you withdraw your permission immediately. 
And I have a lot more to spill out, if it is a question of saving 
the honour and respect of a friend. I am not painting too black 
a picture. 
[There follows a list of titles of the books by Mr X.] 

That is good enough in itself. . . . 

Now the contents. The man has no idea of the seriousness of 
your personality, of what is important and valuable to you and to 
us; otherwise he would neither have written the book nor 
exploited your kindheartedness to wrest your permission from 
you. Your 'conversations' will therefore be conducted at a very 
low level. The gutter press will get hold of it and paint a very 
unpleasant picture of you. And afterwards you will be quoted 
all over the place, and your own jokes will be smilingly thrown 
back at you, to show that people have read the book. Verses will 
be composed in your honour; a completely new and far worse 
wave of persecution will be unleashed, not only in Germany but 
everywhere, until the whole thing will make you sick with disgust. 

And how could we, your good friends, then defend you ? 'But 
look here -Mr Einstein, your "modest friend", surely gave 
permission himself.' Then it would be useless for us to protest 
that you gave permission out of weakness and good nature 
Nobody would believe it. (This is confirmed by my father, who 
studied with X and has told me a great deal about him.) The 
fact is simply that a man in his early forties, a comparatively early age, 
gave permission to an author to record his conversations. If I did not 
know joM well, I certainly would not concede innocent motives 
to any other human being given these circumstances. I would 
put it down to vanity. This book will constitute your moral 
death sentence for all but four or five of your friends. It could 
subsequently be the best confirmation of the accusation of self- 
advertisement. 

We, your friends, are deeply shocked at this prospect. This 
book, if published anywhere at all, would be the end of your 
peace, everywhere and for all time. . . . 



38 



BORN-EINSTEIN LETTERS 

Please reassure us soon about this worry which pursues us 
day and night. Max has just written to me today: 'I have just 
had an express letter from Freundlich with X's answer, which 
is, of course, in the negative. I do not know what to do. I would 
so much like to discuss it with you; every day I have worries of 
this kind.' 

Please, dear friend, quickly relieve our worries, and do not 
refuse our advice and request. I shall never talk to anyone about 
this business, for I have heard enough how much you dislike 
it when women meddle in your affairs. 'Women are there to 
cook and nothing else'; but it sometimes happens that they 
boil over [a play on words in German, where 'cooking' is 
'Kochen', and 'boiling over', 'Ueber-kochen'] . 
Yours 

Hedi Born 



24 



Frankfurt a.M. 
I J October, igso 



Dear Einstein 

The enclosed pages from the bookseller's financial paper have 
come to me from various people. Comment is superfluous. 
It seems that you are less excited about it than your friends. My 
wife has already written to you saying what I think about this 
affair. (She is already regretting that she, too, has tried to turn 
your name into gold by sending me to America; women, poor 
creatures, carry the whole burden of existence, and grasp at 
any relief.) You will have to shake off X, otherwise Weyland 
will win all along the line, and Lenard and Gehrcke will 
triumph. 

According to the advice of experts, the following is best: write 
strongly to X, saying that you can not, after all, agree to the 
publication of the conversations, because you have been accused 
of publicity seeking, and in view of the fact that the advertise- 
ment in the bookseller's financial paper has offered a useful new 
lever to your enemies. If X refuses, as is to be expected, you 
will obtain a provisional order from the Public Prosecutor's 
Office against the appearance of the book, and make sure that 



39 



BORN-EINSTEIN LETTERS 

this is reported in the newspapers (or we could do this). I 
shall send you the details of where to apply soon. The experts 
have established that, just as one can no more print another 
person's photograph without his permission, thoughts expressed 
during conversation may not be published. This is a better 
method than having the proofs sent to you and reading them, 
for you would then have no responsibility for the book whatever. 
If, on the other hand, there were a statement in the introduction 
that you had read the proofs and approved of them, all the 
muck thrown up by the book would fall on you. I implore you, 
do as I say. If not: Farewell to Einstein! Your Jewish 'friends' 
will have achieved what that pack of antisemites have failed to 
do. 

Forgive the officiousness of my letter, but it concerns every- 
thing dear to me (and Planck and Laue, etc.) You do not 
understand this, in these matters you are a little child. We all 
love you, and you must obey judicious people (not your wife) . 

Should you prefer to have nothing further to do with the 
whole business, give me written authority. If necessary, I will 
go to Berlin, or even to the North Pole. 
Yours 

Born 



25 



// October, igso 



Dear Bom 

Your wife has sent me an urgent letter about Mr X's book. She 
is objectively right, though not in her harsh verdict of X. / 
have informed him by registered letter that his splendid work must not 
appear in print. 

With kindest regards to you both 
Yours 

Einstein 

1 would like to thank your wife most sincerely. 



40 



BORN-EINSTEIN LETTERS 



Apparently my wife had succeeded after all in making clear to Einstein 
the danger threatening him if the book were to be published. A postcard 
which followed from Holland on 26 October confirms this. 



26 



[undated] 



Dear Bom 

Have categorically forbidden publication of X's book. Ehrenfest 
and Lorentz advise against legal proceedings, as they would 
only serve to increase the scandal. The whole affair is a matter 
of indifference to me, as is all the commotion, and the opinion 
of each and every human being. Therefore nothing can happen 
to me. In any case, I have used the strongest means at my 
disposal, apart from legal ones, particularly the threat that 
I would break off our relationship. However, I still prefer X 
to Lenard and Wien. The latter two squabble because of a 
passion for squabbling, while the former does it only to earn 
money (which is, after all, better and more reasonable). I will 
live through all that is in store for me like an unconcerned 
spectator and will not allow myself to get excited again, as in 
Nauheim. It is quite inconceivable to me how I could have lost 
my sense of humour to such an extent through being in bad 
company. Lorentz yesterday mentioned your lattice equili- 
brium in his lecture; I was also mentioned! He is a man one can 
admire 1 

Kindest regards to you and your wife. 

I am having a very pleasant time here in Leiden. Weiss and 
Langevin are also here. 



H. A. Lorentz was Professor of Theoretical Physics in Leiden, and in those 
days was held to be the foremost man in his field. He had given the classical 
theory of electrons the form considered final at that time. Ehrenfest, who 
was born in Vienna and educated there in the school of theoretical physics 
(with Boltzmann and Hasenohrl, inter alia) went to Russia and married 
an extremely gifted Russian woman physicist. He became widely known 
for his outstanding works of criticism, particularly in the field of statis- 
tical mechanics (partly in collaboration with his wife, Tatyana), his 

41 



' 



BORN-EINSTEIN LETTERS 

unusual talent for teaching and his sparkling wit. When Lorentz retired 
from his chair, he pushed through Ehrenfest's appointment as his successor. 
The two people mentioned at the end of the letter, Weiss and Langevin, 
were French physicists, the first one from Strasbourg, the second from 
Paris. Both carried out fundamental research into magnetism; Langevin 
had important achievements in other fields as well. 

Einstein's clearly expressed indifference to the opinion of everyone else is 
as characteristic of him as the judgment that he thought more of the 
motives of the journalist than of those of two outstanding physicists. 
With this card, the X affair is substantially at an end, though it is still 
mentioned from time to time in the letters which follow. It may well be 
asked whether there is any justification for giving so much space to it in 
this correspondence. In fact my wife's inflammatory letter (No. 23) was 
originally considerably longer. I have left out the second half, which 
contains some legsil advice from my wife's father, as well as grotesque 
descriptions of the possible consequences of Einstein's compliance. What 
remains is sufficient to show why we, with all respect for Einstein's superior 
intellect, could presume to criticise his behaviour in every-day life. 
The contemporary reader may well think 'much ado about nothing'. 
Nowadays the kind of pubhcity we fought against is commonplace, and 
spares no-one. Every one of us is interviewed and paraded before the 
general public in the papers, on radio and television, or written about in 
pamphlets and books. Nobody thinks anything of it. 
In those days it was different. Only when great discoveries were made did 
brief, factual reports appear in the newspapers. I can remember the way in 
which Roentgen's discovery in 1896 was reported by the press; he himself 
was hardly mentioned. As far as I am concerned, I myself committed a 
minor offence against the rules in my book Einstein's Theory of Relativity. 
The first edition of 1920 contains a photo facing the title page, and at the 
end a short biography of Einstein in which I described not only his 
scientific achievements but also his personality. Immediately after publi- 
cation I received a letter from Max v. Laue, in which he wrote that he 
and many other of my colleagues objected to the photo and biography. 
Such things did not belong in a scientific book, even when addressed to a 
wider audience. Impressed by this, I left out both these personal details 
from the new editions published soon afterwards. I was possibly particularly 
sensitive about Mr X's plan to compile a book from interviews with Einstein 
about all kinds of topics, not only scientific ones, because my own much 
more harmless attempt to describe the person of the author in my book 
on relativity had been rejected by my colleagues. 

But what chiefly caused me and my wife to object to this business was 
its connection with antisemitism. Einstein's theories had been stamped as 
'Jewish physics' by colleagues who did not understand them. And now a 



42 



BORN-EINSTEIN LETTERS 

Jewish author, who had already published several books with frivolous 
titles, came along and wanted to write a similar book about Einstein. It is 
understandable that this upset us greatly. Einstein probably did not 
consider any of this to begin with. He wanted to show his gratitude 
towards X, who had helped him while he was ill in Berlin during the period 
of wartime deprivation. But he saw our point of view and did everything to 
prevent publication of the book. He did not succeed. A copy of it Ues in 
front of me. I have browsed through it a little, and find it not quite as bad 
as I had expected. The scientific part is primitive and contains frequent 
misunderstandings. Otherwise, however, it contains many rather amusing 
stories and anecdotes which are characteristic of Einstein. It is quoted in 
more recent books about Einstein. 

Our agitated correspondence about this affair was thus pointless in the end. 
Large-scale movements such as antisemitism and the prevalence of 
pubUcity, etc., necessarily run down in accordance with the law of 
determinism so often quoted by Einstein in this connection. 



27 



Frankfurt a.M. 
28 October, igzo 



Dear Einstein 

I am very glad that you have taken energetic steps against the 
book by X. Only the future will show whether they are enough 
to prevent any trouble. The main thing is that you are deter- 
mined not to have your peace disturbed in future. Hov^rever, 
when all is said and done, you are not the only person involved, 
as we, who venture to call ourselves your friends, would also be 
affected by the stench and, I fear, would be unable just to hold 
our noses as you have done before. You can simply flee to 
Holland, but we are settled in the territory of Weyland, Wien 
and company. 

I am writing to you quickly in Holland, as I want Mr Fokker's 
address. He has sent me a fine paper in which he expiates one 
of the sins of my youth. The address was actually on the envelope 
but, as I was ill in bed with asthma and unable to be on my 
guard, my children destroyed the envelope. I would very much 
like to thank Fokker ; Ehrenfest will know where he lives. 

Get Ehrenfest to show you a copy of Boguslavski's letter 
which I sent to him, and think how the poor fellow can be 

43 



BORN-EINSTEIN LETTERS 

saved. Planck said that he was willing to help, but thought that 
nothing could be done officially in Berlin. Now I am negotiating 
with Hilbert for him to invite Boguslavski through the Wolf- 
skehl Foundation. 

I am glad that things are going so well for you in Holland. 
But you must not be angry with me if as a result of recent events 
I doubt you as a judge of human nature to the extent that I do 
not share your admiration for Lorentz. In Lenard and Wien 
you see devils, in Lorentz an angel. Neither is quite right. The 
first two are suffering from a political illness, very common in 
our starving country, which is not altogether based on inborn 
wickedness. When I was in Gottingen just recently I saw 
Runge, reduced to a skeleton and correspondingly changed 
and embittered. It became clear to me then what is going on 
around here. On the other hand, Lorentz: he even refused to 
write anything for Planck's sixtieth birthday. I take that very 
much amiss. You can tell him so quietly. One can disagree with 
Planck, but one could only doubt the honesty and nobility of 
his character if one had none oneself. Lorentz is apparently 
more afraid of losing his well-fed friends amongst the Allies than 
he cares about justice. I am not taken in by his using my lattice 
calculations in his lectures. This is not the only thing I hold 
against him, but then I am not writing just to slander someone. 
However, I must confess that I find your association with 
Lorentz, Ehrenfest, Weiss and Langevin far happier than the 
intercourse with the author of '. 

You will also have met Chulanovski from Russia there; 
please ask him for information about G. Krutkov, who has sent 
me a paper of his about adiabatic invariants, which I thought 
excellent. He must be an outstanding theoretician; I had never 
heard of him before. 

My wife sends her best regards. She is driving herself very 
hard, as our cook had to be dismissed a few weeks ago for 
thieving and deceit (countless times). Also, miserable creature 
that I am, I was confined to bed with asthma until yesterday, 
and had to be nursed. The children are well. 
With kindest regards 
Yours 

Max Bom 



44 



BORN-EINSTEIN LETTERS 



Boguslavski was a Russian pupil of mine, extremely talented and an 
attractive and worthwhile person. He suffered from tuberculosis of the 
lungs, and as he came from a tided feimily he suffered great hardships 
during the revolution. Eventually he turned to me for assistance, and I 
tried to do something for him with the help of Planck, Einstein and others. 



28 



Institute for Theoretical Physics 

of the University of Frankfurt a.M. 

Robert Mayer St. s 

8 December, igso 



Dear Einstein 

Enclosed is the circular of the Mathematische Annalen. As I have 
never received any paper intended for this publication, and 
know nothing about it, I have not added any remarks. 

I also enclose a copy of a letter from Russia, from my pupil 
and friend Boguslavski. The letter arrived some time ago. The 
contents may interest you. It can be seen that an attempt should 
be made to invite the poor man (who has TB as well) to Germany, 
to prevent him from starving to death. I have already tried 
everything possible, first Planck, then Klein and Hilbert in 
Gottingen, whom I asked to get the Academy to send an 
invitation of some sort to B. But they all refused; to use Hilbert's 
expression, they want nothing to do with 'foreign polities'. 
Perhaps you can think of a way. Some of what Boguslavski 
writes about his work is clearly nonsense, but this is probably 
due to his piteous condition; he is a fine intelligent man. By the 
way, a mutual friend, Dr Bolza from Wurzburg, has tried to 
send a few things to Boguslavski through the Red Cross; with 
what success I do not know. 

While on this subject: some time ago I sent you a letter from 
Epstein, who was asking for help. In the meantime I have 
received an answer from G. N. Lewis in America, to whom I 
had written about this matter. He has created a position for 
Epstein at the University of California, Berkeley, and offered it 
to him. But I have not heard from Epstein whether he intends to 
accept or not; perhaps the Swiss are keeping him. An attempt 
to bring him here as my successor has been wrecked by the 
opposition of the faculty. I did not succeed in having Stern 



45 



BORN-EINSTEIN LETTERS 

made first choice either, because Wachsmuth wanted Madelung. 
Stern is now second choice, Kossel third. 

As regards science, I have tried a number of things without 
getting enthusiastic about anything. What attracts me most is a 
proper theory for the irreversible processes in crystals, once 
suggested by Debye. But I cannot find reasonable general 
formulations. The measurements in the Institute on free path 
lengths are going quite well ; the main thing was to keep the gas 
pressure constant for the thirty-minute vaporisation of the 
silver; we are now doing it to 5 per cent. However, we have not 
yet completed an exact measurement of the thickness of the 
silver deposit, as we had to get together the optical equipment 
bit by bit. Lande, who was recently at the conference in 
Heidelberg, told me yesterday that Ramsauer {alias Lenard) 
had severely criticised my book on relativity because I had 
given the impression that Maxwell's proposal (for determining 
the absolute movement of the solar system from the eclipse of 
Jupiter's satellites) had in fact been carried out with a negative 
result. I can see that the criticism is not unjustified, and there- 
fore expect vociferous attack by Lenard or one of his associates. 

Healthwise I have been bad for several weeks, as may have 
been apparent from the bilious tone of my last letter to Holland. 
But I am now fairly well again, although the political situation 
depresses me more than I like to admit to myself. 
With kindest regards 
Yours 

Bom 



Saratov 
18 August, igso 

Dear Bom 

At last I have the opportunity to send letters out of the country, 
and I am using it to write to you. For almost two years now I 
have been professor in Saratov at the local University. Although 
I accepted a chair in Moscow as much as a year and a half ago, 
I dare not return there for fear of starving to death. But this 
year even we, here in the South-East, are going to have a bad 



46 



BORN-EINSTEIN LETTERS 

time, as the harvest has been extremely poor. Now I dream of 
being able to go abroad once again; my scientific interests, as 
well as my state of health, demand it. Life in the socialist Eden 
does not seem to be meant for me. I have been feeling ill for 
almost six months now, and am staying in a kind of sanatorium. 

Scientific life has almost ceased to exist here. No journals are 
being published, neither are there opportunities to have 
anything printed. A mimimum of scientific work is being done; 
anyone wanting to do it would soon starve. Furthermore, for 
the last three years we have not received any foreign journals. 
Therefore I now have very little idea of what is currently being 
thought about in scientific circles. I myself have, of course, done 
much during these last few years, and would like to be able to 
talk about it. As recently as last spring I was still working, 
and had just started to write a small book. However, now I feel 
so ill that for the time being I am obliged to give it all up. In my 
book I intended to give a fairly comprehensive description of 
the movement of electrons in different kinds of electromagnetic 
fields. The second part of the book was to contain an outline of 
the theory of atoms. I have investigated several types of move- 
ment presumably for the first time. 

Some time ago I had the following idea which I have not yet 
been able to verify. The nucleus of heavy atoms need not be 
a charged point. By developing the potential of the nucleus as 
powers of ijr and retaining only the term with ijr one can treat 
the nucleus as a positive point charge and a dipole. The problem 
of the movement of the electron in the field of this nucleus can 
be rigorously solved. The projection of the electron path on the 
unit sphere is then the orbit of a spherical pendulum, where 
gravity acts parallel to the dipole axis. The elliptical integral 
representing the action (quantum integral) can be developed 
as a series of powers of the dipole moment, and one can thus 
determine the position of the spectral lines in the presence of this 
dipole. The solution can be most easily written with the help of 
the partial differential equation of Jacobi; the variables can be 
separated for polar coordinates. 

Lately I have been much interested by the following train of 
thought; I still regard it as important, although I have not yet 
obtained positive results. Thermodynamics and electrodynamics 
alone are insufficient for developing a radiation formula. 



47 



BORN-EINSTEIN LETTERS 

because radiation pressure ought to be used only integrally 
(for all frequencies) to obtain the work done. Now we have 
substances which absorb (and reflect) selectively, and one can 
probably use as an ideal limiting conception a piston which 
completely reflects the radiation of a certain spectral range but 
allows all others to pass through. Such a piston would separate 
the radiation of difierent frequencies in the same way as a 
semi-permeable membrane separates molecules of different 
kinds. This concept certainly contains nothing to contradict 
the fundamental laws of electrodynamics and thermodynamics. 
But with the help of such a piston and a Planck coal dust 
particle it is easy to construct a perpetuum mobile of the second 
order. And this can be done for any radiation law. Now a 
radiation law can be regarded as a definition of the temperature 
concept, since the temperature can be derived from it as a 
function of the mechanical quantities 'energy' and 'frequency'. 
How is temperature to be defined so that the contradiction of 
the second law of thermodynjunics can be avoided? The 
answer is: the temperature is a monotonically increasing 
function of frequency only (independent of the energy). For 
instance, T= ay. All this is absurd but very attractive. 

I cannot write much. I only wish I could talk to you in 
person. Do try to get me an official invitation to Berlin to give 
a few lectures there. The invitation will have to look as official 
as possible, so that I can attempt to obtain a passport for leaving 
the country with it. You would be rendering me a great service, 
as I am in urgent need of a few months recuperation. Einstein 
can help you forward the invitation to Russia. It should be sent 
either to my Moscow address, Pokrova, Litde Uspanki 8, or here 
(University of Saratov) . 

It is difficult to describe our living conditions. As a Professor I 
earn approximately 1.5 x lo* roubles per month. With this one 
can buy approximately one pound of bread per day. Everyone 
is allowed to buy only 1 50 g of bread at the controlled price. 
This is, moreover, practically the only thing one does get. 
Everything else has to be bought at 'speculative' prices. Trading 
in the normal sense, as is well known, does not exist here. There 
are only secret 'deafings' whereby one must procure all the 
necessities. One pound of butter costs approximately 2 x 10' 
roubles, sugar somewhat more. A pair of boots costs 3-6 x 10* 

48 



BORN-EINSTEIN LETTERS 

roubles, etc. One frequently meets people who spend their entire 
month's salary in a single day. How this squares with the 
continuity equation of money is extremely puzzling. One must 
assume, however, that the money in circulation is confined to the 
official issue, as the forging of paper currency would hardly 
be a paying proposition. Firewood costs about 100 roubles per 
kilogram! But very few people are able to pay that much. 
Therefore everybody has to cut their own wood. Generally 
speaking, life for the majority of people is quite unbearable. 
Winter will soon be here again, and we can look forward to 
enjoying room temperatures of 4-5°. 

A congress of physicists is due to begin in Moscow in ten 
days' time. Unfortunately I will be unable to make the journey 
because of the state of my health. 

If you see any of my Gottingen friends, please give them my 
regards. I would particularly like to see Bolza and Karman 
again. Please write to Debye and tell him that I am still alive, 
and ask him please to continue to look after my cases of books 
at the Physics Institute. I am not writing to him myself, as I 
cannot at present send more than two letters out of the country. 

Give my regards to your wife. You are all fortunate people. 
You cannot imagine the amount of misery which surrounds one 
here. Look after yourself. 
Yours 

S. Boguslavski 

(Reply through Prof. Dr M. Vasmer, Dorpat, Estland, Teichstr. 
19) 



Gilbert N. Lewis was a distinguished physical chemist in Los Angeles, 
whom I got to know through Fritz Haber. When I later visited California 
(1926), both Lewis and Epstein gave me a very friendly reception. 

The following letter from Einstein begins with a return to the formal 
('Sie') mode of address. This may be connected with the morally presump- 
tuous tone of my previous letter (which I later attributed to my illness). 
Einstein's reference to 'burying the hatchet' had nothing to do with this, 
but with an exchange of letters between my wife and his, of which I 
knew virtually nothing. Einstein chivalrously defended his wife. More of 
this in my next letter. 



49 



BORN-EINSTEIN LETTERS 



29 



30 January, igsi 



Dear Born 

Today I write principally because I want solemnly to bury 
the hatchet. I have had a tiff with your wife for the sake of 
mine, mainly because of a rather exaggerated letter which she 
wrote to her. But a lot has happened since and it is wrong for 
men like us to lose contact over such a trifle. X's unfortunate 
opus has appeared without any earth tremors (so far) and 
without my having read any of it. 

I do not know of anything I could do for Boguslavski, much 
as I pity him; what he says about the theory of radiation is 
curious. It seems to be based on a misunderstanding of what 
can be done with partially reflecting screens. 

I have only thought up some trivialities lately. The best of 
these is an experimental query regarding the radiation field. 
The statistical laws of radiation make one doubt whether 
Maxwell's field really exists in radiation. The mean field strength 
in high temperature radiation is of the order of 100 volts/cm; 
where such a field exists, it must produce a perceptible Stark 
effect on emitting and absorbing atoms. But if the other distri- 
bution of the field's effect according to the statistical laws of 
radiation holds, then the effect should occur only on a few 
molecules, but very strongly so that one would observe a quite 
weak difiuse effect next to a sharp line. I shall investigate this 
with Pringsheim; it is not easy. Have a look at the short paper 
by Byk on the law of corresponding states and quanta in the 
Phys. Z^itschrift - it is a nice piece of work. Your little book on 
relativity has enabled many people to understand the subject. 
E.g. half the Foreign Office are said to have pored over it (now 
nothing can go wrong with it). 

You need not be so depressed by the political situation. The 
huge reparation payments and the threats are only a kind of moral 
nutrition for the dear public in France, to make the situation 
appear rosier to them. The more impossible the conditions, the 
more certain it is that they are not going to be put into practice. I 
hope you are in good health. With kindregardstoyouandyourwife 
Yours Einstein 



50 



BORN-EINSTEIN LETTERS 

This letter contains several scientific observations. Above all, there are 
doubts about Maxwell's radiation field, which cannot be reconciled with 
the statistical laws of radiation. In one of his earliest papers, Einstein had 
shown that, according to one of Lorentz's calculations, the wave theory 
of radiation implies that the mean square fluctuation of radiation energy 
is proportional to the square of the mean energy density. Einstein's 
quantum theory of light, which represents radiation as a kind of gas 
consisting of photons, shows that in an ideal gas the mean square fluc- 
tuation is proportional to the mean energy density itself. According to 
Planck's empirically obtained radiation law, however, the mean square 
fluctuation is exactly the sum of these two terms. This means that radiation 
consists of neither waves alone nor pardcles alone but of both at the same 
time. This was the famous and notorious 'duality' which always worried 
Einstein from then on, and of which much will be said in these letters. 
He was never willing to allow that this, his own result, was final. Here he 
wants to remove Maxwell's field with the consideration that the Stark 
effect of the temperature radiation field is large enough to enable one to 
decide between the particle theory and the wave theory. Whether he ever 
really carried out the experiments planned with Pringsheim, I do not know. 
The remark suggesting that half the Foreign Office had pored over my 
relativity book must have caused me a great deal of amusement at the 
time. 



30 



Frankfurt a.M. 
12 February, igzi 



Dear Einstein 

I should have liked to reply to your kind letter at once, but I had 
to go to Gottingen suddenly, as there was some hope of accommo- 
dation there (a hope which may, by the way, be fulfilled). I know 
about only part of the unpleasant correspondence between our 
wives, as my wife decided one day not to take me into her 
confidence any longer. All the same, I feel guilty, as I did not 
prevent her from writing sharp and hard words. I have taken 
the matter very much to heart, more so than anything else I 
can remember. For everything connected with you affects me 
deeply. Believe me, if it were not so, I would not have been so 
agitated about the X affair. The earth, as it happened, was not 
exactly shaken ; but it is not very pleasant to see the advertise- 
ments on every hoarding. Well, no more of this. I will probably 



51 



BORN-EINSTEIN LETTERS 

get upset again over these relationships with the world, as my 
own time scales do not seem to apply (they are too short) ; but 
you will notice in[future. 

If even you, in BerUn, are unable to do anything for Bogus- 
lavski, I know of no way of helping him. One could at most send 
him an invitation privately, containing our signatures; he 
might get a passport on the strength of it. If he once got here, 
I could soon provide the means to enable him to exist for a few 
months. His theoretical speculations are not worth much; in 
his observations about radiation he clearly forgets that com- 
pression by reflecting pistons alters the frequency. I have given 
quite a lot of thought to this in the past, and know that semi- 
permeable screens do not offer a solution. Your bold idea of 
using the Stark effect of the fields in thermal radiation in order 
to determine their statistical character is very good; I hope 
you will have some success with it. I have read Byk's paper, and 
discussed it with Stern. We were not, however, particularly 
enthusiastic about it; after all, it is only the beginning of the 
beginning of a theory. 

We are all very busy, for we have to complete all research in 
the Institute before the end of the present term. Then comes the 
new master, Madelung. Unfortunately I did not succeed in 
arranging Stern's chair. He is very unhappy about it, for his 
prospects are poor under the current antisemitic conditions. 
He is thinking of going into industry, which I consider a crazy 
idea. He intends to take a few weeks' leave this summer, and to 
come to Gottingen - Bohr will be there from the beginning of 
June. Can you come as well ? 

My path-length measurements are still unsatisfactory. 
Although I now have the knack of keeping the pressure constant 
to within a few per cent with the silver radiation, and can also 
measure the layer thickness of the deposits to within a few 
per cent, the technique is not yet perfect. I make the thickness 
measurement using an interference method developed by 
Wiener for the optics of telescopes; but I do it in the micro- 
scope, and that works much better. The thickness of a layer (of 
about ifi) can be measured almost point by point (in visual 
fields of 0.0 1 mm^). I want to use this method to measure the 
bending constants of very small pieces of crystals - perhaps I 
shall succeed in doing this with diamond, Paul Oppenheim has 




(Photograph by Karsch) 



Plate J. Albert Einstein, late 1940's 



52 



BORN-EINSTEIN LETTERS 

managed to get me a piece f cm long. As Voigt's successor I am 
bound to try something like this. 

I have done little theoretical work. I have recently written an 
account of Caratheodory's thermodynamics, which will appear 
shortly in the Physikalische Zeitung. I am very curious to know 
what you will say about it. Caratheodory himself, to whom I 
sent the proofs in Smyrna, thought that I had interpreted him 
correctly. I have also proved the following proposition, which 
had me considerably puzzled: if the positive and negative ions 
in an NaCl type lattice are somehow interchanged, the electro- 
static lattice energy always increases. The NaCl lattice therefore 
has a minimum energy with respect to such exchanges and this 
may also (partly) explain its frequent occurrence. I need this 
proposition for a theory for the melting of salts I have in mind, 
in which I visualise the ions as tumbUng about through one 
another during melting. But that is difficult! As you can see, it is 
not a very profound piece of research. 

I am also working on my article for the Encyclopaedia, with 
Dr Brody as my private assistant. He is a very clever man. 
(Unfortunately he knows very Uttle German, and is rather hard 
of hearing.) He found a new general quantisation method using 
Poincare's integral invariants; he says that he has told you 
about it. Maybe there is some truth in it. We now have Gerlach 
with us, who really is splendid: energetic, well-informed, 
ingenious and helpful. He has just received an offer from the 
Chilean Government to take over physics and electrotechnology 
there (in Santiago); I wonder if it is the sensible thing to do? 
I think that he has good prospects here, too, but he is an 
enterprising fellow and well suited to an overseas appointment 
of this kind. Franck has now setded in Gottingen (although 
for the time being he is with Bohr in Copenhagen) ; he must 
have enough freedom there, and so I am busily collecting money 
for him. So far I've got 68,000 M. It is not at all easy to inspire 
laymen with some interest in our work. I must have more money. 
Wien got a whole million for re-equipping his Institute in 
Munich. I believe that what Wien has, Franck should also get. 

I must revise my book on relativity, as Springer intends to 
issue a second edition; but I will not get round to it this term. 
If you have spotted any mistakes or omissions, I should be 
grateful for the information. PauU's article for the Encyclo- 



53 



BORN-EINSTEIN LETTERS 

paedia is apparently finished, and the weight of the paper is 
said to be 2| kilos. This should give some indication of its 
intellectual weight. The little chap is not only clever but in- 
dustrious as well. 

I have had some fun here recently, in the form of a substantial 
burglary. The rogues broke in at night through a cellar window 
after breaking the bars, and got away with a lot of silver, linen, 
both bicycles, and even my suit and shoes from the first floor. 
Since then I have slept badly and feel insecure in my own house. 
The police have failed completely. 

I cannot share your optimism in political matters, although 
I do not believe that things are quite as black as they are painted. 
We are not going to pay as much as is asked for. But I can see 
the effect of this power politics on the minds of the people ; it is 
a wholly irreversible accumulation of ugly feelings of anger, 
revenge, and hatred. In small towns such as Gottingen, this is 
very noticeable. I can, of course, understand it. My reason tells 
me that it is stupid to react in this way; but my emotional 
reaction is still the same. It seems to me that new catastrophes 
will inevitably result from all this. The world is not ruled by 
reason ; even less by love. But I hope that the harmony between 
us will not be disrupted again. 

With sincere regards, also from my wife 
Yours 

Max Bom 



Madelung was an old friend of mine, and a physicist of outstanding merit. 
Quite recently, during a congress in Copenhagen in 1963, 1 suggested that 
one of his papers should be acknowledged as the origin of the dynamic 
theory of crystal lattices.* Stern has become a great physicist, as I had pre- 
dicted. The method of molecular radiation which he introduced into atomic 
physics has become one of the main instruments of present-day research ; 
his teaching has spread all over the world, and has produced numerous 
discoveries of the first rank as well as a significant number of Nobel 
prizewinners. 

The micro-interferometer, which Mrs Bormann and I used to measure 
thin layers of silver deposit, was built by Carl Zeiss of Jena and was 
listed in their catalogue for a number of years. I did not manage to measure 
the elasticity constants of the diamond. About thirty years later the Indian 
physicist Bhagavantam was the first to succeed in doing this, using a 



54 



BORN-EINSTEIN LETTERS 

completely different method (ultrasonics). Thus, a generation later, one of 
my old formulae was finally proved correct. 

My interpretation of Carath6odory's thermodynamics did not have the 
effect I had hoped for of displacing the classical method which, in my 
opinion, is both clumsy and mathematically opaque. Only in recent years 
have textbooks appeared which make use of it. 

As for the financial assistance for Franck, the greater part of the sum of 
68,000 M came from the Recklinghausen industrialist Carl Still. Gourant 
had got to know him first and had introduced us to him. Still was the son 
of a Westphalian peasant. He had started off as a lowly mechanic, and 
built up a large firm through his own industry and ideas. The firm built 
coke ovens and installations recovering all kinds of coal by-products. He 
was profoundly interested in science and may even have hoped for help 
from us with his distillation processes. He frequently invited all of us, 
together with the mathematicians Hilbert and Runge and all our wives, 
to hunt hares on his large country estate, Rogatz, on the Elbe, near Magde- 
burg. Although we did no shooting I can still see Hilbert, dressed in rubber 
boots, standing in front of me on the edge of a field. But all the same we 
were all presented with a hare or a fat goose when we left. We introduced 
Max Planck to Still; this was a good thing, for when Planck was bombed 
out of his house in Grunewald (Berlin) during the war, he and his wife 
found refuge in Rogatz. They stayed there until the Russians got close, 
and then the Americans evacuated them to Gottingen. We saw Carl 
Still once more, on our first visit to Germany after the end of the war. 
He was already seriously ill and died shortly afterwards. Our friendship 
with his wife, who is approximately the same age as I, still continues, and 
is now being carried on by our children. Today the firm is fiourishing 
again under his son Karl Friedrich Still. Both father and son have been 
awarded honorary doctorates by the Aachen Technische Hochschule. 
Still's gift was one of the few instances when I received financial assistance 
from a private source. It was, of course, meant for Franck's research and 
not for mine, but I was quite in favour of this. Like Einstein, I have 
always held that a theoretician needs only pen and paper and a few books. 
Though I had initially been offered the post of chief of the whole Gottingen 
Institute, I actually occupied only a very small room there. Later on in 
Edinburgh it was much the same, but that was as it should be. 
The letter ends with some political reflections. When I read through them 
again, I was amazed how accurately I evaluated the situation even then. 
I experienced the growing bitterness of the German people and felt 
that renewed warmongering would result, leading to catastrophe. The 
catastrophe was not avoided. 



55 



BORN-EINSTEIN LETTERS 



31 



Gottingen 
4 August, igzi 



Dear Einstein 

A small boy, Gustav Born, came into the world on July 29th. 
My wife is quite well and sends her regards. I shall remain here 
for another few weeks and then go somewhere to recuperate. 

Unfortunately I have to attend the Physics Congress at Jena 
because of the journals, etc. And I have sworn never to attend 
another congress. Auerbach has invited me to stay with him and 
wrote to tell me that you ought to be there as well. That would 
be nice. Franck is going to visit Bohr in Copenhagen in Septem- 
ber. I am now working with Brody on the equation of state of 
solid bodies for which we are now developing a rigorous theory 
for crystals - a difficult business. It is, however, coming on nicely. 
Warm regards to you and your family, 
Max Bom 



32 



22 August, ig2i 



Dear Born 

Many thanks for the detailed report you sent me. The K. W. I. 
[Kaiser Wilhelm Institute] is rather slow, because I have to 
summon all my dear colleagues for grants. What you want would 
devour the greater part of all our worldy goods, but a good case 
can be made out for it, and I hope to be able to arrange it. 
Just a little patience. 

I have thought of a very interesting and fairly simple experi- 
ment on the nature of the emission of light. I hope to be able 
to carry it out soon. Meanwhile I am again the slave of the 
damned postman, who inundates me mercilessly. I have spent 
a happy month at the lake with my boys. Congratulations to 
you and your wife, and best regards, 
Yours 

Einstein 



56 



BORN-EINSTEIN LETTERS 



33 



Gottingen 
21 October, igsi 



Dear Einstein 

In writing to you today I address the mighty Director of the 
Institute of Physics of the Kaiser Wilhelm Society about the 
X-ray equipment we applied for. Franck has already told 
you how things are. In the meantime, however, something has 
happened. About ten days ago a representative of the Veifa- 
Werke was here and he made the following offer: if we order at 
once, the firm will supply the equipment we want at the current 
price. We could, however, cancel the order before October 31st 
(3 weeks' grace) should no decision have arrived from the Kaiser 
Wilhelm Society by then. If the order were placed later, we 
would be subject to the full price increase caused by the currency 
devaluation, which would amount to about 50 per cent (!!!). 
We have accepted this proposal and placed our order in the 
hope that confirmation of the grant will arrive from the Kaiser 
Wilhelm Society within three weeks. The deadline, October 31st 
is approaching and we are still waiting. Pohl and Franck have 
asked me to write to you and ask what the position really is 
and whether we should cancel the order on October 31st or 
whether the grant is certain enough for us to let the order 
stand. It would be a great pity if we received 100,000 M, but 
so late that the cost of the equipment had increased to 1 50,000 M. 
Maybe the decision could be speeded up a little. In the mean- 
time, we have, by a complicated transfer of equipment, collec- 
tions, toilets etc. cleared out two adjoining rooms and we will 
use them for X-ray research, one room for each department. 
Meanwhile, Dr Kuestner is working under very difficult con- 
ditions at the medical clinic, where there is some Veifa equip- 
ment, so that he can familiarise himself with it. We have lots 
of problems and would be glad to receive the equipment. 

After this official business, some private matters. My health 
was not too good during the holidays; towards the end of 
July I got catarrh and stiU have not got rid of it completely, 
even though I spent three weeks in Ehrwald in the Tyrol. 
Catarrh is not serious in itself, but I always get asthma with it 
and that affects me a great deal. For months I have had dis- 



57 



BORN-EINSTEIN LETTERS 

turbed nights because of asthma. But it is getting very much 
better now, and I hope to be quite free from it in a few weeks' 
time. It is high time too, for the university term begins shortly, 
and there is always a good deal going on here. W. Pauli is now 
my assistant; he is amazingly intelligent, and very able. At the 
same time, he is very human for a 2 1 year old - normal, gay 
and childhke. Unfortunately he wants to go away again in the 
summer, to Lenz in Hamburg, as he had already promised. 
Brody is still with me as well; he is a very clever and stimulating 
man. An attempt will have to be made to find a post for him 
with a living wage; I can only pay him a pittance (from a fund 
collected by Franck, Courant and myself). Polanyi intends to 
discuss this with you. 

Scientifically there is nothing special to report. A large paper 
of mine about thermodynamics is at the printers, but already I 
wish it could be unprinted because the basic arguments seem 
shaky to me. The result (which incidentally I consider to be 
correct in spite of its shaky basis) is curious: Gruneisen's idea of 
the proportionality of energy and thermal expansion is not true 
at low temperatures; the latter is satisfied by a T^-law instead of 
a r*-law. This should be tested experimentally (Nemst?). 
Then another paper of mine about lattice potentials, which is 
quite nice mathematically, is at the printers, Pauli and I are 
tackhng some quantum calculations of atoms, using the approxi- 
mation method which Brody and I recently developed in the 
Zeitschrift fur Physik with the example of the oscillator system. 
Perhaps something will come of it. Apart from this I am thinking 
about a number of things, but mostly without success. The 
quanta really are a hopeless mess. 

My wife and children are well; Gottingen agrees with them 
splendidly. Our little son is flourishing. 

The political situation is once more worrying me a great deal. 
In spite of my good intentions to be objective, my aversion 
towards the Allies grows because they are so disgustingly 
hypocritical. The Germans, it is true, have also robbed and 
stolen when they could, but they have not talked any nonsense 
about 'saving civilisation', etc. But I can't even write about it 
without getting excited so I had better stop. 

Is it true that the Mount Wilson people have now confirmed 
the red shift? Has this already been published, and if so, where? 



58 



BORN-EINSTEIN LETTERS 

I received (as editor of the Physikalische Zeitschrift) a letter from 
Glaser asking me to accept the enclosed manuscript. Debye 
also recommended its acceptance. I read it and found that it 
contains a crude attack on Grebe and Bachmann and some 
mudslinging at you. I have returned it with a request for changes 
and for permission to bring it to Grebe's notice. It would be 
rather nice if the announcement from Mt Wilson about the con- 
firmation could appear in the same issue, for Glaser bases 
his argument mainly on the negative result obtained at St 
Johns. Could you write to them for a brief report for publication ? 
But I must stop now. 

With kindest regards to your family; also from my wife 
(with all due respect, and modesty). 
Yours 

Born 



The last letter touches on a matter of supreme importance -the announce- 
ment of a confirmation of the general theory of relativity by the spectral 
red-shift in the gravitational field. 

The financial matters mentioned are practically incomprehensible today. 
One has to remember that the inflation of the German currency was 
beginning. A drop of one half in the value of money may have taken about 
two to three months at that time. Later on it took only as many days. 
Hence our troubles with the purchase of the X-ray equipment. Officialdom 
and public corporations did not understand the situation. The courts 
supported the currency catastrophe by rigid judgments. I myself lost the 
greater part of my inheritance. A man who owed me money on a mortgage 
sent me the entire nominal value of the mortgage (50,000 M, I believe) 
in one single note of the inflated currency which was actually worth i M at 
the time. This was held to be legal. The High Court had decided that a 
mark is a mark. After such experiences as these, my faith in the wisdom of 
financial and legal experts, instilled into me during my upbringing as the 
son of middle-class parents, was very much weakened. However, at the 
time when Franck and I moved to Gottingen, things were not quite as bad 
as that - yet. Even so, we had to expend a considerable amount of time 
and energy in order to keep the institute going. It was even worse for our 
wives ; they were forced to convert our salaries into food, clothing and other 
necessities immediately. But I am digressing. 

Of the scientific comments, my remarks about calculations of atomic 
structures done in collaboration with my young assistant Pauli are most 
interesting. The aim was to see whether the Bohr-Sommerfeld rules for 



59 



BORN-EINSTEIN LETTERS 

the application of the quantum hypothesis to mechanical systems would 
lead to correct results. We used appropriate approximation methods based 
on Poincare's astronomical perturbation calculation. The results were 
negative, and so it seemed that the quanta were a 'hopeless mess'. 
Soon afterwards, however, I saw it differently. Was it possible that the 
success of Bohr's theory in the case of the hydrogen atom and other 
similar simple systems was a sort of accident? Could there perhaps be 
another, better, theory? This became our programme, especially when 
Heisenberg succeeded Pauli. We began to look systematically for cases 
where Bohr's theory failed, and soon found one with the helium atom. 
(Other cases had already turned up in the dynamics of crystal lattices ; 
atomic lattices built of Bohr's atoms with plane electron orbits led to 
completely wrong compressibilities.) 

The red-shift remained a dubious phenomenon for a long time. Only 
very recently has anyone succeeded in verifying Einstein's result. It 
became possible after a thorough study of the sun's atmosphere, whose 
ascending and descending streams veil the gravitational effect by the 
normal Doppler effect; clouds of sodium vapour were found which hovered 
comparatively quietly over the atmosphere of the sun, and showed the 
gravitational effect in purity. Finally, the red shift has also been verified 
directly on the earth, by y-rays, by means of the Mossbauer effect. 
This, however, is too far from the subject. 

A postcard from Hedi follows with a photograph of her holding our little 
son in her arms ; the few words are meant as an apology for her previous 
abruptness. 



34 



/ November, igsi 



With this card, Gustav Born begs to introduce himself to you, 
and begs you (i) for your goodwill and affection and (2) not to 
bear a grudge to his mother for whom he is, after all, not 
responsible, 

XXX Signed : Gustav 



60 



BORN-EINSTEIN LETTERS 



35 



Gottingen 
sg November, igzi 



Dear Einstein 

The authorities cannot decide whether you are still tarrying in 
the warm countryside of Italy or are already in Berlin. However, 
in the former case, it is probably correct to assume that you will 
soon return. Therefore I am writing and I hope you will get my 
letter soon. 

First of all, I must thank you most sincerely for the magni- 
ficent gift of the X-ray equipment. Franck, Pohl and I are 
delighted with it, for it should be part of any decent institute 
nowadays, and problems frequently arise which can only be 
solved with the help of X-rays. Pohl will write you an official 
letter of thanks, but I must add a few words of my own. This 
valuable gift shows that you people in Berlin have confidence in 
our ability to produce something worth while, and this is very 
gratifying. Pohl is chiefly responsible for purchasing the equip- 
ment, and a great many difficulties have been encountered, such 
as lack of space and unrefiability on the part of the firms. The 
Veifa works in particular have dealt with us in such a manner as 
to make it unlikely that we shall buy from them. Pohl is shortly 
going to Berlin to negotiate with Siemens. We do not want to 
buy any of the sets that are ready-made for medical use; we 
would rather, if possible, assemble a carefully planned unit of 
our own, using the best available components. 

Apart from this, there is not much pleasant news to report, 
for I am almost constantly ill. My summer trip to the Tyrol did 
not help much, for after my return I had asthma almost every 
night and became very run down. About three weeks ago I had 
a very severe attack, accompanied by bronchitis, and had to 
keep to my bed for a long time. I had some treatment from 
our medical specialists (especially E. Meyer) which succeeded 
in curing the asthma. But I still have severe catarrh and am 
unable to lecture. Pauli is deputising for me, and seems to be 
doing quite well in spite of his mere twenty-one years. It is a 
pity that I am so shaky, for in every other way things are good 
here. To be working with Franck is a joy. I'm on good terms 
with Pohl, too. Young PauU is very stimulating - I shall never 

61 



BORN-EINSTEIN LETTERS 

get another assistant as good. Unfortunately, he wants to go to 
Lcnz in Hamburg in the summer. I have been unable to do any 
serious work lately, but I now understand perturbation theory 
rather better and have some inkling of what Bohr is really 
doing. I am also systematically continuing with my work on 
crystals; several papers written during the summer have 
recently appeared in Z^tschriftfiir Physik. 

I would like to know what you think of Polanyi's papers on 
rates of reactions; he maintains that these could not be explained 
without an as yet unknown kind of energy-transmission (the 
transmission of quanta of energy from one molecule to another 
without mechanical reciprocation, simply hopping through 
space). Franck and I do not beUeve it. Langmuir was here 
recently; he thinks on similar lines, but we stiU do not believe 
any of it. Incidentally, we liked Langmuir very much; he knows 
lots of physics. Polanyi's paper about tensile strength is also 
quite crazy and yet it contains a grain of truth. We would so 
much like to talk to you about it ! 

A pupil of mine (a nephew of Minkowski with the same 
first name) is working out an exact theory for streams of slow 
electrons (speed below the smallest hv) in gases. This is based on 
the following idea of Franck's. In an extreme vacuum, the 
Child-Langmuir equation gives the current as a function of the 
voltage (Joe F^'S I think). If one now adds the gas, the electrons 
are thrown about so that the space charge density is increased 
and the JjV law altered. The free path length of the electron 
in the gas should follow from this change, according to the 
existing theory. This is of interest, however, in view of Ram- 
sauer's quite crazy assertion (in Jena) that in argon the path 
length of the electrons tends to infinity with decreasing velocity 
(slow electrons pass freely through atoms!). This we would like 
to refute. My theoretical ideas are: I start with the Maxwell- 
Boltzmann collision equation 



dF 



dF 

dt "^^ dx 



m di 



-l\ 



^. ..+__+... =11 collision integral. 



This equation is usually integrated so that the left hand side is 
equated to zero and in the first approximation the integral 
vanishes because of MaxweU's distribution function. In 
the second approximation this distribution is then inserted 



62 



BORN-EINSTEIN LETTERS 



into the left hand side. I then proceed the other way round. In 
the first approximation, ignoring all collisions and with normal 
space charge distribution, it is necessary to put 



Z= -e 



dX 



and to use the second equation Atjs= -e/Fd^dryd^. In the 
second approximation, one collision is taken into account, and 
so on. This project seems to be going well. Minkowski intends 
to carry out some experiments, together with Miss Sponer, but 
these are sure to be very difficult. 

We were greatly amused by Lenard's Soldner article. I 
do not know if you saw the report on it which appeared in 
Frankfurter JZeitung, as well as Lane's reply on the one hand, and 
Hubert's and mine on the other? 

I am reading Laue's second volume; I must say I like it very 
much after all. All the same, Pauli's article for the Encyclopaedia 
was an even greater achievement. 

My wife is very well; she is breast-feeding the little boy, and 
this agrees with both of them. At the moment, though, she is 
confined to bed with a large and painful boil. The two little 
girls are also well. 

Please give my regards to your wife and the young ladies, 
and to all our friends and acquaintances in Berlin. 
With best wishes 
Yours 

M.Born 



My report about 'young Pauli' is not quite complete. I seem to remember 
that he liked to sleep in, and more than once missed his 1 1 a.m. lecture. We 
used to send our maid over to him at half past ten, to make sure that he 
had got up. He was undoubtedly a genius of the highest order, but my 
fear that I would never get an assistant as good proved unjustified. His 
successor, Heisenberg, was just as gifted, and also more conscientious: 
there was never any need to have him woken up, or to remind him of his 
duties in any other way. 

The comments about the physical chemist Polanyi are too dated to be of 
any interest today. I should just add that later, during the Hitler regime, 
Polanyi went to England and obtained a chair at Manchester - not for chem- 
istry, but for philosophy and sociology ; he was a versatile, imaginative man. 

63 



BORN-EINSTEIN LETTERS 

Ramsauer's assertion that the free path length of the electron in argon 
increases with decreasing velocity was bound to seem crazy at the time. 
But it was nevertheless right. It was first explained by means of dc 
Broglie's wave mechanics: the matter waves of the electrons have a wave- 
length proportional to the velocity. If their collisions with atoms arc 
regarded as diffraction phenomena, it becomes clear immediately that 
slow electrons, that is, those with long wavelengths, are less influenced by 
atomic obstacles. At the time I had no inkling of all this, and thus called 
these important experiments 'crazy'. Did Einstein already have a deeper 
insight then? I do not know. 

Soldner, a German mathematician and geodesist, had predicted the 
deflection of light by the sun as early as 1 80 1. He had actually dealt with 
the beam of light as if it were a comet, moving according to Newton's law. 
(This makes sense, because the path of a small object attracted by a central 
body does not depend on its mass.) He ended up with the same formula as 
Einstein did in his first paper deaUng with this problem; but this differed 
by a factor of two from Einstein's final formula, which took into account 
the change in the gravitational field near the sun as required by the general 
theory of relativity. Naturally, Soldner's work was exploited to the full 
by Einstein's enemies. 



36 



30 December, igsi 



Dear Boms 

Today I wish you a happy new year. We were all delighted with 
the photo of the youngest Born. The fight of the Amazons is 
now forgotten. I am very sorry to hear that you, dear Born, 
have had so much trouble with your health. I hope that you 
are all fit and well again. 

Pauli is a splendid fellow for his 21 years; he can be proud of 
his article for the Encyclopaedia. Polyani's ideas make me 
shudder. But he has discovered difficulties for which I know no 
remedies as yet. In particular I am racking my brains over a 
numerical analysis in connection with radiation-molecular 
balance. There is probaWy a lot of truth in Polanyi's ideas about 
the strength of crystals, but their extension to gases seems wide 
of the mark to me. Your investigation of electron currents 
sounds interesting. I liked your reply about Soldner in Frank- 
furter Z^tung very much. 

64 



BORN-EINSTEIN LETTERS 

The experiment on light emission has now been completed, 
thanks to Geiger and Bothe's splendid cooperation. The result: 
the light emitted by moving particles of canal rays is strictly 
monochromatic while, according to the wave theory, the colour 
of the elementary emission should be different in the different 
directions. It is thus clearly proved that the wave field does not 
really exist, and that the Bohr emission is an instantaneous 
process in the true sense. This has been my most impressive 
scientific experience in years. Ehrenfest writes enthusiastically 
about Bohr's theory of atoms ; he is visiting him. If Ehrenfest 
is convinced, there must be something in it, for he is a sceptical 
fellow. 

Regards to the little ones, and all good wishes to you both 
for the New Year. 
Yours 

Einstein 



Pauli's article for the Encyclopaedia dealt with the theory of relativity. 
Sommerfeld was originally supposed to write it. He got Pauli to help him 
with it, but Pauli made such a good job of it that Sommerfeld handed the 
whole thing over to him. It is truly remarkable that a young student of 
2 1 was capable of writing so fundamental an article, which in profundity 
and thoroughness surpassed all other presentations of the theory written 
during the next thirty years - even, in my opinion, the famous work by 
Sir Arthur Eddington. 

The investigation into the emission of light by positive rays, which Einstein 
carried out in conjunction with Bothe and Geiger, is mentioned again in 
subsequent letters. It was a great disappointment in the end. 



37 



Gdttingen 
I January, igss 



Dear Einstein 

We have been very much shaken by the contents of your letter, 
though in our stupidity we are unable to reconstruct the set-up 
of the positive-ray experiment for ourselves. We have a thousand 
questions in our minds and all sorts of reflections for which we 
need you as a sedative. As this letter cannot run to 50 pages, and 

65 



BORN-EINSTEIN LETTERS 

as we can hardly expect a loo-page reply, we conceived the 
brilliant idea of having you officially invited to visit us in 
Gottingen, at the expense of the Wolfskehl Foundation, to give 
an informal lecture. This means you would also be here for 
Hubert's 6oth birthday, an idea which has delighted the old 
man. His birthday is on January 23rd; the lecture could be held 
on Tuesday, 24th, and we hope that you will devote at least 
Sunday, the 22nd, to us. Maybe your wife would like to accom- 
pany you. It would be wonderful if you could manage that, and 
we look forward to it so much that you must not refuse under 
any circumstances. Sincere regards and best wishes for the 
New Year. 

BomandFranck 



38 



Jan. '22 



Dear Bom 

I shall gladly come and visit you, partly in order to congratulate 
Hilbert in person, and partly to tell you about the experiment, 
and how simple it is. The joke is this: the positive ray particle, 
according to the wave theory, continuously emits variable 
colours in different directions. Such a wave travels in dis- 
persive media with a velocity which is a function of position. 
Thus the wave surfaces should be bent as in terrestrial re- 
fraction. But the experimental result is reUably negative. 
Kindest regards, also to Franck and to your family. 
Yours 

Einstein 



39 



7 January, ig22 



Dear Mr Einstein 

First of all I want to thank you and your wife most sincerely for 
your new year greeting, which showed the warmth of your 

66 



BORN-EINSTEIN LETTERS 

friendship. May all your own dearest wishes come true many 
times over. I hurried over to Hilbert with your card. He could 
hardly beUeve at first that you are really coming, and was then 
tremendously pleased. He wants me to ask you to make sure to 
be there on his birthday, Monday, 23rd, and to put in an 
appearance at the large gathering in the evening. The lecture 
can be held on Tuesday, at any time you like. I hope you will 
not just streak past us like a meteorite, but will be able to 
stay for a few days as our guest. You will see how well we live 
here, and we shall feed you on easily digestible dishes. If 
your wife would like to come with you, she is cordially invited 
and will be very welcome. Max is with Blaschke today and 
tomorrow. He is unfortunately in a very bad state. Perhaps you 
could give him pleasure by visiting him once more? It must 
not look too deUberate. With kindest regards to you and your 
family. 

Yours 

Hedi Bom 



40 



18 January, ig22 



Dear Bom and dear Franck 

I must, with a heavy heart, decline after all. But it really cannot 
be helped. I am so much behind with my writing and other 
obligations that I just cannot afford an escapade into the 
Eldorado of erudition. So I will have to pay homage to Hilbert 
by letter. Please let Courant know as well; he wanted to engage 
me as a musician. 

Laue is violently opposing my experiment, or rather my 
interpretation of it. He maintains that the wave theory does 
not involve any deflection of rays whatever. He suggested a 
nice experiment to investigate the supposed wave bending of 
the rays by means of capillary waves which exhibit con- 
siderable dispersion, as a substitute for a theory which it is so 
hard to develop with the required rigour. 

Today there was a great dispute at the coUoqium, to be 



67 



BORN-EINSTEIN LETTERS 

continued next time. Do not be angry - to postpone is not to 
abandon. 
With warmest regards, also to your wives 
Yours 

A. Einstein 

Many thanks to Mrs Born for the charming picture. The 
other evening I read to Laue and Vegard all the poems she 
dedicated to us. They found them delightful and all saw in her a 
serious competitor to Master Busch. In view of the tussle we had 
with one another, I want to send her my special greetings. 



This letter contains, for the first time, some doubts about the ideas on 
which the positive-ray experiments were based, raised by Max von Laue, 
then unquestionably an expert in all optical matters. Franck and I were 
delighted at Einstein's news of the experiment, not because of our own 
reflections on it but because of our pleasure in Einstein's success in taking 
another important step forward. 



41 



Gottingen, 
30 April, igss 



Dear Einstein 

Laue was here recentiy - we very much enjoyed his stay. He 
told us that you are going to Holland. I hope this letter will 
reach you in time. 

First of all I have to ask for your help again, this time for 
Brody. When I talked to you last Christmas in Berlin, you said 
it might be possible to secure a post for him in Kowno. I have 
recently discussed this with I. Schur in Berlin (you were in 
Paris at the time), who has all kinds of contacts with Kowno. 
He was going to attend to it. It is now a matter of urgency that 
something should be done. My wife, who is looking after Brody's 
family (his wife and small child have been here for some time), 
reports that they live under miserable conditions. I give him 
something from our private fund (about 2000 M per month), 
but that is very little for a family. Apart from that we give what 

68 



BORN-EINSTEIN LETTERS 

help we can. But the man must get out of this humiliating 
situation. I value him very highly as a physicist; if he had more 
energy and was in better circumstances, I am sure he would 
achieve a great deal. A pretty piece of work he did is about to 
appear in Physikalische JZeitschrift, and he is also working with 
me on thermal expansion. Hilbert thinks very highly of him, 
particularly because he speaks extremely well in seminars. I 
could, if I wished, secure a lectureship for him here without much 
difficulty; but I consider it senseless because, as a Hungarian Jew 
and with his decidedly Eastern ways, he would never be offered 
a chair. I already have enough worries and responsibiUties with 
Paul Hertz, who is also on the point of starving. 

Could you perhaps find some modest post for Brody in 
Holland? Or in some other part of the world? I have applied 
to the Academic Assistance Council for a grant for him, but 
they have not yet replied. Could you put in a good word for 
him there ? Or is there some other way ? 

Now to other things. I am spending a good deal of time 
writing the article about lattice theory for the Encyclopaedia. 
I hope to have it finished by May. It is a rather laborious task. 
Unfortunately it now turns out that there is a mistake in my 
recently published theory of the equation of state of crystals. 
I had claimed that Gruneisen's law of the proportionality of 
energy and expansion does not hold throughout but that, at 
low temperatures, the former is proportional to T* and the latter 
to T". This was nonsense, though. It was based on a bad 
blunder. That this could happen to someone of my ripe old age 
is somewhat depressing. But as long as one discovers the mistake 
oneself it is not quite so bad, and I console myself with the know- 
ledge of what a tricky business it is. Moreover, both Pauli and 
Brody read the paper thoroughly without spotting the mistake. 

Pauli has unfortunately gone to Lenz in Hamburg. We 
recently started work on a joint paper, a continuation of the 
one published in collaboration with Brody about the quantis- 
ation of non-harmonic oscillators. The approximation method 
developed there can be applied to all systems where the un- 
perturbed system is quasi-periodic and the flow function can be 
developed in powers of a parameter. The case when the un- 
perturbed system is degenerate can also be included and leads 
precisely to Bohr's method of secular perturbations. As a 



69 



BORN-EINSTEIN LETTERS 

matter of fact we now really understand Bohr's ideas, at least 
in part. We have also started to do calculations for ortho-helium 
(two coplanar electrons) and were able to confirm Bohr's old 
claim that the inner electron moves around fast on an elUptical 
orbit whose major axis always points towards the slowly moving 




outer electron. Pauli took the paper to Hamburg with him and 
wants to finish it there. I cannot find the time because of the En- 
cyclopaedia article. Then, too, the damned term is just starting 
again, an unwelcome interruption of my serene contemplation. 

Franck's Institute is full of doctoral students who do nice 
work under his guidance. Hilbert is in Switzerland and will not 
be back for another 8 days. 

My family are well in spite of the continually frightful 
weather. My wife sends warmest greetings. Please give my 
regards to my coUeages in Holland and Berlin. 
Yours 

Bom 



The plight of younger people like Brody who had to depend on small, 
fixed, constantly devalued salaries was indeed miserable. 
The report of the blunder I made in my article on solids was by way of a 
prelude to the major blunder which Einstein reports in his next letter. 



42 



Berlin 



Dear Bom 

It is extremely difficult at the moment to find posts for theo- 
reticians. Holland suffers from overproduction. Should there be 



70 



BORN-EINSTEIN LETTERS 

any chance of doing something for Brody here, it would be 
because of the extraordinary significance of his achievements. 
There are some excellent theoreticians there (such as Fokker) 
in modest teaching posts in Gymnasia. A few months ago I 
wrote about Brody to Millikan and Epstein in Pasadena, but 
have not yet received a reply. I will talk to Laue who, unless 
I'm very much mistaken, has some influence with the Not- 
gemeinschaft. I got to know your perturbation method through 
Becker's thesis [for a lecturer's qualification] and enjoyed it. 

I too committed a monumental blunder some time ago 
(my experiment on the emission of light with positive rays), 
but one must not take it too seriously. Death alone can save 
one from making blunders. I greatly admire the sure instinct 
which guides all of Bohr's work. It is good that you should be 
working on helium. The most interesting thing at the moment 
is Gerlach's and Stern's experiment. The orientation of atoms 
without colhsions cannot be explained by means of radiation, 
according to current reasoning; an orientation should, by 
rights, last more than a hundred years. I made a little calcu- 
lation about it with Ehrenfest. Rubens considers the experi- 
mental result to be absolutely reliable. 

Make sure you use the money for the purchase of the X-ray 
apparatus quite soon. Why is it taking so long? 
Kindest regards to you all 

Yours 

Einstein 



Here Einstein admits that the considerations which led him to the 
positive-ray experiments were wrong; 'a monumental blunder'. I should 
add that now (1965), when I read through the old letters again, I could not 
understand Einstein's observation at all and found it untenable before I 
had finished reading. This is, of course, quite simply because we have 
learned a good many things about the propagation of light during the 
intervening forty-odd years. The same is true of the idea that the laws of 
the propagation of light in transparent media have nothing to do with 
quanta but are correctly described by the wave theory (Maxwell's 
equations and their relativistic generalisations for moving bodies). It is 
quite possible that Laue had already realised this at that time, and used it 
in argument against Einstein's ideas. 
Now I can hear all Einstein's opponents, the anti-relativists, cry: 'What 



71 



BORN-EINSTEIN LETTERS 

did we tell you? Einstein, too, makes mistakes - why should we believe in 
his crazy theory of relativity?' The answer to this is that we all make 
mistakes. 'Death alone can save us from making blunders.' At first there 
were quite a number of serious scientists who did not want to know 
anything about the theory of relativity; conservative individuals, who were 
unable to free their minds from the prevaihng philosophical principles. 
As long as such people conduct their polemics decently, there is no reason 
why one should object to them. 

Einstein himself belonged to this group in later years; he could no longer 
take in certain new ideas in physics which contradicted his own firmly- 
held philosophical convictions. But Einstein never engaged in polemics, 
subjectively or maliciously. There are always real, disinterested scientists 
who are so ruled by prejudices outside science and philosophy that they 
reject any new ideas suggested by people of whose background, ancestry, 
rehgion, etc., they disapprove. These included the antisemitic physicists 
at whose hands Einstein, and later many other people including myself, 
suffered. 

Finally, there are the pure cranks, outsiders who can point to no 
positive scientific achievements themselves but who believe that they have 
found defects in some new doctrine such as Einstein's theory of relativity. 
One would think that there would be fewer of these as time goes on. But 
this is not so. Over the years a large number of first-class physicists and 
mathematicians have thoroughly investigated the theory of relativity and 
none has found fault with it. It is hard, therefore, today to take seriously 
anyone who believes he has discovered a mistake. I have frequently 
taken the trouble to uncover the errors in papers written by cranks of this 
type, but never in all my experience has any of them admitted that he 
had made a mistake, as Einstein did. 

H. Rubens, professor of experimental physics at the University of Berlin, 
was particularly known for his investigations of infra-red radiation and its 
appUcation to Planck's radiation formula. 

It is strange that Einstein referred me to Stern's and Gerlach's experiment 
as the most interesting. He had forgotten that it had been carried out in 
my Institute in Frankfurt under my very eyes, as a result of discussions 
with me, and that it had been financed with money I myself had raised 
with the aid of my relativity lectures. 

If my memory does not deceive me, Stern also made the little calculation 
which Einstein had made with Ehrenfest, namely that the orientation of 
atoms in the magnetic field, predicted by Sommerfeld and experimen- 
tally demonstrated by the Stern-Gerlach experiment, cannot be interpre- 
ted classically. 



72 



BORN-EINSTEIN LETTERS 



'•^ Gdttingen 

6 August, igs2 
Dear Einstein 

We recently had a visit from a woman physicist who now lives 
in Holland; she mentioned that Michelson's experiment had 
been repeated in America, with positive success. H. A. Lorentz 
is supposed to have brought the news with him. Do you know 
anything about it? The Michelson experiment is one of those 
which seem definitely a priori. I do not believe a word of the 
rumour. But all of us here would be most grateful if you could 
find time to write a postcard. 

Franck and Courant have spoken to me about you. We have 
a lot of worries about professional appointments. Pohl has 
decided to stay on in Gottingcn. This relieves us of the worry 
of selection. But now I fear that Franck may go to Berlin. 
I sincerely want him to be offered the chair, but he would be 
foolish to accept. Courant says that you are of the same opinion. 

Scientifically there is nothing of any importance. My assistant 
Hiickel and I are having a lot of trouble with the quantisation 
of polyatomic molecules in calculations of the infra-red bands 
(in H2O, for example) . We have the right approximation method, 
but the calculations are very complicated. I expect to finish my 
Encyclopaedia article this month ; I am completely fed up with 
it. I have given a good deal of thought to the quantum theory 
of molecule formation. A short notice in Die JVaturwissenschaften 
about the Hj molecule contains some results of interest to 
connoisseurs. But the more unequivocal these turn out to be, 
the crazier the whole system seems. I am not yet on the right 
track as far as questions of principle go. 

My wife and children are well. The girls are staying in the 
country with a former maid of ours; they are due to return 
soon. We shall stay here until the middle of September, when 
we are going to Leipzig and from there to Italy. We received 
;(^22 sterling for the translation of my book, and have turned 
it into lire. This will not take us very far, but we greatly look 
forward to our little journey to the South. With warmest 
greetings, also from my wife, to you and your family. 
Yours 

M.Bom 



73 



BORN-EINSTEIN LETTERS 

The Michelson experiments were made by the American physicist Miller, 
first in flat country and later on top of Mount Wilson, a high mountain. 
To begin with, he claimed to have discovered, using his Michelson inter- 
ferometer, the so-called aether wind. Some time later he withdrew the 
claim; the shift of the interference fringes, on which he had based his 
claim, had been too small. I believe he then attributed it to the movement 
of the solar system. When I was in the United States in 1925/26, Miller's 
measurements were still frequently being discussed. I therefore went to 
Pasadena to see a demonstration of the apparatxis on top of Mt. Wilson. 
Miller was a modest little man who very readily allowed me to operate 
the enormous interferometer. I found it very shaky and unreliable; a 
tiny movement of one's hand or a slight cough made the interference 
fringes so unstable that no readings were possible. From then on I com- 
pletely lost faith in Miller's results. I knew from my visit to Chicago in 
191 2 that Michelson's own apparatus was very reliable and his measure- 
ments accurate. My scepticism has been substantiated by later develop- 
ments. Michelson's result that the aether wind does not in fact exist is 
universally accepted today. 

Then follows a brief report about my work on special problems of the 
quantum theory, which is no longer of any interest today. 



44 



23 December, igss 



Dear Boms 

Splendid sunshine at Christmas. A happy, beautiful country, 
with a delicate, sensitive people. We start for home again on the 
29th, over the great waters, via Java, Palestine and Spain; it 
will probably be April before we get there. 
In the meantime, warmest greetings 
Yours 

Einstein 



This postcard from Japan was the only message we received from Einstein 
during his world trip, which took him and his wife to China, Japan, 
Palestine and many other countries. On his way out there he received the 
news that he had been awarded the Nobel Prize; not for his theory of 
relativity, but for his explanation of the photoelectric effect by means of 
his photon theory. Further details of this can be found in any of the 
numerous biographies of Einstein, such as the one by Carl Seelig.^' 

74 



BORN-EINSTEIN LETTERS 



45 



Gottingen 
7 April, 1923 



Dear Einstein 

They say you are back. I had intended to write you a welcome- 
home letter, but now it is too late. The most important thing is 
for us to congratulate you heartily, if somewhat belatedly, 
on the Nobel Prize. Two more deserving recipients than you 
and Bohr could not be found, and we were as pleased as Punch. 
We also want to thank you sincerely for the beautiful card from 
Japan, We did not know your address, and so were unable to 
reply. But now I would like to re-establish the exchange of 
views between us, if I may lay claim to your time. I would like 
to hear about your experiences during your great trip. I may 
possibly come to Berlin for a few days towards the end of the 
month, in order to visit an American friend and benefactor of 
mine, who helps me to support my students. I hope to see you 
then. We have been living very peacefully and quietly here. 
The only external event of any importance has been a visit by 
Lord Haldane. He seems to be rather confused; all the same, 
the breadth of his education and his qualities as a European 
made a deep impression on us (i.e. Hilbert, Franck, Courant 

and myself). 

If you happen to glance through the last six months' issues 
of scientific journals, you will see that I have been fairly 
industrious, and have kept quite a large number of students 
going. But they are only minor problems that I am struggling 
with. I don't seem to get any closer to the great mystery of the 
quanta, in spite of all my efforts. We have been looking at 
perturbation theory (Poincare's) to determine whether it is 
possible to obtain the observed term values from Bohr's models 
by exact calculation. But it is quite certainly vx)t the case, as was 
demonstrated with helium, where we found any number of 
multiple periodic orbits (to a sufficient approximation). I had 
Heisenberg here during the winter (as Sommerfeld was in 
America) ; he is easily as gifted as Pauli, but has a more pleasing 
personality. He also plays the piano very well. Apart from the 
work on helium, we examined together some questions of 
principle in connection with Bohr's atomic theory - particularly 

75 



BORN-EINSTEIN LETTERS 

with regard to the phase relations in atomic models {^eitschrift 
furPhysik). I have at long last finished my great Encyclopaedia 
article on the lattice theory ; it has grown to about 250 pages, 
and will be published as the second edition of my old book. 
I hope it will come out in May. Then I am going to put this 
subject into cold storage until the question of homeopolar 
binding forces between atoms has been solved from Bohr's 
point of view. Unfortunately every attempt to clarify the con- 
cept fails. I am fairly sure though that in reahty it must all be 
very different from what we think now. But one can draw plenty 
of qualitative conclusions from Bohr's ideas; Franck does that 
magnificently, and is doing some nice experiments again. I live 
in dread of Franck getting the position in Berhn. It would be 
better for him, for physics, and also for Berlin if he were to 
remain here. To say nothing of myself At the moment he has 
gone to Hertz in Holland. 

I hear that you have a new theory about the connection 
between gravitational and electromagnetic fields, which 
allegedly points to a relationship between gravitation and the 
earth's magnetic field. I am very curious. Most of what is 
published about relativistic problems leaves me cold. I find 
Mie's pulpy effusions horrible. Hilbert follows all this half- 
heartedly, as he is completely preoccupied with his new basic 
theory of logic and mathematics. What I know of it seems to me 
the greatest step forward imaginable in this field. But for the 
time being most mathematicians refuse to recognise it. 

The papers report that you have turned your back on the 
League of Nations. I would like to know if this is true. It is, 
indeed, almost impossible to arrive at any rational opinion 
about poHtical matters, as the truth is systematically being 
distorted just as in wartime. The folhes of the French sadden me, 
because they strengthen our nationahsm, and weaken the 
Republic. I give a lot of thought to what I could do to spare my 
own son the fate of participating in a war of revenge. But I am 
too old for America and, moreover, the war hysteria seems to 
have been even worse there than here. The other day I read a 
little essay by Coudenhove-Kalergi : 'Apology for the Technical 
Age', which contained some enlightening arguments. If you do 
not know it, you should certainly try to get hold of it. 

We were in Berhn last March. I talked to Planck, and his 

76 



BORN-EINSTEIN LETTERS 

company gave me much pleasure. On the other hand, the 
German Physical Society, where I gave a lecture, was like a 
waste-land - no trace of participation or discussion. Rubens is 
much missed there; for all his coolness and caution, he was full 
of interest and life as far as science went. My family are well 
and send warmest regards to you all. 
Yours 

Max Bom 



My American friend and benefactor was Henry Goldman, who was 
senior partner of the great banking house Goldman, Sachs & Co. in New 
York. I got to know him when an old friend went to New York after the 
war to marry his American fiancee. Partly as a joke I said that he ought to 
try to find me a rich G«rman-American, who would be prepared to give 
some financial support to my Institute, which had been severely handi- 
capped by the inflation. A few weeks later, I received a postcard from New 
York : I have your man, his name is Henry Goldman, and he lives at. . . . 
With my wife's help I drafted a nice letter to Mr Goldman, and a few 
weeks later received a very charming reply, together with a cheque for a 
few hundred dollars, quite a considerable sum by German standards. I 
went to Berlin to get to know my benefactor. I should like to recount 
briefly how things went with Goldman after that. 

Goldman was a portly, Jewish-looking gentleman; his grandfather had 
emigrated to the U.S.A. from Hessen without a penny, because the Jews 
were treated particularly badly there. In America, he started off as a 
door-to-door salesman, and ended up as the owner of a small bank. 
His sons and grandsons developed this into a giant concern, which 
amongst other things had financed the Woolworth Co. The family's 
German memories meant much to my Henry Goldman and, when the 
war broke out in 1 914, he did not believe that the Germans alone were to 
blame. He even fell out with his family over this issue. Later, he did 
everything he could to help Germans in those difficult times. I introduced 
Goldman to Einstein, and both of them later visited us in Gottingen, and 
stayed in our house. During our American journey in 1926, my wife and I 
visited the Goldmans and spent Christmas Eve with them in their elegant 
flat on Fifth Avenue in New York. Hitler's seizure of power was, of course, 
a terrible blow to Henry Goldman. All his life he had defended the Germans 
against American accusations, and helped them. Now he lived to see 
antisemitism made into one of the main points in the programme of a 
criminal government. I saw Henry Goldman once more (in 1934 or 1935), 
in his London hotel. He was a broken man and died soon afterwards. 
The story of Lord Haldane's visit is as follows : Years ago he had studied in 



77 



BORN-EINSTEIN LETTERS 

Gottingen, and he liked the German culture and language. This must 
have been why he resigned from his post as British War Minister in 
1 9 14, when his country aligned itself with France and Russia. Soon eifter 
the end of the 1914-18 war he visited CJottingen to look up a certain old 
lady, Miss Schlote, in whose house he had lived during his student days. 
My wife knew her, and in this way Haldane found out that we lived 
in Gottingen. He had great admiration for Einstein and had read my 
relativity book. He himself had written a large book. The Reign of Relativity, ^^ 
which, however, had virtually nothing to do with Einstein's theory 
but merely enlarged upon the trivial proposition that 'everything is 
relative'. His visit helped to enliven our usually very quiet existence in 
Grottingen. 

Later I met Haldane again. I had been invited to the opening of a new 
physics laboratory at the University of Bristol, donated by the cigarette- 
manufacturing firm of H. O. Wills. There I was to receive an honorary 
doctorate, my first, together with a number of famous physicists, Lord 
Rutherford, Sir William Bragg, Sir Arthur Eddington, Langevin (from 
Paris) and others. To my surprise the Vice Chancellor, who conducted 
the ceremony in the festive, but cold hall, was none other than Lord 
Haldane. He welcomed me like an old friend. As it happened he, like 
myself, was suffering from a bad cold. This prevented us from attending 
the banquet that evening in that same cold hall, and we had our dinner 
served to us in a small room, where a coal fire gave at least the illusion of 
warmth. I remember that he talked almost the whole time, mainly about 
the negotiations he had conducted in Berhn (known as the Haldane 
Mission) to end the naval arms race between Grermany and Great 
Britian. This foundered because of the stubborn attitude of von Tirpitz 
and the Kaiser, which Haldane described vividly. Many historians believe 
that the first world war might well have been prevented by such a pact, and 
European history would have taken an entirely different course. 
As regards perturbation theory: astronomers normally use simple, well 
proven techniques, and they do not take much notice of the considerable 
developments, systematically made by Henri Poincare. But the perturba- 
tion problems involved in the theory of electron orbits in the atom make 
the general rigorous theory indispensable. We therefore made ourselves 
familiar with it, as did Niels Bohr in Copenhagen, who used it as the basis 
for an interpretation of the periodic system of the elements. Heisenberg 
and I, however, pursued a different objective. We had reason to doubt 
that Bohr's ingenious but basically incomprehensible combination of 
quantum rules with classical mechanics was correct. We therefore intended 
to carry out a thorough calculation of the two-body problem of the helium 
atom (nucleus with two electrons), and thus needed to use Poincar6's 
rigorous approximation technique. The result was quite negative, and that 



78 



BORN-EINSTEIN LETTERS 

led us finally to turn our backs on classical mechanics and establish a new 
quantum mechanics. 

The rumour about Einstein's new investigation, in which he attempted 
the unification of his theory of gravity with Maxwell's theory of the 
electromagnetic field, proved to be correct. At that time he began his 
often repeated, although unavailing, attempts to develop a unified field 
theory along these Unes. 

Hubert's efforts to find a new basis for mathematics enthralled and 
fascinated me to begin with. Later, I was no longer able to follow. I had 
some correspondence with Einstein about these problems, when they became 
the cause of a dispute between Hilbert and the Dutch mathematician 
Brouwer (letter No. 58). 

Einstein repudiated the League of Nations when he resigned his member- 
ship of the Commission for Intellectual Collaboration under the chair- 
manship of the philosopher Henri Bergson. The reason for this step was 
probably hardly political at all, but mainly the lack of time and his dislike 
of travelling. If I am not mistaken, it was Madame Curie who replaced 
Einstein on the committee. 



46 



22 July, 1923 



DearBorns 

Neither my bad conscience, nor even my wife's, was strong 
enough to stir my lazy flesh at last to answer your extremely 
kind letters. But your card, dear Mrs Born, has really stung me 
into action. However, the abortive twinges of a bad conscience 
are the only unpleasant emotions I have when I think of you. 
For not only have you always been so good and kind, but your 
contributions in physics, music, poetry and prose, as well as in 
cosy conviviality, have done much to enrich this curious existence 
of ours. All is well with us. 

Scientifically, I have at present a most interesting question, 
connected with the affine field theory. There are prospects 
now of understanding the earth's magnetic field and the 
electrostatic economy of the earth, and examining the concept 
experimentally. But we will have to wait for the experiment. 

Both my wife and I thank you most sincerely for your kind 
invitation. But I must stay here for a while in this overcrowded 



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BORN-EINSTEIN LETTERS 

place, where one is driven almost to distraction by visitors, 
correspondence and telephone calls. Langevin is making his 
way here for a pacifist demonstration; a splendid fellow. 
However ineffective the good and the just may be, they alone 
make life worth living. With warmest wishes for a happy 
holiday to you both, and the dear children. 
Yours 

A. Einstein 

Kindest regards from my wife, who is very busy and intends to 
write to you herself another time. Franck, who has just been 
here, told me that according to the results of measurements of 
ionised gases already made, the effect I am looking for cannot 
exist. There is to be no understanding the earth's magnetic 
field. I am sending this letter to you, to make sure that it 
arrives safely. But please write and tell your wife that we both 
think of her with affection, and not to be angry about our 
laziness. 



Institute for Theoretical Physics 
4/ of the University 

Gottingen 
Bunsenstrasse g 
25 August, 1923 
Dear Einstein 

Your kind letter gave us much pleasure. Thank you very much. 
Today I should like to askyou something (and would appreciate a 
prompt reply) : one is constantly bombarded with official communi- 
cations from the Helmholtz Society, the German Physical 
Society, etc., asking one to attend the congress of physicists 
in Bonn. If this were to be somewhere else, I would not even 
consider going. But in Bonn, because of the French occupation, 
great importance seems to be attached to receiving large num- 
bers of visitors, and Franck is of the opinion that we should go 
for the sake of good form. In my opinion it would have been 
more sensible not to hold the congress in occupied territory; for 
it is a mistake to mix up scientific meetings with politics in any 
way whatever. But now the folly has already been committed, 
and the question is only whether it is necessary to take part. 

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BORN-EINSTEIN LETTERS 

There could easily be considerable difficulties from an 
embargo on travel and so on. I myself have no desire at all 
for a high concentration of physicists, but would much rather 
live and work quietly by myself, particularly as I have only 
just returned from the North Sea. I would like you to tell me 
what you Berlin physicists are doing (particularly Planck, 
Laue, Haber, Meitner, etc.) and whether you think thisjourney 
would be desirable. Please reply straight away, as one would 
have to try and get a passport quite soon. 

My wife was in Langeoog with the children for more than five 
weeks, and I was there as well for the last three. We have all 
recovered well; the children in particular have gained strength 
and are looking very well. We bathed a lot but otherwise did 
nothing except lie on the beach and laze about. Although I was 
acclimatised, I came down with bad catarrh almost straight 
away. I had imagined that the vacations in Gottingen would be 
quiet and peaceful; but in the first three days after our return 
we have already had two foreign visitors, an Englishman from 
Oxford and Mr Grimm from Munich. But as from tomorrow I 
am going to feign death and refuse to see anyone. It is not really 
that I have anything special on. As always, I am thinking 
hopelessly about the quantum theory, trying to find a recipe for 
calculating helium and the other atoms; but I am not succeed- 
ing in this either. My Encyclopaedia article has been published 
and I will send you a copy soon. Otherwise I spend my time 
reading, going for walks, playing music and occupying myself 
with the children. I am practising systematically and have, I 
think, made some progress. Unfortunately it is very difficult 
here to get a trio or quartet together. 

In the latest issue of the Annalen, containing the nice paper by 
Gruneisen and Goens which verifies your theory of dissociation 
velocity, there is a paper by Gerold v. Gleich about the peri- 
helion of Mercury. I do not like its tone at all. Are you going to 
reply to it ? It is odd that so many people have no feeling for the 
intrinsic probability of a theory. Have you made any progress 
with your affine world ? 

Kindest regards to your wife from both of us. 
Yours 

Bom 



8i 



BORN-EINSTEIN LETTERS 






48 



29 April, 1924 



Dear Boms 

Your letter, dear Mrs Born, was really excellent. Indeed, what 
causes the sense of well-being inspired by Japanese society and 
art is that the individual is so harmoniously integrated into his 
wider environment that he derives his experiences, not from the 
self, but mainly from the community. Each of us longed for this 
when we were young, but we had to resign ourselves to its im- 
possibility. For of all the communities available to us there is 
not one I would want to devote myself to, except for the society 
of the true searchers, which has very few living members at any 
time. 

I called off my visit to Naples; I was pleased that a minor 
indisposition gave me the opportunity. I am going to Kiel for a 
while instead. Bohr's opinion about radiation is of great interest. 
But I should not want to be forced into abandoning strict 
causality without defending it more strongly than I have so 
far. I find the idea quite intolerable that an electron exposed to 
radiation should choose of its own free will, not only its moment 
to jump off, but also its direction. In that case, I would rather 
be a cobbler, or even an employee in a gaming-house, than a 
physicist. Certainly my attempts to give tangible form to the 
quanta have foundered again and again, but I am far from 
giving up hope. And even if it never works there is always that 
consolation that this lack of success is entirely mine. 
Enjoy the beauty of the sunny land, with best wishes. 
Yours 

Einstein 

The remark about the advertising agencies was quite un- 
conscious, the result of a good mood, and I had no idea that 
you were wedded to it in some way. Your pretty remark makes 
me want to stroke your head, if that is at all permissible in the 
case of a married lady. 



The letter from my wife to which Einstein replied is missing. 

The basic reason for the dispute between us on the validity of statistical 



BORN-EINSTEIN LETTERS 

laws was as follows. Einstein was firmly convinced that physics can supply 
us with knowledge of the objectively existing world. Together with many 
other physicists I have been gradually converted, as a result of experiences 
in the field of atomic quantum phenomena, to the point of view that this 
is not so. At any given moment, our knowledge of the objective world is 
only a crude approximation from which, by applying certain rules such 
as the probability laws of quantum mechanics, we can predict unknown 
(e.g. future) conditions. 



49 Gottingen 

'5 J^b>> "925 

Dear Einstein 

Your kind letter gave us much pleasure. My wife left with the 
children for Silvaplana in the Engadine the day before yesterday, 
and I expect she will write to you from there. In the meantime, 
I want to give you some of our news. 

As regards physics, first of all, your kind remarks about my 
activities spring from the kindness of your heart. I am fully 
aware, however, that what I am doing is very ordinary stuff 
compared with your ideas and Bohr's. My thinking box is very 
shaky - there is not much in it, and what there is rattles to 
and fro, has no definite form, and gets more and more compli- 
cated. Your brain, heaven knows, looks much neater; its 
products are clear, simple, and to the point. With luck, we may 
come to understand them in a few years' time. This is what 
happened in the case of your and Bose's gas degeneracy 
statistics. Fortunately, Ehrenfest turned up here and cast some 
light on it. Then I read Louis de BrogUe's paper, and gradually 
saw what they were up to. I now believe that the wave theory 
of matter could be of very great importance. Our Mr Elsasser's 
reflections are not yet in proper order. To begin with, it trans- 
pired that he had made a considerable error in his calculations, 
but I still believe that the essence of his remarks, particularly on 
the reflection of electrons, can be salvaged. I am also speculating 
a little about de Broglie's waves. It seems to me that a connection 
of a completely formal kind exists between these and that other 
mystical explanation of reflection, diffraction and interference 
using 'spatial' quantisation which Compton and Duane proposed 



82 



83 



BORN-EINSTEIN LETTERS 

and which has been more closely Studied by Epstein and Ehrenfest. 

But my principal interest is the rather mysterious differential 
calculus on which the quantum theory of atomic structure 
seems to be based. Jordan and I are systematically (though with 
the minimum of mental effort) examining every imaginable 
correspondence relationship between classical, multiple-peri- 
odic systems and quantum atoms. A paper on this subject in 
which we examine the effect of non-periodic fields on atoms 
will appear soon. This is a preliminary study for an investigation 
of the processes occurring in atomic collisions (quenching of 
fluorescence, sensitised fluorescence a la Franck, etc.); one 
can understand, I think, the essential characteristics of what 
goes on. The different behaviour of atoms depends mainly on 
whether they have an (average) dipole moment, a quadrupole 
moment, or even higher electric symmetry still. As regards 
your objections to Jordan's paper, I still feel very unsure of 
myself; but as I am now coming to grips with these things 
from my own somewhat complicated point of view, I will 
understand them one of these days. On the whole, you are 
certainly right; though Jordan's opinion is based on a somewhat 
different consideration, as he allows coherent bundles of rays, 
whereas you only mention incoherent ones. 

Even if Jordan is mistaken in this, as I now think is highly 
probable, he is still exceptionally intelligent and astute and 
can think far more swiftly and confidently than I, On the whole 
my young people, Heisenberg, Jordan and Hund, are brilliant. 
I find that merely to keep up with their thoughts demands at 
times a considerable effort on my part. Their mastery of the so- 
called 'term zoology' is marvellous. Heisenberg's latest paper, 
soon to be published, appears rather mystifying but is certainly 
true and profound; it enabled Hund to bring into order the 
whole of the periodic system with all its complicated multiplets. 
This paper, too, is soon to be published. In addition, I am busy 
calculating the lattice theory over and over again with some of 
my other, less independent, pupils. We have just finished a paper 
by BoUnow which calculates the relationship between the crys- 
taUographic axes of two crystals of the tetragonal system, rutile 
and anatase, two forms of TiOj, based on the requirement that 
the lattice should be in electrostatic equilibrium. The result is 
quite good. 

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BORN-EINSTEIN LETTERS 

I am tremendously pleased with your view that the unifi- 
cation of gravitation with electrodynamics has at long last 
been successful; the action principle you give looks so simple. 
As we have time, Jordan and I are going to try some variations 
of it. But we would be most grateful if you could send us your 
paper on this subject as soon as possible. This kind of thing 
is much deeper than our petty efforts. I would never dare 
tackle it. 

We have had many visitors again this term. Kramers was 
here for eight days, as I mentioned before, and Ehrenfest, with 
whom both of us, particularly my wife, are now on very firiendly 
terms. Last week Kapitza from Cambridge was here, and Joffe 
from Leningrad. He made a tremendous impression on us : he does 
such beautiful work, and yet has published hardly anything at 
all. Philipp Frank is now here with his wife, and many other 
people as well. For us this is very stimulating, but it is often too 
much for our wives. So they simply run away; my wife and Mrs 
Courant have already left, and Mrs Frank is due to leave in 
two days' time. But do not conclude from that that your visit 
is going to be unwelcome! We are greatly looking forward to 
it ! But it ought to be at a quieter time. In July, most of the 
foreigners are already on holiday, and they descend on us in 
droves. But you know all this business. There is going to be 
another rumpus tomorrow; it is the inauguration of Prandtl's 
new hydrodynamics institute, with guided tour, official dinner 
and gala concert. It will cost me almost an entire working day. 

But I, too, am about to escape. On July 30th I am giving a 
lecture in Tiibingen for Gerlach and Lande, and then I am 
going to join my family in the Engadine. In October I am sup- 
posed to go to Cambridge, at Kapitza's invitation; we are 
also all supposed to be going to the Russian Physicists' Congress 
in Moscow next winter; Joffe is going to pay our travelling 
expenses. As you see, we too get around, though not as far as 
Japan and the Argentine. One more thing: in today's astronomy 
colloquium, Kienle reported a beautiful new piece of work 
(from Mt Wilson, I think) ; the satellite of Sirius is one of those 
minute, mysterious dwarfs of enormous mass - a density of 
28,000 - and, according to Eddington, is a conglomeration of 
naked nuclei and electrons. The red shift (of approximately 
20 km/s) has now been determined, and is exactly proportional 



85 



BORN-EINSTEIN LETTERS 



BORN-EINSTEIN LETTERS 



to the enormous density (and small radius). But I must stop 



now. 



Kindest regards to your wife and daughters, 
Yours Bom 



This letter is the most significant so far, and (to me) the most important. 
The theory of gas degeneracy, proposed by the Indian physicist Bose, had 
immediately been taken up by Einstein and developed further in a 
momentous treatise of his. He transferred the statistical behaviour of 
radiation from a 'photon gas', whose statistical characteristics differ from 
the normal (Boltzmann distribution), to ordinary gases, which should 
then exhibit variations from normal behaviour (degeneracy) at low 
temperatures. But the most important thing about it was its connection 
with de Broglie's wave theory of matter. At Einstein's instigation I studied 
de Broglie's theory, which had been published a few years earher. By a 
strange coincidence, a letter arrived just then from the American physicist 
Davisson, who had obtained puzzUng results with the reflection of elec- 
trons from metal surfaces. The results were supported by graphs and tables. 
While I was discussing this letter with Franck, it occurred to us that the 
curious maxima of Davisson's curves could perhaps be explained by the 
diffraction of the electronic matter waves in the crystal lattice. A rough 
calculation with de BrogHe's formulae resulted in a wavelength of the 
correct order of magnitude. We handed over the development of this idea 
to our pupil Elsasser, who had done experimental work with Franck to 
begin with but who now wanted to change over to theory. In spite of the 
difficulties mentioned in this letter, Elsasser did eventually succeed. His 
paper must be acknowledged as the first confirmation of de Broglie's 
wave mechanics. 

The connection I suggested with Duane's and Compton's 'spatial quan- 
tisation' does indeed exist: de Broglie's spin quantum condition is exactiy 
the same thing, but differentiy and more intuitively expressed. While Duane 
speaks of conceptual decomposition of a radiation process into harmonic 
components, de Broglie regards these as real, material waves, which are sup- 
posed to replace the particles. Later on I showed the relationship between 
particle and waves in another way, which today is fairly generally accepted : 
the waves represent the spread of probability for the presence of particles. 
But this is not the place to pursue these matters in detail. Nor will I go 
into the 'mysterious' differential calculus here, which is the basis of the 
quantum theory of atoms." I would like to draw attention to the book by 
van der Waerden, which contains all the more important treatises on the 
origins of quantum mechanics as well as a thorough introduction to the 
relationship between them.** 

86 



I. 



I 



My praise of my young collaborators, Heisenberg, Jordan and Hund, was 
well deserved. They all rank among today's leading physicists. We used 
the expression 'term zoology' to describe the compilation of experimental 
data about spectral lines and their dissection into 'terms' which, according 
to Bohr, indicate steps of energy in the excitation of the atom. No satis- 
factory theory existed for the regularities found in this way, and they had 
to be accepted as empirical facts, rather like the distinguishing charac- 
teristics of zoological species. 

Then comes the most important matter: a few fines about Heisenberg's 
new paper, which seems to have appeared 'mystifying' but nevertheless true. 
This must have been the treatise in which he formulates the basic concepts 
of quantum mechanics and explains them by using simple examples. As 
my recollection of this time, which marked the beginning of a revolution 
in physical thinking, is a litUe hazy, I wrote to Prof van der Waerden, who 
confirmed my assumption. His book will enable the reader to look up the 
sequence of events in complete detail. I shall just mention those matters 
which have a direct bearing on Einstein's letter. 

Heisenberg gave me his manuscript on the i ith or 12th of July, asking me 
to decide whether it should be published and whether I had some use for 
it, as he was unable to get any further. Although I did not read it straight 
away, because I was tired, I had certainly read it before I wrote to Einstein 
on July 15th. The certainty with which I maintained that it was correct, 
in spite of its mystifying appearance, seems to show that I had already 
discovered that Heisenberg's extraordinary calculus was really nothing 
other than the well-known matrix calculation; moreover, I already knew 
that Heisenberg's reformulation of the conventional quantum condition 
represents the diagonal elements of the matrix equation 

pq-gp= — : 

■^^ ^-^ 2771 

and that therefore the remaining elements of the quantity pq - qp must be 
zero. If this is the case I was cautious enough not to mention any of this to 
Einstein, since the disappearance of the non-diagonal elements had first to 
be proved. Van der Waerden's book describes how he succeeded in this 
with Jordan's help, and how the paper by Heisenberg, Jordan and myself 
came into being. The paper by Hund which I mention follows another, 
slightly earlier, investigation of Heisenberg's. I have gone into these 
matters in so much detail, even though they are not directly connected 
with Einstein, because I am rather proud of the fact that I was the first to 
write a quantum mechanical formula in 'non-commuting' symbols. Two 
further scientific matters of importance are mentioned in this letter: Ein- 
stein's field theory, which was intended to unify electrodynamics and 
gravitation, and the satellite of Sirius. I think that my enthusiasm about 



87 



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BORN-EINSTEIN LETTERS 



the success of Einstein's idea was quite genuine. In those days we all 
thought that his objective, which he pursued right to the end of his life, was 
attainable and also very important. Many of us became more doubtful 
when other types of fields emerged in physics, in addition to these; the 
first was Yukawa's meson field, which is a direct generalisation of the 
electromagnetic field and describes nuclear forces, and then there were 
the fields which belong to the other elementary particles. After that we 
were incKned to regard Einstein's ceaseless efforts as a tragic error. 
A few remarks on the list of the visitors to Gottingen. Kramers was a 
Dutchman, a pupil of Bohr's, extremely gifted, and a likeable person. 
Kapitza was a Russian physicist, who had escaped to England from the 
Bolshevik revolution when he was young and had studied in Cambridge. 
He had a very successful career, working at the Cavendish Laboratory and 
becoming a Fellow of Trinity College. His visits to Gottingen took place 
during this period. Later he returned to Russia, made his peace with the 
Communists, and achieved great distinction. Joffe, older by a generation, 
had remained in Russia and was held to be the leading physicist in the 
Soviet Union. Philipp Frank was a theoretical physicist at the German 
University of Prague, and afterwards went to America. While in Prague he 
made friends with Einstein and later wrote a captivating biography of him. 
Kienle was professor of astronomy at Gottingen. The lecture I men- 
tioned concerns an astronomical observation which can be regarded as a 
confirmation of Bose and Einstein's theory of gas degeneracy. But as the 
letter does not mention this relationship, I rather think that it had not 
been clear to Kienle or to us. 



50 

7 March, igs6 

Dear Mrs Bom 

Your short letter was truly delightful. Stomach aching but head 
held high; only the strong are able to manage that. Even so, it 
must have been a splendid experience to accompany your hus- 
band on his travels, for he had a great deal to give; and to receive 
is also very pleasant, when it is balanced with the giving. The 
Heisenberg-Bom concepts leave us all breathless, and have 
made a deep impression on all theoretically oriented people. 
Instead of dull resignation, there is now a singular tension in 
us sluggish people. You experience only the psychological 
aspect of all this, but no doubt in a purer form than someone 
with a more materialistic outlook. The most important thing 

88 



at the moment is for you to make a complete recovery, so that 
you will be able to run about in the sun again and live your life 
freely. I know from experience how to get well: to exist like 
a plant for a while, and to vegetate quietly and contentedly. 
Unlike most of your sex you have not got the knack of this; I 
imagine that lively little head of yours does not want to be put out 
of action. Remember the past of Asia; then you will experience 
the comforting haziness of all living things, and get well. 
Meanwhile best wishes 
Yours 

A. Einstein 



Apart from Einstein's amiable words about my wife's illness in America 
and how to get well, this letter is remarkable for his attitude to quantum 
mechanics. Heisenberg and I felt pleased, but it was not long before the 
cooling offset in (letter No. 53). 
The following letter is from my wife again. 

During the winter of 1925-26 we were at the Massachusetts Institute of 
Technology (MIT) in Cambridge, near Boston. I gave lectures there on 
two subjects: crystal-lattice dynamics and quantum mechanics. These 
have appeared as a booklet, published by MIT in English and by Springer 
in GJerman; it is probably the first book on quantum mechanics. In this 
book I gave so much prominence to Heisenberg that my own contri- 
bution to quantum mechanics has received very little attention until 
quite recently. When my course ended at the beginning of 1 926, we wanted 
to set out on a journey across the continent, taking in the Grand Canyon in 
Arizona and ending up in California. But my wife fell ill and was sent 
back to Europe. So I had to travel by myself, and proclaimed the new 
quantum doctrine at many universities. The result was that hordes of 
Americans, and soon many other foreigners as well, visited Gkittingen 
during the next few years. My wife went back to Germany and entered 
Prof. V. Noorden's well-known sanatorium in Frankfurt to take the 'cure'. 



51 



II April, igs6 



I 



Dear Einstein 

My thanks for your kind letters are rather late, but the last 
three weeks in Frankfurt were anything but enjoyable (whole- 

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BORN-EINSTEIN LETTERS 

sale dentistry with 5 gold crowns, three extractions, two jawbone 
operations, etc.), so that I was really unable to think of anything 
but teeth. This led to an amusing incident, for one day when I 
was on my way to an extraction, quite absorbed, a gentleman 
whispered in my ear: 'dreaming of spring'. Whereupon I 
repUed drily: 'no, dentist'. And we both grinned and went our 
separate ways. 

I have just asked my friend Elli Rosenberg {nee Husserl, of 
philosophical descent) to send you copies of my American 
reports. You may be able to spare the odd hour or so one day to 
glance through them. Max, too, has now returned to this 
country; his letters from Boston and San Francisco contained 
a lot of physics. I am hoping that we may be able to make a 
short trip to Berlin about the beginning of May, and will be 
able to tell you more then. For example. Max saw Miller's 
experiments on Mt Wilson, and was aghast at the slipshod way 
they were carried out. 

My head is too tired tonight to produce even the slightest of 
thoughts. I find it rather annoying to realise that the output of 
one's brain is proportional to the increase or decrease of the 
amount of fat on one's body. As I have not yet regained any of 
the twenty or so pounds I lost, you can well imagine how short 
of ideas I am. I have never been so sure of Heaven as I am at 
present (see the Sermon on the Mount; and blessed are the 
poor inspirit . . .). 

Look after yourselves. With warm wishes 
Yours 

Hedi Born 



52 

4 December, igzG 

Dear Bom 

You will have to be a little patient. My son-in-law is certain 
to read the play, and will write to you. But the poor man has 
to economise with his strength, as his heart is in poor condition. 
I have reminded him again to give an opinion on the play as 
soon as possible. I hked the beginning of the play very much, 
and I think its impact will not be lost on him. 



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BORN-EINSTEIN LETTERS 

Quantum mechanics is certainly imposing. But an inner 
voice tells me that it is not yet the real thing. The theory says 
a lot, but does not really bring us any closer to the secret of 
the 'old one'. I, at any rate, am convinced that He is not 
playing at dice. Waves in 3-dimensional space, whose velocity 
is regulated by potential energy (for example, rubber bands) . . . 
I am working very hard at deducing the equations of motion 
of material points regarded as singularities, given the differen- 
tial equation of general relativity. 
With best wishes 
Yours 

A. Einstein 



Hedi had sent her play ^ Child of America to Einstein, asking for his opinion. 
Einstein's son-in-law, who had married the eldest of his step-daughters. 
Use, was the then well-known and respected author and critic, Rudolf 
Kayser. 

Einstein's verdict on quantum mechanics came as a hard blow to me : he 
rejected it not for any definite reason, but rather by referring to an 'inner 
voice'. This rejection plays an important part in later letters. It was based 
on a basic difference of philosophical attitude, which separated Einstein 
from the younger generation to which I felt that I belonged, although I 
was only a few years younger than Einstein. 



53 



14 December, 1926 



Dear Mr Einstein 

Today my 'Bill' arrives with his 'new nose', as you so aptly 
called it. I hope you will laugh at the three further acts as 
much as you did at the first one. I am tremendously pleased 
and encouraged to know that you enjoyed it so much. For 
one cannot gain sufficient distance from one's own creation 
oneself; one lived with it so intensely and only parts from it with 
great trepidation. 

At the moment, when I am not planning any work, I feel 
dull and without aim and purpose, and anaesthetise myself 
by attending some fine lectures on the history of art. When one 



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BORN-EINSTEIN LETTERS 

has begun even so modest a work of art, one looks at the creations 
of the masters with very different eyes. 

It would be nice if you could drop me a few lines when you 
have read Bill. Why don't you take him on to the sofa with you 
after lunch ? 

Margot wrote to tell me that your wife is ill. I wish her a 
speedy recovery, and all of you a restful Christmas. 

With kindest regards to you all from Max and myself 
Yours 

HediBom 



54 



6 January, igzy 



Dear Mrs Bom 

I have very much enjoyed reading your play, and I think it 
could be quite successful as a satire on the contemporary scene. 
It is witty and amusing throughout, though it seems to me that 
as a work of art it does not do much to confirm the well- 
documented truth that the centre of gravity for creative 
activity is located in different parts of the body in men and 
women. You make your characters dance like marionettes; 
they are nothing but puppets in your hands, whose purpose is 
to demonstrate your opinion to the child of our times; that is all. 
They are not permitted to have any lives of their own. They are 
rather transparent, like ghosts, more or less abstract. But your 
wit saves the day. Bernard Shaw has often done something 
similar, and his fireworks are enjoyed by everyone. I do not 
know whether Rudi has read it yet; the poor man lives con- 
stantly under a deluge of paper, while conditions have improved 
quite considerably in this respect where I am concerned. 

I am going to give the play to Mr Jessner, and tell him that 
I consider it witty, amusing and up-to-date, and will give 
him some idea of the contents. I hope it will make its mark. 
Kind regards to you and your husband 
Yours 

A. Einstein 



Jessner was then manager at the State Theatre in Berlin. 

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BORN-EINSTEIN LETTERS 



55 

Gbttingen, Plankst. 2 
[undated] 
Dear Mr Einstein 

Thank you very much for your criticism, which has occupied 
my mind a great deal. I have by now had all sorts of criticisms, 
frequently diametrically opposed, e.g., as to the relative value 
of the various acts, but I am, of course, particularly interested 
in a fundamental criticism such as yours. There, too, I have 
already heard quite different opinions, for example from 
Hilbert, who approved of Bill as a character. But I am by now 
sufficiently detached from this child of mine to know myself what 
is wrong with him. I expect you are right in saying that my 
characters are too cerebral. (I am not sure that this is not 
inevitable in any satire, unless one allows Mephistopheles 
himself to appear in person.) For me, the idea, when I have one, 
is the most important thing, not the human being and its fate. 
At best, an idea is closely bound up with a certain person. It is 
not that the idea has to be extracted from my brain with pincers 
and forceps; it arrives of its own accord after a particularly 
powerful emotional experience. I once wrote to Margot: If I 
had not felt such a tremendous disgust with our times (i.e. with 
what I want to attack), I would never have foimd the strength 
for creative expression. Why I experience this so overpoweringly 
I cannot say. The serious purpose which provoked the play 
may now be difficult to detect. It is one of the crazy contra- 
dictions of my nature, though probably lucky for me, that all 
tension and suffering is resolved in a smile. 

I am fully aware that satire on the contemporary scene is, by 
definition, condemned to be of temporary interest only. I still 
hope that if one day I can give shape to more timeless problems 
(which directly influence and control fate) I will find the proper 
note to sound. I hope, but I certainly have no illusions about 
myself. As you were kind enough to call me 'witty', you would 
hardly expect me to be blind to my own nature. 

There is no need to tell you that I myself am able to see, and 
really get to know, my characters in my mind's eye. I was 
'possessed' by them, for otherwise I would not have been able 
to make them speak as they should. But what interests me most 



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BORN-EINSTEIN LETTERS 

in people is their spiritual attitude to life, rather than just their 
fate; most of the so-called tragic destinies are nothing more 
than the brutal vicissitudes of life, which are linked by pure 
chance to one particular individual. When I think of you, for 
example, I do not think of individual talents and achievements, 
but I marvel at your supreme mastery of life itself. I remember 
something you once said, which for me is the key to your per- 
sonality and way of thinking: when you lay gravely ill you 
said: 'I have such a feeling of solidarity with every living 
being, that it does not matter to me where the individual begins 
and ends'. You probably put it much more beautifully, but 
this is what you meant. Individual acts mean nothing to me: 
they are just a momentary flash of light. 

Now to your droll pronouncement about creativity : 'the centre 
of gravity for creative activity is situated in different parts of 
the body in men and women.' Here the usual interpretation of 
'head' and 'heart' does not apply, as, of all things, you have 
conceded me 'wit'. And as to the still cruder, purely geometrical 
interpretation? I would not put it past you. But even in this 
case the contradiction above still applies, for wit is in the head. 
And is the effort of imagination needed for a play that grows 
from nothing, and for its dramatic composition, not really a 
creative activity? Please do not misunderstand me: I am not 
just trying to defend myself, but I cannot quite understand 
what you mean. You could not really mean that women are 
incapable of creating rounded characters. Do you know 
•Kristin Lavranstochter' by Sigrid Undset? (particularly the 
first volume). I beUeve that every creative person shows 
in his characters what is most important to him personally; 
where his own struggles lie. The passionate person over- 
emphasises passion, the ecstatic ectasy, the split personality 
the split, etc. A Shakespeare, who combines everything, is surely 

unique. 

I am most grateful to you for offering to pass the play on. 
I do hope you do not find it embarrassing. At the special request 
of the children, I enclose the result of a writing game we 
played yesterday. They are sketches which are made up as 
follows: one person draws the head, a second the trunk, a third 
the lower part of the body, and none of them knows what has 
been done by the others before him. Finally, a name is written 



94 



BORN-EINSTEIN LETTERS 

underneath at random. You are going to be very pleased with 
your portrait. 

Kind regards to you all from Max and myself, 
Yours 

HediBom 



56 



I J January, igz^ 



Dear Mrs Bom 

A few days ago I gave your manuscript to Jessner, who has 
already promised to examine it. You should not take my 
little joke too literally, nor as an 'either-or'. It is not meant too 
seriously, nor does it claim that the following assertion is 
unambiguous: one smiles, and goes on to the business of the day. 
What applies to jokes, I suppose, also applies to pictures and to 
plays. I think they should not smell of a logical scheme, but of 
a delicious fragment of life, scintillating with various colours 
according to the position of the beholder. If one wants to get 
away from this vagueness one must take up mathematics. And 
even then one reaches one's aim only by becoming completely 
insubstantial under the dissecting knife of clarity. Living 
matter and clarity are opposites - they run away from one 
another. We are now experiencing this rather tragically in 
physics. 

By the way, there is no need for you to defend your work to 
me, for I have every respect for it and enjoy it. It is rarely that 
one finds someone like you who has such a wealth of ideas 
allied with charm. 

The best of luck for your endeavour, for yourself and for 
your family. 

Yours sincerely 
A. Einstein 

Many thanks for the lovely combined photo. 



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BORN-EINSTEIN LETTERS 



57 

[undated] 

Dear Born 

I have just noticed that in my slovenliness I forgot to send you 
the enclosed paper. You v/ere therefore unable to understand 
the rest. Please forgive me. 

Last week I handed in a short paper to the Academy, in 
which I show that one can attribute quite definite movements to 
Schrodinger's wave mechanics, without any statistical inter- 
pretation. This will shortly be published in the minutes of the 
meetings. 

Kindest regards 
Yours 
A. Einstein 



These lines had been added to a letter of Ehrenfest's to Einstein. They 
concern some professional appointment, no longer of interest today. 
The note shows that Einstein rejected the statistical interpretation of 
quantum mechanics not just because of his 'inner voice'. He had tried a 
different, non-statistical interpretation of Schroedinger's wave mechamcs 
and was submitting a paper about it to the Academy. I cannot remember 
it now; Uke so many similar attempts by other authors, it has disappeared 

without trace. 

At this point there is an interval of a year and a half in the correspondence. 

Whether letters have been lost, or whether silence really reigned, I do not 

know. 



58 



Institute for Theoretical Physics 

of the University 

Gottingen 

Bunsenstr. g 

so February, igzS 



Dear Einstein 

After consultation with Harald Bohr, who is in Gottmgen 
this term, I want to write to you about a matter which is, 
strictly speaking, none of my business, but which nevertheless 
has caused me alarm and uneasiness on many occasions. I am 

96 



BORN— EINSTEIN LETTERS 

referring to the Hilbert and Brouwer affair. Up to now I have 
merely followed it from a distance, and have only recently been 
initiated into all the details by Bohr and Courant. In this way I 
learnt that you remained neutral with regard to Hilbert's letter 
to Brouwer, on the grounds that one should permit people to be 
as foolish as they wish. I find this quite reasonable, of course, but 
you seem not to be quite in the picture on some points, and so I 
want to write briefly and tell you about it. There will probably 
be a conference soon at Springer's about this matter, and Bohr 
told me that he considered it very important for the inner 
editorial staff to present a united front. I would therefore ask 
you please to maintain your present neutrality, and not to take 
any action against Hilbert and his friends. It would help to 
restore my peace of mind, as well as Bohr's and that of many 
other people, if you could write a few words to me about this. 

I would like to tell you briefly why this business interests me. 
It only matters to me because I am worried and concerned 
about Hilbert. Hilbert is very seriously ill, and has probably 
not very long to live. Any excitement is dangerous for him, and 
means losing some of the few hours left to him in which to live 
and to work. He still has, however, a powerful will to live, and 
considers it his duty to complete his new basis for mathematics 
with whatever strength is left to him. His mind is clearer than 
ever, and it is an act of extreme callousness on Brouwer's part 
to spread the rumour that Hilbert is no longer responsible. 
Courant and other friends of Hilbert's have frequently said 
that the sick man should be protected against any excitement, 
and Brouwer has misrepresented this to mean that one should 
no longer take Hilbert's actions and opinions seriously. Hilbert 
is quite in earnest about his proposed action against Brouwer. 
He talked to me about it a few weeks ago, but only in quite 
general terms and without going into any detail. In his opinion 
Brouwer is an eccentric and maladjusted person to whom he 
did not wish to entrust the management of Mathematische 
Annalen. I think Hilbert's evaluation of Brouwer has been shown 
to be correct in view of Brouwer's most recent actions. In my 
experience, Hilbert's judgment is almost always clear and to 
the point in human affairs. 

I have followed the previous history of the whole business, 
including the quarrel about the visit to the Congress in Bologna, 



97 



BORN-EINSTEIN LETTERS 



from a distance only. But I do know that the visit to this 
Congress was a heavy burden for Hilbert; anything of this kind 
meant a tremendous exertion for him because of his illness. 
Hilbert is not politically very left-wing; on the contrary, for my 
taste and even more for yours, he is rather reactionaiy. But 
when it comes to the question of the intercourse between 
scientists of different countries, he has a very sharp eye for 
detecting what is best for the whole. Hilbert considered, as wc 
all did, that Brouwer's behaviour in this affair, where he was 
even more nationalistic than the Germans themselves, was 
utterly foolish. 

But the worst of it all was that the Berlin mathematicians 
were completely taken in by Brouwer's nonsense. I would like 
to add that the Bologna business was not the decisive factor - 
only the occasion for Hilbert's decision to remove Brouwer. I 
can understand this in Erhard Schmidt's case, for he always 
did lean to the right in politics, as a result of his basic emotions. 
For Mises and Bieberbach, however, it is a rather deplorable 
symptom. I talked to Mises about it in August, during our 
journey to Russia, and he said right at the beginning of our 
discussion that the people in Gottingen were blindly following 
Hilbert, and that he was probably no longer responsible. 

Thus the allegation about Hilbert's weakened mental powers 
was made even then. I then immediately broke off my discussion 
with Mises, for I do not consider him significant enough to 
allow himself the liberty of passing judgment on Hilbert. I 
also enclose a paper which Ferdinand Springer sent to Bohr 
and Courant. This shows that Brouwer and Bieberbach have 
threatened to denounce Springer as lacking in national feeling, 
and that they would do him harm if he remained loyal to 
Hilbert. I need not tell you what I think of such behaviour. 
Forgive me for bothering you with so long a letter. My only 
desire is to see that Hilbert's earnest intentions are put into 
effect without causing him any unnecessary excitement. I 
would have no objection to your showing this letter, or part of it, 
to Schmidt, if you consider it correct. As an old friend of 
Schmidt's I believe that it is possible to negotiate successfully 
with him even if he is of a different opinion. I hope that you 
yourself are feeling much better now. I get news of you from 
time to time in Margot's letters to my wife. Those two are very 

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BORN-EINSTEIN LETTERS 

close friends indeed, and suit each other. I myself am busy 
completing a book on quantum mechanics, which I have been 
writing for the last year. Unfortunately I have overtaxed my 
strength a little in doing this, and will probably have to go on 
leave for a time during January. It is really not at all easy to 
find the time and strength for that kind of work, on top of all 
the lectures and other professional duties. 

With kindest regards, also from my wife to yours 
Yours 

Max Bom 



Harald Bohr, a brother of the physicist Niels Bohr, was a notable mathe- 
matician who frequently visited us in Gottingen. 

David Hilbert, my revered teacher and friend, was then (and still is) 
considered to be the foremost mathematician of his time. At that time he 
was busy trying to find sounder logical foundations for mathematics, in 
order to eliminate the intrinsic contradictions found by Bertrand Russell 
and others in the theory of infinite sets, without sacrificing any previous 
mathematical knowledge. This led him to consider true mathematics as 
a kind of logical game with symbols, for which arbitrary axioms are found. 
The latter, however, should be applied by a 'metamathematics' based on 
evident, real conclusions. Brouwer rejected this concept of mathematics, 
and suggested another, termed intuitionism. The two ways of thinking 
differed in one essential result. Hilbert's concept justified the so-called 
existence proofs, whereby the existence of a certain number or a mathe- 
matical truth is deduced from the fact that to assume the contrary would 
lead to a contradiction. Brouwer, however, postulated that the existence of 
a mathematical structure could only be taken for granted if a method 
could be found that would actually construct it. As it happened, many of 
Hilbert's greatest mathematical achievements were precisely such abstract 
proofs of existence, which for some time had not only been accepted by 
the mathematical world, but had been celebrated as great feats. 
It is therefore no wonder that Brouwer's behaviour greatly upset Hilbert, 
and that he expressed his opposition in no uncertain terms; whereupon 
Brouwer replied with even greater rudeness. To make matters worse, a 
political quarrel broke out on top of the scientific one. After the 1914-18 
war, 'International Unions' had been founded for all the principal 
branches of science; the Germans, however, had been excluded from 
them. The hatred directed against Germany gradually diminished, and 
at the time this letter was written (1928) the German mathematicians 
were about to be admitted to the 'International Union for Mathematics', 



99 



BORN-EINSTEIN LETTERS 

on the occasion of a large mathematical congress in Bologna. But a group 
of 'national' German mathematicians protested against this; they felt 
that it would not be right to join the Union without further ado after 
having been excluded for such a long time, and that one should protest 
against it in Bologna. Three important BerUn mathematicians were 
amongst the leaders of this movement: Bieberbach, who was a good 
analyst; von Mises, a research worker of some significance, who was also 
concerned with theoretical physics; and Erhard Schmidt, the most 
outstanding of the three. Schmidt and I had been friends ever since my 
student days and, although poUtically we were poles apart, we always 
remained on the best of terms. But the Dutchman Brouwer was more 
nationalistic than aU these proved to be. Hilbert went to Bologna, despite 
his grave illness, and faced his adversaries. As far as I can remember, he 
got his way and the Germans joined the Union. But the whole business 
had annoyed him so much that he expelled Brouwer from the management 
of the Mathematische Annalen.This started a new storm amongst German 
mathematicians. But Hilbert finally got the upper hand. 
The whole affair was, strictly speaking, no concern of mine. But, as I said 
in the letter, I was moved to intervene by my anxiety about the state of 
Hilbert's health. Hilbert suffered from pernicious anaemia, and would 
no doubt have died within a short time had not Minot in the United 
States discovered the specific remedy, a Uver extract, just in time. This 
was not yet commercially available, but the wife of the Gottingen 
mathematician Edmund Landau was a daughter of Paul Ehrlich, the 
founder of chemotherapy and discoverer of Salvarsan. It was due to his 
good offices that Hilbert was able to receive regular supplies of the 
extract and so to live for many more years. 

I doubt whether my letter to Einstein had any influence on the course 
of the great mathematical quarrel. 

As for the further development of the fundamental problems of mathe- 
matics, Brouwer had many supporters to begin with, including some 
important ones such as Hermann Weyl. But gradually Hilbert's abstract 
interpretation was, after aU, reaUsed to be by far the more profound. 
Things took a new turn when Godel discovered the existence of mathe- 
matical theorems which can be proved to be incapable of proof. Today, 
mathematics is more abstract than ever, and exacdy the same is true of 
theoretical physics. , . . , 

The journey to Russia I mention was a kind of wandering physicists 
congress, organised in Leningrad by Joffe, who has been mentioned 
before. It began in Leningrad, and was continued first in Moscow and 
then in Nizhni-Novgorod; there the participants boarded a Volga steamer 
and travelled down river, stopping at all the large towns en route to con- 
tinue the congress. The whole thing was very fascinating and stimulating. 



100 



BORN-EINSTEIN LETTERS 



but extremely fatiguing. I went as far as Saratov, and from there returned 
to Germany by train. 

The book about quantum mechanics I mentioned at the end of the letter 
was written in collaboration with Jordan over a period of several years. 



59 



Gottingen 
12 August, igsg 



Dear Einstein 

A young Russian turned up here some time ago with a six- 
dimensional theory of relativity. Since I was already uneasy 
about the various five-dimensional theories, and as I was 
not at all convinced that it could lead to anything worthwhile, 
I was very sceptical. But he talked very intelligently and soon 
convinced me that there is something to his ideas. 
Although I understand less than e of this matter, I have sub- 
mitted his paper to the Academy of Gottingen, and enclose a 
copy of it and urgently request you to read it and evaluate it. 
The man, whose name is Rumer, left Russia because relati- 
vists are badly treated there (truly!). The theory of relativity is 
thought to contradict the official 'materialist' philosophy and, 
as I have already been told by Joffe, its adherents are persecuted. 
Rumer came to Germany, and has somehow managed to study 
at the technical school in Oldenburg, where he is now going 
to sit for the technical exam. Afterwards he intends to try and 
make a living here as best he can, and if he fails, to emigrate to 
South America. 

If the paper makes a good impression on you, I would ask 
you please to do something for this man. He is familiar with the 
literature of mathematics, from Riemann's geometry right up 
to the very latest publications, and may well be the ideal assistant 
for you. He has a pleasant personality, and gives the impression 
of being extremely intelligent. I do not know whether he is 
really Russian, or Jewish; but I think the latter the more 
likely. His address is: Georg Rumer, Oldenburg, Am Festungs- 
graben 8. 

I am still not feeling particularly well. I spent eight days in 
Waldeck with my children, but it was noisy and restless. My 



lOI 



BORN-EINSTEIN LETTERS 

nerves are in a bad state. Next week I travel alone to the 
Vierwaldstatter See, where an acquaintance (a Swiss solicitor) 
has a cottage and a motorboat in Kehrsiten-Burgenstock 
(my address there is : Hotel Schiller) . I saw your picture in the 
last issue of the Illustrierte in a sailing boat, looking sunburnt. 
Hedi is suflfering from colitis, and is undergoing a strict dietary 
cure. 

With kindest regards, also to you wife and to Margot. 
Yours 

Max Born 

I enclose an outline of the contents of a book Rumer intends to 
write. 



I continued to find Rumer's six-dimensional theory of relativity alarming. 
Later on we wrote a short paper together on nuclei; its purely speculative 
nature was more representative of his mentality than of mine. 
The hostile attitude of official Communist philosophy towards the theory 
of relativity continued for a long time. Perhaps Rumer's fate was connected 
with this. When I flew to Moscow as a member of the English delegation 
to the 25th Jubilee celebrations of the Soviet Academy in June 1945, soon 
after the end of the war, and enquired after Rumer, it was hinted that he 
was in disgrace and had disappeared. I heard nothing from him until 
he sent me congratulations on my 75th birthday, from Novosibirsk. 
I wrote asking what had happened to him, and he replied with a long 
letter saying that he had been deported and had lived for many years 
in one of the terrible camps near the Arctic Ocean. He had managed to 
survive only because of the help of a kindly nurse, who was now his 
wife. After the death of Stalin he received a telegram, which not only 
gave him back his freedom but also recalled him to Moscow, where he 
was appointed head of the Institute of Physics at the new scientific 
centre in Novosibirsk. He is now one of the most important men in 
Soviet science. 

The strange thing is that his long period of suffering in northern Siberia had 
aroused no bitterness, no hostility towards the regime. On the contrary, 
he wrote me long letters in which he tried to convince me that the Soviet 
system is superior to Western institutions, not only politically and econo- 
mically, but also morally. 



102 



BORN-EINSTEIN LETTERS 



60 



Institute for Theoretical Physics 

Gottingen 

Bunsenstr. g 

13 January, igsg 



Dear Einstein 

The upheavals of the beginning of the university term have 
prevented me from answering your good long letter until 
now. I also wanted to discuss your remarks with Jordan and 
he has only recently arrived here. We are very grateful to 
you for your criticism, and have altered the relevant passage in 
our book accordingly. You are, of course, absolutely right that 
an assertion about the possible future acceptance or rejection 
of determinism cannot be logically justified. For there can 
always be an interpretation which lies one layer deeper than 
the one we know (as your example of the kinetic theory as 
against the macroscopic theory shows). Jordan and I are not 
much inclined to beUeve in anything like that, but of course we 
should not claim anything for which we have no rigorous proof, 
and therefore we have altered the passage in question ac- 
cordingly. . . 

I am now reading the theory of relativity, not only because 1 
have to teach it to my students, but also to feel at home again 
in this field. I hope to progress as far as your most recent papers, 
and will then study them carefully and let you know my opinion. 

Rumer is staying here in Gottingen. He has obtained a grant 
from Warburg in Hamburg, which enables him to study here 
a little longer. 

My wife is now quite well again; but she would very much 
like Margot to come here for a visit. I would like to enter into 
a conspiracy with you. Hedi's birthday is on December 14th, 
and I wonder if it would be possible for Margot to pay us a 
surprise visit on that day ? That would give us a lot of pleasure. 

With kindest regards to your wife and to Margot. 
Yours 

Max Bom 



The letter in which Einstein criticises a passage in our book seems 
unfortunately to have been lost. But the gist of his remarks is clear from 



103 



BORN-EINSTEIN LETTERS 

my letter. At this point I would like to say a few words about that book. 
Shortly before the discovery of quantum mechanics, I had published a 
book in collaboration with Friedrich Hund (then my assistant) . ** This book 
was still based on the Bohr-Sommerfeld theory, which grafts 'quantum 
conditions' on to the classical laws of mechanics; it has recently been 
re-issued in America in an English version by Fisher and Hartree. In the 
introduction it says: 'I have called this book Volume One; the second 
volume is to contain a closer approximation to the "ultimate" atomic 
mechanics. I realise that it is rash to promise such a second volume, as 
for the time being there are only a few vague indications as to the nature of 
the changes which must be made to the classical laws in order to explain 
the properties of the atoms.' But before the end of that same year, papers 
by Heisenberg, Jordan and myself were published, laying the foundations 
for the new mechanics. Thus I was soon able, with Jordan's assistance, 
to tackle the writing of the promised second volume. In the introduction to 
this volume it says : 'My hope that the veil then still obscuring the essential 
structure of the atomic laws would soon fall h£is been realised with sur- 
prising speed and thoroughness'. It took several years to write the second 
volume. In the meantime, Schroedinger's wave mechanics appeared, 
and won the approbation of theoretical physicists to such an extent that 
our own matrix method was completely pushed into the background, 
particularly after Schroedinger himself had shown the mathematical 
equivalence of wave and matrix mechanics. 

Jordan and I, however, were convinced that our method was the better 
one, and that Schroedinger's wave equation was preferred because it 
took as its point of departure traditional ideas of mathematical physics 
(eigenvalue problems of oscillating systems). Schroedinger himself even 
claimed, and maintained throughout his lifetime, to have eliminated 
quantum theoretical peculiarities such as quantum jumps by his theory. In 
our opinion Heisenberg's method was more deeply penetrating. Wave equa- 
tions in more than three dimensions are no 'return to classical concepts'. It 
is true that I had supported my statistical interpretation of quantum 
mechanics (1926) by the argument, inter alia, diat I considered the 
collision of particles with other particles as a scattering of waves. But this 
was only a simple borderline case, where the three-dimensional, intuitive 
description could be used. Jordan and I regarded quantum mechanics, 
as developed by us in Gottingen and independently by Dirac in Cam- 
bridge, as the implementation of Bohr's correspondence principle; that 
is why our book is dedicated to Niels Bohr. We planned a third volume 
which was to put wave mechanics into its rightful place, but we did not 
get that far. The completion of the second volume took much longer than 
we had expected, and then our ways parted. Because of the general 
predisposition in favour of Schroedinger, our second volume was not 



104 



BORN-EINSTEIN LETTERS 

favourably received. I recall in particular a review published by Pauli, 
which was utterly destructive. 

Now the situation seems to be changing. At the conference of Nobel 
prizewinners for physics in Lindau in the summer of 1965, Dirac said in 
a lecture that he believed the reason for the great difficulties with the 
quantum field theory, which were leading to almost grotesque tricks such 
as infinite renormalisation, to he partly in the fact that Schroedinger's 
ideas, and not those of Heisenberg, were used as a starting point. He went 
so far as to say, 'For the purpose of setting up quantum electro-dynamics, 
Schroedinger's is a bad theory, Heisenberg's a good one.' I believe that 
Dirac is right, and that the preference for Schroedinger is based only on 
the fact that he works with familiar thought processes. Our old book may 
thus enjoy a renaissance. Almost all the textbooks published in the 
meantime deal principally with wave mechanics. 

After this digression into physics, I return to Einstein's letter. Jordan 
and I had apparently sent him the proofs of our book, possibly in the hope 
of changing his negative attitude towards quantum mechanics. But it did 
not succeed. He particularly objected to a passage in the book (presumably 
in the introduction) in which we called the statistical interpretation of 
physics the final one. We gave in to his request to alter this passage, 
although we did not change our opinion. Today this view is probably 
shared by the vast majority of physicists. 



61 



14 December, igsg 



Dear Bom 

Your lucid letter gave me much pleasure. The complete 
person is revealed by both important and unimportant actions. 

I liked Rumer very much. His idea of using a multidimen- 
sional treatment is original, and formally well developed. Its 
weakness lies in the fact that the known laws are incomplete, 
and there seems no logical way of completing them. 

In any case, it would be gratifying if one could make it 
possible for him to do scientific work, and this could, of course, 
best be done by giving him some routine job which would leave 
him enough spare time for independent work. Unfortunately, 
such opportunities do not exist. Would it really be impossible 
to create grammar school teaching posts or similar official 
appointments for this kind of case, with a reduced number of 



105 



BORN-EINSTEIN LETTERS 

teaching hours and pay? This would be definitely more 
satisfactory than grants for a limited period, for the stork is 
Bohemian when it comes to intellectual births, and refuses to 
accept a fixed delivery date. 
Kind regards, 
Yours 

[no signature] 



62 



Institute for Theoretical Physics 

Gdttingen 

Bunsenstrasse g 

ig December^ igsg 



Dear Einstein 

I am very pleased that you want to take Rumer under your 
wing. The idea of giving him some sort of routine job which 
would leave him enough spare time for his scientific work is, 
of course, good in theory but extremely difficult to implement 
in practice. The establishment of grammar school teaching 
posts with reduced hours of teaching and lower pay is desirable, 
but would of course be very difficult to achieve, and then 
probably only after years of preparatory work. My own 
relations with the Ministry are far too tenuous for me to be able to 
effect anything in this direction. But perhaps your influence would 
be successful. This seems to me a practical problem where you 
could well use the full weight of your name to benefit young 
people. Would it be possible for you to make an appointment 
with Richter, the permanent head of the ministerial department, 
and put the case to him ? 

But such wild hopes as these will not help Rumer at this 
moment. Incidentally, he has completed a technical training 
course at the Technical School in Oldenburg, and passed his 
finals there. He could therefore look for a job in practice, but 
while there is so much unemployment a foreigner has practically 
no chance of finding a job in Germany. In my opinion we can 
do nothing else now but get him a grant, for at least one year. 
My wife told me that you and Ehrenfest had offered to do 
this, and to obtain it from the Rockefeller Foundation. I do 
not want to approach them under any circumstances just now, 

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BORN-EINSTEIN LETTERS 

as they have treated me rather badly. Tisdale was here last 
spring, and when he saw how badly my nerves were playing me 
up he suggested that he would have me sent to California for 
a few months, at the expense of the Rockefeller Foundation. At 
the time I declined his offer because I hoped to recover suffi- 
ciently during the holidays. But when I was not very much 
better after the long vacation, I wrote to Tisdale again and 
reminded him of his proposal. Thereupon he refused rather 
brusquely to support my application at Head Office. I can 
really only think of one explanation for this, and that is that 
the Rockefeller people have something against Gottingen. 
Maybe something I don't know about happened when the 
Mathematical Institute was being established. Therefore I 
should not like to put a proposal to him just at the moment. 

Please, therefore, be kind enough to write to Tisdale (The 
Rockefeller Foundation, 20 rue de la Baume, Paris), and apply 
for a grant for Rumer for a year's stay with you, or with me 
perhaps, or someone else, and please add that Ehrenfest and I 
would wholeheartedly support it. But I will not conceal the 
difficulties from you: generally the Rockefeller people strictly 
obey the rule to hand out stipends only to those who can prove 
that they have a definite salaried position in their own country. 
This does not apply in Rumer's case. But it is just possible that 
your name may be enough to have an exception made in this 

case. 

Laue has sent me an attractive invitation to lecture to the 
Physical Society [Physikalische Gesellschaft] in Beriin in January. 
I accepted with pleasure, as I have not seen any of you for such 
a very long time. I'm afraid I have no very special news for you 
as regards physics. 

Hedi sends her best wishes to you all, and particularly to 

Margot. 

Yours 

Max Born 



Einstein expressed over and over again the thought that one should not 
couple the quest for knowledge with a bread-and-butter profession, but 
that research should be done as a private spare-time occupation. He 
himself wrote the first of his great treatises while earning his Uving as an 



107 



BORN-EINSTEIN LETTERS 

employee of the Swiss Patent Office in Berne. He believed that only in 
this way could one preserve one's independence. His proposal to create a 
part-time grammar school teaching post for Rumer was in accordance 
with this. What he did not consider, however, was the organisational rigidity 
of almost all professions, and the importance which individual members 
of a profession attach to their work. No professional pride could develop 
without it. To be able successfully to practice science as a hobby, one has 
to be an Einstein. 



63 



Pasadena 
5 February, igji 



For the last five weeks we have been loafing in this paradise 
without, however, forgetting our friends. 
Kind regards 
Yours 

A.E. 



64 



Gottingen 

Wilhelm Weberstrasse 4s 

22 February, zgji 



Dear Einstein 

When Hedi saw your entry into California on film, she thought 
of you as completely caught up in the hectic turmoil of American 
life. We were all the more pleased to receive your card, which 
arrived today. It is nice to feel that you think of us from time 
to time. I expect you are brooding on cosmology, expansion of 
the universe, and similar matters. We were lectured on these 
questions in the astronomy seminar, where Weyl intervened 
with explanatory comments. Weyl is altogether a most valuable 
addition to our circle. He often attends the physics colloquium, 
regularly visits my theoretical seminar, frequently takes part 
in the discussion, and everything he has to say is, as a rule, 
tremendously lively, intelligent and ingenious. My young 
people have learned a great deal from him, but then the seminar 
has inspired him to write two short papers about the application 

108 



BORN-EINSTEIN LETTERS 

of group theory to molecules and valencies for the Gottinger 
J^achrichten. Our personal relationship with the Weyls is also very 
pleasant, as both of them have a variety of literary interests, 
and this brings them into contact with Hedi. 

I am glad that the term will soon be at an end, for I have 
been working extremely hard. I worry about quantum electro- 
dynamics; I feel I have made a promising start, but it is 
abominably difficult. The problem is to eliminate the infinite 
self energy of the electron and everything connected with it. In 
addition I have been writing up my optics lectures, which I 
want to publish some day in order to earn some money. Apart 
from that, there is little to report from Gottingen. Occasionally 
we go to the cinema to see how beautiful it is elsewhere, and 
your card with the orange trees has reawakened our longing 
for faraway places. A few years ago, in Como, I think, Millikan 
asked me if I would like to go to Pasadena for six months. At 
that time I replied that I did not want to be separated from my 
children for such a long time when they were so young. Now the 
girls are almost grown-up, and we could get away easily in a 
few years' time. Could you please ask Millikan, when the 
opportunity arises, whether he could perhaps use me in eighteen 
months' or two years' time? I could not do it earlier than that 
for other reasons; from next October I have to be Dean for 
a year. For all of ten years I have shirked this office by my 
partly genuine, partly feigned blockheadedness in official 
business matters, but it will not do any longer. Well, I hope to 
get through this year, too. My collaborator Rumer, on whose 
behalf I once wrote to you, will now be able to remain with me 
for another year as my assistant. Heitler is going to America 
this summer to Columbus, Ohio, and Rumer is going to replace 
him. I have scrounged some money for the winter. 

At Christmas I spent twelve days in Switzerland as the guest 
of an industrialist friend of mine, and visted Zurich on the way 
back. I gave a lecture there at the invitation of the student body, 
and afterwards, when we continued our session in a local pub, I 
met your son. I liked him very much; he is a fine, intelligent 
fellow and laughs in exactly the same wonderful way as you do. 
Well, what else is there to tell you? Things in Europe do not 
look pleasant, either politically or economically. We also have 
personal worries, like so many other people about 'displaced' 



109 



BORN-EINSTEIN LETTERS 

relatives. But things must surely improve in spite of Hitler and 
his consorts. I know all sorts of things about California, as I am 
just reading Ehrenfest's wonderfully vivid, descriptive letters 
about his travels which he has sent to Hedi. How well that 
fellow observes and describes his experiences. While reading I 
can quite clearly see the Californian landscape in front of me, 
as well as the dear people there; particularly the Tolmans, 
Epstein and the Millikans. Please give them all my warmest 
regards. I expect Hedi will want to add a few words of her own. 
This letter is meant to be a birthday greeting, so will have to 
reach you at approximately the right time. 

Best wishes to your wife. From Margot, the young wife, we 
hear little. 

Yours 

Max Bom 

Dear Einsteins 

I just want to add my loyal good wishes. Keep well, both of you. 
I am always very amused to see and hear you in the weekly 
newsreel - being presented with a floral float containing lovely 
sea-nymphs in San Diego, and that sort of thing. The world 
has, after all, its amusing side. However crazy such things may 
look from the outside, I always have the feeding that the dear 
Lord knows very well what he is up to. In the same way as 
Gretchen sensed the Devil in Faust, so he makes people sense in 
you - well, just the Einstein. For none of them will ever be 
able to really know you - however thoroughly they may have 
studied the theory of relativity. 

God bless you all. Our little Margot remains silent - silent - 
silent. 

In warmest friendship. 
Yours 

Hedi Bom 

I do envy you the orange trees and the blue skies. 



The allusion to cosmology and expansion of the universe refers to the 
discovery by the American astronomer Hubble, which created a sensation 
in those days. He showed that the more distant star systems, called 



1X0 



BORN-EINSTEIN LETTERS 

galaxies, which all resemble our own Milky Way, are moving apart with a 
velocity which is greater the further away they already are. It was as a 
result of this discovery that the renewed interest in cosmology initiated 
by Einstein's theory of relativity, gained further momentum. 
Hermann Weyl, who had been a student and private lecturer in Gdttingen 
at the same time as I was, became Hilbert's successor. Weyl was one of the 
last of the great mathematicians to concern himself with theoretical physics 
and astronomy. He made important contributions to both. When Hitler 
came to power he went to Princeton, to the 'Institute for Advanced 
Study', where Einstein too had gone. 

The year I was Dean was one of the worst of my academic life. The 
German Cabinet, under Chancellor Briining, was forced to take extreme 
economic measures as a result of the crisis in Europe caused by the collapse 
of the American financial system. An order thus went out to the univer- 
sities to dismiss immediately a large proportion of the younger assistants and 
other paid staff. Many members of our scientific faculty found this shocking : 
firstly, because it was cruel to single out the young, struggling ones, many 
of whom were married, for dismissal, and to deprive them of their already 
meagre incomes; furthermore, it would paralyse the activities of the 
institutes, practically bringing them to a standstill. We formed a com- 
mittee and decided to propose to the faculty that we would pay most of 
the people affected out of our own pockets by offering to make a volun- 
tary contribution which amounted to less than lo per cent of our salaries. 
The battles this caused within the faculty still make me shudder. In the 
course of an interminable meeting we won with a considerable majority. 
But those who were outvoted displayed an animosity we had never 
before experienced; amongst them were some historians, but most of them 
were agriculturalists and forestry people. Six months later we knew what 
they really were : disguised Nazis, who considered solicitude for the indi- 
vidual just as superfluous as the existence of scientific institutes. The 
only bright spot occurred when I personally told the Curator of the 
University, Geheimrat Valentiner, the faculty's decision. He was so 
moved that tears came to his eyes; he said something Uke, 'if all corporate 
bodies acted as unselfishly as your faculty, our country would soon be 
rid of its problems.' 

Walter Heitler was my assistant for many years, together with Lothar 
Nordheim. While the latter went to America (California) during the Hitler 
period, Heitler first went to England, and later became Professor at the 
Institute for Advanced Studies in Dublin. He eventually became pro- 
fessor in Zurich as a result of his significant work with F. London on the 
quantum theory of chemical components and on cosmic radiation, as well 
as his splendid book about the quantum theory of radiation. 
The industrialist friend mentioned in the letter was Carl Still, from 



III 



BORN-EINSTEIN LETTERS 

Recklinghausen, whom I mentioned before (commentary to letter No. 30). 
As regards my optimism about the political situation, this letter must 
have been written during one of my momentary spells of hopefulness. 
But I remember very well that I was just as prone to moments of complete 
despair. The poor condition of my nerves, frequently mentioned in these 
letters, was due not only to overwork but also to other worries, mainly 
political ones. At the beginning of the year 1929, I think, I was sent to a 
sanatoriimi at Constance on Lake Constance; there I was kept in bed 
at first, but was later allowed to sit in the lounge and talk to people. But 
the conversation of the patients, who were manufacturers, doctors, 
lawyers, or at any rate all people from the upper middle classes, was 
almost wholly about Hider and the high hopes they had of him, inter- 
spersed with virulent attacks on the Jews. This drove me back to my room 
again. I was only able to recover completely when I escaped from the 
sanatorium and went to Konigsfeld in the Black Forest. During lone 
treks on skis I got the better of my worries, and towards the end of my 
stay I got to know Albert Schweitzer. While walking past a church I 
heard wonderful organ music, and went inside. There at the organ I 
found Dr Schweitzer, well-known to me from photographs. I spoke to 
him during an interval in his playing. In the course of several long walks 
he told me about his life and his work in Lambarene. This helped me to 
recover my equilibrium. The political optimism displayed in my letter 
may well have been connected with this. The American friends mentioned 
in connection with Ehrenfest's letters from the United States are all high- 
ranking physicists : Tolman, who was mainly known for his work on the 
theory of relativity and cosmology; Epstein, through his contributions to 
Bohr's theory of atomic structure; Millikan, for his final confirmation of 
the corpuscular structure of electricity and his exact measurement of the 
charge of the electron. 



65 



Institute for Theoretical Physics 

Gottingen 

Bunsenstr. g 

6 October, 1Q31 



Dear Einstein 

By the same post I am sending you a new paper by Rumer, 
which shows, it seems to me, real progress in the direction he 
has pursued for many years. I am well aware that you are 
occupied with an entirely different range of ideas, but perhaps 
you will find time to have a look at Rumer's paper. I think his 



112 






BORN-EINSTEIN LETTERS 

Statement is quite correct; the assumption of a Riemann space 
leads inevitably to certain assumptions about the matter 
tensor and fairly necessarily to a curious new kind of field 
theory of matter. The question is, should one continue in this 
direction and elaborate this field theory, or should one - as you 
are trying to do - change over to a wholly new geometry ? I have 
no opinion on this. However, I think that every avenue should 
be explored. 

With kind regards, also from my wife. 
Yours 

M.Bom 



There are about eighteen months between this letter and the next, during 
which time so much happened that scientific matters receded into the 
background. Several elections for the Reichstag were held, which increa- 
sed the number of Nazi delegates, and Hitler's power grew accordingly. 
His brown hordes terrorised the country. Then came Hitler's seizure of 
power. And one day (at the end of April, 1933), I found my name in the 
paper amongst a list of those who were considered imsuitable to be civil 
servants, according to the new 'Laws'. Franck was not amongst them; as 
a front-line warrior during the first world war he was excused for the time 
being. 

Einstein was in the United States during this period. He returned to 
Europe in the spring of 1933, but went to Belgium and England and not 
to Germany, where his life could have been in danger. 
After I had been given 'leave of absence', we decided to leave Germany at 
once. We had rented an apartment for the summer vacation in Wolken- 
stein in the Grodner valley (Selva, Val Gardena in Italian), from a farmer 
by the name of Peratoner. He was willing to take us immediately. Thus 
we left for the South Tyrol at the beginning of May (1933) ; we took our 
twelve-year old son, Gustav, with us, but left our adolescent daughters 
behind at their German schools. From Selva I apparently wrote to 
Einstein via Ehrenfest in Holland, and this is his reply: 



66 Oxford 

30 May, 1933 
Dear Bom 

Ehrenfest sent me your letter. I am glad that you have resigned 
your positions (you and Franck). Thank God there is no risk 



"3 



BORN-EINSTEIN LETTERS 

involved for either of you. But my heart aches at the thought of 
the young ones. Lindemann has gone to Gottingen and Berlin 
(for one week). Maybe you could write to him here about 
Teller. I heard that the establishment of a good Institute of 
Physics in Palestine (Jerusalem) is at present being considered. 
There has been a nasty mess there up to now, complete char- 
latanism. But if I get the impression that this business could be 
taken seriously, I shall write to you at once with further details. 
For it would be splendid if something good were to be created 
there; it could develop into an institute of international renown. 
But for the time being I have not much faith in it. 

Two years ago I tried to appeal to Rockefeller's conscience 
about the absurd method of allocating grants, unfortunately 
without success. Bohr has now gone to see him, in an attempt 
to persuade him to take some action on behalf of the exiled 
German scientists. It is to be hoped that he'll achieve something. 
Lindemann has considered London and Heitler for Oxford. 
He has set up an organisation of his own for this purpose, taking 
in all the English universities. I am firmly convinced that all 
those who have made a name already will be taken care of. 
But the others, the young ones, will not have the chance to 
develop. 

You know, I think, that I have never had a particularly 
favourable opinion of the Germans (morally and politically 
speaking). But I must confess that the degree of their brutality 
and cowardice came as something of a surprise to me. 

I originally intended to create a university for exiles. But it 
soon became apparent that there were insurmountable obstacles, 
and that any efforts in this direction would impede the exertions 
of individual countries. 

I do hope I shall soon be able to write to you with more 
concrete news. Meanwhile I wish you and your family a peace- 
ful time in the mountains. 
Yours 

Einstein 



I've been promoted to an 'evil monster' in Germany, and all 
my money has been taken away from me. But I console myself 
with the thought that the latter would soon be gone anyway. 



114 



BORN-EINSTEIN LETTERS 

Lindemann, a thorough-going Englishman despite his Grerman name, 
was well known to me, almost a friend, since my days as a lecturer. He 
studied with Nernst in Berlin, and often came to Gottingen. His work was 
so good that he rose quickly: Fellow of Christ Church College, Oxford, 
Professor of Experimental Philosophy and Head of the Clarendon Labora- 
tory. In the second world war he was Churchill's most influential scientific 
adviser. It was his idea to break the fighting spirit of the German people by 
air attacks on the centres of the large cities. In 1933 he came to Germany 
to get the dismissed German scholars for England. He was especially keen 
on promoting physics in Oxford. Oxford was traditionally given over to 
the humanities, while at Cambridge, Newton's university, the sciences 
blossomed. And so Lindemann travelled all over Germany trying to 
obtain physicists of note for Oxford. In July he even came to Selva 
(Gardena) to negotiate with me. I had, however, just accepted an invita- 
tion to go to Cambridge. Einstein's letter also says that Lindemann had 
considered Heitier and London for Oxford. Heitler had, as already 
mentioned, been my assistant in Gottingen for many years. London, the 
son of one of my mathematics professors from my student days in Breslau, 
had studied mainly with Sommerfeld in Munich. London and Heitler 
jointly published a fundamental work in which the chemical (non-polar) 
valency forces were for the first time explained in physical terms by means 
of quantum mechanics. This theory has since been successfully developed 
by the American chemist Linus Pauling; he was awarded the Nobel Prize 
for chemistry for this, but Heitler and London did not get the prize 
for physics. Neither went to Oxford. Instead, Lindemann got Franz 
Simon, Professor of Physical Chemistry at Breslau, and some younger 
research workers, Mendelssohn, Kurti and Kuhn inter alia. They soon 
brought the Clarendon Laboratory to full bloom. In the end Simon 
became Lindemann's successor, was knighted and so became Sir 
Francis. The main research effort at his institute was in low temperature 
studies. 

It is evident from Einstein's letter that at that time I was trying 
to do something for Edward Teller, but I cannot remember it. He 
had been in Gottingen for some time and had helped me to write one 
of the chapters in my book on optics (the theory of the Raman effect). 
He later became famous in America as the 'father of the hydrogen 
bomb' and has always tried passionately to influence public opinion in 
favour of power politics and against any compromise between East and 
West. 

Einstein's severe judgment of the Germans would no doubt have been 
subscribed to by all of us who had been expelled by Hitler, as well £is our 
friends in other countries. But what we experienced then was child's play 
in comparison with what happened later. And yet I am now living in 



115 



BORN-EINSTEIN LETTERS 



Germany again. These pages will show how this came about. Einstein 
himself never again set foot on German soil. 

One of Einstein's letters appears to have been lost between this letter and 
the one that follows. 



67 



Selva-Gardena 

Villa Blazzola 

2 June, 1933 



Dear Einstein 

Many thanks for your kind letter. I wish I could help you to 
look after the young exiled physicists and others like them, but 
I am in the same position myself. I spend my time trying to 
improve my rather run-down nerves (sleep is still a problem), 
and thinking about physics a little. I do have, after all, one 
advantage: for quite some time now I have had plenty of time 
at my disposal. But it is not too easy without a library. One of 
my pupils, an Englishman, has come here and I do a little 
work with him. 

Many thanks for your concern about my - or rather our - 
future. I see my task as being more to make my children's lives 
worth living, rather than to spend the rest of my days in pleasure 
and comfort. I have not given up, by any means, but I share 
Ehrenfest's opinion that those who are younger have a better 
chance of achieving something. It is all the more sad that their 
prospects in life are so poor. As regards my wife and children, 
they have only become conscious of being Jews or 'non- Aryans' 
(to use the delightful technical term) during the last few months, 
and I myself have never felt particularly Jewish. Now, of course, 
I am extremely conscious of it, not only because we are con- 
sidered to be so, but because oppression and injustice provoke 
me to anger and resistance. I would like my children to become 
citizens of a Western country, preferably England, for the 
English seem to be accepting the refugees most nobly and 
generously. Also, I studied in England 26 years ago, know the 
language, and have many friends there. But I do not know 
whether it will be possible for anything as good as that to 
happen. You seem to have it in mind to recommend me (or 
Franck?) to the Institute of Physics to be created in Palestine. 

116 



BORN-EINSTEIN LETTERS 

In the interests of my wife and children I would rather not 
do that, though I admit that I know next to nothing about life 
and conditions in Palestine. 

Meanwhile I have already received several invitations for 
the immediate future : one to go for a few months to Columbus, 
Ohio, where Lande is, and one to go to Paris for a whole year, 
free from teaching obligations. The latter, of course, would 
appeal to me greatly, and even more to Hedi; but the salary 
offered is too small to live on with a wife and three children for a 
whole year. Once I got to Paris, I expect the same thing would 
happen to my money as has happened to yours : you would then 
be the big monster, I the small monster. But if it could be 
arranged, we would be very pleased : just imagine, Paris after 
ten years in Gottingen! There is yet another possibility: I have 
been informed that I have received (or am going to receive) a 
post in Belgrade (Yugoslavia); however, the letter was not 
official. Hedi is attracted to anything adventurous and strange. 
I am put off by the scientific wasteland which probably still 
exists there, and the language. I have absolutely no talent for 
languages, and to learn a Slav language seems almost impossible 
to me. But if nothing else comes along, I would undertake it. 
But younger people should really be picked for such posts, 
people who would find it easier to adapt themselves. 

I am going to write to Lindemann about the Teller business, 
and will also ask him to take care of this letter, as you did not 
give any address. I received direct news from Gottingen 
through my English pupil the other day about Franck, Weyl and 
my daughter Irene, who is staying with the Weyls there and is 
enjoying her life, without taking much notice of current events. 
Happy youth that makes that possible! And yet she is not at 
all superficial in her emotions. Courant spent a few days 
with H. Bohr in Copenhagen and his condition seems to have 
improved a little. Franck is resolutely determined not to go 
abroad while he has the slightest prospect of finding work 
in Germany (though not as a civil servant). Although there is, 
of course, no chance of this, he remains in Gottingen and waits. 
I would not have the nerve to do it, nor can I see the point of 
it. But both he and Courant are, in spite of their Jewishness 
which is far more pronounced than in my case, Germans at 
heart. 



117 



BORN-EINSTEIN LETTERS 



Hedi sends her kind regards to you and yours. I am most 
deeply grateful to you for all you are doing on our behalf 
Yours 

M.Bom 



The pupil who looked me up in Selva was Maurice Blackman, a South 
African Jew; he did valuable work later on, and is now professor at 
Imperial College, London, and a Fellow of the Royal Society. Soon another 
EngUsh pupil of mine, Thomson from Oxford, also arrived. I gave them 
little lectures on a bench in front of our house or in the woods of the narrow 
valley, Val Lunga. We were very proud of this Uttle Selva University. 
I never seriously considered going to Jerusalem, for the reasons mentioned 
in the letter, to which I should Uke to add a few words of explanation. 
My parents were both of Jewish extraction. My mother died while I was 
still a child. My father, who was Professor of Anatomy and Embryology 
at the University of Breslau, was a member of the Jewish community; he 
was a liberal of the previous century, for whom religious tolerance was 
natural. Though he suffered professionally more than once from anti- 
semitism, he refused to change his religion, for merely practical reasons. 
The atmosphere in his house was one of urbanity and tolerance. I grew up 
in this and have tried to preserve it in my own home. An involvement with 
Judaism can hardly be said to have existed. It was even less so in the case 
of my wife; although her father, the well-known lawyer Viktor Ehrenberg, 
was of Jewish descent, her mother was of Frisian stock, a daughter of the 
world-famous lawyer Rudolf von Ihering. My wife was in later years a 
Christian in more than name. In Edinburgh her conviction became even 
more strongly rooted when she joined the Religious Society of Friends 
(Quakers) . Neither she nor our children had any ties with Judaism, other 
than love for Jewish relatives, and certainly none with Zionism or with 
Palesdne. 

We took the call to Yugoslavia seriously. I wrote to a colleague in Vienna 
whom I knew to be famiUar with the Balkan countries. His reply was a 
humorous description of the situation in Belgrade : how everything de- 
pended on personal relations, and that it was far more important to 
entertain a Minister of State with a few amusing stories over a glass of 
wine than to do research, and so on. This deterred us. 

Shortly afterwards came the invitation to England. The next letter, again 
from myself to Einstein, was written from Cambridge, where my wife had 
rented a small house. 



ii8 



BORN-EINSTEIN LETTERS 

Cambridge 
8 March, ig34 
Dear Einstein 

I have had news of you from time to time through Weyl, just 
as you have probably heard in the same way about us from him. 
Today I am writing to you direct, because I would like to know 
if there is any prospect of assistance for exiled German scholars, 
and for physicists in particular, from America. You, with your 
warm heart, are no doubt following all these disastrous events 
in detail, but from a distance, after all. Here, where I am, it is 
all very real indeed. Almost every week some unfortunate wretch 
approaches me personally, and every day I receive letters from 
people left stranded. And I am completely helpless, as I am my- 
self a guest of the English and my name is not widely known; 
I can do nothing except advise the Academic Assistance 
Council in London and the Notgemeinschaft [Emergency Aid 
Society] in Zurich. But neither of these institutions has any 
money. As a result of your address in the Albert Hall, Ruther- 
ford had hoped to get a movement under way which would 
produce greater amounts ; but nothing much seems to have come 
of it. Most of the grants from the Academic Assistance Council 
come to an end in the autumn, and cannot be renewed. In the 
meantime many more have arrived in need of help, for whom 
nothing is available. 
What I would like to know is this: 

1 . Is America still able to take people, and particularly younger 
people ? In which professions ? Could teachers of physics be 
placed? To whom would one have to apply? (Dugan 
Committee ?) 

2. Would it be possible for you to collect a really large sum by 
making use of your popularity, and to send it to Rutherford 
for the Academic Assistance Council? I would then devote 
my entire time and energy to make sure that it is used 
sensibly. (You would have to write to Rutherford and suggest 
that I should be asked to do this.) Frequently it is not the 
most capable but the most pushing who are given preference. 

3. What other possibilities are there? Could one not start a 
publicity campaign in South America ? What is the position 
in regard to Jerusalem ? 



"9 



BORN-EINSTEIN LETTERS 

The Notgemeinschaft in Zurich has, partly with my assistance, 
established connections with Russia and India, which offer 
good prospects. 

I myself have been asked by Raman whether I would accept 
a professorship in Bangalore. But because of my predisposition 
to asthma, I would rather avoid any such abrupt change in 
climate as long as the Cambridge people want to keep me on. 

I feel very much at home here, and can work better than in 
Gottingen. Hedi has not settled down as well; her health, 
particularly her nervous condition, is not at all satisfactory. 
My daughters are arriving in England in a fortnight's time and 
want to stay at home for the time being. Hedi will then enter a 
sanatorium. 

The other day I sent you my paper which appeared in the 
Proceedings of the Royal Society. It is not yet satisfactory. I am 
very satisfied, however, with a second paper which is at present 
being printed; it contains a 'classical' treatment of my field 
theory, in which everything happens to fall into place most 
splendidly. You may not agree with it, as I have not dealt with 
gravitation at the same time. This is a matter of principle, in 
which I differ from the ideas expressed in your papers on the 
unified field theory. I hope soon to be able to develop my idea 
about gravitation. I have made some progress with the quanti- 
sation of my field equations, but I still face towering difficulties. 

Are you going to come to Europe in the summer ? I expect I 
will have to remain here for financial reasons. Hedi would very 
much like to know Margofs address. How is your wife ? Please 
give my sincere regards to her and our colleagues at Princeton. 
Yours 

Max Bom 



While Einstein occupied a firm, highly paid academic teaching post at 
Princeton, my employment in Cambridge was only provisional. But I 
was soon given the 'degree' of Master of Arts (MA.) . and the title of 
'Stokes lecturer'; I had a small room in the Cavendish Laboratory and 
did not have to give many lectures, which left me enough time for my own 
work. Our economic position was, however, very tight. I spent a great 
deal of my time in correspondence or discussions to try to accommodate 
exiled scholars. 
Parting from Gottingen, and from all I had built up there, was bound to 



1 20 



BORN-EINSTEIN LETTERS 

weigh heavily upon me. But I found some compensation in my scientific 
life, which flourished under Rutherford's leadership at the Cavendish 
Laboratory. I was also granted the hospitality (dinner rights) of two col- 
leges, Gonville and Caius (of which I had been a member years ago as an 
'advanced student'), and St. Johns (where Dirac was one of the Fellows). 
My wife had none of these things. She had been torn away from every- 
thing she knew and loved - landscape, language, friends, and the home- 
town where her parents and grandparents had lived. Cambridge offered 
her nothing but heavy domestic drudgery, and well-meaning invitations 
to afternoon tea. There is no letter from her to Einstein during this 
period. 

As regards my research, the investigations mentioned in the letter concern 
an attempt, begun in Selva, to modify Maxwell's electrodynamics so 
that the self energy of the point charge is finite. In Cambridge I was 
fortunate in getting the Polish physicist Leopold Infeld as my colleague. 
The theory is usually referred to as the 'Born-Infeld theory' now. We gave 
it a generally relativistic look without pursuing this aspect of it any further. 
Einstein rejected the idea right from the beginning. We tried very hard to 
reconcile it with the principles of the quantum theory. But we did not 
succeed, and today, possibly with good reason, the whole thing has been 
forgotten. I then warmly recommended Infeld to Einstein, and he became 
his collaborator and assistant. They published a popular book. The 
Evolution of Physics,^ which is brilliantly written and has helped to bring 
Einstein's ideas to a much wider public. The pinnacle of their scientific 
collaboration was the reduction of the laws governing the movements of 
celestial bodies to Einstein's field equations. These will be mentioned 
again. 



69 



Princeton, N.J. 
22 March, 1934 



Dear Bom 

It gives me great pleasure to see your handwriting again, even 
if the main cause of your letter is so regrettable. Unfortunately 
I can see no possibility of being able to contribute directly to 
the health of the English Assistance Fund, as I was able to do 
last year. I regret that, for a variety of reasons, it is impossible 
for me to hold travelling lectures in America. 

It is particularly unfortunate that the satiated Jews of the 
countries which have hitherto been spared cling to the foolish 



121 



BORN-EINSTEIN LETTERS 

hope that they can safeguard themselves by keeping quiet and 
making patriotic gestures, just as the German Jews used to do. 
For the same reason they sabotaged the granting of asylum to 
German Jews, just as the latter did to Jews from the East. This 
applies just as much in America as in France and England. 

I am greatly interested in your attempt to attack the quantum 
problem of the field from a new angle, but I am not exactly 
convinced. I still believe that the probability interpretation 
does not represent a practicable possibility for the relativistic 
generalisation, in spite of its great success. Nor has the reasoning 
for the choice of a Hamiltonian function for the electromagnetic 
field, by analogy with the special theory of relativity, convinced 
me. I am afraid that none of us will Uve to see the solution of 
these difficult problems. 

If at all possible, I am going to fritter away the summer 
somewhere in America. Why should an old fellow like me not 
enjoy relative peace and quiet for once? I hope that your 
position in England is now ensured for some time to come. 
Conditions are very difficult here, as the universities, which in 
the main have to live from hand to mouth on a combination of 
private contribution and diminishing capital, have to struggle 
for their existence, and for this reason many capable young 
local people are unemployed. 
Kind regards 
Yours 

A. Einstein 

Margot's address: 5 rue du Docteur Blanche, Paris i6me. 



Einstein's objections to my ideas were twofold. The first was based on his 
rejection of the probability of quantum mechanics. This concerns a matter 
of principle. It did not really apply to the theory devised by Infeld and 
myself, because we ourselves did not in fact manage to make it fit in with 
quantum mechanics ; he judged our efforts in this direction to be wrong 
in principle. Einstein's second objection concerned our original classical 
field theory, which was complete in itself and free from inconsistencies. It 
was based on the following analogy: in the special theory of relativity the 
kinetic energy of a particle, which in classical mechanics is proportional 
to the square of its velocity, is represented by a rather complicated expres- 
sion; for velocities which are small compared with that of light it tends to 



122 



BORN-EINSTEIN LETTERS 

the classical expression, but deviates from it when the velocity approaches 
that of light. In Maxwell's electrodynamics the energy density is a 
quadratic expression containing the field intensity. I replaced this with a 
general expression which approximates to the classical expression whenever 
the strength of the field is small compared with a certain field intensity, 
but diverges from it when this is not the case. From this it followed auto- 
matically that the total energy of the field of a point charge is finite, while 
it becomes infinite in the Maxwellian field. The absolute field has to be 
regarded as a new natural constant. Einstein did not find this analogical 
construction convincing. Infeld and I found it attractive for a long time. 
We abandoned the theory for completely different reasons, namely, 
because we did not succeed in reconciling it with the principles of the 
quantum field theory. In any case this constituted the first attempt to 
overcome the difficulties of microphysics by means of a non-linear theory. 
Heisenberg's theory of elementary particles, which is much talked about 
today, is also non-linear. But I am guessing. 



70 



'Haus Simon', Neue Wiese 

Karlsbad 

24 August, igsG 



Dear Einstein 

Please let me know as soon as possible how one should evaluate 
the work of Prof. Y. He has approached me and seems to be in 
great distress. I understand nothing of his work, but he seems 
to have had closer contact with you (and indeed has even 
written a book about you). My personal impression is that he is 
a poor wretch who rather overrates himself But I may be 
wrong, and in any case I would like to help him. Please write 
to me completely objectively. 

I am here to take the cure; my gall-bladder pains have already 
disappeared. I will be back in Cambridge in a fortnight's time 
(address : 246 Hills Road) ; please write to me there. 

We are moving to Edinburgh shortly, where I have been 
appointed Darwin's successor. 

During my holidays I spoke to many Americans (Franck, 
Ladenburg, Courant), who all talked to me about you. I am 
extremely sorry to hear that your wife is ill. My family are all well . 
With kind regards 
Max Bom 



123 



BORN-EINSTEIN LETTERS 

My chief memory of my stay at this spa is my meeting with Chaim 
Weizmann, the Zionist leader. He accompanied me almost daily on the 
early morning constitutionals which were part of my cure, and I learned 
a great deal about the Zionist movement. The beneficial effect of the cure, 
however, lasted only a short time. A few years later I had to undergo a 
gall-bladder operation in Edinburgh. 

My appointment to the University of Edinburgh is mentioned here for the 
first time. To us it meant the end of uncertainty, and the beginning of a 
new life in Scotland. 



71 



[undated] 



Dear Born 

Y. is a somewhat pathological case. He has an independent but 
unfortunately not very clear mind. His papers about surfaces 
contain much that is useful, even if it has unfortunately never 
been put in order or given clear form. He is a little difficult as a 
person. For example, he made use of our very casual personal 
acquaintance over many years to make money by writing a 
biographical book about me, though I had expressly forbidden 
him to do so. But he was having a very difficult time, and was 
constantly in some kind of distress; always, or almost always, 
without employment. At the same time his exaggerated 
opinion of himself makes it hard to help him, particularly as I 
am not sure whether he would do well in a subordinate position. 
But it is quite possible that his hard experiences have made him 
more amenable. Therefore, help him if you can, but be cautious 
with your recommendations to save yourself from possible 
reproach. He is able to do experimental and technical work, 
and seems at times to have supported himself by it in the past. 
Some time ago I tried to put a word in on his behalf with 
J. Franck. But he refused quite brusquely, on the grounds that 
one should make efforts to help more valuable people. But I 
believe that this attitude towards an older man, who is in 
great distress and who, after all, has certain merits, is far too 
harsh. 

I am quite extraordinarily pleased that you have found a 



124 



BORN-EINSTEIN LETTERS 

permanent and highly respected chair in Edinburgh, and that 
you and your family are well. My wife is unfortunately very 
seriously ill. I personally feel very happy here, and find it 
indescribably enjoyable really to be able to lead a quiet fife. It 
is, after all, no more than one deserves in one's last terms, 
though it is granted to very few. 

Next term we are going to have your temporary collaborator 
Infeld here in Princeton, and I am looking forward to discus- 
sions with him. Together with a young collaborator, I arrived 
at the interesting result that gravitational waves do not exist, 
though they had been assumed a certainty to the first approxi- 
mation. This shows that the non-linear general relativistic field 
equations can tell us more or, rather, limit us more than we 
have believed up to now. If only it were not so damnably 
difficult to find rigorous solutions. I still do not beUeve that the 
statistical method of the quantum theory is the last word, but 
for the time being I am alone in my opinion. 
With best wishes 
Yours 

A. Einstein 



At the end of the letter, Einstein again rejects the statistical quantum 
theory, with the admission that he is alone in this. At the time I was 
quite certain that I was in the right on this question. All theoretical 
physicists were in fact working with the statistical concept by then; this 
was particularly true of Niels Bohr and his school, who also made a 
vital contribution to the clarification of the concept. However, I 
consider it unjustified that this is usually cited as having originated in 
Copenhagen. 



72 



S4 Grange Loan 

Edinburgh 

24 January, ig^y 



Dear Einstein 

Today I have to ask for your help in two different matters: 
I. Prof. R. Samuel, a pupil of Franck's and mine from Got- 
tingen; we did not regard him as outstanding in those days 



J 25 



BORN-EINSTEIN LETTERS 

(more than ten years ago), but he has developed well. He 
went to India, to the MusHm University of Aligarh, and 
created an up-to-date institute there under extraordinary 
difficulties (such as one could not imagine here). A new 
vice-chancellor (my wife calls him the most amiable rogue 
she has ever met) is getting rid of all non-Mohammedans; 
as a result, Samuel has to leave on April ist. The beautiful 
institute, which we inspected last winter, is going to sink 
back once more into the lap of Allah. Samuel has been a 
convinced Zionist from his youth; his dearest wish is to 
live in Palestine. His wife, also a Zionist of long standing, 
and his son, are already there. Samuel is applying for a 
position as experimental physicist in Jerusalem (or elsewhere 
in the country). 

As regards his suitability, it is like this: he is no genius, but 
intelligent and extremely energetic. The establishment of 
the institute in Aligarh is a considerable achievement. His 
papers are based on ideas of Franck's (the Unking together 
of chemistry and spectroscopy). During the last few years he 
has tried hard to demonstrate experimentally that the ori- 
ginal valency interpretation by Heitler and London is 
better than the so-called 'improvements' by Hund, Herzberg 
and Millikan. 

At first I was very sceptical, but have become more and 
more convinced that Samuel's empirical material proves 
him right. London, who is very sceptical, shares my opinion. 
Be that as it may, the experimental material is valuable in 
itself because of the systematic selection of the materials 
and clean workmanship. 

My motive for interceding so energetically on Samuel's 
behalf is as follows: a convinced Zionist of long standing, 
provided he is otherwise suitable, should be given precedence 
over people who want to go to Palestine for purely personal 
reasons. Moreover: a most unpleasant clique seems to be in 
control at the university in Jerusalem; people who lead 
rather lazy lives, and do not want to be disturbed. They 
object to Samuel as not being sufficiently distinguished; I 
believe the opposite to be true - he is too energetic for them. 
I think your word will still have influence there. I hope you 
did not take it amiss that I did not go there myself. I am 



126 



BORN-EINSTEIN LETTERS 

just not a Zionist. I do not belong there; but Samuel wants 
to go there, and is entirely suitable. He wrote to me that, if 
all else failed, he would even settle there as a bricklayer or 
shoecleaner. I had a very detailed discussion with Weizmann 
this summer. He also takes Samuel's part; but this does not 
seem to be enough. 

Please do something in this matter, if you think it right 
to do so. 
2. Dr Hans Schwerdtfeger: young mathematician from Got- 
tingen. Lone wolf, earned his university education by doing 
factory and similar work. Pure 'Aryan'. Was not popular 
with Weyl and Courant, as he used to go his own way. I 
believe him to be talented, but lacking in self-criticism; his 
enthusiasm has up to now been greater than his achieve- 
ment. Herglotz had a good opinion of him; but he does 
nothing for his people. Schwerdtfeger is married to a young 
chemist of whom my wife is very fond, and they have a baby. 
Schwerdtfeger was a violent opponent of the Nazis right 
from the beginning, and has therefore no chance of a 
position in Germany in spite of his 'spotless' ancestry. It is 
people such as this whom we should help. 
A friend of his, Cohn-Vossen, went to Russia and obtained 
a good post in Moscow in 1933. He tried to get Schwerdt- 
feger to follow him. Negotiations got under way; to facilitate 
them, S. went to Prague (one risks one's life in Germany if 
one has any contact with Russia). Hardly had he arrived 
there when he received the news that Cohn-Vossen had 
died. Thereupon the negotiations gradually came to an end. 
Schwerdtfeger and his wife and child were in considerable 
trouble. We helped a little, as did the Notgemeinschaft in 
London. Eventually, after a year, I succeeded in establishing 
a direct link with the Russians through my former pupil 
Weisskopf, who is now with Bohr and who went on a trip to 
Russia. He wrote of the great fear of German 'spies' which 
prevails there. But, in spite of this, the employment of S. 
might possibly be considered if someone like you or Lan- 
gevin put in a word for him. I have written to Langevin, 
but have not received a reply. Therefore I address myself to 
you: could you write to Molotov, to Prof. Schmidt or to 
Garbunov, to the effect that S. has been highly recommended 



127 



BORN-EINSTEIN LETTERS 

to you (you can use my name) as an absolutely honest, 
decent person, who has a burning desire to work in Russia; 
he as a mathematician, his wife as a chemist. Both would be 
satisfied with nominal positions. But if you do not want to 
do this, please say so openly; I can well understand that no 
one gladly gets involved in Russian affairs. The new trial 
against Radek and associates seems to me extremely dis- 
gusting. 

My wife, who is beginning to get on to her feet again, sends her 
warmest regards. She would very much like to hear from 
Margot. 

With kind regards 

Yours Max Bom 

This letter is an example of the voluminous correspondence I carried on 
not only with Einstein, but with many people all over the world, on the 
subject of help for exiled scientists. 

Samuel, as far as I know, did go to Palesdne. After many vain attempts 
I eventually managed to place Schwerdtfeger in Australia, with the help 
of the great physicist Sir William Bragg, who came from there. 
Weisskopf was one of my best pupils and one of the last of those who were 
working for their doctor's degree in Gottingen. He subsequently had a 
distinguished career, and was for many years head of the European 
Institute for Nuclear Research, CERN, in Geneva. 



73 



[undated] 



Dear Born 

First of all, I am extremely delighted that you have found such 
an excellent sphere of activity, and what's more in the most 
civiUsed country of the day. And more than just a refuge. It 
seems to me that you, with your well-adjusted personality and 
good family background, will feel quite happy there. I have 
settled down splendidly here: I hibernate like a bear in its cave, 
and really feel more at home than ever before in all my varied 
existence. This bearishness has been accentuated still further 
by the death of my mate who was more attached to human 
beings than I. 

128 



BORN— EINSTEIN LETTERS 

The tasks you gave me are no simple matter. 

1. Palestine is unquestionably the right place for Samuel. But 
from the university's point of view, the first priority is to 
obtain a proficient theoretician, preferably London. I 
cannot appear on the scene with Samuel until this has been 
accomplished, because it would only add to the confusion. 
There is as yet no proper theoretician there, and while this 
is so it is going to remain a desolate place. But when the time 
comes, I am quite prepared to put in a word for Samuel, 
particularly as his organising ability could prove to be of 
great importance there. 

It is really rather a comforting thought that in India, too, 
the all-too-human trait of knavery predominates. After all, 
it would be just too bad if this were to be the privilege of the 
proud white race. I believe that all creatures who can have 
young ones together are very much the same. 

2. Schwerdtfeger. Nothing can be done for him here. This is 
because Weyl and Courant are up in arms at the suggestion. 
Besides, I have had a closer look at one of his papers, and 
have the impression of a lack of really profound questioning. 
Because of the widespread unemployment amongst local 
people, it is, in any case, very difficult to place anyone here, 
and if one does succeed, it usually means a lowering of status. 
But in this case I cannot even attempt it with a clear conscience. 

Now Russia. After a certain amount of to-ing and fi:o-ing I 
was able to place one of my former assistants there satisfactorily, 
and am going to try and get in another very able and original 
man there, whose position here is threatened by the very con- 
siderable antisemitism in academic circles. But should I ever 
recommend a mediocrity to them, even just once, my credit 
there would be at an end, and I would never again be able to 
help. It is sad that one is forced to treat human beings like 
horses where it matters only that they can run and pull, 
without regard to their qualities as human beings. But what can I 
do ? In the last resort it is precisely humane considerations which 
compel me to adopt this kind of attitude. 

This would, however, not prevent me from giving a friendly 
account of Schwerdtfeger to Russia, if they could be induced to 
ask me. This is how it should be done. This is frequently more 
effective than if one takes the initiative oneself. 



lag 



BORN-EINSTEIN LETTERS 

By the way, there are increasing signs that the Russian trials 
are not faked, but that there is a plot among those who look 
upon Stalin as a stupid reactionary who has betrayed the ideas 
of the revolution. Though we find it difficult to imagine this 
kind of internal thing, those who know Russia best are all more 
or less of the same opinion. I was firmly convinced to begin 
with that it was a case of a dictator's despotic acts, based on 
lies and deception, but this was a delusion. 

Margot is spending the week in New York, and is hewing 
stone with unrivalled enthusiasm. She has really been saved by 
art, she could hardly have born her grievous human losses as 
well as her divorce without it. She often speaks of you with 
affection. 

Kind regards to you and your family 
Yours 

A. Einstein 

P.S. Infeld is a splendid chap. We have done a very fine thing 
together. Problem of astronomical movement with treatment of 
celestial bodies as singularities of the field. The institute has 
treated him badly. But I will soon help him through it. 



The incidental way in which Einstein announces his wife's death, in the 
course of a brief description of his bear-like existence, seems rather strange. 
For all his kindness, sociability and love of humanity, he was nevertheless 
totally detached from his environment and the human beings included in 
it. 

For me the most remarkable passage in the letter is the one about the 
all-too-human trait of knavery which ends with the confession : I believe 
that all creatures who can have young ones together are very much the 
same; a typical formulation of Einstein's rejection of racial discrimination 
and national pride. 

It is typical of his kindness that he apparently suffered because he could 
only advance exceptionally able people by his recommendation as if they 
were horses. For my wife and myself it was brief remarks such as these which 
were, time and again, a source of renewed affection for Einstein the man. 
The Russian trials were Stalin's purges, with which he attempted to 
consolidate his power. Like most people in the West, I believed these 
show trials to be the arbitrary acts of a cruel dictator. Einstein was 
apparently of a different opinion: he believed that when threatened by 



130 



BORN-EINSTEIN LETTERS 

Hitler the Russians had no choice but to destroy as many of their enemies 
within their own camp as possible. I find it hard to reconcile this point of 
view with Einstein's gentle, humanitarian disposition. 
The 'good thing' which he and Infeld had done has been mentioned 
before. It concerns a fundamental simplification of the foundations of the 
general theory of relativity. Infeld described in a short autobiographical 
sketch of his^ how the idea seemed so daring to him at first that he did 
not want to believe in it. At that time, the theory had two pillars. Firstiy, 
the movement of mass points is determined by the geodetic lines of the 
space-time world; secondly, the metrics of this world satisfy Einstein's 
field equations. Now Einstein asserted that the first of these assumptions 
is redundant, because it follows from the field equations by going to the 
limit of infinitely thin, mass-covered world lines, on which the field becomes 
singular. The calculations were at first so extensive that only excerpts 
could be published, and the massive manuscript was deposited in the 
Institute for Advanced Study in Princeton. ShorUy afterwards, and quite 
independentiy, the Russian physicist W. Fock (who had collaborated with 
me on several papers in Grottingen) and his students tackled the same 
problem in a somewhat different manner. This work was later incorporated 
in his well-known book on relativity. Einstein's theory, as elaborated by 
Infeld and Hoffman, was presented in an improved form after Einstein's 
death by Infeld and Plebanski in their brilliant hook Motion and Relativity.'^ 
In his short autobiography, Infeld tells how Einstein had said to him 
more than once: 'here in Princeton I am considered an old fool'. He was 
regarded as an historical relic, and this at a time when he was engaged 
upon this great work. 



74 



84 Grange Loan 

Edinburgh 

II April, igj8 



Dear Einstein 

Your paper with Infeld and Hofmann has impressed me 
enormously. I will not say that I understand it - that would 
need long and intensive study, for which I have not got time 
at present. But I believe I have understood the concept, the 
manner of approximation and the method of development, 
which treats the time and space components in different ways. 
In any case, the result is beautiful ; it is the first really satisfactory 
deduction of the equations of motion from field equations. 
You know I have never concerned myself particularly with 



131 



BORN-EINSTEIN LETTERS 

the theory; just enough to be able to lecture to average 
students. 

Except for your fundamental work, it all seemed excessively 
formalistic to me, and, apart from a few papers by Weyl, not 
very profound. But this new work is both profound and beautiful, 
I shall keep studying it until I understand the details better. 
Infeld wrote to me the other day and said you were interested 
in my reciprocity speculations, and he would like material 
for a lecture. But I did not have anything decent available, 
and did not want to part with what I did have. This may not 
have been terribly nice. But this work is still in the early stages, 
quite unfinished, and over there you have, after all, so many 
terribly clever people who can do everything so much more 
quickly than my frayed old brain. On the other hand, I would 
have no hesitation about writing something on it for you 
personally, which you may also show to Infeld. It is like this : 

The cosmic rays demonstrate the existence of a physical 
world in which the energy of the particles is many times that of 
their mass when at rest. The velocities are therefore almost c 
because 



P = 



mv 



E=- 



mc^ 



J{i-v^lc^)' J{i-v'/c^) 



This means that the v are not suitable physical parameters; 
so much can happen in a minute range of v, which contains 
an enormous range of /> and E values. I interpret this in the 
sense that p and E cannot be reduced to, or measured by, v, 
but have an independent significance. There are other indi- 
cations in support of this, but we cannot go into this here. 
[Nuclei with v of the order c/5 to c/io (for protons or neutrons) 
are an intermediate stage.] The problem is to extend classical 
mechanics so as to include this hypothesis. I use the fact that 
the canonical transformations are symmetrical in x and p; 
e.g. if they are defined through the Poisson brackets: 



(«, v) ■■ 



-y(— 



dv 

Sp,c 



du 



3xJ 



then the transformation {x, p) -^{X, P) is canonical when 
(Z„ZO=o, (P*,PO=o, {Xu,Pi)-^u . 



132 



BORN-EINSTEIN LETTERS 



If one now takes a line element d5* =^ gi^ dx^. dxi 

in ;c-space and carries out a canonical transformation, it 
becomes the eight-dimensional 

di^ =X [Em dxj dxi +Fki dx^ dpi + G« d/>4 dxi + H„i dp„ dpi) 



kl 



where Ej^ and //^j are symmetrical and F^i^Gi^. But this is, of 
course, not the most general case! There are four identities 
between the matrices E, F, G, H. They are best found as 
follows: first establish that canonically the following invariant 
equations exist between E, F, G, H; I am using matrix notation 
(matrices of matrices) : 



H-G> 

■F E) 



/E FN / H-GN_/A o\ 
VG hJ'Uf EJ~Vo A/ 



where A is a 4 by 4 diagonal matrix. It is now very easy, viz. 
by A=o, to characterise the case where d5* is reducible to the 
four-dimensional Ar-space. But if A i^o one has a general case! 
This is precisely what I want. For, if A is small (in c.g.s. units) 
it becomes conceivable that A ^^ o applies to the 'real' mechanics, 
but that for less precise observations the limiting case A=o 
applies. 

Fuchs and I are busy developing this new hyper-dynamics. 
We hope it will work. The characteristic feature is the appear- 
ance of a new natural constant for, since x and p are always 
treated as equivalent, a constant (H) of the dimension [P] arises. 
Planck's constant (A) has the dimension [x p]. If we now equate 

j^ 
H=-p-, h=XoPo, 

then X^ = J{Hh) and Po = J{hlH) define an absolute length 
and an absolute momentum. A pure 'momentum mechanics' 
would be valid wherever p'^Po, i-e. ds^ — Yjykidp^dpi (to a 
good approximation). *' 

I have discussed this case in my papers (manuscript accepted 
for Proc. R. Soc.) and in the letter to Nature,^ where I singled out 
rather arbitrarily a closed spherical /(-space and discussed some 
of the conclusions. These are so reasonable that they have 
encouraged me in my delusions. In any case, I think it good 
fun to pursue them further; so please do not pour too much 



133 



BORN-EINSTEIN LETTERS 

cold water on my head. When one Hves in Europe - even here 
in far Caledonia - one has to have something which diverts one 
from political anxieties. How disgusting it all is. You are lucky 
to be over there. 

Hedi is very well, having got over her eye operation. She is 
attending a Quaker meeting on the west coast with our son 
Gustav, and I am going to meet her there tomorrow for a few 
days' rest by the sea. Our elder daughter is happily married 
and living in the south of England ; the second one is still studying 
in Vienna, and hopes to be able to hold out until her final 
exams in June. My brother was fortunately able to obtain a 
small post in St. Louis as Professor of Fine Arts. How is Margot? 
Kind regards to her, and to the Infelds, as well as to all our 
friends at the Institute, the Weyls, v. Neumanns, Veblens, 
Ladenburgs. Also please tell Robertson that I liked his papers 
very much. I wish he did not still bear me a grudge. I suppose 
he has reason, as I treated him badly when he was in Gottingen. 
In old friendship 
Yours 

Max Bom 



My speculations about reciprocity, which I explain in this letter, have 
occupied me and a variety of collaborators for many years. The one 
mentioned here is the same Klaus Fuchs who later became notorious as 
an 'atom spy'. He spent many years at my Institute in Edinburgh, did 
excellent work and, if I remember rightly, obtained two doctorates, a 
Ph.D. and a D.Sc. (doctorate of philosophy and of science, of which the 
latter was more difficult to get and rated more highly). He was a quiet, 
friendly, likeable man. My wife and I are convinced that he acted from 
purely idealistic motives in the spy affair. He was a convinced Communist, 
and believed it to be his duty to prevent capitalist America from being 
able to dominate the whole world as the sole possessor of the atom bomb. 
As regards my reciprocity theory, this is based on a demand for symmetry, 
requiring the fundamental laws of nature to remain unaltered when the 
four quantities - space coordinates and time - are interchanged with the 
four quantities - momentum components and energy. 
All the efforts I made in Edinburgh at that time to deduce from this 
postulate concrete conclusions which could be proved experimentally 
were in vain. Later it was shown that this was due to the lack of suitable 
experimental material. Meanwhile great progress has been made in 
experimental research into elementary particles, and to my surprise and 



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BORN-EINSTEIN LETTERS 

joy my old reciprocity principle now plays an important part in the 
interpretation of phenomena. Relations of that kind have been discovered 
quite independently in three different places, in the United States, Japan 
and Australia. Among the scientists involved is Yukawa, the great 
Japanese physicist and Nobel prizewinner, who predicted the existence of 
mesons. My former collaborator H. S. Green, Professor at the University 
of Adelaide, is working successfully in this direction and keeps me up to 
date. But I am unfortunately too old to be able to follow this line of 
research. 



75 



84 Grange Loan 

Edinburgh 

2 September, igjS 



Dear Einstein 

I would very much like to send you another peaceful letter 
about my physical and geometrical phantasies, but things 
pohtical occupy my mind to such an extent that I feel com- 
pelled to write about them first of all. We hear such horrible 
things from Germany, and particularly firom Vienna, where 
people are literally starving. Until recently I still had property 
and income in Germany, and we were able to use this to help 
not only a few of our relatives but others as well. Hedi, who has 
become a Quaker, has achieved a lot with the help of these good 
people. A short time ago, however, I learnt that my property 
in Germany had been confiscated by the secret police. Thus, 
even this chance of helping people has come to an end. This 
depresses me more than the general political situation and the 
threat of war. For you are probably right in your confidence in 
the deep-rooted stupidity of our one-time fellow-countrymen: 
they will once again succeed in having the whole world against 
them, and then attack - if not this year against the Czechs, then 
next year against the Poles or whoever it may be. And that will 
be the end of them. But what a horrible thought: all those 
hundreds of thousands of young men, who will perish as a result. 
I have two English sons-in-law, fine, peace-loving people 
(you know one of them, Maurice Pryce, who has become 
engaged to our Gritli). But one is unable to change the course of 
these events. They run their course Uke a thunderstorm. 

I have in mind, however, another matter, where one might 



135 



BORN-EINSTEIN LETTERS 

perhaps be able to do something. Mussohni has passed a 'law', 
according to which all Jews who have settled in Italy since 1919 
are required to leave the country within six months. It is not 
clear whether he did this in order to grovel before Hitler, or to 
do a favour to the Arabs in Palestine. I think this offers America 
a chance to take reciprocal action. Surely a certain amount of 
Italian emigration to America is still going on. Could one not 
get the American government to use this in order to apply 
some pressure on the Itahans? And could you not address 
President Roosevelt? Simply to send back the same number of 
Italians as there are Jews forced to leave Italy would, I fear, 
hardly be possible. But it should be possible to construct some 
means of applying pressure. Of course, innocent people are 
bound to suffer again as a result, and I feel inwardly ashamed 
even to think of such a thing. But in the present situation there 
is really no other method but force against force. If the Western 
powers would only show by example that the methods of the 
dictators can also be used against them, they would probably 
have second thoughts. 

Forgive me for disturbing the peace of your holiday by 
writing to you about these things. We are so close to these 
matters and events here that one cannot find peace. Hedi and 
I are alone at home at present, as the children are staying in 
different parts of Scotland. But we intend to go away for a short 
time in about a week to the west coast. 

My idea of reciprocity pursues me constantly, although no- 
one else is taking it seriously. However, we did not succeed in 
giving it a useful form. One of Heisenberg's more recent papers 
in the ^eitschrift fur Physik shows that he, too, has now realized 
that it is essential to hmit the 'moment' p by an absolute con- 
stant. I was in Cambridge the other day at the meeting of the 
British Association, where I had a thorough discussion with 
Niels Bohr amongst others. The nuclear theory, which can be 
formulated in so beautifully unrealistic a way, gives him so 
much satisfaction that for the moment he is putting aside the 
question of the nature of the elementary particle, which I find 
so fascinating. Let us hear from you some time. 

With kind regards, also to Margot, from Hedi and myself. 
Yours 

Max Bom 

136 



BORN-EINSTEIN LETTERS 

A political letter. The prediction that the folly of the Germans would 
drive them into wild adventures and eventually to their ruin was confirmed 
by events. 

My proposal to use the Italian immigrants to America as a means of 
applying pressure on Mussolini to mitigate the persecution of the Jews 
was somewhat naive. What I find of interest in this paragraph today is 
the shame I felt because it was not the real culprits who would be likely 
to be hit by such measures, but innocent people. It is precisely this which is 
so horrible about foreign politics, and what makes it so repulsive to any 
decent person. 

The subject of the principle of reciprocity comes up again at the end, and 
in this connection a new paper of Heisenberg's is considered. Since those 
days he has switched from 'purely critical' observations to constructive 
ones. His non-linear spin theory of matter is a great gamble which has led 
to a number of successes. But time alone will show whether it is the real 
thing. 



76 



Department of Natural Philosophy 

The University 

Drummond Street 

Edinburgh 

31 May, 1939 



Dear Einstein 

I saw a report in the paper yesterday about a speech of yours 
on Palestine, and seize this opportunity to write to you once 
again. I quite agree with what you are supposed to have said, 
according to this report. Without wishing to defend the 
wavering and unrehable British poUcy, I am of the opinion 
that the Jews could do nothing more stupid than to assume an 
antagonistic attitude towards the English. The British Empire 
is still a place of refuge and protection for the persecuted, and 
particularly for Jews. I also completely subscribe to what you 
are reported to have said concerning the need for and the 
possibility of coming to an understanding with the Arabs. I am 
glad that you said what you did; your voice will be heard. I can 
only think my own thoughts in silence. 

Hedi, at least, is doing something for the refugees. Her 
domestic servant office flourishes; she has already succeeded in 
saving many people from the Nazis, unfortunately virtually only 



137 



BORN-EINSTEIN LETTERS 

women. My sister and other relatives have also escaped - 
except for a few unfortunate cousins. What can one do with a 
55-year-old dentist? Unless he emigrates soon, the Gestapo will 
put him in a concentration camp. But his American registration 
number is 60,000 ! 

My children are well provided for. I had an operation for 
removal of my gall bladder last April. The operation was a 
success, I have no more pain and am feeling fine, and I am 
able to work again. My Department is growing, I have a 
capable staff; next term there will be nine of them. We are 
working on a variety of things, nuclear structure, crystals, etc. 
I have written a paper about melting, which I have sent to 
Bridgman in America for publication, as I considered his high 
pressures in it. This is a new way of treating the thermodynamics 
of crystals (statistical mechanics), which is applicable up to 
very high temperatures and pressures. This work is being 
continued by some of my pupils. I hope also to be able to work 
on a new treatment of the soHdity problem. I have not heard 
from Infeld for a long time; I do not even know his address. 
Franck wrote to me the other day quite contentedly from 
Chicago. 

With kind regards, also from Hedi, 
Yours 

Max Bom 

There is litde to say about this. P. W. Bridgman was Professor of Physics 
at Harvard University, the leading expert in the generation and handling 
of extremely high pressures, for which he received the Nobel Prize. 



77 



Department of Natural Philosophy 

The University 

Drummond Street 

Edinburgh 

10 April ig4o 

Dear Einstein 

At the beginning of the war I wrote a letter to Niels Bohr in 
order to get news from Heisenberg. Today I have to write to 
you for news, if possible, about Niels himself I am terribly 

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BORN-EINSTEIN LETTERS 

worried. A year ago Niels was here - he received the Copley 
Medal of the Royal Society, our highest honour, and came to 
Edinburgh, where he stayed with us and gave us a lecture. He 
was quite excited and shocked by the indifference of most of 
the British people to the imminent danger of war, and he tried 
to convince all people he met (he met important people, of 
course) about the danger. He said to me confidentially that he 
believed his own little country to be in much greater danger than 
Great Britain, since it is so small and helpless, but that nobody 
would be spared to fight for its existence - though at that time 
many people here denied this and still beUeved in 'appease- 
ment'. Well, he was right. You might be able to get news from 
him and his family. Let me know if you hear anything. 

We are well so far. Hedi works very hard, as maternity nurse 
in a slum quarter in the morning, and in refugee and Quaker 
committees in the afternoon. At present she is in the country 
for a short holiday. We had both our daughters here for longer 
visits, one with her husband (M. Pryce, whom you know), 
the other with her fat and merry baby. My son is studying 
medicine here. I continue my work undisturbed; soon my 
department will be the only spot in Great Britain where 
theoretical work is still done. 

My chief interest is concentrated on my 'reciprocity' idea; 
Fuchs and I have made nice progress, and PauU, the super- 
critical man, wrote to me the other day: 'I think you are on the 
right track'. A series of papers will appear in June or July; but 
we have refrained from publishing short notes, as Lande does. 
He is working along the same lines (though with very primitive 
methods and rather unclear ideas). I am sure you will be 
interested in the thing because it is the proper way of unifying 
wave mechanics and relativity. There are many interesting 
mathematical features, but one of the main points is the 
discovery of representations of the Lorentz group by infinite 
(not finite) matrices which belong nevertheless to the Hilbert 
space (square integrable). I think that Wigner has some 
similar results in a very abstract way; but what we are trying 
to do is to show that these representations are connected with 
the 'structure' of the elementary particles. A letter is much too 
restricted a space for indicating these things even superficially. 
In the summer term (starting next week) I am going to 



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BORN-EINSTEIN LETTERS 

lecture to my advanced students on general relativity, concen- 
trating my attention on Fock's (the Russian) most interesting 
paper on the derivation of the equations of motion for finite 
bodies from the field equations. We have further quite inter- 
esting results on the thermodynamics of crystals, melting, etc. 
Fiirth, from Prague, who is here as my guest, has found a most 
surprising connection between the tensile strength (breaking) 
of a solid and the heat of melting. The agreement of his formula 
with the empirical facts is perfect; the theoretical derivation 
is amusing, but will be criticised. 

It is sometimes not easy to work under the strained con- 
ditions of war. But it is the best way to avoid worrying. We hear 
very little from American friends. Sometimes I think they 
consider us as lost outposts of civilisation. But I think that is 
quite wrong. This nation and France as well are tremendously 
strong and internally sound. But most of what we hear about 
American opinion seems to us strange. I am convinced that 
you look at the present struggle with the same attitude as I do. 

Remember me to all friends in Princeton, Weyls, Veblens. 
Ladenburg, v. Neumann and the others. 
Yours ever 

Max Bom 

Pauli writes: 'I just got a letter from Guido Beck. He is in a 
camp (Camp de Chamberau, 27e Compagnie, Isere, France). 
He lost his post in Lyon (with Thiband) and needs money very 
urgently. Perhaps one could make a collection for him; it 
would facilitate his position very much. I shall try this here in 
Zurich.' I cannot do anything (export of money is not permitted, 
and we have innumerable liabiUties). 

Can you do it ? 
M.B. 



This is the first letter in English. I was not more fluent in it than in German 
m those days, but after the outbreak of war it was more in accordance 
with my frame of mind. 

My anxiety about Niels Bohr was well founded. After Hitler's army 
marched into Denmark, he was left in peace at first (as I found out later). 
When measures were taken in Denmark, as elsewhere, to exterminate the 

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BORN-EINSTEIN LETTERS 

Jews, he was warned in time (he was half Jewish) and escaped to Sweden. 

From there he went to America and, under a pseudonym, took part in 

the 'Manhattan Project', which led to the producdon of the first atomic 

bomb. 

The work of the Quakers in saving Jews and other victims of persecution, 

in which my wife had a great interest, deserves the greatest praise. 

The progress Fuchs and I made in the reciprocity investigations was 

probably, in spite of Pauli's approval, merely formal; as mentioned 

above, it has only quite recently (1965) really become physics. 

Fock's paper on the deduction of the equations of motion in the general 

theory of relativity from the field equation was mentioned in connection 

with the paper by Einstein, Infeld and Hoffmann deahng with the same 

problem (commentary to letter No. 73) . 

Reinhold Furth, Professor of Theoretical Physics in Prague, escaped to 

Great Britain with his wife after Hitler's invasion of Czechoslovakia, and 

was taken on by my institute, where he worked successfully and helped 

me with the teaching. 

In my assessment of the strength of France and Great Britain, I was very 

much mistaken about France (which is understandable, as I did not 

know it well) ; but I was right where Great Britain was concerned. 

Guido Beck was a gifted theoretical physicist. As far as I know, he was 

rescued when France was threatened, and found asylum in South America. 



78 



Department of Natural Philosophy 

The University 

Drummond Street 

Edinburgh 

10 May, 1943 



Dear Einstein 

A geographical colleague of mine, Dr Arthur Geddes, has 
asked me to write to you about the following matter: he has 
found a short essay of yours on the 'Meanders of Rivers in 
Alluvium, and the Earth's Rotation' [Life as I see it, Library 
Ed.). He is deeply interested in this problem and wishes to 
know whether you have published a full account of your 
considerations, or whether other people have followed your 
ideas. He could find no reference in the (rather scarce) literature 
in French, English, German which is available here. You would 
oblige me very much by letting me know what you are able to 
tell me. I take this opportunity to tell you about ourselves. Hedi 



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BORN-EINSTEIN LETTERS 

had a serious operation last October and has recovered extreme- 
ly slowly. But now she is almost well. Our son is now a doctor 
in a hospital and will join the forces in August. Our daughters 
both have two children each, and their husbands are in the 
Air Force and in the Admiralty. So we are four-fold grand- 
parents. My department consists now only of Furth and two 
half-time research students. But I have quite a lot of elementary 
teaching. 

I have not done much research, but I watch what Schroe- 
dinger is doing with great interest. He writes to me regularly 
and I hope to visit him in Dublin during the summer. He has 
taken up an old paper of yours, from 1923, and filled it with 
new life, developing a unified field theory for gravitation, 
electrodynamics and mesons, which seems to me promising. 
But I suppose he has written to you about it. 

I have just been informed that Joh. v. Neumann is in this 
country and will visit me next week, accompanying a man from 
the Admiralty for whom he will do some war research. 

How is Margot? Give her our love. 

Kind regards from both of us. 

The war looks much better now, and I hope it will be over 
before Europe is completely destroyed. I had just a letter from 
Brillouin (Providence USA) . 
Yours 

Max Born 



I myself had once observed the meanderings of the great rivers, which is 
the subject I wrote to Einstein about at Dr Geddes' suggestion. It was 
during the Russian congress when we travelled down the length of the 
Volga. 

I can no longer remember the towns, which now lie a few kilometres 
from the river, while it is quite obvious that they were originally built 
on its banks. The explanation of the phenomenon by means of the so- 
called 'Coriolis forces', which the rotation of the earth exerts upon bodies 
which have a component of motion in a south-north or north-south 
direction, is trivial and universally known. I cannot quite understand what 
induced Einstein to write anything on this subject, or why Dr Geddes 
should have been interested in it. 

I can no longer remember anything about the contents of Schroedinger's 
unified field theory. My correspondence with him was sporadic and 



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BORN-EINSTEIN LETTERS 

explosive. It would languish for a while; then there would be an out- 
break of letters from him, often one every day, so that I found it difficult 
to keep in step with my repHes. I have a clear recollection of the series of 
letters about the general theory of relativity and its generalisation, but 
I cannot remember their contents. In the end, when I left Edinburgh 
(''954)> I bad a mountain of Schroedinger's letters and have destroyed 
most of them - because of lack of space in my tiny study in Bad Pyrmont. 
Today I realise how silly this was; for even if there was much chaff" 
amongst the corn, there were also some precious grains, turns of phrase 
which were truly characteristic of Schroedinger. 

John von Neumann was a Hungarian mathematician who spent some time 
in Gottingen soon after the discovery of quantum mechanics. He then 
published a book which today is regarded as a standard work on the sub- 
ject. It contains the rigorous proof of the mathematical concepts and 
methods used by Heisenberg, Jordan and myself He represents the 
matrices I introduced as operators in an infinite dimensional space, the so- 
called 'Hilbert-space'. For this I used results of Hilbert's, although I was 
aware that the basic premises made in physics were less than those cus- 
tomary in the mathematics of this space up to that time. Von Neumann 
succeeded in the anything but easy task of finding rigorous proof amongst 
the further suppositions. His book contains other results of importance 
and useful creative concepts. During the Nazi period he emigrated to 
America, became professor at the Institute for Advanced Study at 
Princeton and worked there with Einstein and Weyl. He was considered 
to be the greatest mathematician in America, and possibly in the whole 
world. Unfortunately he contracted an incurable disease while still 
comparatively young, and died an agonising death. 



79 



2 June, 1 943 



Dear Born 

My remark about the influence of the curvature of rivers and 
of the Coriolis force on the erosion of waterways was only a 
casual one. I have not published anything further on the subject, 
as I am convinced that the idea must have been known for a 
long time. I have, however, never searched the literature. 

I was very interested in your news about yourself and your 
family. The multifariousness of our destinies is really remarkable. 

Schroedinger was kind enough to write to me himself and tell 



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BORN-EINSTEIN LETTERS 

me about his work. At one time I was rather enthusiastic about 
this trend of thought. Its weakness lies in its rather artificial and 
weak construction from the point of view of affinitive space. 
Moreover, the connection between the antisymmetrical curve 
and the electrical properties of space results in a linear relation 
between electric fields and charge densities. I have of course 
written to Schroedinger about it in detail. 

I myself am engaged in a rather daring attempt to get to a 
unified physics, after trying vainly so many times before. 
Certainly, to make real progress will require a mighty leap 
forward in our thinking. 

Kind regards to you and yours 
Yours 

A.Einstein 



80 



84 Grange Loan 
Edinburgh 



Dear Einstein 

Our newspaper. The Scotsman, had a note about you : that you 
have called upon intellectual workers to unite and organise 
some protection against new wars of aggression and to secure 
their influence in the political field. I was very glad when I 
read that, for I feel that you are the only man who could do 
anything in this direction, as your name is known to everybody 
in the world. Of course, we are all getting old and have the 
desire to rest and to be left alone, and there are not many 
younger fellows. 

Concerning myself, I had a kind of breakdown last winter 
from which I have not quite recovered. It was the result of 
many causes : a little overwork, the stress of the war in general 
and the extinction of the European Jews, the transfer of my son 
to the Far East (he is after many adventures quite safe on a 
pathological course in Poona, India), etc. But the most de- 
pressing idea was always the feeling that our science, which is 
such a beautiful thing in itself and could be such a benefactor 
for human society, has been degraded to nothing but a means of 
destruction and death. Most of the German scientists have 



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BORN-EINSTEIN LETTERS 

collaborated with the Nazis, even Heisenberg has (I learned 
from reliable sources) worked full blast for these scoundrels - 
there are a few exceptions, e.g. v. Laue and Hahn, The British, 
American, Russian scientists are fully mobiUsed and rightly so. 
I do not blame anybody. For under the given circumstances 
nothing else can be done to save the rest of our civilisation. Yet 
I think that we must have an international organisation and, 
even more important, an international code of behaviour or 
ethics (like the very strict rules which the British physicians 
have inside their profession), by which our scientific com- 
munity could act as a regulating and stabilising power in 
the world, not, as at present, being no more than tools of 
industries and governments. There is a definite ethical standard 
upon which all religions agree. Christian, Jewish, Moslem and 
Hindu. But some branches of biological science, logically 
backward and based on poor evidence, have been tools in the 
hand of criminal politicians for throwing us back in the state 
of the jungle. There must be a way of prohibiting a repetition 
of such things. We scientists should unite to assist the formation 
of a reasonable world order. If you have any definite plans please 
let me know. I am rather powerless, sitting at this pleasant but 
backward place. But I should try my best. Fowler, who would 
be the proper man to take the initiative in this country, is 
unfortunately very ill; he had a breakdown much worse than 
mine. I do not know where Niels Bohr is at present. I should 
like to get in touch with him. Here in Britain it is very difiicult 
to keep up connections with people. Travelling is possible only 
in the most urgent cases, and meetings in the South are res- 
tricted by the flying bombs. 

But the military situation is excellent and we hope the Euro- 
pean part of the war will be over soon. 

Hedi is quite well and sends her best wishes to you and 
Margot. My son is a medical officer in the army and has seen a 
lot of India. My daughters and their families are all right, 
though one of them is living in an area over which the flying 
bombs are passing and occasionally dropping. 

I have tried, together with my Chinese pupil Peng, an 
excellent man, to improve the quantum theory of fields, and I 
think we are on the right track. Schroedinger on the other hand 
has improved your and other people's attempts to unite the 



H5 



BORN-EINSTEIN LETTERS 

different fields in a classical way. I think the next step should 
be a combination and merging of these two approaches. But I 
am too old and worn out to try it. 

With kind regards and best wishes 
Yours ever 

Max Bom 



In writing about the responsibility of the scientist I have said more than 
once that the news of Hiroshima affected the issue decisively. This is true 
in so far as a new situation existed from that day on. It was no longer 
merely a question of ethics, whether political differences can ever 
justify technical mass murder, but of the continued existence of civili- 
zation itself, perhaps even of life on the earth. This letter shows that the 
ethical question, and the abhorrence of war waged with technical means, 
had been occupying me for a long time. 

I would like to add a few more words on this subject here. It was during a 
meeting of the British Association that I first learnt of the possibility of 
developing a weapon of enormous effectiveness by splitting uranium 
nuclei with the help of a chain reaction, a technique which had just 
been discovered by Hahn and Strassmann. Before that, Leo Szilard, a 
Hungarian physicist who had worked with Einstein for some time, had 
appeared on the scene. He was completely obsessed with the idea of a 
nuclear explosion. As the discovery of the splitting of the atom had taken 
place in Germany, he was haunted by the fear that Hitler might be able 
to develop this horrible weapon, and he talked of nothing else. This was 
the first occasion I heard of fission, chain reactions, neutron exploitation, 
and so on. It alarmed me but, for all that, seemed a long way off. 
Then the war really started. After Dunkirk, all Germans in Great Britain 
were interned, irrespective of whether they were Nazis or victims of Nazi 
persecution. I escaped this fate, as I had become a British subject a few 
weeks before the outbreak of the war. But my German collaborators, 
Klaus Fuchs among them, were interned, and had to spend the next few 
months in camps, first on the Isle of Man and later in Canada. There 
their political reliability was investigated, and those who passed the test 
were sent back to England. 

Thus, Fuchs returned to my Institute after a few months and took up his 
work again. But a little later he received a letter from Peierls, a German 
physicist who had emigrated and had become a professor in Birmingham. 
He asked Fuchs whether he would like to collaborate on an important, 
top-secret war project. I knew at once that this could only mean one thing; 
nuclear fission. As the possible consequences of the development of such 

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BORN-EINSTEIN LETTERS 

a means of destruction filled me with horror, I tried as hard as I could to 
dissuade Fuchs, but in vain. His hatred of the Nazis was boundless, and he 
was glad to be able to do something against them. So he went to Peierls 
in Birmingham, and later accompanied him to the United States; what 
followed is common knowledge. 

I myself was never directly invited to take part in the fission project. I 
had never done any work in nuclear physics; but so many other branches 
of physics were tied up with it that I could certainly have collaborated if I 
had offered my services. 

Thus I was spared any real temptation to participate; this is where my 
fate was different from Einstein's. At the time I wrote this letter to 
Einstein, about a year before Hiroshima, we still knew next to nothing 
about the Manhattan Project. It was not until much later that I found out 
that it was Einstein who, under pressure from Szilard and a number of 
other physicists, had written a letter to President Roosevelt which had set 
the whole thing in motion. I assume that Einstein, too, did not subsequentiy 
receive much further information about the progress of the project. 
Einstein, like Szilard, was motivated by the idea that Hider must be 
prevented from being the first to use this weapon. That it should then be 
used against defenceless people was a horrible thought for him and one 
which cast a shadow over the evening of his life. Einstein's fate shows more 
clearly than almost any other in history that even the greatest intellectual 
powers and the purest of intentions are no protection against having to 
make a decision between two possible courses of action, both equally 
detestable. 

Had all this been known to me, I would hardly have written the preceding 
letter. I had been under the impression that Einstein was an absolute 
pacifist, like the Quakers, with whom I came into frequent contact 
through my wife, who had become a member of the Society of Friends. 
But this he was not. He hated the use of force, particularly when it was 
directed against non-combatant, defenceless people. He considered no 
political or economic ideology, no state, no constitution to be worth the 
sacrifice of masses of human lives. But the events of our lifetime had taught 
him, and me, that the ultimate ethical values, on which all human 
existence is based, must, as a last resort, be defended even by force and 
with the sacrifice of human lives. We never again had an opportvmity of 
exchanging our ideas on the subject. But I am convinced that we would 
have understood one another. The following letter, his answer to my 
suggestion, confirms this. 



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BORN-EINSTEIN LETTERS 



8i 



7 September, ig44 



Dear Bom 

I was so pleased about your letter that to my surprise I feel 
compelled to write to you, although no one is wagging a finger 
at me to do so. But I cannot write in English, because of the 
treacherous spelling. When I am reading, I only hear it and am 
unable to remember what the written word looks like. 

Do you still remember the occasion some twenty-five years 
ago when we went together by tram to the Reichstag building, 
convinced that we could effectively help to turn the people 
there into honest democrats ? How naive we were, for all our 
forty years. I have to laugh when I think of it. We neither of us 
realised that the spinal cord plays a far more important role than 
the brain itself, and how much stronger its hold is. 

I have to recall this now, to prevent me from repeating 
the tragic mistakes of those days. We really should not be 
surprised that scientists (the vast majority of them) are no 
exception to this rule, and if they are different it is not due to 
their reasoning powers but to their personal stature, as in the 
case of Laue. It was interesting to see the way in which he 
cut himself off", step by step, from the traditions of the herd, 
under the influence of a strong sense of justice. The medical 
men have achieved amazingly little with a code of ethics, and 
even less of an ethical influence is to be expected from pure 
scientists with their mechanised and specialised way of thinking. 
It is, of course, quite correct for you to allot the relevant priest- 
hood to Niels Bohr. For there is some hope that he would dis- 
sociate his priestly side from physics, and use it in some other 
way. Apart from this, I do not, however, expect much from such 
an undertaking. The feeling for what ought and ought not to 
be grows and dies like a tree, and no fertilizer of any kind 
will do very much good. What the individual can do is to 
give a fine example, and to have the courage to uphold ethical 
convictions sternly in a society of cynics. I have for a long 
time tried to conduct myself in this way, with a varying degree 
of success. 

Your 'I feel too old. . . .' I am not taking too seriously, 



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BORN-EINSTEIN LETTERS 

because I know this feeling myself Sometimes (with increasing 
frequency) it surges upwards and then subsides again. We can 
after all quietly leave it to nature gradually to reduce us to dust 
if she does not prefer a more rapid method. 

I have read your lecture against Hegelianism with great 
interest. It represents to us theoreticians the quixotic element, or 
should I say the seducer? Where this evil or, rather, vice is 
altogether missing, the inveterate philistine rules. I am therefore 
confident that 'Jewish Physics' is not to be killed. Moreover I 
have to confess that your deliberations remind me of the beauti- 
ful proverb : 'Junge Huren - alte Betschwestern' [Young whores 
- old bigots] particularly when I think of Max Born. But I 
cannot really believe that you have completely and honestly 
struggled your way through to the latter category. 

We have become Antipodean in our scientific expectations. 
You believe in the God who plays dice, and I in complete law 
and order in a world which objectively exists, and which I, in a 
wildly speculative way, am trying to capture. I firmly believe, 
but I hope that someone will discover a more realistic way, or 
rather a more tangible basis than it has been my lot to find. Even 
the great initial success of the quantum theory does not make me 
believe in the fundamental dice-game, although I am well 
aware that our younger colleagues interpret this as a consequence 
of senility. No doubt the day will come when we will see whose 
instinctive attitude was the correct one. 

With kind regards to you and your family (now freed 
from flying bombs) 
Yours 

A. Einstein 



The incident of twenty-five years ago, which Einstein remembers here, was 
as follows: when the German Supreme Command suddenly capitulated 
towards the end of 191 8 and the revolution broke out all over (rermany, I 
was in bed with influenza and thus only witnessed the events in Berlin 
from a distance. Just after I had recovered, Einstein rang me up (the 
telephone functioned even during the wildest days) and reported that a 
student council had been formed at the university, modelled on the 
workers' and soldiers' councils (German Soviets). One of its first actions 
had been to depose and lock up the Rector and some of the other digni- 
taries. Einstein, because of his left-wing political views, was believed to 



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BORN-EINSTEIN LETTERS 

have some influence with the more radical of the students, and he was 
asked to negotiate with the 'council' in order to bring about the release 
of the prisoners and the restoration of reasonable order. Einstein had 
discovered that the student council met in the Reichstag building, and 
asked me whether I would accompany him. I accepted despite the weak 
state I was in after my bout of influenza. 

First there was the long march from my house in the Grunewald to 
Einstein's in the Bavarian quarter, for there were no trams or buses 
running in our district; then three of us - Einstein had asked the psycholo- 
gist Max Wertheimer to come too - went by tram to the Reichstag. I will 
not go into the difficulties we had in penetrating the dense crowds which 
surrounded the Reichstag building and the cordon of revolutionary soldiers, 
heavily aimed and red-beribboned. Eventually someone recognised 
Einstein, and aU doors were opened. 

Once in the Reichstag building, we were escorted to a conference room 
where the student councU was in session. The Chairman greeted us 
politely, and asked us to sit down and wait until an important point in the 
new statutes for the university had been dealt with. So we patiently 
waited and listened. Eventually the point at issue was settled and the 
Chairman said: 'Before we come to your request, Professor Einstein, may 
I be permitted to ask what you think of the new regulations for the 
students?' Einstein thought for several minutes, and then said something 
like this: 'I have always thought that the German universities' most 
valuable institution is academic fireedom, whereby the lecturers are in no 
way told what to teach, and the students are able to choose which lectures 
to attend, without much supervision and control. Your new statutes 
seem to abolish all this and to replace it by precise regulations. I would be 
very sorry if the old freedom were to come to an end.' Whereupon the 
high-and-mighty young gentleman sat in perplexed silence. Then our 
business was discussed; but the student council decided that it had no 
authority in the matter, and referred us to the new Grovernment in the 
Wilhelmstrasse, issuing us with a pass for this purpose. 
Accordingly we walked on to the Reich Chancellor's palace. This was 
a hive of activity. The footmen of the Emperor's time still stood in 
corners of the passageways and stairs but, apart from them, the people 
running about the corridors were more or less shabbily dressed and 
carrying briefcases - socialist delegates and delegations from the workers' 
and soldiers' councils. The main hall was full of excited people talking in 
loud voices. But Einstein was recognised at once, and we had no difficulty 
in getting through to the newly appointed President Ebert, who received 
us in a small room and said that we would appreciate that he was unable 
to pay attention to minor matters that day, when the very existence of the 
Reich itself was in the balance. He wrote a few words on our behalf to 



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BORN-EINSTEIN LETTERS 

the appropriate new minister, and in no time at all our business had been 

concluded. 

We left the Chancellor's palace in high spirits, feeling that we had taken 

part in a historical event and hoping to have seen the last of Prussian 

arrogance, the Junkers, and the reign of the aristocracy, of cliques of 

civil servants and of the military, now that German democracy had won. 

Even the long journey back to the Grunewald, mostly on foot, could not 

dampen my elated mood. 

In those days we believed in the triumph of reason, of the 'brain'. We had 

yet to learn that it is not the brain which controls human beings but the 

spinal cord - seat of the instincts and of blind passions. Even scientists are 

no exception to this. 

Einstein had criticised Max Laue earlier on (Letter No. 3) but in this 

letter he gladly acknowledges his bravery towards the Nazis. 

Einstein did not think much of an 'ethical code'. The words contained in 

this letter about Bohr, about 'the feeling for what ought to be, and what 

ought not to', and about the role of the individual in the society of 

cynics, are of profound wisdom. 

Finally, Einstein concerns himself with my lecture 'Experiment and 

Theory in Physics'. ^^''^ Scientifically, we had indeed drifted far apart. He 

concentrated on speculations about his unified field theory, while I tried 

to keep a tight reign on my inclination to speculate. My little book is a 

sharp attack against certain papers by the astronomers Eddington and 

Milne, who both, though in completely different ways, tried to solve the 

enigma of the world of atoms and of the cosmos by means of pure thought 

alone. I still, to this day, believe my arguments to be reasonable but, on 

the other hand, Einstein is quite right in that empiricism alone, without 

bold ideas, does not get one anywhere. He is a master who finds the 

right proportions. 

The last paragraph deals again with the fundamental dice-game in 

quantum mechanics, and is probably the best and most lucid formulation 

of Einstein's point of view. I have discussed it thoroughly in my book 

J^atural Philosophy of Cause and Chanc^^ and there is no need to go into it 

again. 



82 



84 Grange Loan 

Edinburgh 

g October, 1944 



Dear friend Albert Einstein 

It was wonderful to get a letter from you; that is, it was Max 
who got it. I have read it several times, and once again had 



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BORN-EINSTEIN LETTERS 

that feeling of liberation which I used to get from our talks 
during the war. Somehow all the essentials are said in it, and I 
feel as if I were standing in crystal clear air on the top of Mount 
Everest. In the last few years, I have thought again and again 
about two things you once said to me. When I asked you 
whether you were at all afraid of death (when you were so 
serene during your serious illness), you said: 'I feel such a sense 
of solidarity with all living things that it does not matter to 
me where the individual begins and ends'. You also said: 
'There is nothing in the world which I could not dispense with 
at a moment's notice'. For me these are very 'religious' remarks 
in the idiom of the twentieth century. I hope you do not mind 
my calling them that. It is a joyous consciouness of submission 
to a law allied with a stem sense of responsibility for ethical 
convictions. As to the latter: to live one's ethical convictions 
before one is reduced to dust again is something which you 
simply cannot renounce. I hope you will not regard this as a 
sermon - the Quakers (I've been one for the last six years) 
have no sermons. Nor have I become a Betschwester [bigot]. I 
am very bad at praying, as I think that we have no right to it. 
Once we have recognised how we should live, we can pray 
through the very quaUty of our life; and if the quality of our 
lives is not up to that level, in spite of our awareness, then we 
are even less entitled to pray with words. But usually there is 
this awareness of unity with God and with all living things. I, 
too, am unable to believe in a 'dice-playing' God, nor am I 
able to imagine that you believe - as Max has just told me 
when we were discussing it - that your 'complete rule of law' 
means that everything is predetermined, for example, whether 
I am going to have my chUd inoculated against diphtheria or 
not, etc. . . . 

Things would then be as in Omar the tentmaker: 

'That I would drink during my lifetime 
God has known for all eternity. . . .' 

I have forgotten what follows, but it must have been: where 
then is ethics, the consciousness of striving? 

You could probably explain this to me with just a few of 
those vigorous words of yours. 

Just a fortnight ago I wrote two remaining sonnets to add to 



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BORN-EINSTEIN LETTERS 

the three I wrote in India in 1935, where I try to express the 
thought that love alone binds and liberates one (from the ego) 
at one and the same time. They came into being from Indian 
'non-attachment'. It seems to me that you have achieved such 
non-attachment - but how? You have landed yourself in a 
fine pickle with that letter of yours ! I hope it has been pre- 
determined that you are going to answer me on this ! 

You are quite right in your attitude towards ageing - that 
we can simply leave it to nature to reduce us to dust again. 
What Max was trying to express must have been that feeling of 
being 'used up' which we are both constantly aware of now, 
and which is constantly being confirmed by certain facts: 
for example, by the fact that neither of us is any longer 
physically capable of coping with the constant calls for help 
from our daughters, who want us to put them up with their 
babies for weeks on end. I have just had one such visit, lasting 
four weeks, from Gritli and Sylvia (eighteen months old) which 
led to a mighty breakdown on my part. Gritli wanted to have a 
rest, just when I was entirely without help in the house; then 
too, Maurice came home on leave, and I had to do absolutely 
everything (and wanted to do it) - cooking, washing-up, 
shopping and queuing, looking after the baby, etc. etc. . . . 
Also, I can draw lip quite a list of illnesses and operations since 
we came to Edinburgh - six months of pleurisy, an operation 
for detachment of the retina, and finally, less than two years 
ago, a major gynaecological operation for the removal of (your 
expression) my complete production centre with all accessories. 
You once said: 'where you females are concerned, your pro- 
duction centre is not situated in the brain' - you see how well 
all your shameful sayings are fixed in my memory! Yes, all 
these illnesses, together with the constant wear and tear caused 
by the vastly increased difficulties of everyday life, as well as 
three years of voluntary nursing service, have all contributed 
to the feeling of 'being used up'. This feeling of being old and 
tired is different from the 'normal' ageing process, which still 
seems to exist in America, far removed from the war. To 
recover from our kind of 'ageing', it would have to be peace- 
time again, with one's children and friends once more in peace- 
time occupations, when one would no longer have to be a 
constant witness of suffering. 



153 



BORN-EINSTEIN LETTERS 

Your letter -just as in the old days, during the last war, your 
cheerful objectivity - has done me a power of good. I wish I 
could hear you roar with laughter once again ! How is my little 
Margot? Did she ever receive my letter with the Hiddensee 
photos ? Wish I could see you all again sometime ! 
God bless ! 

Your old friend 
Hedi 



My wife's answer to Einstein's letter was written a few days before mine, 
but both were apparently sent off at the same time. She uses the familiar 
'Du' to address Einstein here, which she had never done before. This 
familiarity may have been brought about by their feeling of mutual 
affinity. This letter, recollecting some of Einstein's remarks and contem- 
plating on his philosophy of life, is indeed a testimony to our friendship 
and accord. 

Although my wife had not been schooled in philosophy, her reservations 
about Einstein's attitude to nature hit the nail exactly on the head. 
Strict determinism seemed to us then, as it still does today, to be irrecon- 
cileable with a belief in responsibility and ethical freedom. I have never 
been able to understand Einstein in this matter. He was, after all, a highly 
ethical person, in spite of his theoretical conviction about predetermina- 
tion. As far as I am concerned, the discrepancy between ethical freedom and 
strict natural laws - which even modern physics does not deny but merely 
conceives of in a different way - only became intelligible with the help 
of Niels Bohr's complementarity principle. How much longer will it be 
before the professional philosophers come to understand and adopt these 
ideas? I also mention the 'dice-playing God' in my letter. Today I still 
consider my objection, that Einstein's way of thinking in physics could not 
do without the 'dice-playing God', to be absolutely correct. For in classical 
physics the initial conditions are not determined by natural laws, and in 
every prediction one either has to assume that the initial conditions have 
been determined by mesisurement, or else one has to be content with a 
statement of probability. I basically believe that the first case is illusory; 
even the best of measurements offer only statistical evidence, which is 
more or less restricted by the scatter of the initial configuration. The 
letters which follow deal with this subject in greater detail. 



154 



BORN-EINSTEIN LETTERS 



83 



10 October, 1344 



Dear Einstein 

Your letter gave both Hedi and myself great pleasure, and 
Hedi was so excited and stimulated by it that she replied 
straight away. In my case it takes a little longer. 

I have not held any lectures for the last nine months, as I 
suffered a collapse in January from which I recovered very 
slowly, and today I lectured again for the first time after this 
long interval. I had to prepare myself for it, and eventually 
one single student turned up, whom I gave a private lesson. 
All the other fellows are somewhere in the army and navy or 
the R.A.F. Our expedition to the Reichstag building is still 
quite fresh in my memory. (Wertheimer was there, too, wasn't 
he?). In those days, I must admit, we completely misjudged 
the forces in German politics. But it was, after all, only by a 
hair's breadth that everything went as wrong as it did. Of 
course I agree with you completely that all human actions 
spring from the depths of an ethical feeling which is primary 
and almost completely independent of reason. But after 
agreeing with you on this point, I must now switch over to our 
disagreement in physics. For I am unable to separate the two 
and I cannot understand how you can combine an entirely 
mechanistic universe with the freedom of the ethical individual. 
Hedi, who knows nothing about physics, has all the same 
formulated it excellently in her enclosed letter to you. To me a 
deterministic world is quite abhorrent - this is a primary 
feeling. Maybe you are right, and it is as you say. But at the 
moment it does not really look like it in physics - and even less 
so in the rest of the world. I also find your expression, the 'dice- 
playing God', completely inadequate. You have to throw dice 
as well in your deterministic world; this is not the difference. 
You know what that difference really is, as well as I do, and if 
you are not in possession of all the arguments at the moment, 
give Pauli a cue, and he will trot them all out. I think first of all 
that you underestimate the empirical fundamentals of the 
quantum theory (I attach less importance to the mass of 'proof 
than to single blatant instances, such as Gibb's paradox or the 



155 



BORN-EINSTEIN LETTERS 

Stern-Gerlach experiment) ; and secondly that your philosophy 
somehow manages to harmonise the automata of lifeless objects 
with the existence of responsibility and conscience, something 
which I am unable to achieve. 

Now with regard to my anti-Eddington and Milne essay, it 
was written in accordance with the British style of courtesy. I 
myself would have summed it up as 'rubbish'. But something 
of that kind had to be written as Eddington is regarded as a 
kind of prophet in this country. I believe, though, that you have 
the right to speculate, but that other people do not, myself 
included. Did I sin so in days gone by (or rather, as you put it, 
whore) ? 

I have always appreciated your good Jewish physics, and 
have greatly enjoyed it; but I have done it myself on only one 
occasion, in the case of non-linear electrodynamics, and this 
was hardly a success. It is my honest opinion that when average 
people try to get hold of the laws of nature by thinking alone, 
the result is pure rubbish. Schroedinger may be able to do it. I 
would like to know what you think of his affine field theory. 
I find it all beautiful and ingenious, but is it true? He has now 
published his lectures about statistical thermodynamics (auto- 
graphed) ; I find them better and more substantial. 

In spite of the war, I still have a small group of people doing 
scientific research here. Fiirth too has done some experimenting; 
he has built a photoelectric microphotometer, as well as an 
harmonic analyser, which is also photoelectric. At the moment 
he is constructing a Fourier transformer which I have invented ; 
this produces the Fourier coefficient curve for any given curve 
on the screen of an oscillograph. It would amuse you. We are 
also working on crystals and X-rays, but mainly on the improve- 
ment of the quantised field theory. You are, of course, absol- 
utely right if you detest this in its present form. But I think 
that we (that is, my Chinese collaborator Peng and I) have 
already improved it considerably, and we are fairly certain that 
we will be able to discard everything unsatisfactory (diverging 
integrals, etc.). I believe it is going to be at least as beautiful 
as any respectable classical theory. 

Unfortunately I am still unable to get much work done. My 
heart cannot stand the slightest exertion. For this reason I am 
not going to do anything further vwth regard to the matter which 



156 



BORN-EINSTEIN LETTERS 

was the subject of my last letter to you and of your reply, 
particularly as your reply was not encouraging. Moreover, I 
do not know where Niels Bohr is, and therefore cannot appoint 
him referee in this business. You are probably right in saying 
that it is even more difliicult for scientists than for ordinary 
people to develop a conscience and a sense of right and wrong. 
In regard to Laue, I have also heard that his conduct was 
decent and courageous. One can only hope that he will survive 
the last, and presumably the most gruesome, period of the war. 

I hope that you will write again from time to time. A letter 
from you gives us the very greatest pleasure. It causes long 
discussions; for Hedi, as a Quaker, often interprets your remarks 
very differently from the way I do, old heathen that I am (I am 
not one really, in fact I am quite devout; it is only in compari- 
son with Hedi). Give my regards to our friends in Princeton - 
Neumann, Ladenburg, Weyl and the caustic Pauli. 
In old friendship 
Yours 

Max Born 



Fiirth's experimental work contained only one idea of mine; this was the 
photoelectric Fourier transformer. Later on the Edinburgh branch of 
Ferranti developed this further, but it was not, however, introduced in 
practice. 



84 



3 March, ig4y 



Dear Born 

If I were not a confirmed old rogue, with a fossilised bad 
conscience, I would not have been able to go for such a long 
time without writing to you. For firstly, your wife's poem about 
the Indian ideal of life made so deep an impression on me that 
I would not have been surprised if it had been written by old 
Goethe himself; secondly, I was very impressed with your 
contribution to that peculiar schoolmaster Schilpp's volume 
which is dedicated to me. It has so much warmth and proves 



157 



BORN-EINSTEIN LETTERS 

SO clearly that you consider my attitude towards statistical 
quantum mechanics to be strange and archaic. Finally, I 
particularly like your soUcitude for your Chinese protege's 
transportation; fortunately he has happily and silently slipped 
away from you without my intervention. I had consulted Weyl 
about him, and we both agreed that we would not have been 
able to solve the problem in the way you had suggested, and 
that I should approach the EngUsh ambassador, who would 
bring the matter honourably to a satisfactory conclusion. 
Fortunately I avoided making this step for several days, and 
then your letter arrived, releasing me. 

I cannot make a case for my attitude in physics which you 
would consider at all reasonable. I admit, of course, that there 
is a considerable amount of validity in the statistical approach 
which you were the first to recognise clearly as necessary given 
the framework of the existing formalism. I cannot seriously 
believe in it because the theory cannot be reconciled with the 
idea that physics should represent a reality in time and space, 
free from spooky actions at a distance. I am, however, not yet 
firmly convinced that it can really be achieved with a continuous 
field theory, although I have discovered a possible way of doing 
this which so far seems quite reasonable. The calculation diffi- 
culties are so great that I will be biting the dust long before I 
myself can be fully convinced of it. But I am quite convinced 
that someone will eventually come up with a theory whose 
objects, connected by laws, are not probabilities but considered 
facts, as used to be taken for granted until quite recently. I 
cannot, however, base this conviction on logical reasons, but can 
only produce my little finger as witness, that is, I offer no 
audiority which would be able to command any kind of respect 
outside of my own hand. 

I am glad that your life and work are fruitful and satisfying. 
This helps one to bear the craziness of the people who deter- 
mine the fate of homo sapiens (so-called) on the grand scale. 
Maybe it has never been any better, but one did not see it as 
clearly in all its wretchedness, nor were the consequences of 
the bungling quite as catastrophic as under present conditions. 
Best wishes to you and your family 
Yours 

A. Einstein 



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BORN-EINSTEIN LETTERS 

My wife's 'Indian Sonnets' have been published in an anthology of her 
poems,33 'Stille Gauge' [Silent Corridors]. 'Schoolmaster' Schilpp's 
volume is one of the series published in the United States called The 
Library of Living Philosophers, under this title: Albert Einstein, Philosopher- 
Scientist. Each volume of this collection begins with a short autobiography 
of the philosopher concerned; this is followed by critical reviews of his 
work by different authors, and ends with the subject's reply to his critics. 
I had undertaken to write about Einstein's statistical theories; this essay 
is also published in German in my book Physik im Wandel Meiner y^eit. 
Towards the end of the article I go into Einstein's attitude towards 
quantum mechanics, and contrast the empirical creed of his youth with 
his later inclination towards speculation. In an obituary that Einstein 
wrote for Ernst Mach,^* he says: 'concepts which have proved useful for 
ordering things easily assume so great an authority over us, that we forget 
their terrestial origin and accept them as unalterable facts. They then 
become labelled as "conceptual necessities", "a priori situations", etc. 
The road of scientific progress is frequently blocked for long periods by 
such errors. It is therefore not just an idle game to exercise our ability 
to analyse familiar concepts, and to demonstrate the conditions on which 
their justification and usefulness depend, and the way in which these 
developed, little by little, from the data of experience. In this way they 
are deprived of their excessive authority. Concepts which cannot be 
shown to be valid are removed. Those which had not been coordinated 
with the accepted order of things with sufficient care are corrected, or 
they are replaced by new concepts when a new system is produced which, 
for some reason or other, seems preferable'. In my article in the Schilpp 
book I contrast this creed of his with his attitude towards quantum 
mechanics, by quoting from his earlier letters. The present letter can 
equally well serve as paradigm, particularly the paragraph which begins : 
'I cannot make a case for my attitude which you would consider at all 
reasonable.' The decisive sentence is the one where he says: 'that physics 
should represent a reality in time and space, free from spooky actions 
at a distance'. I too had considered this postulate to be one which 
could claim absolute validity. But the realities of physical experience had 
taught me that this postulate is not an a priori principle but a time- 
dependent rule which must be, and can be, replaced by a more general 
one. 

My article in the Schilpp book is not by any means the only one which 
deals with this subject. There is, for example, an article by Niels Bohr, 
in which he reports on some detailed discussions he had with Einstein. 
In the course of it he picks to pieces Einstein's ingenious thought-experi- 
ments, which were intended to refute quantum mechanics. 
But even this difference of opinion in print did not interfere with our 



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BORN-EINSTEIN LETTERS 

friendship in the slightest degree. Einstein expressly acknowledges the 
warm tone of my article. 

I cannot now remember what was the point about the transportation of 
my Chinese protege. I had a number of extremely gifted Chinese colla- 
borators, who presumably wanted to return home because of the con- 
stantly increasing threat of war without having to pass through either 
Germany or Russia, but by way of America. 

The last paragraph of the letter is a resigned complaint about the craziness 
and wretchedness of homo sapiens, which at that time (end of 1947) was 
becoming more and more obvious. 



85 



Magdalen College, Oxford 
4 March, ig48 



Dear Einstein 

A few days ago I saw a film here about atomic energy, and 
there you were, as large as life, talking with that familiar and 
well-loved voice, and smiling your amiable, half-serious, half- 
cynical grin. I was quite moved - it will soon be twenty years 
since we last saw you. And when I vwote about this experience 
to Hedi in Edinburgh, she replied at once that she wanted to 
see the film as well. I am going to try and persuade the atomic 
physicists here to send the film there. It also contained some 
fine shots of J. J. Thomson and Rutherford but, though I have 
always greatly admired them, they are nowhere near as close 
to my heart as you are. As to the rest of the film, it is quite good, 
but it will not alter the course of world history very much. 
We've really put our foot in it this time, poor fools that we are, 
and I am truly sad for our beautiful physics! There we have 
been trying to puzzle things out, only to help the human race to 
expedite its departure from this beautiful earth! I no longer 
understand anything about politics: I understand neither the 
Americans, nor the Russians, nor any of the numerous little 
stinkers who are now, of all times, becoming nationalistic. Even 
our good Jews in Palestine have discredited their cause in this 
way. It is better to think about something else. 

Today I gave the last of my Waynflete Lectures, in which 
inter alia I produced certain passages from your letter to me. I 
assumed that you would have no objection, as you did not return 

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BORN-EINSTEIN LETTERS 

my manuscript in protest. My stay in a luxurious Oxford 
college was very pleasant. The (relatively) good food does not 
mean much to me; but the many conversations with a variety of 
intelligent people did, as well as the beautiful old town itself 
with its grey old buildings; visits to my daughter Gritli (her 
husband, Maurice Pryce, was unfortunately ill for almost the 
whole time) and playing with my grandchildren. Occasionally 
we played music on two pianos - all delightfiil things. I have 
prepared the lectures for printing in book form. Hedi stayed at 
home in order to re-arrange our house: moving the kitchen 
upstairs, to save us old people from having to climb so many 
stairs. She is happy because a religious (and very fine) article of 
hers has appeared in an Indian periodical. Could you not 
arrange to have her poems printed in a German periodical in 
America ? They are very beautiful, aren't they, but here in Eng- 
land nobody understands German, and in Germany there are 
enough poets, more than the country can suppert. Much of 
Hedi's time is taken up with sending parcels to starving people in 
Germany. It is particularly the anti-Nazis who are suffering 
again at the moment. But then, we are rationed ourselves and 
so cannot do much to help. 

What we are doing in physics will not interest you very much. 
We concluded our kinetic theory of liquids with a paper about 
the crazy helium II (which has not yet been published). 
One of my Chinese pupils is working on superconductivity, 
and I consider his theory (which is based on a few suggestions 
of mine) to be better than Heisenberg's. My collaborator 
Green is hard at work on elementary particles; he is a brilliant 
man, the best I have had since Pryce. All this keeps me reason- 
ably young. I still have five more years in office, and then I 
have to retire on a pension, which is not enough to live on (it 
is a kind of insurance, and the amount depends on one's length 
of service), so I will probably have to go on working, right to 
my blissful end. Not a bad fate, really. 

Although a letter from you gives me great pleasure, you need 
not reply unless you really feel like it. All the best, and kind 
regards to Margot. 
Yours 

Max Bom 



161 



BORN-EINSTEIN LETTERS 

When I wrote 'we've really put our foot in it', I apparently still did not 
know that it was Einstein who, through his letter to President Roosevelt, 
had started it all off. Had I known, I would hardly have written this 
passage. 

This letter comes from Oxford. The Vice-Chancellor of the old university, 
Sir Henry Tizard, known for his conflict with Lindemann-Cherwell over 
the technical conduct of the war, had personally invited me to hold the 
Waynflete Lectures while on a visit to Edinburgh. It was an honour I 
gladly accepted, although it meant a considerable amount of work for me. 
The lectures have been published under the title: Natural Philosophy of 
Cause and Chance.*^ They contain a report about the advance of the 
probability concepts into causal physics, which culminated in quantum 
mechanics. It also contains quotations from Einstein's letters which will 
be the subject of further comments. 

The statistical mechanics of condensed systems, devised by Green and 
myself, which was intended to lead to a kinetic theory of liquids, has been 
summed up in a booklet called A General Kinetic Theory of Liquids,^ and has 
made some contribution towards the development of this field. But the 
use of helium, which has a Hquid phase that behaves curiously, was not 
as successful as we had hoped. The theory accepted today originated with 
the Russian Nobel prizewinner of 1962, L. D. Landau. 



86 



18 Marchy ig48 



Dear Born 

Today I was looking for something in my igloo, that is, on my 
desk in the Institute. I did not, however, find what I was looking 
for, but your letter instead, which I had taken to be printed 
matter (because of the large envelope), and had therefore left 
unopened together with many others. Now I have read it, of 
course, and moreover with such interest that I arrived home an 
hour late for lunch. 

There are several misunderstandings in your quotations from 
my letters, presumably caused by my illegible handwriting, 
which distort the meaning as you will see from my marginal 
notes. But even if it has already been printed it is not a disaster 
because the 'patience of paper' will certainly be preserved 
in this case as well. I have got my own back by means of several 
caustic marginal comments, which will delight you; for I 

1 6s 



BORN-EINSTEIN LETTERS 

believe that you enjoy rough language, which after all goes with 
the Scottish climate. 

It is really rather a pity that we cannot spend some time 
together at leisure. For I really understand very well why you 
consider me an impenitent old sinner. But I feel sure that you 
do not understand how I came by my lonely ways; it would 
certainly amuse you, even if there is not the slightest chance of 
your approving of my attitude. I would enjoy picking your 
positivistic philosophical attitude to pieces myself. But this is 
hardly likely to happen during our lifetime. I have greatly, 
although belatedly, enjoyed your and your wife's letters, and 
remain, with kind regards, 
Yours 

A. Einstein 



I am only going to quote a few of the 'caustic comments' here. In the last 
chapter of my book ('Metaphysical Conclusions') I assembled some of 
the fundamental concepts of physics, which cannot be traced back to 
other more fundamental ones, but have to be accepted as an act of faith. I 
then continue: 'Causality is such a principle if it is defined as the belief in 
the existence of mutual physical dependence of observable situations. 
However, all specifications of this dependence in regard to space and time 
(contiguity, antecedence) and to the infinite sharpness of observation 
(determinism) seem to me not fundamental but consequences of the actual 
empirical laws'. 

Einstein's marginal comment was: 'I am well aware that no causality 
exists in relation to the observable ; I consider this realisation to be conclu- 
sive. But in my opinion one should not conclude from this that the theory, 
too, has to be based on fundamental laws of statistics. It is, after all, 
possible that the (molecular) structure of the means of observation 
involves the statistical character of the observable, but that it is expedient 
in the end to keep the basis of the theory free from statistical concepts.' 
My text then continues: 'Another metaphysical principle is incorporated 
in the notion of probability. It is the belief that the predictions of statis- 
tical calculations are more than an exercise of the brain, that they can be 
trusted in the real world.' 

Einstein comments briefly: 'I agree with this, of course.' 
These comments are calm and matter-of-fact. But there are also some 
short, sharp remarks. My text deals with the question of whether the 
beauty and simplicity of a theory are of importance; it reads as follows: 
'With regard to simpUcity, opinions will differ in many cases. Is Einstein's 
law of gravitation simpler than Newton's? Trained mathematicians will 

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answer yes, meaning the logical simplicity of the foundations, while others 
will say emphatically no, became of the horrible complications of the 
formaUsm.' 

Einstein's comment on this is simply: 

'The only thing which matters is the logical simphcity oi the foundations'. 
I agree with this, as a trained mathematician, but I am unable to condemn 
the other point of view entirely. After all, what really matters in the end 
is whose formulae do more justice to the observations, Newton's or 
Einstein's. 

I then discuss what I call the 'principle of objectivity' : 'It provides a 
criterion for distinguishing subjective impressions from objective facts, 
namely by substituting for given sense data others which can be checked 
by other individuals'. I have recently dealt in detail with this favourite 
idea of mine in an essay entitled: 'Symbol and Reality'.** Einstein's brief 
comment was simply: 'Blush, Bom, Blush!' 

Elsewhere I try to explain that the application of the objectivity principle 
can sometimes be out of place by using a work of art as an example (a 
Bach fugue), and he just comments: 'Ugh!' 

At the end he adds a somewhat longer passage in his elegant handwriting, 
which I reproduce in its entirety: 'Remark: you should not interpret the 
omission of marginal comments in the latter part of your article as agree- 
ment. The whole thing is rather sloppily thought out, and for this I must 
respectfully clip your ear. I just want to explain what I mean when I say 
that we should try to hold on to physical reality. We all of us have 
some idea of what the basic axioms in physics will turn out to be. 
The quantum or the particle will surely not be amongst them; the 
field, in Faraday's and Maxwell's sense, could possibly be, but it is 
not certain. But whatever we regard as existing (real) should somehow 
be localised in time and space. That is, the real in part of space A should 
(in theory) somehow 'exist' independently of what is thought of as real in 
space B. When a system in physics extends over the parts of 
space A and B, then that which exists in B should somehow exist indepen- 
dently of that which exists in A. That which really exists in B should 
therefore not depend on what kind of measurement is carried out in part 
of space A; it should also be independent of whether or not any measure- 
ment at all is carried out in space A. If one adheres to this programme, one 
can hardly consider the quantum-theoretical description as a complete 
representation of the physically real. If one tries to do so in spite of this, 
one has to assume that the physically real in B suffers a sudden change as a 
result of a measurement in A. My instinct for physics bristles at this. 
However, if one abandons the assxmiption that what exists in different 
parts of space has its own, independent, real existence, then I simply 
cannot see what it is that physics is meant to describe. For what is thought 



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to be a 'system' is, after all, just a convention, and I cannot see how one 
could divide the world objectively in such a way that one could make 
statements about parts of it.' 

According to his letter, Einstein believes that I would disapprove of this 
attitude, even if we had the opportunity to discuss it personally. He calls 
my philosophical ideas 'positivistic', and would love to pull them to pieces. 
I myself certainly do not regard my philosophy as a variety of positivism if 
this implies that only sensory impressions have any claim to reality, and 
that everything else, not only scientific theories but also one's ideas about 
real things of daily life, is merely constructed, created for the purpose of 
establishing reasonable relationships between the various impressions of 
the senses. My reply to Einstein's comments is contained in a later letter. 



87 



84 Grange Loan 

Edinburgh 

31 March, ig48 



Dear Einstein 

Many thanks for the return of my manuscript with your 
marginal comments, and for your letter. It takes some time to 
get things printed here. Meanwhile the manuscript is nowhere 
near completion, and even if I should send it to the publishers 
in May it is unlikely to appear before January '49. This will 
enable me to make any corrections which seem necessary. 
I am very grateful to you for allowing me to reprint the two 
passages from your letters. I will make the corrections you 
suggest in their text, even though the wording of your original 
version was absolutely clear, while the second is entirely 
ambiguous. I have made a careful copy of your words; here is 
the result: 

1 . 'I firmly believe, but I hope that. . . .' 

The words are curious, I admit. But the 'believe' has been 
underlined by you. I am leaving it out, and am going to replace 
it by: 'I hope. . . .' 

2. Skin - as you are talking about the little finger, I took it to 
be 'hand'. But your reading is equally justified, particularly as 
it is in accordance with the writer's interpretation. 

As to the rest, I will bear your earclipping and scolding with 
humility. There is nothing to be done. But in order fully to 
understand what you are criticising, one has to be familiar, of 

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course, with the six preceding lectures as well. But I am quite 
sure that they would not have helped to convert you to my 
point of view either. I will make good use of your remarks and, 
if I can find the time, improve my wording. I am very sorry 
indeed that you do not like my 'observational invariants'. They 
are descendents of Wertheimer's Gestalt, in a new form. I think 
quite highly of it. But I am annoyed that you reproach me 
for my positivistic ideas; that really is the very last thing I am 
after. I really cannot stand those fellows. Again, my sincere 
thanks. 

Hedi and I are travelling to France the day after tomorrow. 
First to Bordeaux, where a congress on light dispersion and the 
Raman effect is taking place. Raman and I are to receive 
honorary doctorates there. This is very funny, as for the last 
three years we have been engaged in a violent feud about 
crystal theory. That is, he has encouraged his pupils to attack 
me in Nature, and I have answered back rather energetically at 
times. Now we shall have to keep the peace and allow ourselves 
to be honoured. He is used to it, I am not. In the case of quantum 
mechanics, which you think so Httle of, the adulation has 
aUghted entirely on Heisenberg and Schroedinger. And yet 
Heisenberg did not even know what a matrix was in those days 
(he was my assistant, that is how I know). By the way, he 
visited us last December, as pleasant and intelligent as ever, but 
noticeably 'Nazified'. I have recently talked to him again in 
Oxford. Once more we are on the same trail: superconductivity. 
He has published a theory which we consider absolute rubbish. 
We first of all carefully deduced the kinetic theory of dense 
matter (liquid and solid bodies), and then explained helium II 
very satisfactorily, and are at present engaged in producing a 
decent theory of superconductivity. It all seems to work out 
quite well. Do you really believe that the whole of quantum 
mechanics is just a phantom ? 

Do come over to Europe some time. In England and Scotland 
little has been destroyed, and even in France enough has been 
left intact. How beautiful are the ancient towns, churches 
and castles of pre-machine days ! Hedi and I were in Switzerland 
last summer, and were completely intoxicated with the loveli- 
ness not only of the landscape but also of the small towns such 
as Berne, Lucerne, Thun, etc. Oxford, too, is not to be despised. 



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BORN-EINSTEIN LETTERS 

Or have you, with your leaning towards puritanism, lost the 
ability to enjoy such impressions ? 

With kind regards, also from Hedi 
Yours 

Max Born 



When I used the expression 'observational invariants' in my book, I 
meant the following: when one sees a bird flying away, what one really 
perceives is usually a bird, recognisable as such, which then becomes 
smaller and smaller until one can no longer distinguish any details and 
finally sees only a small point. All the same, one is aware that one is 
looking at the same bird all the time. Thus there is something constant 
and invariable in totally different sensual perceptions, which one's 
brain deals with unconsciously. This is what I call the 'observational 
invariant'. 

Wertheimer was the same man who accompanied Einstein and me to the 
Reichstag during the revolution, as described in the commentary to letter 
No. 8i. He was one of the founders of the Gestalt theory, together with 
Kdhler, Hornbostel and others, which teaches that perception consists, 
not of sense perceptions which coexist side by side, but of the recognition 
of complete and meaningful Gestalten. 

The meeting with Sir C. V. Raman in Bordeaux was most dramatic. 
At his invitation we had spent the winter of 1935-36 at the Indian 
Institute of Science in Bangalore, where I gave some lectures. Wc had 
got on well together, apart from some minor differences of opinion, and 
had become friends, or so I thought. He even tried to obtain a permanent 
position for me there, but spoilt this plan by some rather clumsy manoeuv- 
ring. Although he had regularly attended almost all my lectures on the 
dynamics of crystal lattices, he developed a very primitive theory of his 
own about lattice vibration, and induced his pupils to attack me in Nature. 
In Bordeaux, after a friendly greeting, we clashed almost immediately; 
he was running down the theoreticians who want to make experiments, 
when I said: 'And what about experimentalists who try their hand 
at theory?' This made him see red; during the banquet, at which my 
wife sat next to him, he declared that I had insulted him to such an 
extent that he would have to leave, and she had great difficulty in 
dissuading him. The tension persisted for the whole of the congress. And 
even later, during a meeting of Nobel prizewinners in Lindau, he cut us 
as much as possible. 

My opinion of Heisenberg was probably not justified. Later on he explained 
to me what his work had been during the Hitler period and how this had 
governed his relations with the regime. In the meantime (1969) objective 

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evaluations of German work on the splitting of the atom during the 
war have appeared, in particular that by the EngUsh historian David 
Irving,* which confirms Heisenberg's statement and justifies his behaviour. 
As I have said before, nothing much came of our theory of the super- 
fluid phase of helium, and of the superconductivity of metals. 



88 

5 April, jg48 

Dear Bom 

I am sending you a short essay which, at Pauli's suggestion, I 
have sent to Switzerland to be printed. I beg you please to 
overcome your aversion long enough in this instance to read 
this brief piece as if you had not yet formed any opinion of your 
own, but had only just arrived as a visitor from Mars. I am not 
asking you to do this because I imagine that I can influence your 
opinion, but because I think that it will help you to understand 
my principal motives far better than anything else of mine you 
know. However, it tends to express the negative aspect, rather 
than the confidence I have in the relativistic group as represent- 
ing a heuristic limiting principle. In any case, I will be extreme- 
ly interested to hear your counter-arguments, beyond the 
obvious fact, of course, that quantum mechanics alone has up 
to now been able to encompass the wave-particle character of 
light and matter. 

With kindest regards 
Yours 

A. Einstein 



Quantum Mechanics and Reality 

In what follows I shall explain briefly and in an elementary 
way why I consider the methods of quantum mechanics 
fundamentally unsatisfactory. I want to say straight away, 

* David Irving, The Virus House''' (pseudonym of a German nuclear research 
laboratory in Berlin). Also the issue oi Bulletin of the Atomic Scientists" devoted to 
the 'German atom bomb', which, in addition to a leading article by the editor, 
E. Rabinovich, contains contributions by Heisenberg himself and by Hans Suess 
(once a member of the German nuclear research team, now Professor of Chemistry 
in the University of California at San Diego). 

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BORN-EINSTEIN LETTERS 

however, that I will not deny that this theory represents an 
important, in a certain sense even final, advance in physical 
knowledge. I imagine that this theory may well become a part 
of a subsequent one, in the same way as geometrical optics is 
now incorporated in wave optics: the inter-relationships will 
remain, but the foundation will be deepened or replaced by a 
more comprehensive one. 



I consider a free particle described at a certain time by a 
spatially restricted ^-function (completely described - in the 
sense of quantum mechanics). According to this, the particle 
possesses neither a sharply defined momentum nor a sharply 
defined position. In which sense shall I imagine that this represen- 
tation describes a real, individual state of affairs ? Two possible 
points of view seem to me possible and obvious and we will 
weigh one against the other : 

(a) The (free) particle really has a definite position and a 
definite momentum, even if they cannot both be ascertained by 
measurement in the same individual case. According to this point 
of view, the i^-function represents an incomplete description of 
the real state of affairs. 

This point of view is not the one physicists accept. Its accept- 
ance would lead to an attempt to obtain a complete description 
of the real state of affairs as well as the incomplete one, and to 
discover physical laws for such a description. The theoretical 
framework of quantum mechanics would then be exploded. 
{b) In reality the particle has neither a definite momentum nor a 
definite position; the description by i/«-function is in principle a 
complete description. The sharply-defined position of the par- 
ticle, obtained by measuring the position, cannot be interpreted 
as the position of the particle prior to the measurement. The 
sharp localisation which appears as a result of the measurement 
is brought about only as a result of the unavoidable (but not 
unimportant) operation of measurement. The result of the 
measurement depends not only on the real particle situation 
but also on the nature of the measuring mechanism, which in 
principle is incompletely known. An analogous situation arises 
when the momentum or any other observable relating to the 
particle is being measured. This is presumably the interpretation 

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preferred by physicists at present; and one has to admit that it 
alone does justice in a natural way to the empirical state of 
affairs expressed in Heisenberg's principle within the framework 
of quantum mechanics. 

According to this point of view, two ^-functions which differ 
in more than triviaHties always describe two different real 
situations (for example, the particle with well-defined position 
and one with well-defined momentum). 

The above is also valid, mutatis mutandis, to describe systems 
which consist of several particles. Here, too, we assume (in the 
sense of interpretation lb) that the ^-function completely 
describes a real state of affairs, and that two (essentially) 
different ^-functions describe two different real states of affairs, 
even if they could lead to identical results when a complete 
measurement is made. If the results of the measurement tally, 
it is put down to the influence, partly unknown, of the measure- 
ment arrangements. 

II 

If one asks what, irrespective of quantum mechanics, is charac- 
teristic of the world of ideas of physics, one is first of all struck 
by the following: the concepts of physics relate to a real outside 
world, that is, ideas are estabhshed relating to things such as 
bodies, fields, etc., which claim a 'real existence' that is inde- 
pendent of the perceiving subject - ideas which, on the other 
hand, have been brought into as secure a relationship as 
possible with the sense-data. It is further characteristic of these 
physical objects that they are thought of as arranged in a space- 
time continuum. An essential aspect of this arrangement of things 
in physics is that they lay claim, at a certain time, to an existence 
independent of one another, provided these objects 'are situated 
in different parts of space'. Unless one makes this kind of 
assumption about the independence of the existence (the 
'being-thus') of objects which are far apart from one another in 
space — which stems in the first place from everyday thinking - 
physical thinking in the famiUar sense would not be possible. 
It is also hard to see any way of formulating and testing the 
laws of physics unless one makes a clear distinction of this 
kind. This principle has been carried to extremes in the field 
theory by localising the elementary objects on which it is 

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based and which exist independently of each other, as well as 
the elementary laws which have been postulated for it, in the 
infinitely small (four-dimensional) elements of space. 

The following idea characterises the relative independence 
of objects far apart in space (A and B) : external influence on A 
has no direct influence on B; this is known as the 'principle 
of contiguity', which is used consistently only in the field 
theory. If this axiom were to be completely abolished, the idea 
of the existence of (quasi-) enclosed systems, and thereby the 
postulation of laws which can be checked empirically in the 
accepted sense, would become impossible. 

Ill 

I now make the assertion that the interpretation of quantum 
mechanics (according to lb) is not consistent with principle 11. 

Let us consider a physical system S12, which consists of two 
part-systems Si and 83. These two part-systems may have been 
in a state of mutual physical interaction at an earlier time. 
We are, however, considering them at a time when this inter- 
action is an at end. Let the entire system be completely described 
in the quantum mechanical sense by a i/(-function ^12 of the 
coordinates qx, • • • and q^, . . . of the two part-systems (^^a 
cannot be represented as a product of the form ^^ ^^ but only 
as a sum of such products). At time t let the two part-systems be 
separated from each other in space, in such a way that t/(i2 only 
differs from o when q^, • • ■ belong to a limited part Ri of space 
and q^,... belong to a part Rg separated from Ri. 

The i/f-functions of the single part-systems Si and Sg are then 
unknown to begin with, that is, they do not exist at all. The 
methods of quantum mechanics, however, allow us to deter- 
mine 1^2 of S2 from ^12. if a complete measurement of the part- 
system Si in the sense of quantum mechanics is also available. 
Instead of the original i^ij of S12, one thus obtains the ^- 
function ifj^ of the part-system Sj. 

But the kind of complete measurement, in the quantum 
theoretical sense, that is undertaken on the part system Si, that 
is, which observable we are measuring, is crucial for this deter- 
mination. For example, if Si consists of a single particle, then 
we have the choice of measuring either its position or its 
momentum components. The resulting ^^ depends on this 



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choice, so that different kinds of (statistical) predictions 
regarding measurements to be carried out later on Sj are 
obtained, according to the choice of measurement carried out on 
Sj. This means, from the point of view of the interpretations of 
lb, that according to the choice of complete measurement of 
Si a different real situation is being created in regard to Sg, 
which can be described variously by ^2> 'Pz, '/'2> etc. 

Seen from the point of view of quantum mechanics alone, 
this does not present any difficulty. For, according to the 
choice of measurement to be carried out on Si, a different real 
situation is created, and the necessity of having to attach two 
or more different i/t-functions ifi^, ^2, . . . to one and the same 
system Sg cannot arise. 

It is a different matter, however, when one tries to adhere 
to the principles of quantum mechanics and to principle II, i.e. 
the independent existence of the real state of affairs existing in 
two separate parts of space Ri and Rj. For in our example the 
complete measurement on Sj represents a physical operation 
which only affects part Ri of space. Such an operation, however, 
can have no direct influence on the physical reaUty in a remote 
part Rg of space. It follows that every statement about Sg 
which we arrive at as a result of a complete measurement of 
Si has to be valid for the system S^, even if no measurement 
whatsoever is carried out on Si. This would mean that all 
statements which can be deduced from the settlement of ^^ 
or ^ must simultaneously be valid for Sg. This is, of course, 
impossible, if ip^, ^ etc., should represent different real states 
of affairs for Sg, that is, one comes into conflict with the lb 
interpretation of the i/r-function. 

There seems to me no doubt that those physicists who regard 
the descriptive methods of quantum mechanics as definitive in 
principle would react to this line of thought in the following 
way: they would drop the requirement II for the independent 
existence of the physical reality present in different parts of 
space; they would be justified in pointing out that the quantum 
theory nowhere makes expHcit use of this requirement. 

I admit this, but would point out : when I consider the physical 
phenomena known to me, and especially those which are being 
so successfully encompassed by quantum mechanics, I still 

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cannot find any fact anywhere which would make it appear 
likely that requirement II will have to be abandoned. 

I am therefore inclined to believe that the description of 
quantum mechanics in the sense of la has to be regarded as an 
incomplete and indirect description of reality, to be replaced 
at some later date by a more complete and direct one. 

At all events, one should beware, in my opinion, of commit- 
ting oneself too dogmatically to the present theory in searching 
for a unified basis for the whole of physics. 
A. Einstein 



This short article" is so closely linked with the letter that I had to include 
it here. Also, my reply cannot be understood without it. The discussion 
is, of course, comprehensible only to those who have some knowledge of 
the development of modern physics and of its philosophical basis. 



89 



84 Grange Loan 

Edinburgh 

g May, 1948 



Dear Einstein 

I am very sorry not to have replied at once to your letter of 
April 5th with the manuscript. I was in Oxford for two months, 
then at home for only a fortnight, and off again to France with 
Hedi to take part in two meetings, one in Bordeaux and one in 
Paris. After my return I had to look after my long neglected 
pupils, prepare my Oxford lectures for the printer, and write an 
official obituary on Planck for the Royal Society, a considerable 
task which has to be completed by the middle of June. This is 
why I am only just getting around to answering your letter. I am 
pleased that you seem to attach some importance to my opinion. 
I have the feeling that I hardly deserve it. But, if you like, you shall 
hear what came into my mind while reading your manuscript. 

Let me begin with an example. A beam of light falls on to a 
plate of doubly refracting crystal, and is split into two beams. 
The direction of polarisation of one of the beams is determined 
by measurement: it is then possible to deduce that that of the 
second beam is perpendicular to the first. In this way one has 



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been able to make a statement about a system in a certain part 
of space as a result of a measurement carried out on a system in 
another part of space. That this is possible depends on the 
knowledge that both beams have originated from one beam 
which has passed through a crystal; in the language of optics, 
that they are coherent. It seems to me that this case is closely 
related to your abstract example, which is apparently connected 
with collision theory. But it is simpler and shows that such 
things happen within the framework of ordinary optics. All 
quantum mechanics has done is to generalise it. 

It seems to me that your axiom of the 'independence of 
spatially separated objects A and B', is not as convincing as 
you make out. It does not take into account the fact of coherence; 
objects far apart in space which have a common origin need 
not be independent. I believe that this cannot be denied and 
simply has to be accepted. Dirac has based his whole book on 
this. You say: The methods of quantum mechanics enable 
one to determine ip^ of S^ from ip^^, provided a complete 
measurement, in the quantum mechanical sense, of the spatial 
system Si exists as well. You evidently assume that ^^ is 
already known. Therefore a measurement in S^ does not really 
give any information about events occurring in far distant Sj, 
but only in association with the information about ^12, that is, 
with the help of additional earlier measurements. In the optical 
example, we have the information that both partial beams are 
produced from one single beam by one crystal. 

Your example is too abstract for me and insufficiently precise 
to be useful as a beginning. 'Measurement' is often loosely 
defined in quantum mechanics. It means either the deter- 
mination of the possible eigenvalues of a quantity, or the 
determination of the actual state corresponding to the particular 
eigenvalue of a system, or, more generally, the determination 
of the weight \an\^ corresponding to the different eigenvalues 
K = I, 2, ... in the mixture tfi{x) =X„fl„i/'„ (x). It is not clear to 
me what you mean by 'measurement' in your example. I 
would find it more convenient to consider a real collision 
process, in which two originally independent particles collide and 
are deflected. The wave functions after the collision would then 
correspond to your ip^ and i/t^- Moreover, it is relevant whether 
you mean a stationary current of falling particles or just two 



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particles, one of each kind. In the latter case, nothing normally 
happens. But in addition to the direction of collision the times 
must be accurately known, and if they are so adjusted that 
deflection does occur, then it seems plausible to me that the 
particles are not independent after the collision. For in order 
for anything to happen at all, one must know and arrange so 
much before the collision. But if we are dealing with a stationary 
current of particles, with statistical arrival times at the place of 
collision, it is obvious that the statistics must have an effect 
on the distribution after the collision, i.e. the two partners 
are still not independent. I cannot really find any particular 
difficulty. 

But I feel that I am not expressing my opinion as lucidly as I 
would like to do. Basically I am coming back again to the fact 
of coherence, which cannot be denied. But as the usefulness of 
mechanical analogues cannot be denied either, one must be 
content with a formalism which covers both. This does not go 
too much against the grain with me. I am therefore inclined to 
make use of the formalism, and even to 'beHeve' in it in a 
certain sense, until something decidedly 'better' turns up. I have 
expounded all this in some detail in my Oxford lectures, which 
you may have the chance to see one of these days. As for my 
expectation of 'something better' I am, of course, of a com- 
pletely different opinion from you. For progress in physics 
has always moved from the intuitive towards the abstract. And 
this will probably remain so. Quantum mechanics and the 
quantum field theory both fail in important respects. But it 
seems to me that all the signs indicate that one has to be prepared 
for things which we older people will not like. I believe that 
even the days of the relativistic group, in the form you gave it, 
are numbered ; the transportability of the line element is fine 
mathematically but, to my mind, physically unsatisfactory. 
Now, the divergencies in quantum mechanics seem to indicate 
that an absolute length does in fact exist in the world. I presume 
that this will have to be included in the general transformation 
group. We have gone to a great deal of trouble over this. 
My pupil Green, a highly gifted man (whom I am going to 
send to you in Princeton next year), may possibly make some 
progress with it; he has good ideas and great mathematical skill. 

We are at present working on superconductivity, and I 



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think our theory is the right one. It is not so terribly com- 
plicated. 

With kind regards, also from Hedi. 
Yours 

Max Born 

The root of the difference of opinion between Einstein and me was the 
axiom that events which happen in different places A and B are inde- 
pendent of one another, in the sense that an observation of the state of 
affairs at B cannot teach us anything about the state of affairs at A. My 
argument against this assumption is taken from optics, and is based on the 
concept of coherence. When a beam of light is split in two by reflection, 
double-refraction, etc., and these two beams take different paths, one can 
deduce the state of one of the beams at a remote point B from an observa- 
tion at point A. It is curious that Einstein did not admit this objection to 
his axiom as valid, although he had been one of the first theoreticians to 
recognise the significance of de Broglie's work on wave mechanics and had 
drawn our attention to it. The axiom cert£iinly does not apply to light; but 
if the movement of matter can be described as 'wave motion' - and it was 
Einstein himself, after all, who supplied some powerful arguments for 
this - then the concept of coherence can be applied to beams of matter: 
from this it follows that, as in the case of light, one can under certain 
circumstances draw conclusions about the state at B by determining the 
state at A. Einstein declared that any theory which could lead to such 
conclusions was incomplete. Therefore, in his eyes, the theory of light must 
be considered to be incomplete as well. He looked forward to the creation 
of a more profound theory which would do away with this state of 
imperfection. So far his hopes have not been realised, and physicists have 
good reasons for believing this to be impossible, based mainly on studies 
carried out by J. von Neumann (see commentary to letter No. 78). 



Department of Mathematical Physics 
90 TTie University 

Drummond Street 
Edinburgh 8 
22 May, ig48 
Dear Einstein 

Unlike my last letter, which I hope you received, this one has 
nothing to do with quantum theory, but with Palestine. You 
will say : 'Why does this concern you ?' Indeed, when you wrote 
to me in 1933 suggesting that I should go to Palestine, I refused 

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for the sake of my wife and children, who are entirely without 
any Jewish tradition. Also I had no clear picture of the situation 
in Europe. Later, I was in daily contact with Weizmann in 
Karlsbad for a number of weeks. I learned a great deal. How- 
ever, I do believe that he could have saved many more Jews if 
he had accepted the offer of the English to give them a part of 
Kenya in East Africa. As things are now, Palestine is the only 
possible place of refuge. I was very sad when the Jews started to 
use terror themselves, and showed that they had learned a lesson 
from Hitler. Also I was so grateful towards my new 'fatherland', 
Britain, that I expected nothing evil from it. But it gradually 
dawned on me that our Mr Bevin is playing a wicked game : first 
the Arabs are supphed with arms and trained; then the British 
army pulls out and leaves the dirty business of liquidating the 
Jews to the Arabs. Of course, I have no proof that it is so. 
Moreover, I detest nationalism of every kind, including that of 
the Jews. Therefore I could not get very excited about it. But 
gradually it has become quite obvious to me that my worst 
suspicions were correct. A leading article in today's Manchester 
Guardian openly attacks Bevin for doing precisely what I had 
suspected. I am feeling very depressed, for I am completely 
powerless and without influence in this country. The main 
purpose of this letter is to tell you that you have my whole- 
hearted support if you take any action to help. Could you not 
induce the American government to act before it is too late? 
The Russians would cooperate and this could perhaps help to 
reduce the tension between America and Russia. Let me know 
what people think of this business in your part of the world. 
With kind regards, also from Hedi 
Yours 

Max Bom 



91 



/ June, 1948 



Dear Bom 

Your Palestine letter has moved me very deeply. Without any 
doubt, you have summed up Bevin's policy correctly. He seems 



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BORN-EINSTEIN LETTERS 

to have become infected with the infamy germ by virtue of the 
post he occupies. You have, however, rather too optimistic an 
idea of the opportunities I have to influence the game in 
Washington. The latter can be summed up with the maxim: 
never let the right hand know what the left is doing. One 
thumps the table with the right hand, while with the left one 
helps England (by an embargo, for example) in its insidious 
attack. 

Your letter about the interpretation of the quantum theory 
goes into quite a lot of detail but does not keep to my logical 
system, so that I am unable to reply without fatiguing you with 
tiresome repetitions. Perhaps one day we will have that personal 
discussion after all. I should just like to add that I am by no 
means mad about the so-called classical system, but I do consider 
it necessary to do justice to the principle of general relativity in 
some way or other, for its heuristic quality is indispensable to 
real progress. 

Kind regards 
Yours 

A. Einstein 



My Palestine letter and Einstein's reply hardly require comment. The 
assessment of Bevin's Palestine policy was quite correct. But he did not 
take into account the toughness and desperate determination of the Jews, 
who succeeded in getting the better of the Arabs. 

As regards Einstein's remarks about physics at the conclusion of his letter, 
his reproach that I had not kept to his logical system seems to me quite 
unjustified. He was so thoroughly convinced that his ideas were right that 
he could not accept any different method, while he for his part reproached 
me for doing the same. We had come to different philosophical points of 
view between which there could be no bridge. But, even so, I believe that I 
followed the teaching of the young Einstein, as defined by him in his 
obituary for Ernst Mach, which I mentioned in the commentary to letter 
No. 84. 



178 



BORN-EINSTEIN LETTERS 



92 



84 Grange Loan 

Edinburgh 

23 January, ig4g 



Dear Einstein 

This communication is intended mainly in reply to Margot's 
letter to Hedi. Please pass my enclosed letter on to her - you 
can, of course, read it. We are very pleased to hear that you 
are feeling better. Look after yourself and take it easy. 

By the way, what has happened to the Schilpp book? I sent 
off my contribution to it more than two years ago, and it has 
still not been published. 

I worked very hard during the last term and, I think, with 
success. Green and I have developed a theory for elementary 
particles, and I am convinced that it is correct, though I 
express myself a little more cautiously in the literature. You 
will not believe in it, however, for we use the quantum-mechani- 
cal 'spook' which you so much dislike. There are going to be 
two short letters of ours in the next issue o? Nature. 

Our idea is as follows : 

Previously one knocked together a Lagrange function for each 
kind of particle (photons, electrons, protons, mesons, etc.) as 
best one could, introducing the mass arbitrarily as a character- 
istic constant. We beUeve that a completely different approach 
should be made. For it is certain that the number of different 
mesons is very large, probably infinite. The huge unknown is 
the Lagrange function L itself, not the solution of the associated 
mechanical problem. We find it from a very general principle: 
the laws of nature are invariant with respect not only to the 
relativistic transformations but also to the substitutions x'-^p^, 
jf*. -»■ - ^" where r- denotes space-time coordinates and p^ energy 
and momenta. Classically this is of course meaningless, but 

quan turn-mechanically it makes sense because now p^= -ih — . 

OX' 

It boils down to the fact that your fundamental invariant 

x^x^ =Ris replaced by the symmetrical quantity S=R + P where 

P=P°Pa- ^ is an operator, the integral eigenvalues of which are 

the distances and the eigenfunctions of which are substantially 

the Lagrange functions L. {x^ and/, must of course be measured 

in 'natural' units.) This indeed produces infinitely many Ls, 



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and the masses of the known mesons are calculated correctly. 
No offence! 

Kindest regards 
Yours 

Max Bom 



Margot's letter contained the news of Einstein's serious illness. 
The Schilpp book did eventually appear in the same year {1949). 
The physical information which comprises the greater part of my letter 
is based on the idea which I had already submitted to Einstein in an 
earher letter, and which we called the 'reciprocity principle'. But our 
considerations went off in a new direction, and this, as previously stated, 
has recently assumed renewed importance in connection with the theory 
of elementary particles. 



93 



[undated] 



Dear Bom 

Thank you very much for your friendly words. I am once again 
crawling about quite cheerfully. But the machinery isn't much 
good any longer. The Schilpp affair is temporarily buried be- 
cause Schilpp is at present busying himself somewhere in Ger- 
many. When he returns, something will happen. I am truly sorry 
to hear that your wife's nerves are in such a bad state. Her poem 
about the Indian philosophy of life made such a deep impression 
on me at the time. It shows a noble mind and a genuine poetic 
talent. I am sorry to hear that you are worried about the mean 
pension. However, this sort of thing is virtually an obligation in 
Scotland, for the sake of all those jokes about the nation's 
thrifty habits. Here, too, the pensions are none too generous 
nowadays, as a result of inflation. I have more or less under- 
stood your theoretical hints. But our respective hobby-horses 
have irretrievably run off in different directions - yours, how- 
ever, enjoys far greater popularity as a result of its remarkable 
practical successes, while mine, on the other hand, smacks of 
quixotism, and even I myself cannot adhere to it with absolute 
confidence. But at least mine does not represent a blind-man's 



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BORN-EINSTEIN LETTERS 

buff with the idea of reality. My whole instinct rebels against it 
irresistibly. My hope of talking it over with you once more 
before my departure is unlikely to be fulfilled. Perhaps I can 
still arrange for the institute to send you an invitation. 
Kind regards and wishes 
Yours 

A.E. 



Einstein's handwriting in this letter clearly shows the effect of his illness, 
and is difficult to read in parts. But in spite of his premonition of death he 
lived for another six years. 

His remark about retirement pay is funny, but unjustified. There is no 
pension to professors in the whole of Great Britain, except for a kind of 
compulsory insurance, to whose premiums the universities make quite 
considerable contributions. Anyone who serves for a long period of time 
thus receives a more or less adequate old age pension. As I became a pro- 
fessor at Edinburgh rather late in Ufe, that is, at the end of my fiftieth year, 
I could only expect a small pension. The university was no doubt unable to 
make an exception by increasing the amount in my case, to avoid creating 
a precedent. As regards the parsimony of the Scots, we never encountered 
it anywhere. It only exists as a subject for jokes, and probably originated 
during the time when ScoUand, in comparison with England, was rela- 
tively poor and forced to economise. 

Einstein's hope that we would see one another once more before his 
'departure' and discuss things was not to be fulfilled. 



94 



12 April, 1949 



Dear Boms 

I was delighted with the wonderful photographs, the con- 
tributions on causality and probability, and the interesting 
article on how to overcome the moral decay of contemporary 
life. You, dear Born, have exposed to public view the frivolous 
remarks I made in my letter. The entire subject dealt with in 
your book has been very well integrated into the framework of 
development, and I understand your point of view very well. 
All the same, I am convinced that your principles, which are 



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BORN-EINSTEIN LETTERS 



at present shared by almost everyone, will not stand the test of 
time. You did the right thing in your letter when you expressed 
the wish that you could be invited to the institute for a longish 
period. As a matter of fact, I did advocate this, but I lack 
influence, as I am generally regarded as a sort of petrified 
object, rendered blind and deaf by the years. I find this role 
not too distasteful, as it corresponds fairly well with my temper- 
ament. 

Your thesis, Mrs Born, that liberation from the bondage of 
the self constitutes the only way towards a more satisfactory 
human society, I regard as absolutely right. But is it not also a 
fact that one cannot put everything down to the individual, as 
the social orientation of the individual is bound to wither in a 
society geared to ruthless competition? The effort to improve 
must therefore take both these sources of human behaviour 
into account. 

Now you ask me what my attitude is towards the simple life. 
I simply enjoy giving more than receiving in every respect, do 
not take myself nor the doings of the masses seriously, am not 
ashamed of my weaknesses and vices, and naturally take things 
as they come with equanimity and humour. Many people are 
like this, and I really cannot understand why I have been made 
into a kind of idol. I suppose it is just as incomprehensible as 
why an avalanche should be triggered off by one particular 
particle of dust, and why it should take a certain course. 
Kind regards and wishes 
Yours 

A.E. 



Einstein explains the failure of his efforts to obtain an invitation to his 
institute for me, by claiming that he was regarded as a kind of petrified 
object. I am sure that I, too, was regarded as the fossilised relic of a bygone 
epoch. Two fossils at the same time were too much for the up-to-date 
gentlemen at the institute. 



182 



BORN-EINSTEIN LETTERS 



95 



The Institute for Advanced Study 

Princeton 

New Jersey 

8 January, IQ50 



Dear Bom 

The mischief in the press about my latest paper is very annoying. 
I have no copies of the manuscript, which is to be reprinted in 
the course of the next few weeks as an appendix to my booklet. 
Meaning of Relativity.*^ I will send you an offprint. 

Meanwhile, my warmest greetings to you, as one of my 
favourite antipodes, 
from Your 

A. Einstein 



At that time the American papers, and consequendy many European 
ones as well, made much of a statement Einstein had made in one of his 
papers to the effect that the unified field theory expounded in it was, in 
his opinion, satisfying and probably conclusive. 

I received a newspaper cutting on a postcard, dated 12th January 1950, 
which, together with some unintelfigible 'elucidations' (in English), 
contains the four basic equations : 

gik = o; r = o; Rik = o; g'=o 
+ - 1 •• 

This is a typical example of the Einstein-idolatry, which he rejected at 
the conclusion of his previous letter with words little short of desperation. 



Q^ Dpt. of Mathematical Physics 

{Applied Mathematics) 

The University 

Drummond St. 

Edinburgh 8 

J September, igjo 

Dear Einstein 

The periodical Xature has sent me your book Out of my later 
years to review. I was not going to write to you until I had 
finished reading it. But I would like to tell you straight away 

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BORN-EINSTEIN LETTERS 

how much I enjoy reading those beautifully lucid and concise 
articles. Hedi was wondering whether they exist in a German 
edition; she thinks it most likely that you wrote them originally 
in German, and that no translation could possibly do justice to 
your characteristic style. I have just read the 'open letters' 
between you and four Russians. One wonders whether these 
four gentlemen are now beginning to see that you are right 
that international anarchy is bound to lead to a terrible 
catastrophe, beside which all conflicts about social and economic 
issues appear trivial by comparison. But most likely they are so 
entirely cut off from everything non-Russian that they can 
form no independent opinion. I am acquainted with the state of 
mind of committed Communists from examples in this country. 
A local doctor is one of them. He is a very good doctor, good- 
natured and wilUng to help, and would not hurt a fly; but 
he is apt to remark glibly that no sacrifice is too great in 
order to achieve the realisation of Marxist ideals, not even the 
destruction of miUions of human lives. To him everything 
printed in our newspapers, including the Manchester Guardian, 
is American propaganda, while his Communist rag, the Daily 
Worker, proclaims absolute truth. It is useless to argue with 
such people. It is unfortunate, however, that they are right in 
so many things: for example, that America, with us in tow, 
always supports governments in Asia which are reactionary 
and corrupt, bombs civiUan populations, and never does any 
of the things which the economically backward countries them- 
selves need and desire. The world is enough to make one 
despair. But it is possible that we are experiencing the crisis of 
the illness, and that recovery will follow. Churchill said in one 
of his last cautionary speeches: 'It is a miracle that the enormous 
Red Army has not yet overrun the whole of Europe, in spite of 
the atom bomb'. I think that maybe it is not a 'miracle' at all. 
It looks to me as if the Russians really do not want a major war; 
their peace overtures are not pure humbug. I have the feeling 
that neither the Russians nor the Americans can go on ir- 
ritating each other much longer, without the Europeans getting 
tired of it and going their own way. No one here wants to fight 
for Chiang Kai-Shek. I would very much like to hear your 
comments on world events. 

I have also read the articles on physics in your book and en- 



184 



BORN-EINSTEIN LETTERS 

joyed them very much, apart from our well-known difference 
of opinion on the subject of quantum mechanics. I have 
defined my position in regard to the argument of 'the incomplete 
description' in an article which I am going to send to you. In it I 
have the audacity to refer to you by claiming that this incom- 
pleteness is sometimes necessary, as, for example in the case of 
the theory of relativity. 

Hedi and I spent three weeks in England, first in a small 
town called Lewes from where we paid a visit to Glyndebourne, 
and were allowed to see a rehearsal o^ Figaro, Then we went to 
Guernsey, one of the Channel Islands, where the weather was 
warm and southerly. Now we are back in cold Scotland once 
more, but enjoy the warming Festival of Music and Drama. 
We saw here the finished performance of Figaro given by the 
Glyndebourne Opera, and various other things. Our son 
Gustav married, in July, a Catholic girl from the Highlands. 
Hedi, by her tact and intelligence, managed to iron out various 
difficulties with her strictly orthodox and snobbish parents. My 
son-in-law, Maurice Pryce, will arrive in Princeton in October 
with his entire family, except for one son, and I hope you will 
get to know him and my daughter Gritli. 

I am at present working on the completion of a book I began 
a year ago on the quantum mechanics of crystal lattices, 
together with a Chinese collaborator. The subject matter is 
completely beyond me by now, and I am glad if I can under- 
stand any of what young Kun Huang writes in both our names. 
But most of the ideas in it date back to my younger years. I see 
from the newspapers that Blackett has once again announced 
the discovery of several new short-Uved mesons to the British 
Association in Birmingham. There is a paper of mine in the 
issue of Rev. of Modem Physics dedicated to you, where I make 
the existence of masses of short-lived particles of this sort seem 
plausible. The details of these calculations are probably wrong 
but the principle seems to have proved itself. 

Hedi sends her kindest regards to you and Margot. Once 
more, many thanks for the book. 
Yours 

Max Bom 



185 



BORN-EINSTEIN LETTERS 

4 September, 1Q50 

Before I send this letter off, I want to add two comments. 
One of them concerns a paragraph in your book, where you 
explain the responsibility of the whole German people for the 
monstrous crimes of the Nazis. I did share your opinion, but 
have now come to another conclusion. I think that in a higher 
sense responsibility en masse does not exist, but only that of 
individuals. I have met a sufficient number of decent Germans, 
only a few perhaps, but nevertheless genuinely decent. I assume 
that you, too, may have modified your wartime views to some 
extent. 

The other remark concerns your interpretation of the i/r- 
function; it seems to me that it completely agrees with what I 
have been thinking all along, and what most reasonable 
physicists are thinking today. To say that ifi describes the 
'state' of one single system is just a figure of speech, just as one 
might say in everyday life: 'My life expectation (at 67) is 4.3 
years'. This, too, is a statement about one single system, but does 
not make sense empirically. For what is really meant is, of course, 
that you take all individuals of 67 and count the percentage 
of those who live for a certain length of time. This has always 
been my own concept of how to interpret |^|^. Instead you 
propose a system of a large number of identical individuals - 
a statistical total. It seems to me that the difference is not 
essential, but merely a matter of language. Or have I misunder- 
stood you, do you mean something much more fundamental? 
If we were able to reach agreement on this point, there would 
seem to me also some hope of our reaching agreement on the 
question of 'incompleteness' as well. But more of this later. 
M.B. 



Since this was written, there have been so many crises that it is hardly 
likely that anyone will remember the one of 1950. The state of the world 
is still just as 'desperate'. Perhaps the difficulty in communicating with 
Communists has been somewhat reduced. I still believe now, as I did 
then, that the Russians do not intend to overrun Europe without extreme 
provocation. 

I had begun the book on crystals at the outbreak of war, in order to build 
up the theory of crystal lattices systematically on a quantum-mechanical 



186 



BORN-EINSTEIN LETTERS 

basis. But the task proved beyond my strength; I had to put the manu- 
script aside. Later I gave it to one of my talented Chinese collaborators, 
Dr Kun Huang, to read, and he declared himself willing to help me with 
its completion. As it happened, it was he who bore the main burden of the 
work, as described in my letter. It was only in the final stages that this once 
more fell to my lot. He was an enthusiastic Communist and, when the 
news of Mao Tse-Tung's victory over Chiang Kai-Shek was received, he 
wanted to take part in whatever happened, and he returned to China with 
his (English) wife, taking the last, still unfinished chapters of the book 
with him. After many exhortations he eventually returned it to me. I 
then had to get the large manuscript ready, check all the calculations, and 
read the proofs, etc., all by myself, which was not easy for me at the age of 
70. The book. Dynamical Theory of Crystal Lattices,*^ is widely known and is 
fulfilling its purpose. 

The news of the existence of many short-lived particles pleased me, as our 
reciprocity theory had predicted something of this kind. Today this theory 
seems also to contribute to their classification and to an understanding of 
their properties. 

The postscript contains first of all an observation about the reponsibility 
of the masses. Einstein's reply to this is in the next letter. Then follows an 
attempt to put an end to the difference of opinion between us about the 
interpretation of quantum mechanics, by saying that it was due to an 
inaccurate, abbreviated expression. But this observation misses Einstein's 
most essential point, as the following letter clearly shows. 



97 



75 September, ig^o 



Dear Born 

I am sorry that you have been bothered with my series of 
articles. Nothing they contain can lay any claim to originality; 
they are only jottings which I wrote, not because I wanted to, 
but in answer to certain demands made on me. 

People such as your Bolshevik doctor come by their fantastic 
attitude as a result of their objection to the harshness, injustice 
and absurdity of our own social order (escape from reality) . 
If he happened to be living in Russia, no doubt he would be a 
rebel there as well, only in that case he would take care not to 
tell you about it. Nevertheless it seems to me that our own 
people here make an even worse job of their foreign policy than 



187 



BORN-EINSTEIN LETTERS 

the Russians. And the idiotic pubUc can be talked into any- 
thing. And they really are very shortsighted, for technological 
superiority is transitory, and if it comes to an all-out conflict, 
the decisive factor is sheer numerical superiority. 

There is nothing analogous in relativity to what I call 
incompleteness of description in the quantum theory. Briefly 
it is because the ^-function is incapable of describing certain 
qualities of an individual system, whose 'reality' we none of us 
doubt (such as a macroscopic parameter) . 

Take a (macroscopic) body which can rotate freely about an 
axis. Its state is fully determined by an angle. Let the initial 
conditions (angle and angular momentum) be defined as pre- 
cisely as the quantum theory allows. The Schroedinger equation 
then gives the i/r-function for any subsequent time interval. If 
this is sufficiently large, all angles become (in practice) equally 
probable. But if an observation is made (e.g. by flashing a 
torch), a definite angle is found (with sufficient accuracy). This 
does not prove that the angle had a definite value before it was 
observed - but we believe this to be the case, because we are 
committed to the requirements of reality on the macroscopic 
scale. Thus, the i/r-function does not express the real state of 
affairs perfectly in this case. This is what I call 'incomplete 
description'. 

So far, you may not object. But you will probably take the 
position that a complete description would be useless because 
there is no mathematical relationship for such a case. I do not 
say that I am able to disprove this view. But my instinct tells me 
that a complete formulation of the relationships is tied up with 
complete description of its factual state. I am convinced of this 
although, up to now, success is against it. I also believe that the 
current formulation is true in the same sense as e.g. thermo- 
dynamics, i.e. as far as the concepts used are adequate. I do not 
expect to convince you, or anybody else - 1 just want you to 
understand the way I think. 

I see from the last paragraph of your letter that you, too, take 
the quantum theoretical description as incomplete (referring to 
an ensemble). But you are after all convinced that no (complete) 
laws exist for a complete description, according to the posi- 
tivistic maxim esse est percipi. Well, this is a programmatic 
attitude, not knowledge. This is where our attitudes really 



1 88 



BORN-EINSTEIN LETTERS 

differ. For the time being, I am alone in my views - as Leibniz 
was with respect to the absolute space of Newton's theory. 

There now, I've paraded my old hobby-horse once again. 
But it is your own fault, because you provoked me. I am glad 
to hear that your children are going to visit our dovecote. I 
have not changed my attitude to the Germans, which, by the 
way, dates not just from the Nazi period. All human beings are 
more or less the same from birth. The Germans, however, have 
a far more dangerous tradition than any of the other so-called 
civihzed nations. The present behaviour of these other nations 
towards the Germans merely proves to me how little human 
beings learn even from their most painful experiences. 
Kind regards 
Yours 

A.E. 



This IS probably the clearest presentation of Einstein's philosophy of 
reahty. The last but one paragraph is particularly reveaUng. He calls my 
way of describing the physical world 'incomplete'; in his eyes this is a 
flaw which he hopes to see removed, while I am prepared to put up with 
It. I have in fact always regarded it as a step forward, because an exact 
description of the state of a physical system presupposes that one can make 
statements of infinite precision about it, and this seems absurd to me 
It seems to me that I have followed Einstein's own way of thinking in accor- 
dance with his theory of relativity, which recognises the impossibility of 
locating any point in time and space absolutely, and therefore concludes 
that the concept of absolute place and time determination does not make 
sense. This is at the base of the whole of his mighty edifice. But he did not 
want to acknowledge the analogy of the situation in the quantum theory. 



98 

4 May, ig^s 
Dear Einstein 

As you can imagine, the death of Ladenburg grieves me very 
much. He was my oldest and, until fate cast us into different 
countries, my closest friend, with whom I have corresponded all 
the time. Since we came to Scotland I have only seen him once 
briefly in London. Else Ladenburg wrote that you had spoken 

189 



BORN-EINSTEIN LETTERS 

very movingly at the cremation ceremony. It is very painful 
to me that I was unable to be present. I hope that Else is 
materially well provided for. Perhaps you could give me some 
information about this some time. 

A few days ago more sad news reached me — of Kramer's 
passing. He had of course been ill for a long time, and was not 
as strong and robust a man as Ladenburg. With him, too, I was 
on terms of close, though not quite as intimate, friendship. The 
last time I saw him was three years ago during a congress in 
Florence, when he was not at all well, and spent most of his 
time in bed. I had hoped to meet him in June at a conference on 
thermodynamics. So we old fellows become more and more 
lonely, and I am writing to you in order to keep intact the few 
remaining Unks with our contemporaries which still exist. Hedi 
and I have come throught the winter rather well. It is already 
the second time that we have spent the Christmas holidays in 
the Bavarian Alps (Oberstdorf), and the sun, snow, good food 
and Bavarian beer have worked like a fountain of youth. We 
intend to return there again next summer. My pension in 
Germany has been restored to me (as Professor Emeritus), and 
so I can afford these hoUdays. While there, we live entirely for 
ourselves, and only see close friends and simple people, such as 
maids, waitresses, peasants, who, there as elsewhere, are still 
pleasant and unspoilt. 

I am engaged in completing two books, one with my Chinese 
collaborator, Dr Huang Kun, on crystal theory, and one about 
optics with a Czech, Dr E. Wolf The American 'Custodian of 
Alien Property', who appropriated my German book on optics 
without paying any compensation, has actually demanded that 
we should apply for a licence for the new book (which is going 
to be much larger and more up-to-date). But the British 
government has taken up my case, and my pubUsher, Dr 
Rosbaud, whom you may remember, now hopes to fight it out 
with their assistance. 

Freundlich was here yesterday and gave us a very lucid 
lecture about the state of light-deflection by the sun. It really 
looks as if your formula is not quite correct. It looks even worse 
in the case of the red shift; this is much smaller than the 
theoretical values towards the centre of the sun's disk, and much 
larger at the edge. What could be the matter here? Could it be 



190 



BORN-EINSTEIN LETTERS 

a hint of non-linearity? (The scattering of light by light?) 
Have you done anything about this problem? Schroedinger is 
pursuing these ideas - I have given them up. 
Hedi sends her best wishes; also to Margot. 
In old friendship 
Yours 

Max Bom 

Since those days when I lamented the death of two dear friends, thirteen 
more years have gone by. In the meantime many more have died, in- 
cluding Einstein himself. Working on this correspondence helps me to 
combat increasing loneliness. 

The new book on optics was written at the instigation of the principal 
of the University of Edinburgh, Professor Edward Appleton, himself a 
physicist who had made a great name for himself by investigating the 
upper layers of the atmosphere with the help of radio beams. He received 
the Nobel Prize for this work. He told me that my old optics book of 1933 
was being reprinted photomechanically in the United States and had sold 
widely during the war because it contained material important to the war 
effort - the spreading of radar waves along the earth's surface, for example. 
I was unable to accept his suggestion that I should have the book trans- 
lated into English, because it seemed to me to be out of date. So I decided 
to write a new book in English, based on the old one, and I succeeded 
in finding an excellent collaborator in Dr E. Wolf, now (1965) Professor 
in Rochester, N.Y., U.S.A. This book, Principles of Optics,*^ was very 
successful; the first edition of 8000 copies was sold out within a year, and 
the third is now in preparation. The negotiations with the Custodian 
of Alien Property in Washington had to be continued for several more 
years. I had, after all, become a British citizen at the beginning of the war, 
and I alone owned the copyright. The confiscation of the book was there- 
fore completely unjustified. But several more years went by before I 
received justice and compensation. 

The astronomer Freundlich tried right from the start to obtain proof of 
Einstein's theory of gravitation with the help of astronomical observations; 
he first worked at the Einstein Tower telescope in Potsdam, and later, 
after his enforced emigration in 1933, at St Andrews, a small university 
not far from Edinburgh. At that time (1952) it did not really seem that the 
predictions of the theory about the bending of light by the sun, and about 
the red shift of the spectral lines, were correct. More recent observations, 
however, have eliminated these difficulties. But this is not the place to 
enlarge on them. A brief report can be found in the latest edition of my 
book Die Relativitatstheorie Einsteins.^" 



191 



BORN-EINSTEIN LETTERS 



99 



12 May, 1Q52 



Dear Bom 

First of all I must express my admiration for your wife's poems. 
Most of them are among the most beautiful I have ever come 
across. My compliments! You are right. One feels as if one were 
an Ichthyosaurus, left behind by accident. Most of our dear 
friends, but thank God also some of the less dear, are akeady 
gone. Ladenburg was taken very suddenly - apparently by a 
virus infection of the internal organs. He was a good man who 
did not take things lightly. During the last few years he even 
avoided reading the newspapers because he could not bear all 
the hypocrisy and mendacity any longer. Over there with you 
things seem on the whole to be cleaner and less wild. 

It really is sweet of the Germans to pay you a pension which 
you can convert on the spot into sausages and beer. The victory 
over the cunning publisher is also rather gratifying. The general- 
isation of gravitation is now, at last, completely convincing and 
unequivocal formally unless the good Lord has chosen a totally 
different way of which one can have no conception. The proof 
of the theory is unfortunately far too difficult for me. Man is, 
after all, only a poor wretch. Freundlich, however, does not 
move me in the slightest. Even if the deflection of light, the 
perihelial movement or line shift were unknown, the gravitation 
equations would still be convincing because they avoid the 
inertial system (the phantom which affects everything but is 
not itself affected). It is really rather strange that human beings 
are normally deaf to the strongest arguments while they are 
always incUned to overestimate measuring accuracies. 

Have you noticed that Bohm believes (as de Broglie did, by 
the way, 25 years ago) that he is able to interpret the quantum 
theory in deterministic terms? That way seems too cheap to me. 
But you, of course, can judge this better than I. 
Kindest regards to you both 
Yours 

A. Einstein 



1 9a 



BORN-EINSTEIN LETTERS 

My report on Freundlich's doubts about the astronomical confirmation of 
the theory of relativity left Einstein quite cold. He considered the logical 
foundations of his theory of gravitation to be imshakeable. The latest 
observations have proved him right. 

It is curious that he does not acknowledge the analogy with quantum 
mechanics. He condemns the term 'inertial system' as a 'phantom' 
which affects everything but is not affected by anything. This must surely 
mean: as a hypothesis, produced ad hoc and uncheckable. But he would 
not admit that processes in the atomic world can be described by means of 
things which can be fixed in time and space, which are sturdy and real 
according to the standards of the everyday world, and which obey deter- 
ministic laws. The remark he makes about David Bohm's theory is connected 
with this. Although this theory was quite in line with his own ideas, to 
interpret the quantum mechanical formulae in a simple, deterministic 
way seemed to him to be 'too cheap'. Today one hardly ever hears about 
this attempt of Bohm's, or similar ones by de Broglie. 



100 



sg May, 1932 



Dear friend Albert Einstein 

This is just a little thank-you for your dear, kind words about 
my poems; after all, their sole significance and purpose is to 
give a little pleasure to someone. How happy I would be if I 
could see you and Margot again; but I'm afraid that wish will 
never be fulfilled, for if we old folks travel it is either to visit 
children and eight grand-children or to the tranquillity of moun- 
tains, meadows and forests. In Germany we live mostly very 
much by ourselves, but have several times invited children and 
children-in-law. And I have formed many connections with 
German Quakers. I also have my brother and his family still 
living in Germany, as well as two old aunts almost ninety years 
old and many cousins of both sexes. There are now 500 German 
Quakers; last July I took part in their annual meeting held 
in Bad Pyrmont, a really beautiful experience. This year Max is 
coming with me, provided he gets 'permission', to attend some 
of the sessions, but apart from that will just be 'holiday-making'. 
The German Quakers still address each other with 'Du' while 
the EngUsh and American ones have abandoned 'Thou'. 



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BORN-EINSTEIN LETTERS 

Germany is and will remain a cause for concern. I, at least, 
have not torn up my roots so completely that I no longer feel 
'responsible'. In some ways, surely, everyone shares the respon- 
sibiUty for everything. There can be no true 'world-citizen- 
ship' until everybody becomes very much more aware of this. 
The German Quakers fully realise this. It is, of course, the most 
decent of the Germans who are most profoundly conscious of 
German guilt. And there are many circles and classes of people 
working for reconstruction from the inside. Seen from outside, 
it is always the loud-mouthed and brutal which attract at- 
tention. By sinking one's roots into new ground one has, of 
course, grown away from it all in many essential respects, but 
one feels all the more responsible. It is a pity that one is so old 
and has insufficient energy for anything but a very modest effort. 

By the way. Max is reading aloud to me from a very delightful 
book just now: the biography of Adolf v. Harnack, written by 
his daughter Agnes Zahn-Harnack, Do you know it? Harnack 
was undoubtedly a fine, energetic and upright man, 

I hope that you and Margot are in good health. Old age is 
not so bad really, provided one does not have too many twinges. 
What have you got against being an Ichthyosaurus ? They were, 
after all, rather vigorous little beasts, probably able to look back 
on the experiences of a very long lifetime. 

In any case, we two old ones will go on thinking of you and 
Margot with unchanging loyalty, even if we should never be 
able to meet again. 

With all my heart 
I remain 

Your old Hedi 



lOI 



28 October, 1Q52 



Dear Einstein 

A few days ago I received a book by Dr Carl Seelig about you 
and Switzerland. As I happened to be in bed with a cold, I had 
time to read it right through, and liked it very much. Dr 
Seelig had written to ask me for a contribution to the book. 



194 



BORN-EINSTEIN LETTERS 

and when he had assured me that you had agreed I copied 
some characteristic sentences from your letter, which he has now 
printed. I do hope that it is really all right by you, I have written 
to him to draw his attention to several inaccuracies (for example, 
he credited me with honours I do not have, and calls Wertheimer 
Paul instead of Max, etc.). The book took me back to old times 
and rekindled the desire to see you again. I met Courant in 
Gottingen this summer; he would very much like to invite me 
to New York, but I am afraid that will not be possible - for as I 
was born in Breslau, on the far side of the Iron Curtain, I am 
excluded from the U.S,A. by your 'McCarthy Act', 

I would like to know what you think of contemporary 
politics, particularly American. Seen from here, it all seems 
horrible - British politics included (for example, the Mau Mau 
uprising in Kenya). And then on the other side, the trial of 
tried and trusted Communists in Prague, with its strong anti- 
semitic overtomes; I am being bombarded with propaganda 
from China, wildly anti-American, My sensible Chinese col- 
laborators, dear, fine fellows that they are, seem from their 
letters to have gone crazy poUtically since they returned to 
China. What a lovely, promising world! As I have eight grand- 
children, it matters to me; it could be a matter of indifference 
to you, were it not for your kind heart. 

Next week I am due to hold a series of lectures at the Univer- 
sity of London, Schroedinger was supposed to come for a public 
discussion that week. He dishkes the statistical concept of 
quantum mechanics, just as you do, but believes that his waves 
constitute the final deterministic solution. It is not quite as 
simple as that, however, and I'm afraid I would have been very 
hard on him had this discussion taken place. But unfortunately 
he had to undergo a serious operation for a perforated appendix, 
was in great danger, and is not strong enough to travel to 
London. Instead, there is now going to be a discussion with 
several philosophers, which promises to be a somewhat wishy- 
washy adventure. Afterwards we are going to celebrate my 
70th birthday in Cambridge with the children and grand- 
children. 

Hedi and I are going to spend our holidays in Oberstdorf 
again. Life in Germany is very pleasant after the austerity in 
this country (for those who have some money - I receive my 



195 



BORN-EINSTEIN LETTERS 



pension). Nice, fine, good people exist there, too; most of them 
have suffered terribly during the Hitler period. I will have to 
retire from my academic chair in another 9 months' time, and 
then we are going to five for six months in Germany and six 
months here, for financial reasons. I want to finish two books 
before then. One of them, about crystals (with my Chinese 
collaborator), has just gone off to the Oxford University Press. 
The other one, about optics, is going to be ready in a year's 
time. Maybe it is silly to put so much work into these things. 
But for the bigger problems I am too old and too stupid. By 
the way, it causes me some amusement that Heisenberg has 
taken up my old idea of non-linear electrodynamics, and has 
applied it, mutatis mutandis, to meson fields. 

Let me know from time to time what you are doing and how 



you are. 



With kindest regards, also from Hedi 
Yours 

Max Born 



The discussion with philosophers in London did in fact take place, and in 
Schroedinger's absence turned out to be wishy-washy as I had predicted. 
The discussions have been published in E. Schroedinger's 'Are there 
Quantum Jumps?'** and my own 'The Interpretation of Quantum 
Mechanics'.*^ 

Schroedinger was, to say the least, as stubborn as Einstein in his conservative 
attitude towards quantum mechanics; indeed, he not only rejected the 
statistical interpretation but insisted that his wave mechanics meant a 
return to a classical way of thinking. He would not accept any objection 
to it, not even the most weighty one, which is that a wave in 3n-dimen- 
sional space, such as is needed to describe the n particles, is not a classical 
concept and cannot be visualised. 

Heisenberg's non-linear theory was intended to serve not only for meson 
fields but for all elementary particles. Today it is the centre of a great 
deal of interest. 



196 



BORN-EINSTEIN LETTERS 



102 



84 Grange Loan 

Edinburgh 

26 September, igj3 



Dear Einstein 

Very often I feel the need to write to you, but I usually suppress 
it to spare you the trouble of replying. Today, though, I have 
a definite reason - that Whittaker, the old mathematician, 
who lives here as Professor Emeritus and is a good friend of 
mine, has written a new edition of his old book History of the 
Theory of the Ether, of which the second volume has already 
been published. Among other things it contains a history of 
the theory of relativity which is pecuUar in that Lorentz and 
Poincare are credited with its discovery while your papers 
are treated as less important. Although the book originated in 
Edinburgh, I am not really afraid you will think that I could 
be behind it. As a matter of fact I have done everything I could 
during the last three years to dissuade Whittaker from carrying 
out his plan, which he had already cherished for a long time 
and loved to talk about. I re-read the originals of some of the 
old papers, particularly some rather oflf-beat ones by Poincare, 
and have given Whittaker translations of German papers (for 
example, I translated many pages of PauU's Encyclopaedia 
article into English with the help of my lecturer, Dr Schlapp, 
in order to make it easier for Whittaker to form an opinion). 
But all in vain. He insisted that everything of importance had 
already been said by Poincare, and that Lorentz quite plainly 
had the physical interpretation. As it happens, I know quite 
well how sceptical Lorentz was and how long it took him to 
become a relativist. I have told Whittaker all this, but with- 
out success. I am annoyed about this, for he is considered a 
great authority in the English speaking countries and many 
people are going to believe him. It is particularly unpleasant in 
my opinion that he has woven all sorts of personal information 
into his account of quantum mechanics and that my part in it is 
extolled. Many people may now think (even if you do not) 
that I played rather an ugly role in this business. After all, 
it is common knowledge that you and I do not see eye to 
eye over the question of determinism. What is more, I have 
written a small article which is shortly to appear in which I 



197 



BORN-EINSTEIN LETTERS 

give a theoretical interpretation of an idea of Freundlich's about 
stellar red shift, which could, if correct, cause difficulties for 
the relativistic interpretation. Therefore my feeling towards 
you is that of a cheeky urchin who can get away with certain 
liberties without offending you, But it may well seem less 
harmless to other people. Well, I had to write this and get it 
off my chest. 

Hedi and I have just returned from Germany. We have been 
in Gottingen, attending the town's thousandth anniversary, 
when Nohl, Franck, Courant and I were given the freedom of 
the city. It was a harmonious celebration. Franck and Courant 
will be able to tell you about it. Afterwards we went to Bad 
Pyrmont, where we are building a small house where we can 
settle down and spend our old age. I am about to retire from 
my academic post. Life in Germany is quite pleasant again; 
the people have been thoroughly shaken up and anyway there 
are many fine, good people. We have no choice, as I receive 
a pension in Germany but not here. Hedi sends kindest regards 
to you and Margot. 

In old friendship 
Max Bom 



Sir Edmund Whittaker's book is a brilliant and historic philosophical 
work which I found extremely useful in my early years. During my time in 
Edinburgh we had become very close friends. It grieved me all the more 
that he should dispute Einstein's merits in the special theory of relativity. 
As far as Lorentz is concerned my account is, if anything, too kind; he 
probably never became a relativist at all, and only paid lip service to 
Einstein at times in order to avoid argument. 

The celebration in Gottingen caused us quite a headache to begin with. 
Franck at first did not want to accept the invitation under any circumstances. 
Courant and I were in two minds; when we eventually decided to go, 
plain curiosity played a certain part in our decision, and Franck even- 
tually joined us. Our choice of Bad Pyrmont as the place where we would 
spend our old age was really due to sentimental memories. During our 
engagement my fiancee's parents in Leipzig had sent her, together with 
two of her girl friends, to Bad Pyrmont for the sake of her health. At that 
time it was known specifically as a spa for women, renowned for the treat- 
ment of anaemia and so on. I was then a private lecturer in Gottingen and 
travelled every weekend by train to Pyrmont. There we spent some delight- 
ful days together, which we liked to remember later on. When we decided 



198 



BORN-EINSTEIN LETTERS 



to return to Germany in 1953 we looked around for a quiet and beautiful 
place in the Black Forest and elsewhere. Finally we remembered the period 
of our engagement that we spent in Bad Pyrmont. We stayed there for a 
few weeks of our summer holidays and, as we liked it, searched for and 
found a plot on which to build our small house. 



103 



12 October, ig^s 



Dear Bom 

Don't lose any sleep over your friend's book. Everybody does 
what he considers right or, in deterministic terms, what he 
has to do. If he manages to convince others, that is their own 
affair. I myself have certainly found satisfaction in my efforts, 
but I would not consider it sensible to defend the results of 
my work as being my own 'property', as some old miser might 
defend the few coppers he had laboriously scraped together. 
I do not hold anything against him, nor of course against you. 
After all, I do not need to read the thing. 

If anyone can be held responsible for the fact that you are 
migrating back to the land of the mass-murderers of our 
kinsmen, it is certainly your adopted fatherland - universally 
notorious for its parsimony. But then we know only too well 
that the collective conscience is a miserable Uttle plant which 
is always most likely to wither just when it is needed most. 

For the presentation volume to be dedicated to you, I have 
written a little nursery song about physics, which has startled 
Bohm and de Broglie a little. It is meant to demonstrate the 
indispensability of your statistical interpretation of quantum 
mechanics, which Schroedinger, too, has recently tried to 
avoid. Perhaps it will give you some amusement. After all, 
it seems to be our lot to be answerable for the soap bubbles we 
blow. This may well have been so contrived by that same 'non- 
dice-playing God' who has caused so much bitter resentment 
against me, not only amongst the quantum theoreticians but 
also among the faithful of the Church of the Atheists. 
Best regards, also to your wife 
Yours 

A. Einstein 



199 



BORN-EINSTEIN LETTERS 

Einstein's reaction to my complaint about Whittaker's account of the 
theory of relativity proves his utter indifference to fame and glory. 
Then follows the harsh expression 'land of mass-murderers'. This was his 
opinion, and he never deviated from it. He was never able to understand 
why I returned to Germany, and never approved of it. 
It may thus be appropriate to say something about it here. During the war 
and for some time afterwards, particularly when the atrocities of Ausch- 
witz, Buchenwald and Belsen became known, we were of the same opinion. 
But when we began to re-establish connections with our relatives and 
friends in Germany the matter took on a different aspect. Many of them 
had undergone terrible experiences and sufferings. My wife tried to 
help as much as the scarcity in Great Britain permitted. 
My post in Edinburgh came to an end in 1953. The fact that I could not 
look forward to an adequate provision in my old age was not, as Einstein 
thought, due to 'Scottish parsimony' ; all over England, as well as Scotland, 
there are no pensions for professors. There are only contributory insurance 
schemes whose yield depends on the length of one's service, which in my 
case had been too short. My income would have been less than that of an 
unskilled labourer. Another factor which influenced us was the tough 
Scottish climate, which for anyone not brought up there is hard to bear. 
During this time (1947) I was offered the directorship of the Dublin 
Institute of Advanced Studies as successor to Schroedinger, who had been 
recalled to Vienna, his native town. I declined after lengthy negotiations, 
because I did not feel confident that my strength was equal to taking on a 
new task; besides, after five years in office I would still have reached 
retirement age and would have faced the same problem once again. In the 
meantime I had been reinstated in Gkittingen as Professor Emeritus on full 
salary. Quite some time went by before it was decided to allow this to be 
paid in foreign countries. 

The first sortie into Germany was to be made by my wife. She had been 
invited to Gottingen by the philosopher Herman Nohl to give a talk there 
on British democracy as we had experienced it. But she was prevented 
from making the journey, which would have been subsidised by the Foreign 
Office in London, because on her arrival at King's Cross station in London 
all her luggage was stolen. 

In 1948 I was awarded the Max Planck medal of the Deutsche Physi- 
kalische Gesellschaft (German Physical Society). This had been founded 
at Max von Laue's and my instigation a short time before we emigrated. 
The annual general meeting of the society was held in September 1948 
in Clausthal-Zellerfeld. We took part and were given a friendly reception, 
but we were at that time still regarded as visitors from England, watched 
over and taken care of by the occupying power. 
The impression made on us by the Harz moimtains, and the small towns 



SCO 



BORN-EINSTEIN LETTERS 

such as Goslar which had not been destroyed, was deep and moving. 
In the following few years we spent our summer holidays in Oberstdorf 

in the Allgau. 

In 1953 the town of Gottingen celebrated its thousandth anmversary. 
Franck, Courant and I were among those who were to be given the free- 
dom of the city on this occasion. Franck wanted to turn it down at first, 
but after a lengthy correspondence we decided not to reject this gesture 
of reconciUation. The celebrations took place with due solemnity and 
friendliness, and even the sceptical Franck found no reason to complain. He 
paid frequent visits to Gottingen later on, and it was during one of these 
that he died (in 1964) . 

After these experiences we decided to settle down m Germany. In 
choosing Bad Pyrmont we took into account its beautiful situation sur- 
rounded by wooded hills, the fact that as a watering place it was quiet and 
well cared for, the close proximity of Gottingen and, most important of all, 
the Quaker house, the headquarters of the ReUgious Society of Friends m 
Germany. My wife had joined this society in Edinburgh, and she had my 
full sympathy in this respect. The Quakers' creed had been one of strictest 
pacifism for many centuries, and because of this they had suffered greatly 
under the Nazi regime. We were certain not to find any mass-murderers 
amongst them. We wanted to five the quiet life, indoors with books and 
music, out-of-doors in the garden, the Spa's park and in the forests. But 
it turned out rather differently, because in the year we moved to our new 
home (1954) I was awarded the Nobel Prize. In this way my name 
became known all over Germany, and my voice was listened to. This 
resulted in a new task for the rest of my life. 

Many of my German colleagues shared my anxiety about the future of 
mankind, because of the atomic bomb. Foremost among these were 
Otto Hahn, the discoverer of atomic fission. Max von Laue, G. F. von 
Weizsacker and Walter Gerlach. They succeeded in bringing about the 
well-known 'Declaration of the Eighteen from Gottingen', which was 
directed against the atomic re-armament of the Federal Repubkc. My 
name appears on the document, and I had some part in its accomplish- 
ment, if not in its formulation. I felt it to be my duty to continue the 
task of enlightenment about the dangers of nuclear war and other 
technical developments, and the fight against war and militarism. I 
tried to do this by means of lectures, radio talks, television discussions 
and books. There would not have been any point in doing this in England. 
The British people are poUtically mature, and need no advice from an 
immigrant. The Germans however, have destroyed their national 
tradition by two lost wars, and the misdeeds of a criminal government. 
Here there was the chance of making one's influence felt. I regarded this 
work as my duty, but it also gave me pleasure. But today (at the end of 



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BORN-EINSTEIN LETTERS 

1965) it seems more than doubtful to me whether it has had any success. 
The unteachable are in the ascendancy again. 

The matter of the presentation volume was as follows. On my retirement 
from my chair in Edinburgh the university organised a small celebration, 
where a presentation volume was handed over to me: 'Scientific Papers, 
presented to Max Born on his retirement from the Tait Chair of Natural 
Philosophy in the University of Edinburgh'.« It contains papers by 
friends and former pupils of mine. Among these, however, were not only 
adherents of my statistical interpretation of quantum mechanics, but 
also four outspoken opponents. The first of these was Schroedinger, 
although he dealt with a different theme. Our differences had akeady 
been thrashed out in the papers from the British Journal for the Philosophy 
of Science that I mentioned in my commentary to letter loi. Contribu- 
tions also came from de BrogUe, David Bohm and Einstein, which dealt 
with the interpretation of quantum mechanics. As these questions play 
quite an important role in the correspondence with Einstein which follows, 
I should like to enlarge upon them here so that I can deal briefly with 
them thereafter. 

Schroedinger's point of view is the simplest; he thought that by his develop- 
ment of de Broglie's wave mechanics the whole paradoxical problem of 
the quanta had been settled: there are no particles, no 'quantum 
jumps' - there are only waves with their well-known vibrations, charac- 
terised by integral numbers. The particles are narrow wave-packets. The 
objection to this is that one generally (i.e. for processes which are classi- 
cally described with the help of several particles) needs waves in spaces of 
many dimensions, which are something entirely different from the waves 
of classical physics, and impossible to visualise; that wave packets 
representing solutions of the Schroedinger equations do not propagate 
without change of shape, but disperse; and other similar objections. 
Schroedinger's point of view has, I think, definitely been abandoned 
today. 

De Broglie, the creator of wave mechanics, and Bohm accepted the 
results of quantum mechanics just as Schroedinger did, but not the 
statistical interpretation. They tried to develop ideas in which the 
deterministic character of the elementary processes were preserved, 
assuming that concealed mechanisms exist which were hidden by the waves' 
or suggesting that the formulae should be re-written so that they looked 
like deterministic mechanical laws. These attempts did not get far; it 
seems to me that today (1965) they have virtually disappeared. Even 
Einstein considered this point of view 'too cheap' (letter 99). 
His ideas were more radical, but 'music of the future'. He saw in the 
quantum mechanics of today a useful intermediate stage between the 
traditional classical physics and a still completely unknown 'physics of 



302 



BORN-EINSTEIN LETTERS 

the futiu-e' based on general relativity, in which - and this he regarded as 
indispensable for philosophical reasons - the traditional concepts of 
physical reality and determinism come into their own again. Thus he 
regarded statistical quantiun mechanics to be not wrong but 'incomplete'. 
His reasons were essentially philosophical and therefore difficuU to 
shake, least of all by purely physical arguments. Nevertheless I tried to 
answer him, and thus a sharp but always friendly dispute arose, which 
is expressed in the following letters. 

At the end of his letter, Einstein talks about the effect of his phrase, the 
'non-dice-playing God', and uses the expression so typical of him, 'Church 
of the Atheists'. He had no beUef in the church, but did not think that 
reUgious faith was a sign of stupidity, nor unbeUef a sign of intelligence; 
he knew, as did Socrates, that we know nothing. One should tell this to 
the Communists when they claim that he shared their beliefs. 



104 



Department of Mathematical Physics 

{Applied Mathematics) 

The University 

Drummond Street 

Edinburgh 8 

8 November, 1953 



DearEinstein 

Your kind letter of 12.10.53 has reassured me that old Whit- 
taker's peculiar pranks do not trouble you particularly. You 
say that it is unreasonable to behave like some old miser m 
defence of his property, who tries to hold on to the few pence 
he has managed to scrape together. I agree with you whole- 
heartedly, and I too have tried to keep my mouth shut when- 
ever my own few coppers have disappeared into other people's 
pockets. But I have sinned against this good doctrine a little 
lately. I am sending you several of my papers on general themes, 
including my Guthrie lecture (given to the Physical Society, 
London), in which I have explained my contribution to 
quantum mechanics with as much modesty as I was able to 
muster, not only with regard to the statistical interpretation but 
also to the theory itself. That Heisenberg's matrices bear his 
name is not altogether justified, as in those days he actually had 
no idea what a matrix was. It was he who reaped all the 
rewards of our work together, such as the Nobel Prize and that 



203 



BORN-EINSTEIN LETTERS 

sort of thing. I do not begrudge it him in the least, but for the 
last twenty years I have not been able to rid myself of a certain 
sense of injustice. Purely practical matters are involved, such 
as the return to Germany, for example, which you clearly regard 
with a certain amount of suspicion. You are wrong in casting 
aspersions on my dear Scots; the inadequate provision for the 
old age of teachers and professors is quite general all over Bri- 
tain, and is just as wretched in Oxford and Cambridge. If 
anyone is to blame it is the Swedes, who could quite well have 
found out about my contribution to quantum mechanics. But 
that happened in the year of Heil-Hitler, 1933. Now they have 
realised it, apparently, for six months ago they made me a 
member of their academy. Though this does not help me with 
my practical problems such as the choice of a place to live. But 
to be quite honest, I must admit that I would probably return to 
Germany even if I had the chance to remain here. Hedi is still 
homesick for the Weser mountains and I, too, love the beautiful 
countryside around Pyrmont, where we are building a small 
house (which will have central heating, of course, which does 
not exist here, because the Scots are such hardy fellows that 
they do not worry about chilblains and arthritis). As for the 
people, I only want to teU you that the German Quakers have 
their headquarters in Pyrmont. They are no 'mass-murderers', 
and many of our friends there suffered far worse things under 
the Nazis than you or I. One should be chary of applying 
epithets of this sort. The Americans have demonstrated in 
Dresden, Hiroshima and Nagasaki that in sheer speed of ex- 
termination they surpass even the Nazis. 

I must wait a little longer for the presentation volume to 
which you have contributed. It is to be ceremoniously presented 
to me on November 24th. I am keenly looking forward to your 
treatment of the assertions by Schroedinger and Bohm. You will 
find my comments on them in a small package of papers which 
IS on its way to you. After the confession of my weaknesses 
contained in this letter, there is no need to tell you how much 
pleasure I derive from being thus honoured by the most 
distinguished members of my profession. 

Hedi is in a nursing home at the moment. She suffered a 
Uttle breakdown, caused by all kinds of family worries and an 
excessive burden of domestic and social obligations. I am all 

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BORN-EINSTElN LETTERS 

alone in the house and am muddling through somehow. She is 
improving, and may well return home in a few day's time. 

If she knew that I was writing to you she would want to add 
her kindest regards to you and Margot. 
Yours 

Max Bom 



I have nothing to add to this 'confession of my weaknesses', except to wish 
that its publication today, when I am almost 86 years old and have been 
decorated with various honours, will not be held too much against me. 
I still fully subscribe today to my reply to Einstein's 'the land of mass- 
murderers.' One would have to have been brought up in the 'spirit of 
militarism' to understand the difference beiween Hiroshima and Nagasaki 
on the one hand, and Auschwitz and Belsen on the other. The usual 
reasoning is the following : the former case is one of warfare, the latter of 
cold-blooded slaughter. But the plain truth is that the people involved 
are in both instances non-participants, defenceless old people, women and 
children, whose annihilation is supposed to achieve some political or 
military objective. The first of the terrible attacks on Dresden was carried 
out by British bombers; the Americans came later. I mentioned the 
Americans in my letter as Einstein was living in America. I am certain 
that the human race is doomed, unless its instinctive detestation of 
atrocities gains the upper hand over the artificially constructed judgment 
of reason. 



105 



26 November, igjj 



Dear Einstein 

The presentation of the volume was made yesterday during a 
little celebration at the university. It gives me tremendous 
pleasure that so many of my old friends and colleagues have 
contributed to it. For the time being I have read only a few of 
the articles - yours was the first, of course, and you are also the 
first to receive my heartfelt thanks. 

Your philosophical objection to the statistical interpretation 
of quantum mechanics is particularly cogently and clearly 
expressed. But even so I must take the liberty of asserting that 



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BORN-EINSTEIN LETTERS 

your treatment of the example (that of a ball rebounding 
between two walls) does not prove what you say it does: namely, 
that in the limiting case of macroscopic dimensions, the wave- 
mechanical solution does not become the classical motion. 
This is due to the fact that - forgive my cheek - you have chosen 
an incorrect solution which is inappropriate to the problem. 
When it is done according to the rules, it results in a solution 
which, in the Hmiting case (mass^-oo), becomes exactly the 
classical, deterministic motion; although it always, of course, 
produces statistical statements of enormous probability only 
for finite (large) values of the mass. If one wants to describe 
a sequence of events, one has to use the 'time-dependent* 
Schroedinger equation: 

2m ox^ dt 

where ^ = hji-n (Planck's constant) , and m = mass ; and not, as you 
are doing, the special case, that ^ is proportional to e'"* (^ =£) ; 
for this is appropriate to sharply defined energy, hence an 
indeterminate position. 
The right solution in the range o <x <l is : 

00 

ip {x, = 2 An eK« sin b„x 



where <On 



2ml*' 



TTtl 

"T 



and A„ =j ip{x, o) sin -j- x dx. 



ili{x, o) is the arbitrary initial state. This has to be selected 
to express: at the time t=o the ball is close to point x^, with 
the approximate velocity v. Therefore ip{x, o) has to be zero 
everywhere except within the small range about point Xq, and 
it also has to be asymmetrical about Xq, so that the value to be 

expected for the velocity _L * ■"• 



.fjV. 



m 



[V^dA: 



has a predetermined 



value. One can easily add these ifi{x, o); with three arbitrary 

2o6 



BORN-EINSTEIN LETTERS 

constants, one for normalisation, one for y and one for imprecision 
of the range about x^. For example: 

i/i{x, o) =x{l-x){<x+px) e-('-*<>>'/2« 

(I do not know whether this function is convenient for calcu- 
lations). The result is certain to be (one can see it qualitatively 
without calculations) that the wave packet ^(;c, t) bounces to 
and fro in exactly the same way as a particle, while it becomes 
a little more indeterminate in the process. But these imprecisions 
become infinitesimally small as m-^oo. 

I am convinced that in this sense quantum mechanics also 
represents the motion of macroscopic single systems according 
to deterministic laws. I am going to carry out a thorough 
calculation of it with my collaborator (which is not easy to do 
formally), and will send you the result. Ultimately you will 
certainly admit that I am right, and when that happens it will 
somehow have to be made known to the readers of the pre- 
sentation volume. 

I more or less agree with what you said about de Broglie, 
Bohm and Schroedinger. Incidentally, Pauli has come up with 
an idea (in the presentation volume for de Broglie's 50th birth- 
day) which slays Bohm not only philosophically but physically 
as well. 

Another letter of mine is on its way to you by ordinary mail. 
With sincerest thanks and kindest regards, also from Hedi, 
Yours 

Max Bom 



Every quantum theoretician would probably recognise that my objection 
to Einstein's example was correct. It formed the basis for my printed 
reply which was subsequently published, and which will be the subject 
of further discussion. But, as Einstein pointed out in his next letter, it 
misses the point of his basic philosophical thoughts. 



207 



BORN-EINSTEIN LETTERS 



io6 



3 December, igjj 



Dear Bom 

Today I received (and read) your letter, as well as your printed 
material, which I intend to read thoroughly too. I was very 
pleased that you have taken my simple ideas seriously and did 
not dismiss them with a few superficial remarks like most 
people. 

I must say first of all that your point of view surprised me. 
For I thought that an approximate agreement with classical 
mechanics was to be expected whenever the relevant de 
Broglie wavelengths are small in relation to the other relevant 
spatial measurements. I see, however, that you want to relate 
classical mechanics only to those i/r-functions which are narrow 
with respect to coordinates and momenta. But when one 
looks at it in this way, one could come to the conclusion that 
macro-mechanics cannot claim to describe, even approxi- 
mately, most of the events in macro-systems that are con- 
ceivable on the quantum theory. For example, one would then 
be very surprised if a star, or a fly, seen for the first time, 
appeared even to be quasi-localised. 

But should one now adopt your point of view in spite of this, 
one should at least demand that a system which is 'quasi- 
localised' at a certain time should remain so according to the 
Schroedinger equation. This is a purely mathematical problem, 
and you expect that the calculations would bear out this 
expectation. But this seems quite impossible to me. The easiest 
way to realise this is to consider the three-dimensional case (of a 
macro-body), which is represented by a 'narrow' Schroedinger- 
function in relation to position, velocity and direction. There it 
seems obvious, even without a mathematical 'microscope', 
that the position must become more and more diffuse in the 
course of time. The one-dimensional case is similar, as the 
group-velocity depends on the wavelength. I think it would be 
a pity to waste your assistant's time when the result can never 
be in doubt. But if you are not convinced, by all means have 
the calculations done. Oppenheimer has extricated himself by 
claiming that the time required by the process of getting more 

ao8 



BORN-EINSTEIN LETTERS 

and more out of focus would be on a 'cosmic' scale, and that 
one could ignore it for that reason. But one could easily quote 
some quite pedestrian examples where the divergence time is 
not all that long. I consider it too cheap a way of calming 
down one's scientific conscience. All the same it is not difficult 
to regard the step into probabalistic quantum theory as final. 
One only has to assume that the ^-function relates to an en- 
semble, and not to an individual case; then one can use my 
example to describe, with the expected approximation (statisti- 
cally conclusive), what classical mechanics also describes. 
According to the interpretation which you support in your letter, 
one has to regard this circumstance as a kind of coincidence. 
The interpretation of the ^-function as relating to an ensemble 
also eliminates the paradox that a measurement carried out in 
one part of space determines the kind of expectation for a 
measurement carried out later in another part of space (coupling 
of parts of systems far apart in space) . 

One can safely accept the fact that, according to this concept, 
the description of the single system is incomplete, if one assumes 
that there is no correspondingly complete law for the complete 
description of the single system which determines its develop- 
ment in time. 

Then one need not become involved with Bohr's interpreta- 
tion that there is no reality independent of the probable subject. 

I do not believe, however, that this concept, though consistent 
in itself, is here to stay. But I maintain that it is the only one 
which does justice to the mechanism oftheprobabilisticquantum 
theory. 

I am very much looking forward to reading the rest of your 
ideas on matters of principle. You call these thoughts 'philoso- 
phical', but unjustifiably so in my opinion. I am quite satisfied 
if one has the machinery for making predictions, even if we 
are unable to understand it clearly. 
Kindest regards 
Yours 

A.E. 



This letter marks the beginning of the period of mutual misunderstanding. 
Even today it seems to me that Einstein's reflections resulted from his 



209 



BORN-EINSTEIN LETTERS 

inadequate knowledge of quantum mechanics. His statement that 
'approximate agreement with classical mechanics is to be expected 
whenever the relevant de Broglie wavelengths are small in relation to 
the other relevant spatial measurements' is, of course, correct. The 
example he used to point out the weaknesses in quantum mechanics was 
that of a particle which bounces to and fro between two parallel, elastic 
and reflecting walls. He regards the distance between the walls to be the 
only relevant length to be taken into account. But this is only the case 
when nothing else is known about the position of the particle. Einstein 
now wants to compare the quantum mechanical with the classical 
treatment of this situation, where in the latter case it is taken for granted 
that the initial condition is known. The situation is somewhat different 
in the case of the analogous quantum-mechanical treatment, because 
of Heisenberg's relation of indeterminacy; the point of origin and the 
initial velocity can only be prescribed to an accuracy which is limited 
by this relation. But this one can and must do if one wants to compare the 
quantum-mechanical with the classical treatment. It is therefore both 
necessary and possible to state the range within which the particle 
initially lies; and this constitutes a second 'relevant measurement'. 
The next consideration, concerning the question of whether a particle 
which is 'quasi-localised' at a certain time must remain precisely locaUsed 
according to the Schroedinger equation, is based on a simple misunder- 
standing. I never expected this to be so for a moment. The initial impre- 
cision of the velocity brings about an imprecision which increases in the 
course of time. It was precisely this point which was of such importance 
to me from the beginning, for it is equally valid for classical mechanics, 
and shows that the usual assertion, that this is deterministic, only applies 
when one admits infinitely precise statements about the initial position 
and the initial velocity; and this seems to me metaphysical nonsense. 
Einstein admits that one can regard the 'probabilistic' quantum theory as 
final if one assumes that the i/^-function relates to the ensemble and not to 
an individual case. This has always been my assumption as well, and I 
consider the frequent repetition of an experiment as the realisation of the 
ensemble. This coincides exactly with the actual procedure of the experi- 
mental physicists, who obtain their data in the atomic and sub-atomic 
area by accumulating data from similar measurements. 
The last sentence of this letter is characteristic of Einstein in his old age. 
The 'it does not make sense' itself only makes sense when related to a 
definite philosophy. The same argument was used by the opponents of 
the young Einstein, who alleged that the consequences of the relativity 
theory did not make sense ; as for instance that if one of two twins goes 
on a journey through space while the other remains at home, the first, 
on his return, is younger than the other. 



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BORN-EINSTEIN LETTERS 



107 



Goldsborough Hotel 
Hills Road 
Cambridge 

S2 December, igj3 



Dear Einstein 

It was very nice of you to write to me again and to go into the 
details of my letter. As a matter of fact, I was very impressed by 
your article in my 'presentation volume', and could not rest 
until I had found a final answer to it. Your example needed to 
be calculated exactly from beginning to end at some time or 
other. The learned gentlemen at your institute and in other 
places do not concern themselves with such trivial problems 
But it is not at all easy, and I really had to rack my brain. 
Then too we started to move house at the same time, and en- 
countered considerable difficulties with both the German and 
British financial authorities, and so on. In the end I finished 
the work here in Cambridge, in an ice-cold hotel (as they all 
are in this country), where one is roasted in front by the fire 
while one's back freezes. But even so I managed to finish it 
and, what is more, all by myself, without the help of an assistant. 
You see, I have taken your warning to heart, but not out of 
sympathy for the man (or to prevent him from working in 
vain) but because I had the ambition to accomplish it by 
myself. It all turned out exactly as I had thought, and as I 
indicated in my last letter. The result is completely rigorous 
and incontrovertible, and it overcomes your objections, which 
are due only to the fact that these simple problems have not 
been considered thoroughly in any of the literature. You cannot 
do anything about it. But I hope to be able to convince'you at 
last that quantum mechanics is complete and as realistic as the 
facts permit. 

I am going to have the paper typed, and will hand it over to 
the Royal Society. I will send you a copy on thin paper and 
I will ask the publications assistant to accept anything you 
want to insert. His address is: Dr D. C. Martin, Assistant 
Secretary, The Royal Society, Burlington House, Piccadilly, 
London W. 1 . 

I would be very pleased if you would like to add a few lines 
or pages, if you agree, or have some new objections; the old 



211 



BORN-EINSTEIN LETTERS 



ones have, I believe, finally been settled. For many years your 
critical dissociation from the general business of quantum 
mechanics has been quite unbearable to me. Much happens 
there which is contestable, particularly in Princeton; but the 
foundations laid down by Heisenberg and myself are quite in 
order, and there is no other way. Perhaps it is presumptuous of 
me to contradict you, as you did not concede anything to 
Niels Bohr. But Bohr's expressions are frequently nebulous and 
obscure. I am simpler and possibly clearer. Well, do not hold 
it against me. 

Kind regards from Hedi, also to Margot, and good wishes 
for Christmas and the New Year. 
Your old 

Max Born 



1 08 



/ January, 1954 



Dear Bom 

Your concept is completely untenable. To demand that the 
i/r-function of a macro-system should be 'narrow' in relation to 
the macro-coordinates and momenta is incompatible with 
the principles of quantum theory. A demand of this kind is 
irreconcilable with the superposition principle for i/<-functions.* 
As against this the following objection, which also appHes in 
almost every case, is only of secondary importance: that the 
Schroedinger equation in time leads to a dispersion of the 



narrowness 



You claim that the latter does not apply to the system I have 
been considering. But I am convinced that this result (not 
very important when seen from the point of view of the problem 
in general) is based on a mistaken conclusion. I do not want to 
take part in any further discussion, such as you seem to envisage. 
I content myself with having expressed my opinion clearly. 
With best regards and wishes for 1954 
Yours 

A. Einstein 



212 



BORN-EINSTEIN LETTERS 

♦Leti/riand^abe two solutions of the same Schroedinger equations. 
Then ip='l'i + 4'i also represents a solution of the Schroedinger 
equation, with an equal claim to describing a possible real state. 

When the system is a macro-system, and when ipi and ifr^ are 
'narrow' in relation to the macro-coordinates, then in by far 
the greater number of cases this is no longer true for ^. 

Narrowness in regard to the macro-coordinates is a require- 
ment which is not only independent of the principles of quantum 
mechanics but, moreover, incompatible with them. 



109 



ic Howitt Road 

Belsize Park 

London JV. W.3 

2 January, 1954 



Dear Einstein 

I enclose a short paper of mine, which links up with your 
contribution to the presentation volume. I am grateful to you 
for having forced me to think your simple example over 
thoroughly in my own way. That I have thereby arrived at a 
result which is different from yours, you will have to accept 
into the bargain. Presumably you will stick to your own way of 
thinking. I am going to hand over the papers to be published in 
the Proceedings of the Royal Society and will, as I mentioned, tell the 
Secretary, Dr Martin, that you might want to add a reply. I would 
be pleased if you did, even if you are going to contradict me. 

These considerations have provided the impetus for me to 
make a new advance in the direction of the elementary particles, 
with the help of the reciprocity principle which I formulated 
years ago. Nothing has come of it up to now, but this time it 
seems to be working, thanks to the simple realisation which I 
have drawn from the inspiration you gave me. 

I am in London visiting my nephew, but am shortly going to 
return to Edinburgh, where I still have quite a lot to do. I am 
going to live with our doctor. Hedi is in Germany and I am 
going to follow her in four weeks' time. Our household in 
Edinburgh has been disbanded. 

With bestwishesfor a happy New Year, and kindest regards 
Yours Max Bom 



213 



BORN-EINSTEIN LETTERS 



BORN-EINSTEIN LETTERS 



IIO 



12 January, igj4 



Dear Born 

Thank you for sending me your paper for the Royal Society, 
from which I see that you entirely missed the point which 
matters to me most of all. As I do not feel inclined to appear 
before the circus publicum in the role of fencing master, but as 
on the other hand I wanted to give you an answer, I herewith 
send you the kind of reply I could have made. In this way, too, 
there may be some hope of your thinking the matter over 
dispassionately, a hope which has already melted away 
considerably. 

With best regards 
Yours 

A.Einstein 

The above paper by M. Born merely shows me that my 
contribution to the presentation volume dedicated to him did 
not succeed in formulating the problems I posed with sufficient 
clarity. In particular, I did not intend to raise objections 
against the quantum theory, but to make a modest contribution 
to its physical interpretation. 

In the quantum theory the state of a system is characterised 
by a 0-function which, in its turn, represents a solution of the 
Schroedinger equation. Each of these solutions (i/r-functions) 
has to be regarded, within the sense of the theory, as a descrip- 
tion of a physically possible state of the system. The question is : 
in what sense does the (/(-function describe the state of the system ? 

My assertion is this: the i/«-function cannot be regarded as a 
complete description of the system, only as an incomplete one. 
In other words: there are attributes of the individual system 
whose reality no-one doubts but which the description by 
means of the ^-function does not include. 

I have tried to demonstrate this with a system which contains 
one 'macro-coordinate' (coordinate of the centre of a sphere of 
I mm diameter). The ^-function selected was that of fixed 
energy. This choice is permissible, because our question by its 
very nature must be answered so that the answer can claim 



\ 



validity for every 0-function. From the consideration of this 
simple special case, it follows that - apart from the existing 
macro-structure according to the quantum theory - at any 
arbitrarily chosen time, the centre of the sphere is just as likely 
to be in one position (possible in accordance with the problem) 
as in any other. This means that the description by (/(-function 
does not contain anything which corresponds with a (quasi-) 
localisation of the sphere at a selected time. The same applies 
to all systems where macro-coordinates can be distinguished. 

In order to be able to draw a conclusion from this as to the 
physical interpretation of the (/(-function, we can use a concept 
which can claim to be valid independently of the quantum 
theory and which is unlikely to be rejected by anyone: every 
system is at any time (quasi-) sharp in relation to its macro- 
coordinates. If this were not the case, an approximate descrip- 
tion of the world in macro-coordinates would obviously be 
impossible ('localisation theorem'). I now make the following 
assertion : if the description by a ^-function could be regarded 
as the complete description of the physical condition of an 
individual system, one should be able to deduce the 'local- 
isation theorem' from the ^-function, and indeed from any 
^-function belonging to a system which has macro-coordinates. 
It is obvious that this is not so for the specific example which has 
been under consideration. 

Therefore the concept that the (/(-function completely describes 
the physical behaviour of the individual single system is 
untenable. But one can well make the following claim: if one 
regards the ^-function as the description of an ensemble, it 
furnishes statements which - as far as we can judge - cor- 
respond satisfactorily to those of classical mechanics and, at the 
same time, account for the quantum structure of reality. In my 
opinion the 'localisation theorem' forces us to regard the 
0-function generally as the description of an 'ensemble', but 
not as the complete description of an individual single system. 
In this interpretation the paradox of the apparent coupling 
of spatially separated parts of systems also disappears. Further- 
more, it has the advantage that the description thus interpreted 
is an objective description whose concepts clearly make sense 
independently of the observation and of the observer. 
A.E. 



214 



215 



BORN-EINSTEIN LETTERS 



BORN-EINSTEIN LETTERS 



III 



20 January, ig54 



Dear Einstein 

Your letter of January 12th gave me pleasure and relieved me 
of the anxiety which your last letter had caused me. Its tone 
was irritable and angry, as if you had regarded the difference of 
opinion between us as a personal attack. I am glad that you 
have now given me an objective reply, even if I by no means 
agree with your opinion and, what's more, for reasons which are 
objective and completely 'dispassionate'. I have understood 
your ideas, but I am convinced that your starting point is an 
untenable one: the ^-function, which you rely on, is inappro- 
priate to the problem you intend to deal with. Although it 
represents a solution of the Schroedinger equation and fulfils 
the boundary conditions, it does not satisfy the initial conditions. 
Indeed, it lacks, in your own words, the properties required for 
the description of an individual system. But other solutions 
produced by superposition exist which satisfy the initial 
conditions required when one wants to follow an individual 
system. This can, of course, only be done approximately, but 
the greater the mass m, the more accurate it is. I have just 
calculated this limiting transition m^-oo, by using your example, 
and have found that it leads exactly to the classical description. 
The calculation is free from difficulty, and has been confirmed 
not only by my collaborators, but also by my successor. Prof. 
Kemmer, and by the critical and sceptical Schroedinger. 
If you are in any doubt, ask Johann V. Neumann to read the 
manuscript, or Weyl, who is probably now in Princeton. 

You were probably affronted because I used the opportunity 
to hit out at classical determinism. But I am convinced that 
even this will eventually seem plausible to you too, if you take 
plenty of time to read it, and discuss it with Weyl and Neumann. 
In any case, you must not be angry with me. My intentions are 
sincere and objective, and my respect for you is undiminished, 
even if I do not share your opinion. But you need not write to 
me any more if you consider me a hopeless case. Should that 
be so, write to Hedi, who is delighted with every line she 
receives from you. She suffers from constant noise in one ear, 

216 



and cannot sleep for this reason; she is taking a cure in the 
Harz mountains, where I am also going shortly. 

I am taking part in another piece of heresy in company with 
Erwin Freundlich. It has already been printed, and I am going 
to send you a copy. Incidentally, Freundlich has been seriously 
ill, arterial thrombosis of the heart. 

Hoping that you are not angry with me, with sincere 
regards 

Yours 

Max Bom 



The preceding letters show how two intelligent people can misunderstand 
each other while discussing concrete problems. Each was convinced that 
he was right and the other wrong. This happened because each proceeded 
from a different point of view, which he regarded as incontestable, and 
was thereby prevented from accepting that of the other. 
In this situation it was fortunate that a third person intervened and acted 
as intermediary: Wolfgang Pauli. I have included three of his letters to 
me below. He has already appeared in this correspondence as my assis- 
tant in Gottingen, the first of a series of outstanding young people. He 
had then, when barely twenty years old, already written a great work, the 
article about the theory of relativity in the Encyclopaedia, which was for 
a long time the best representation of the theory of relativity and is 
today still regarded as one of the authoritative sources. Pauli became a 
professor in Zurich. He went to America during the second world war, 
as he feared that Switzerland, like other small countries such as Belgium, 
Holland and Norway, would also be overrun by Hitler's armies. He became 
a close friend of Einstein's and regarded himself, probably with some 
justification, as the designated 'successor' in theoretical physics. With me, 
too, he remained in constant contact, although mainly by letter. 



112 



Princeton, N.J. 

The Institute for Advanced Study 

3 March, 1934 



Dear Mr Born 

I am here on a brief visit. I intend to be back in Zurich by the 
middle of April. In my spare time I have read many things, 
including the 'Scientific Papers' which were dedicated to you 



217 



BORN-EINSTEIN LETTERS 



on the occasion of your retirement. They contain some inter- 
esting contributions, and I think the photograph of you is very 
good. Einstein's article arrested my attention, of course, 
particularly as I was able to talk it over with him in person, 
which is much easier than a discussion by letter. He also told me 
that there had been some correspondence with you on this 
subject. I believe I am fairly well able to understand what he 
means, as I know both Einstein and quantum mechanics, but 
what jowr point of view was I could not quite see from Einstein's 
remarks. As I am interested in this matter in general, and in the 
discussion between you and Einstein in particular, I would be 
grateful if you could write a brief summary for me of the point 
of view represented by you (details are not important to me). 
It is clear that quantum mechanics must, in principle, be 
able to claim validity for small macroscopic spheres; their finer 
structure (atomic constitution) clearly does not come into 
play. 

Now from my conversations with Einstein I have seen that 
he takes exception to the assumption, essential to quantum 
mechanics, that the state of a system is defined only by specification 
of an experimental arrangement. [By the way, Einstein says instead of 
'specification of the experimental arrangement' : 'that the state 
of a system depends on the way one looks at it'. But it boils down 
to the same thing. M. Born.] Einstein wants to know nothing of this. 
If one were able to measure with sufficient accuracy, this would 
of course be as true for small macroscopic spheres as for electrons. 
It is, of course, demonstrable by specifying thought experiments, 
and I presume that you have mentioned and discussed some of 
these in your correspondence with Einstein. But Einstein has the 
philosophical prejudice that (for macroscopic bodies) a state 
(termed 'real') can be defined 'objectively' under any circum- 
stances, that is, without specification of the experimental 
arrangement used to examine the system (of the macro-bodies), 
or to which the system is being 'subjected'. It seems to me that 
the discussion with Einstein can be reduced to this hypothesis 
of his, which I have called the idea (or the 'ideal') of the 
'detached observer'. But to me and other representatives of 
quantum mechanics, it seems that there is sufficient experi- 
mental and theoretical evidence against the practicability of 
this ideal. 



2l8 



BORN-EINSTEIN LETTERS 

For the rest, however, I believe that it represents pure logic. 
Now I would very much like to know what you think of it. 
Kind regards 
Yours 

W.Pauli 



113 



Bismarckstrasse g 

Bad Pyrmont, Germany 

77 March, igj4 



Dear Einstein 

A letter inviting me to contribute to a collection of congratula- 
tory messages for your 75th birthday arrived here too late. 
Please overlook the fact that my congratulations are too late 
as well - I wish you health, cheerfulness and the strength to 
work. I would so much like to see you again some time! For 
there is no one in the world for whom I have more profound 
admiration, and to whom I am more indebted, than you. This 
is not at all affiected by our temporary difference of opinion. I 
have had several invitations to come to America recently, one 
for example to give the Messenger Lectures at Cornell Univer- 
sity. But I was unable to accept any of them. We are only just 
settling down here, and cannot leave again so soon. Moreover, I 
have two books in preparation : one about the theory of crystals 
is at the proof stage, and the manuscript of the other on optics is 
almost completed. I cannot take on any further obligations such 
as the invitation to Cornell would inevitably involve. In 
addition I was born on the other side of the Iron Curtain and 
am a member of the Russian Academy of Sciences. This would 
mean that one would be treated rather horribly at the con- 
sulates. My successor in Edinburgh, Kemmer, did not get a visa 
for a short visit to America because he was born in St Petersburg 
more than forty years ago. But it is still possible that Hedi and I 
may one day come to the United States and visit you. 

Pauli has written to me to say that you have talked to him 
about our correspondence. But it was not clear to him what it is 



aig 



BORN-EINSTEIN LETTERS 

I am asserting, and he asked for information. Could you perhaps 
give him my manuscript? That would save me a great deal of 
trouble. 

With best wishes and kind regards, 
Yours 

Max Bom 



This letter came from Bad Pyrmont, where we had moved at the beginning 
ofi954. 

Among the invitations to America was one from the University of California 
at Berkeley (perhaps it arrived after this letter had been sent off). This 
tempted me, as I had come to know and love this area during previous 
visits, with its blue skies, orchards, mighty mountain ranges, magnificent 
coastline and friendly people. One of the reasons why I refused this 
invitation was that Edward Teller Uved there. He used to work with 
me in Gkittingen, but had in the meantime risen to become 'father of the 
atom bomb'. I did not want to have anything to do with him. 



114 



1 2 March, igj4 



Dear friend Albert Einstein 

There can never be enough opportunities to wish other people 
well, especially when the other person has meant so much and 
been so helpful as you were to me during our years in Berlin. 
You may not even be aware of this yourself. But whenever the 
war really got me down and I came to see you, something of 
your Olympian outlook on life rubbed off on me and, happy 
once more, I went on my way. Now we are all of us approaching 
those years of which Henriette Feuerbach in her Altersgedanken 
[Thoughts of Old Age] wrote that 'the spirit floats above still 
waters'. I now wish you, in unchanging loyalty and friendship, 
many years of peaceful old age and the spirit to enjoy them. 
When Max reached seventy, I was reminded of a poem which 
our then eight-year-old Irene wrote for my father's seventieth 
birthday. It began like this: 

'Merkwiirdig ist's auf dieser Welt 

Wie lang ein Menschenkind doch halt! . . .' 



230 



BORN-EINSTEIN LETTERS 

['It is a strange thing in this world of ours that a human being 
lasts for such a long time' !] 

But when one gets old oneself, it does not seem such a long time 
at all; particularly when, unlike you, one cannot look back 
upon so long a chain of products of one's mind as you are able 
to do, as one has spent so much of one's time dreaming and 
vegetating as I have done. 

Give a kiss to dear Margot on my behalf. 
As always 

oldHedi 



115 



Princeton, The Institute for 

Advanced Study 

31 March, 1954 



Dear Bom 

Thanks for your letter. I am writing from here after all, for 
when I get back to Zurich on April nth I will probably find 
work waiting for me and will have no time. Also, Einstein gave 
me your manuscript to read; he was not at all annoyed with you, 
but only said you were a person who will not listen. This agrees 
with the impression I have formed myself insofar as I was un- 
able to recognise Einstein whenever you talked about him in 
either your letter or your manuscript. It seemed to me as if you 
had erected some dummy Einstein for yourself, which you then 
knocked down with great pomp. In particular, Einstein does 
not consider the concept of 'determinism' to be as fundamental 
as it is frequently held to be (as he told me emphatically many 
times), and he denied energetically that he had ever put up a 
postulate such as (your letter, para. 3) : 'the sequence of such 
conditions must also be objective and real, that is, automatic, 
machine-like, deterministic'. In the same way, he disputes that 
he uses as criterion for the admissibility of a theory the question : 
'Is it rigorously deterministic ?' 

Einstein's point of departure is 'realistic' rather than 'deter- 
ministic', which means that his philosophical prejudice is a 
different one. His train of thought can be reproduced briefly 
thus: 
I. A preliminary question: Do all mathematically possible 



221 



BORN-EINSTEIN LETTERS 



X, 



solutions of the Schroedinger equation, even in the case of a 
macro-object, occur in nature under certain conditions 
{in my opinion this question has to be answered in the affirmative 
whatever happens) or only in those special cases where the 
position of the object is 'exactly', 'sharply' defined ? 
Comment: If the latter class of solutions (which we denote 
[Axf <Ll) is described by K», it has the following attributes : 
i. When ^^{x) and ^a(x) also belong to K», but their mean 
positions 

are widely separated, that is to say {xz-x;f>Ll, then 
{A) Ci-^i [x) + C2<^2 {x) =4>{x) does not belong to K". 
ii. If ^i(Ar, to) belongs at a certain time ^o to K", then (^i {x, t) 
no longer belongs to K" when \t-to\ is sufficiently large. 
It therefore seems impossible to me to confine oneself in 
principle to the solutions of the Schroedinger equation of the 
special class K", and this cannot in principle be different for 
a macro-body than, let us say, for an H atom or for a single 
electron. For if quantum mechanics is correct, then a macro- 
body has in principle to show diffraction (interference) 
phenomena, and the difficulties are only going to be technical 
because of the small size of the wavelength. 

In that case, however, one also needs the superpositions of 
type (A) from solutions of class K" which do not themselves 
belong to K". This is, for example, the case with interference 
phenomena, when a particle passes through two (or more) 
openings (in this case it does not matter whether they are 
'spheres which are visible under the microscope' or 'elec- 
trons'). 

Up to this point, it seems to me, there is agreement. 
2. Now to Einstein's essential question: How are those solutions of 
the Schroedinger equation which do not belong to class K^ {for 
example, macro-objects) to be interpreted in physical terms ? 

Here Einstein's reasoning is as follows : 
A. When one 'looks at' a macro-body, it has a quasi- 
sharply-defined position, and it is not reasonable to invent a 
causal mechanism according to which the 'looking' fixes 
the position. 



222 



BORN-EINSTEIN LETTERS 

Comment: Instead of 'looking at', I would say 'illuminating 
with convergent light', and instead of the further 'looking', I 
would say 'a suitable experimental arrangement'. Apart 
from that I am still in agreement, because in this case I do 
not consider that the appearance of the definite position or, 
what amounts to the same thing, its appearance as a result of 
the observation, can be deduced by natural laws. 
Einstein's reasoning continues : 

B. Therefore a macro-body must always have a quasi- 
sharply-defined position in the 'objective description of 
reality'. As those i/r-functions which do not belong to class K" 
cannot in principle be 'thrown away', and must also be in 
accordance with nature, the general ^-function can only be 
interpreted as an ensemble description. If one wants to assert 
that the description of a physical system by a i^i-function is 
complete, one has to rely on the fact that in principle the natural 
laws only refer to the ensemble-description, which Einstein 
does not believe (not only in those at present known to us). 
What /do not agree with is Einstein's reasoning B (please note 
that the concept of 'determinism' does not occur in it at all!). I 
believe it to be untrue that a 'macro-body' always has a quasi- 
sharply-defined position, as I cannot see any fundamental 
difference between micro- and macro-bodies, and as one always 
has to assume a portion which is indeterminate to a considerable 
extent wherever the wave-aspect of the physical object concerned 
manifests itself. The appearance of a definite position Xo during 
a subsequent observation (for example, 'illumination of the 
place with a shaded lantern') above the opening in the figure* 
on the previous page, and the statement 'the particle is there', is 
then regarded as being a 'creation' existing outside the laws' of 
nature, even though it cannot be influenced by the observer. 
The natural laws only say something about the statistics of these 
acts of observation. 

As O. Stern said recently, one should no more rack one's 
brain about the problem of whether something one cannot 
know anything about exists all the same, than about the ancient 
question of how many angels are able to sit on the point of a 
needle. But it seems to me that Einstein's questions are ul- 
timately always of this kind. 

* The figure was not with the letter. 



223 



BORN-EINSTEIN LETTERS 

Einstein would not agree with this, and he would demand 
that the 'complete real description of the system' even before the 
observation must already contain elements which would in 
some way have to correspond with the possible differences in the 
results of the observations obtained by 'illumination with a 
shaded lantern'. / think, on the other hand, that this postulate 
is inconsistent with the freedom of the experimenter to select 
mutually exclusive experimental arrangements (for instance, 
radiation with long parallel light wavelengths !) . 

To summarise I should like to say this : while I have no objection 
to the formal calculations your manuscript contains - which 
incidentally, were not unknown to me - it completely bypasses 
the problems which are of interest to Einstein. In particular it 
seems to me misleading to bring the concept of determinism 
into the dispute with Einstein. 

A further remark here, independently of Einstein, to illus- 
trate the difference between classical mechanics and quantum 
mechanics when 'measuring' a 'path'. 

A. Classical mechanics. Let us consider, for example, the deter- 
mination of the path of a planet. One should measure the 
position repeatedly (at different moments of time to, ^, . . •) 
always with the same accuracy Axq. If one is in possession of the 
simple laws for the motion of the body (for example, Newton's 
law of gravitation), one is able to calculate the path (also position 
and velocity at any given time) of the body with as high an 
accuracy as one likes (and also to test the assumed law again at 
different times). Repeated measurements of the position with 
limited accuracy can therefore successfully replace one measure- 
ment of the position with high accuracy. The assumption of 
relatively simple laws of force Uke that of Newton (and not 
some irregular zig-zag motion or other on a small scale) then 
appears as an idealisation which is permissible in the sense of 
classical mechanics. 

B. Quantum mechanics. The repetition of positional measurements 
in sequence with the same accuracy Ax(, is of no use at all in 
predicting subsequent positional measurements. For every 
positional measurement to an accuracy Axg at the time f„ 
implies the inaccuracy 



234 



BORN-EINSTEIN LETTERS 



Axt. 



mAx, 



iUl-tn) 



at a later time, and destroys the possibility of using all previous 
positional measurements within these limits of error \ (If I am not 
mistaken, Bohr discussed this example with me many years 
ago.) 

The main difference between the theories A and B, which is 
that in B information obtained as a result of earlier measure- 
ments can be lost after one measurement, has not been ex- 
pressed clearly enough in your manuscript. 
With kind regards 
I remain 

Yours 

W.Pauli 



Pauli's discussion of the fundamental difTerence between classical and 
quantum mechanics is now probably the common property of all physi- 
cists. But his formulations are so simple and striking that they deserve to 
be preserved here. 

His next, shorter letter comes from Zurich. It is even more technical than 
the last one, but deserves to be reproduced here for the same reasons. 



ii6 



Physikalisches Institut der Eidg. 

Technischen Hochschule 

Zurich 

15 April, 1 954 



Dear Mr Born 

Having returned home safely, I found your letter of April loth. 
I doubt, however, whether there is much more to be said. 
I . Einstein. I entirely agree with your opinion that Einstein has 
'got stuck in his metaphysics'; though I would call his meta- 
physics 'realistic', not 'deterministic'. It is always those wave 
functions which do not belong to the special class K»* from 
which he wants to make a rope to hang quantum mechanics 
by, claiming: those solutions which do not belong to K» (which 
* An example: \ji=Ae^'^ cos Cx. 'Class K"' is just my abbreviation. 



225 



BORN-EINSTEIN LETTERS 

are the case in general) are 'only' an 'incomplete' ensemble-de- 
scription of 'reality' because, according to his metaphysics, the 
place of a macro-object must always be 'quasi-sharply-defined' 
in the objectively real state (in quantum mechanics, however, 
this is only the case for the special solutions of class K", and only 
for limited time intervals) . 

Thus I have already tried in my last letter to explain Ein- 
stein's point of view to you. It is exactly the same in Einstein's 
printed work and in what he said to me. What is more, on the 
occasion of my farewell visit to him he told me what we 
quantum mechanicists would have to say to make our logic 
unassailable (but which does not coincide with what he himself 
believes): 'Although the description of physical systems by 
quantum mechanics is incomplete, there would be no point in 
completing it, as the complete description would not agree with the 
laws of nature.' I am not, however, altogether satisfied with this 
formulation, as it seems to me to be one of those metaphysical for- 
mulations of the 'angels on the point of a needle' type (whether 
something exists which nobody can know anything about). 
2. Independent of Einstein. The solutions Q^^ {x)+C^2 W> 
where ^^ {x) and ^g (x) do not coincide: Jf(x) <j>i{x) (fi^ix) dx 
'^o in the x-space results in nothing other than classical mech- 
anical ensembles (which can be described by densities P), but 
does so (after Fourier decomposition) in the p-space, as long as the 
phase a in Ci^Cjt^" is well defined. There is, of course, no 
difficulty in this; on the contrary, it is satisfactory. After 
averaging over a one obtains a mixture (which cannot be de- 
scribed by a single wave-function, but - as in wave mechanics - 
by a density matrix P, after v. Neumann), which is then quite 
indistinguishable from a mixture in classical mechanics. 

Einstein has, of course, no objection to ensembles in classical 
mechanics, as these admittedly represent an incomplete 
description of the system in the sense oi classical mtchdimcs. He is 
only interested in his assertion that the characterisation of a 
state by a wave-function ('pure case' after v. Neumann) is 
also 'incomplete', as the 'true objective state of reality' always 
has a quasi-sharp location (even when the wave-function does 
not have it). 

Sincerely 

Yours P. 



226 



BORN-EINSTEIN LETTERS 

These letters of Pauli's clearly show that my draft for a reply to Einstein'^ 
paper in my presentation volume was completely inadequate. I had 
failed to understand what mattered to him. When now, twelve years later, 
I try to think how this was possible, I can find only one explanation: as 
an unconditional follower and apostle of the young Einstein, I swore by 
his teachings; I could not imagine that the old Einstein thought differently. 
He had based the theory of relativity on the principle that concepts 
which refer to things that cannot be observed have no place in physics: 
a fixed point in empty space is a concept of this kind, in the same way as 
the absolute simultaneity of two events happening in different parts of 
space. The quantum theory came into being when Heisenberg applied 
this principle to the electronic structure of atoms. This was a bold and 
fundamental step which made sense to me immediately and which 
caused me to concentrate all my efforts in the service of this idea. It was, 
then, clearly incomprehensible to me that Einstein should refuse to accept 
the validity of this principle, which he himself had used with the greatest 
success, for quantum mechanics, and that he insisted that the theory should 
supply information about questions of the type of 'how many angels can 
sit on the point of a needle'. For this is what Einstein's requirement, that 
a physical state must have an objective real existence even when it 
proves impossible to postulate a principle for it, amounts to, as Pauli 
clearly explains. And he claims, moreover, that any theory which 
offends against this is incomplete. In an earlier letter he expressed this 
by saying that he was opposed to the philosophy ofesseestpercipi. 
Pauli's analysis of our fundamental difference of opinion was the correct 
answer to Einstein's paper; I had to leave it to him to publish a reply. 
As far as I know he has never done so. 

My own manuscript seemed to me to contain certain thoughts which I 
had not yet come across elsewhere. I rewrote it completely, with only 
casual allusions to Einstein's article; I did this by proceeding from his 
example of the particle oscillating between two elastic reflecting walls, 
developing it further mathematically, and using it to explain my own 
philosophical ideas about relativity and determinism. 
At this time I received an invitation from the Danish Academy to contri- 
bute to a volume of the Academy's reports, which was to be published on 
the occasion of Niels Bohr's seventieth birthday. I therefore sent my paper 
not to the Royal Society in London, as previously planned, but to the 
Danish Academy in Copenhagen. It was published there under the title 
'Continuity, Determinism and Reality'. In a letter from Zurich of nth 
December 1955, in which he first of all tells me about the sudden death of 
Hermann Weyl, Pauli then writes as follows: 'Your paper in the Danish 
presentation volume to Bohr makes very pleasant reading now; its 
epistomological content has now become very clear, and I agree with all 



227 



BORN-EINSTEIN LETTERS 

of it. I had used the mathematics of the example of the mass point between 
two walls, and of the wave-packets which belong to it, in my lectures in 
such a way that the transformation formula of the theta-function comes 
into play. But that is a mere detail.' It is more than a detail. It shows that 
PaxiH had long been familiar with all I had to say. But this did not embar- 
rass me. For ever since the time he had been my assistant in GJottingen, I 
had been aware that he was a genius, comparable only with Einstein 
himself. Indeed, from the point of view of pure science he was possibly 
even greater than Einstein, even if as an entirely different type of person 
he never, in my opinion, attained Einstein's greatness. 
His remark about the theta-function made me take up this example later 
when I had moved to Bad Pyrmont. In a paper that I wrote with W. 
Ludwig,*' the movement of the oscillating particle was represented not only 
by the superposition of Schroedinger waves (wave representation) but 
also by a solution in the form of integrals, which could be regarded as 
superposition of Gaussian distributions of decreasing sharpness (particle 
representation). The first form corresponds to the quantum domain 
proper, the second to the almost classical domain. Each of them can be 
transformed into the other by means of the theta transformations men- 
tioned by Pauli. Up to this point it was certainly familiar to Pauli. What 
we added to it was a method which could be used to transform these two 
separate descriptions into a single one, which can be used and is valid for 
all velocities and all masses. I was familiar with this method from the 
theory of crystals, where it had been used with great success by P. P. 
Ewald to calculate electrostatic and electromagnetic potentials. 
Although this problem deals with a case which is physically trivial and 
unimportant in practice, it gives a clear insight into the connection between 
classical and quantum mechanics, and seems to me to be more useful 
than any philosophising about the question. It should be brought into, and 
discussed in, every elementary lecture about quantum mechanics. 

In the letters which follow, the controversy which has been described here 
is merely hinted at. In spite of its occasional bitterness, it did not leave 
even the slightest stain on our relationship. 



117 



112 Mercer Street 

Princeton, New Jersey 

U.S.A. 



Dear Bom 

I was very pleased to hear that you have been awarded the 
Nobel Prize, although strangely belatedly, for your fundamental 



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BORN-EINSTEIN LETTERS 

contributions to the present quantum theory. In particular, of 
course, it weis your subsequent statistical interpretation of the 
description which has decisively clarified our thinking. It seems 
to me that there is no doubt about this at all, in spite of our 
inconclusive correspondence on the subject. 

And then the money in good currency is not to be despised 
either, when one has just retired. With sincerest regards to you 
and your wife. 
Yours 

A. Einstein 



The fact that I did not receive the Nobel Prize in 1932 together with 
Heisenberg hurt me very much at the time, in spite of a kind letter from 
Heisenberg. I got over it, because I was conscious of Heisenberg's superior- 
ity. By the time we returned to Germany this wound had long healed. 
My surprise and joy were thus all the greater, especially as I was awarded 
the prize, not for the work done jointly with Heisenberg and Jordan, but 
for the statistical interpretation of Schroedinger's wave function, which 
I had thought of and substantiated entirely by myself. It is not surprising 
that this acknowledgement was delayed for twenty-eight years, for all the 
great names of the initial period of the quantum theory were opposed to 
the statistical interpretation: Planck, de Broglie, Schroedinger and, not 
least, Einstein himself. It cannot have been easy for the Swedish Academy 
to act in opposition to voices which carried as much weight as theirs; 
therefore I had to wait until my ideas had become the common property 
of all physicists. This was due in no small part to the cooperation of 
Niels Bohr and his Copenhagen school, which today lends its name 
almost everywhere to the line of thinking I originated. 



118 



Dr Earner'' s Sanatorium 

Braunlage, Harz 

28 November, 1954 



Dear Einstein 

I read in the paper recently that you are supposed to have said: 
'If I were to be bom a second time, I would become not a 
physicist, but an artisan'. These words were a great comfort 
to me, for similar thoughts are going around in my mind as well, 

229 



BORN-EINSTEIN LETTERS 



in view of the evil which our once so beautiful science has 
brought upon the world. Now they have given me the Nobel 
Prize, essentially for the statistical interpretation of the >p- 
function, work which dates back twenty-eight years. I can really 
only think of one explanation for this: the intention was to 
honour something which has no immediate practical appli- 
cation, something purely theoretical. Linus Pauling received 
the chemical prize at the same time, a man known for his up- 
right political conduct and his rejection of the misuse of 
scientific discoveries. (It was even rumoured here that he had 
not received an exit permit from the United States, but this 
does not seem to be true.) This could be chance, but it does 
appear to have been done on purpose, and that would be 
gratifying. It is for this reason that I am glad to go to Stockholm, 
although neither Hedi nor I will feel any the better for it. For we 
both suffer from heart complaints, and are only free from pain 
when we live very quietly. Hedi is at present in a clinic in 
Gottingen, in order to be revitalized a little; I am up here in the 
Harz mountains for the same reason. It is unlikely that I will 
manage to do any more scientific work (except for my optics 
book, begun eight years ago), and I am thinking of using my 
present popularity in two countries (here I am the 'German', 
over there the 'British' physicist) to try and arouse the con- 
sciences of our colleagues over the production of ever more 
horrible bombs. Even before I knew anything about the Nobel 
Prize I had written an article in this vein for the Physikalischen 
Blatter, which is widely read here. I am reading a book at the 
moment with the nice title Kapitza, the Atom Tsar, which 
contains a dramatic description of the development of 
nuclear explosives in Russia. It makes one feel quite sick. 
Kapitza himself comes out of it quite well; in those days he 
tried everything he could to put the brakes on and to take 
delaying action, in much the same way as his opposite number 
R. O. [Robert Oppenheimer] did on your side (if my information 
is correct). 

Someone wrote and told me that you were ill. Please accept 
my best wishes for a speedy recovery, and do not trouble to reply. 
We understand one another in personal matters. Our difference 
of opinion about the incompleteness of quantum mechanics is 
quite insignificant by comparison. 



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BORN-EINSTEIN LETTERS 

If Hedi were here, she would join me in sending you her 
sincere regards. 

In old friendship 
Yours 

Max Bom 



Even today I cannot say with any certainty whether I was right 
that the simultaneous award of the Nobel Prize to Linus Pauling and 
myself had anything to do with the fact that neither of us had had any- 
thing to do with the practical application or the misuse of science for 
political purposes. For, after all, other scientists besides ourselves were 
honoured with the prize at the same time. The physicist Walther Bothe 
was one, and my assumption hardly applies to him. 

We found the Nobel celebrations in Stockholm tiring but extremely 
enjoyable, and sustained no injury to our health as a result. The Nobel 
Prize has helped me a great deal in public appeals for reason in the use of 
scientific discoveries. 

The book Kapitza, the Atom Tsar apparently did not circulate widely in 
Germany, in spite of its fetching title. I have never met anyone who knew 
it, and did not see it reviewed in any paper or periodical. The greater 
part of it is probably pure invention, for those few features of Kapitza's 
life which we knew about in detail were either not mentioned at all or 
misrepresented. 

The next letter, the last I had from Einstein, refers to the beginning of my 
previous one where I mention a newspaper report according to which 
Einstein said that if he were to be born a second time, he would 
become not a physicist, but an artisan. I thought at the time that he was 
referring to the atom bomb. Here is Einstein's brief reply (typewritten; 
apparently he was already seriously ill) . 



119 



/; January, 1955 



Dear Bom 

I enclose the text of my letter to the Reporter, which you have 
asked for. Just one comment. The hired hacks of an accom- 
modating press have tried to tone down the impact of this 
statement, either by making it appear as if I regretted having 



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BORN-EINSTEIN LETTERS 

been engaged in scientific endeavour, or by trying to give the 
impression that I had attached little value to the practical 
occupations I mentioned. 

What I wanted to say was just this: In the present circum- 
stances, the only profession I would choose would be one where 
earning a living had nothing to do with the search for know- 
ledge. 

Kind regards from 
Yours 

A.E. 



Unfortunately I no longer possess the letter to the Reporter. When I gave 
an account of Einstein's letters (my own letters to him were not at my 
disposal at that time) to the meeting of Nobel Laureates in Lindau this 
svunmer (1965), I still believed, as I have just mentioned, that Einstein's 
remarks referred to the atomic bomb. In the meantime I have heard from 
the executor of Einstein's estate, Dr Otto Nathan in New York, that this 
is not so. Einstein's statement referred to the crisis of civil rights, which had 
been brought about by the appearance of Senator McCarthy. Any teacher 
or scientist who dared to express his poHtical opinion freely and openly 
risked being asked to appear before the Committee of the Senate presided 
over by Senator McCarthy, and the loss of his position, if not worse. 
Anyone interested in this can read about it in the notes by Otto Nathan in 
the book Einstein on Peac^ (pages 613, 614), which also contains the 
letter to the Reporter with the sentence that has since become famous 
because of its incorrect interpretation: 'rather to become a plumber or a 
peddler than a physicist'. 



120 



Bad Pyrmont 

Marcardstrasse 4 

West Germany 

29 January, 1955 



Dear Einstein 

Many thanks for sending me the text of your letter to the 
Reporter so promptly. I can well imagine that the press people 
have tried to tone down the impact of your words. 

I myself am forced to say that your text is not free of ambi- 
guity. I took it to mean something other than you explained, 
but even this explanation does not satisfy me. For even when one 



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BORN-EINSTEIN LETTERS 

selects a method of making a living which is independent of the 
search for knowledge, one must then also decide to keep one's 
knowledge to oneself, or to interchange ideas only privately 
amongst friends, as was customary during the 17th and i8th 
centuries, for otherwise others are still going to misuse the 
results for evil purposes, and I feel that one would then never 
be free of responsibility. 

I think a great deal about these things, and have got in 
touch with Bertrand Russell. He has made an effective state- 
ment over the British radio, which is printed in the Listener of 
December 30th. I will let you know whether this discussion 
leads to any conclusions, of either a personal or a more far- 
reaching nature. A Japanese periodical has asked me to agree 
to the publication of my correspondence with Yukawa about the 
atom bomb, etc., and sent me a letter by Y. This did in fact 
actually appear, together with my reply (I am unable to read 
it, as I do not know any Japanese). It will not have amused any 
Americans who read it. But this is only a miserable beginning. 
With kindest regards, also from Hedi 
Yours 

Max Bom 



This letter contains my attitude towards the 'plumber and peddler' 
question. It goes beyond Einstein's; even if one does not earn one's 
living by science, but publishes the results of one's research, one cannot 
rid oneself of the responsibility for the use which is made of them. I have 
stuck to this point of view right up to the present. 

Hideki Yukawa is a brilliant theoretical physicist, the only Japanese 
Nobel prizewinner. He received this in 1949 for his prediction of the 
existence of a new kind of particle, called a meson (with a mass which is 
between that of an electron and a proton). I correspond with him and 
see him from time to time, for example at the meeting this year of Nobel 
prizewinners in Lindau (1965). We are united not only by our ideas 
about physics -he recognised my reciprocity principle as the leading 
heuristic idea in the theory of elementary particles -but also by our 
attitude towards the misuse of scientific research resvJts for the purposes 
of war and destruction. 

Einstein died soon after this last exchange of letters between us (on the i8th 
of April, 1955). In a letter to my wife, his step-daughter Margot describes 
her last visit to his sickroom: 'Did you know that I was in the same 



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hospital as Albert? I was allowed to see him twice more and talk to him 
for a few hours. I was taken to him in a wheel-chair. I did not recognise 
him at first - he was so changed by the pain and blood deficiency. But his 
personality was the same as ever. He was pleased that I was looking a 
httle better, joked with me, and was completely in command of himself 
with regard to his condition; he spoke with a profound serenity -even with 
a touch of humour -about the doctors, and awaited his end as an imminent 
natural phenomenon. As fearless as he had been all his life, so he faced 
death humbly and quietly. He left this world without sentimentality 
or regrets.' 
With his death, we, my wife and I, lost our dearest friend. 



234 



REFERENCES 



1. Einstein, A., 'On the electrodynamics of moving bodies', in Ann. 
Phjs.Lpz., 17, 8gi {igo^). 

2. Einstein, A., 'On a heuristic viewpoint concerning the production 
and transformation of light', in Ann. Phys. Lpz., 17, 132 (1905). 

3. Einstein, A., 'The presumed movement of [suspended particles in 
static fluids', in Ann. Phys. Lpz., 17, 549 (1905)- 

4. Born, M., Der Matkematische und Maturwissenschaftliche Unterricht, 9, 97 

(1956). 

5. Born, M., Ausgewahlten Aghandlungen, Gottingen Akademie. 

6. Born, M., Physik im Wandel meiner Zeii> Braunscheweig, 1957, 1966. 
6a. Born, M., Physics in my Generation, Longmans, 1970. 

7. Born, M., Von der Verantwortung des Naturwissenschaftlers (The Scientist's 
Responsibility), Nymphenburger Verlagshandlung, Munich, 1965. 

8. Born, M., and Born, H., Der Luxus des Gewissens (The Luxury of 
Conscience), Nymphenburger Verlagshandlung, Munich, 1969. 

9. BoTn,M., PhysikalischeZeitschriJi, 17,51 (1916). 

10. Born, M., Die Relativitatstheorie Einsteins, Springer, Berlin, 1920. 

1 1 . Born, M., Einstein's Theory of Relativity, Dover Publications, New York, 
1962. 

12. Born, M., Enzyklopadie der Mathematik, Teubuer, Leipzig, 1920. 

13. Herneck, F., Albert Einstein, Bookpublishers der Morgen, Berlin, 

1933. 

14. Rabindranath Tagore, The Home and the World, Macmillan, 1919. 

15. A. Einstein, A. Sommerfeld Briefwechsel,SchvfaheT, Basel, 1968. 

16. Bom,M., Physikalische Zeitschrift, II, 1234-1257 (1910). 

17. SeeUg, C, Albert Einstein, Europa Verlag, Zurich, i960. 

18. Haldane, R. B., The Reign of Relativity, JohnMuira.y, London, 1921. 

19. Born, M., and Jordan, P., Z^tschriftfiir Physik, 33, 32 (1925)- 

20. van der Waerden, B. L., Sources of Quantum Mechanics, North Holland, 
Amsterdam, 1967; see also Hund, F., Geschichte der Quantentheorie, 
Bibliographisch. Mannheim, 1967. 

21. Heisenberg, W., ^eiteAn/i/urPAj5fA:, 35, 879 (1925). 

22. Born, M., and Hund, F., Vorlesungen iiher Atommechanik, Springer, 
Berlin, 1925. 

22a. Born, M., and Hund, F., The Mechanics of the Atom, tr. J. W. Fisher, 
G. Bell and Sons Ltd, London, 1927; Fredk. Ungor, New York, 
i960. 



235 



BORN-EINSTEIN LETTERS 

23. Einstein, A., and Infeld, L., The Evolution of Physics, Simon and 
Schuster, New York, 1938. 

24. Infeld, L., Bulletinof the Atomic Scientists, Feb. 1965. 

25. Infeld, L., and Plebanski, Motion and Relativity, Pergamon Press, 
Oxford, i960. 

26. Born, M., Nature, 141, 328 (1938). 

27. Einstein, A., Mein Weltbild, Amsterdam, 1934. 

28. von Neumann, J., Mathematische Grundlagen der Quantenmechanik, 
Springer, Berlin, 1932. 

29. Nathan, O., and Norden, H., Einstein on Peace, Simon and Schuster, 
New York, i960. 

30. Born, M., Experiment and Theory in Physics, University Press, Cambridge, 
1943; reprinted by Dover Publications, New York, 1956. 

31. '&OTn,'M..,ExperimentundTheorieinderPhysik,yi.oshdL<^, 1969. 

32. Born, M., Natural Philosophy of Cause and Chance, Clarendon Press, 
Oxford, 1949. 

33. Born, H., Stille Gdnge (Silent Corridors), Leonard Friedrich, Bad 
Pyrmont. 

34. Einstein, A., Physikalische Z^itschrift, I'j, loi (1916). 

35. Born, M., and Green, H. S., A General Kinetic Theory of Liquids, 
Cambridge University Press, 1949. 

36. Born, M., Physikalische Blatter, 20, 554 (1964) ; 21, 53 (1965). 

37. Irving, D., The Virus House, New York, 1968. 

38. Bulletin of the Atomic Scientists, June 1 968. 

39. Einstein, A., 'Quantum Mechanics and Reality', in Dialectica, 320 
(1948). 

40. Einstein, A., Meaning of Relativity, 4 lectures translated by Edwin 
PUmpton Adams, Methuen & Co., London, 1922, 6th ed. 1956. 

41. Einstein, A., Out of my Later Tears, translated by Alan Harris, Watts 
& Co., London, 1940. 

42. Born, M., and Huang, K., Dynamical Theory of Crystal Lattices, 
Clarendon Press, Oxford, 1954. 

43. Bom, M., and Wolf, E., Principles of Optics, Pergamon Press, Oxford, 
1959- 

44. Schroedinger, E., The British Journal for the Philosophy of Science, 109, 
Aug. 1952; 233, Nov. 1952; 95, Aug. 1953. 

45. Scientific Papers presented to Max Born on his retirement from the Tail Chair 
of Natural Philosophy in the University of Edinbrugh, Oliver and Boyd, 
Edinburgh/London, 1953. 

46. Born, M., Kong. Dansk Videnskabernes Selskah, Matematiskfysiske 
Meddelelser, 30, 1 (1955). 

47. Bom, M., and Ludwig, W., Zeitschriftfur Physik, 150, 106 (1958). 



236 



Index 



Althoff,F., 12 
Andersen, H. C, 5 
Appleton, E. V., 191 
Auerbach, 56 

Bachmann, 59 
Beck, G., 140, 141 
Becker, C. H., 27, 71 
Bergson, H., 79 
Berliner, A., 24, 30 
Bevin, E., 177, 178 
Bhagavantam, S., 54 
Bieberbach, L., 12,98, 100 
Blackett, P. M. S., 185 
Blackman, M., 118 
Blaschke,W.,67 
Boguslawski, 43-4, 45, 49, 50 
Bohm, D., 192, 193, 199, 202-3, 

207 
Bohr, H., 96, 99 
Bohr, N., 27, 53-104 pofjim, 117, 

125, 127, 136-59 passim, 212, 

225,227,229 
Boltzmann, L., 41, 62, 86 
Bolza, O., 45, 49 
Bormann, E., 54 
Born, G., 56, 1 13, 134 
Bose,J. C.,83,86,88 
Bothe,W.,65, 231 
Bragg,W.,78,i28 
Bridgman, 138 
Brillouin, L., 142 
Brod, M., 3 

Brody, E., 53, 56, 58, 68-9, 70-1 
Broglie, L. de, 64, 83, 86, 176, 192, 

i93> 199, 202, 207, 208, 210, 229 
Brouwer, L. E. J., 79, 97-9, 100 
Byk, A., 50, 52 

Carathdodory, C, 53, 55 
Clemenceau, G., 22 



Cohn-Vossen, 127 
Compton, A. H., 83, 86 
Coudenhove-Kalergi, 76 
Courant, R., 55, 58, 67, 74, 75, 85, 

97, 98, 117, 123, 127, 129, 195, 

198,201 
Curie, M., 79 

Darwin, C, 123 

Davisson, C. J., 86 

Debye, P., 25, 27, 28, 46, 49, 59 

Dehlinger, 23 

Descartes, 23 

Dirac, P. A. M., 104, 121, 174 

Drill, 18, 19 

Duane, W., 83, 86 

Ebert, F., 150 

Eddington, A. S., 24, 65, 78, 85, 

151,156 
Ehrenberg, V., 1 18 
Ehrenfest, P., 41-2, 44, 65, 71, 83, 

85,96,106, 107, 112 
Ehrenfest, T., 41, 43, 72, 84, no, 

113,116 
Ehrlich, P., 100 
Elsasser,W.M.,83,86 
Engels, F., 24 
Epstein, P. S., 32, 45, 49, 71, 84, 

no, 112 
Erzberger, M., 22 
Euclid, 23 
Ewald, P. P., 8, 228 

Fajans, K.,21,24 
Faraday, M., 164 
Fitzgerald, G. F., i 
Fock,V.,3, 131,140,141 
Fokker, A. D., 43, 71 
Fowler, R., 145 



237 



INDEX 



Franck, J., 20, 27, 31, 53-76 
passim, 80, 84, 86, 113, 116, 117, 
123,124,126,138,198,201 

Frank, P., 85, 88 

Freundlich, E., 21, 39, 190, 191, 
192, i93> 198,217 

Fuchs,K., 134, 139, 141, 146-7 

Fiirth, R., 140, 141, 142, 156 

Garbunow, 127 

Geddes, A., 141, 142 

Gehrcke, E., 39 

Geiger, H., 65 

Gerlach, W., 24, 53, 71, 72, 85, 201 

Gibbs,J.W.,i55 

Glaser, D. A., 59 

Gleich,G.v.,8i 

Godel, K., 100 

Goens, 81 

Goldman, H., 77 

Grebe, L., 59 

Green, H. S., 161, 162, 175, 179 

Griineisen, 58, 69, 81 

Haber, F., 6, 7, 12, 19, 20, 21, 24, 

49.81 
Hahn, O., 145, 201 
Haldane, R. B., 75, 77-8 
Harnack, A. v., 194 
Hasenohrl, F., 41 
Heisenberg, W., 63, 75, 78, 84, 87, 

88, 89, 104, 105, 136, 137, 138, 

143, 161, 166, 167-8, 170, 196, 

203, 210, 212, 227, 229 
Heitler, W., 109, in, 114, 115, 126 
Hellinger, E., 17 
Herglotz, 127 
Hertz, G., 27, 69, 76 
Herzberg, G., 126 
Hilbert, D., i, 17, 25, 44, 45, 55, 

63-79 /xMjJm, 93, 97-9, 100, III, 

139, 143 



Hitler, A., 24, 63, 77, no, in, 112, 
ii3> ii5> i3i> 136, 140, 146, 
167, i77> 196,217 

Hoffj J. H. van't, 2 

Hofmann, 131, 141 

Hornbostel, E. M. v., 167 

Hubble, E. P., no 

Hiickel, E., 74 

Hume, D., 7, 8 

Hund, F., 84, 87, 104, 126 

Infeld, L., 121, 122, 125, 130, 131, 

141 
Irving, D., 168 

Jacobi, K.,47 
JofK,A.T.,85,88, 100 
Jordan, P., 84-5, 87, 103, 104-5, 
143,229 

Kant, I., 7, 8 

Kapitza, P. L., 85, 88, 230, 231 

Karmin, T. v., 2, 49 

Kemmer , 216,219 

Kienle, H., 85, 88 

Klein, F., 45 

K6hler,W., 167 

Koppel, A., 12 

Kossel, A.,31,46 

Kramers, H., 85, 88, 190 

Krutkow, G., 44 

Kuhn, H., 115 

Kun Huang, 185, 187, 190 

Kiirti, 1 1 5 

Kiistner, F. K., 57 

Ladenburg, R., i, 2, 123, 134, 140, 

157,189-90,192 
Lagrange,J.L., 179 
Landau, E., 100 
Landau, L. D., 162 
Land6,A.,46,85, 117, 139 
Langevin, P., 41, 42, 44, 78, 80, 127 



238 



INDEX 



Langmuir,J., 62 
Larmor, J., i 

Laue, M. v., 5, 6, 31, 40, 42, 63, 
68, 71, 81, 145, 148, 157, 200, 201 
Leibniz, G. W. v., 189 
Lenard,P.,36,39,4i,44,63 
Lenin, W. L, 24 
Lenz,W.,3i,58,62,69 
Lertes, P., 20, 27 
Lewis, G. N., 45, 49 
Lindemann, F., 114, 115, 117, 162 
London, F., in, 114, 115, 126 
Lorentz, H. A., i, 27, 41-2, 44, 51, 

73> 139, 197, 198 
Lorenz, R., 19, 31 
Loria, S., i 
Ludendorff, E., 1 1 
Ludwig, W., 228 
Lummer, O., i 

Mach,E., 159, 178 

Madelung,G.,46,52,54 

Marx, K., 24n 

Maxwell, J. C, 46, 50, 51, 62, 71, 

79, 121, 164 
McCarthy, J., 232 
Meitner, L., 81 
Mendelssohn, E., 1 15 
Michelson, A., 73, 74 
Mie, G., 76 
Miller, 74., 90 

Millikan, R. A., 71, 109, no, 112 
Milne, E. A., 151, 156 
Minkowski, H., i, 62 
Minot, G. R., 100 
Mises, R. v., 98, 100 
Molotow, W. M., 127 
MuUiken, R. S., 126 

Nathan, O., 232 
Nernst, W., 58, 115 
Neumann, J. v., 134, 140, 142, 143, 
157, 176,216,226 



Newton, L, 6, 64, 1 15, 189, 224 
Nikolai, 22 
Nohl, H., 189,200 
Nordheim, L., in 
Nordstrom, 6, 7 

Oppenheim, 12, 18,35,52 
Oppenheimer, R., n, 34, 208, 
230 

Pauli, W., 21, 53-75 passim, 105, 
139, 141, 155, 157, 168, 198, 
207,217,219,225,227,228 

Pauling, L. K., 1 15, 230, 231 

Peierls, R., 146-7 

Peng,H.W., 145, 156 

Planck, M., 5, 6, 18, 34, 40, 44, 
45, 48, 51, 55, 72, 76, 81, 133, 
173,200,229 

Plebanski, 131 

Pohl,R.,25,26-7,57,6i,74 

Poincare, H., i, 53, 60, 75, 78, 198 

Polanyi, M., 58, 62, 63 

Prandtl, L., 85 

Pringsheim, A., i, 50, 51 

Pryce,M., 135, 139, 161,185 

Radek,K.B.,22, 128 

Raman, G. V., 1 15, 120, 166, 167 

Ramsauer, K., 46, 62, 64 

Reiche, F., 1,31 

Richter, 27, 106 

Riecke, E., 25 

Riemann, B., loi, 1 13 

Robertson, 134 

Rontgen, W.,42 

Roosevelt, F. D., 136, 147, 162 

Rosbaud, 190 

Rubens, O., 71, 72 

Rumer, G., 101-12 passim 

Runge, C, 44, 55 

Russell, B., 99, 233 

Rutherford, E., 78, 119, 121, 160 



239 



INDEX 



Samuel, R., 125-7, 128, 129 

Schilpp, P. A., 157, 179, 180 

Schlapp, R., 197 

Schlick, M., 18, 19 

Schmidt, E., 98, 100, 127 

Schoenflies, A., 31 

Schroedinger, E., 96, 104-5, 142-4) 

145, 156, 166, igi-22g passim 
Schur, I., 68 
Schweizer, A., 112 
Schwerdtfeger, H., 127-8, 129 
Seelig, C, 74, 194 
Simon, F., 115 
Soldner, J. G., 63, 64 
Sommerfeld, A., 11, 23, 59, 65, 

72,75,104,115 
Spengler, O., 22 
Stark,J., 36, 50,51,52 
Stern, O., 12, 23, 24, 31, 32, 45-6, 

51,52,71,72,223 
Still, C, 55, III 
Still, K.F., 55 
Strassmann, F., 146 
Strindberg, A., 12 
Szilard, L., 146, 147 

Tagore, R., 34 

Teller, E., 1 14, 1 15, 1 1 7, 220 

Thiband, 140 

Thomson,J.J., i, 160 

Tisdale, 107 

Tizard, 162 

Toeplitz, O., 17 



Tolman, no, ii2 

Undset, S., 94 

Vasmer, M., 49 
Veblen, T., 134, 140 
Vegard, 68 
Voigt, W., 25, 26-7, 52 

Wachsmuth, F. B. R., 24, 31, 32, 46 
Waerden,B. L.,86,87 
Warburg, E., 103 
Weiss, P., 41, 42, 44 
Weisskopf, V. F., 127, 128 
Weizmann, C, 124, 127, 177 
Weizsacker, C. F. v., 201 
Wende, 26-7 
Wertheimer, M., 150, 155, 166, 

167, 195 
Weyl, H., 21, 100, 108-9, "I, "7> 

"9, 127, 129, 132,134, 140, 143, 

157,158,216,227 
Weyland, P., 35, 39, 43 
Whittaker, E., 197, 198, 200, 203 
Widman,J. v., 32 
Wien, M. E., 41, 43, 44, 53 
Wiener, N., 52 
Wolf, E., 191 

Yukawa, H., 88, 233 

Zahn-Harnack, A. v., 194 
Zeiss, C, 54 



240 



' 'You believe in the God who plays dice, 
and I in complete law and order in a world 
which I, in a wildly speculative way, am 
trying to capture.' Thus Einstein, writin; 
to Max Born in 1944, summed up two 
utterly contrasted attitudes to science 
which were never reconciled throughout 
this long series of letters. Born, in holdin 
that the basis of the material world was 
the purely random behaviour of the 
constituent particles of atoms, shared the 
majority viewpoint among quantum 
scientists; yet Einstein persisted in 
thinking that every event must have its 
cause, and searched constantly for a 
deeper explanation which might bring 
order into the seemingly chaotic sub- 
atomic world. Their conflicting views 
provide the intellectual stimulus of 
much of this correspondence. 

But at a time when politicians were 
realizing the terrifying power of atomic 
physics to provide weapons of unforeseen 
destructiveness neither Born nor Einstein 
could turn their backs on the social 
implications of the new science. At first 
their letters share atone of concern; in 
the end, when the atomic bomb has been 
used and the innocence of science has 
been left far behind, they can only regret 
'the evil which our once-so-beautiful 
science has brought upon the world'. 
The wider effects of war dominate many 
of the letters, for both Born and Einstein 
were fd'rced to flee from Germany during 
the Hitler regime, and the scars of the 
experience lasted so long with Einstein 
that he never felt able to return. 



In spite of their scientific differences 
Born and Einstein sustained a rare and 
close friendship for more than forty years, 
until Einstein's death in 1955 (Max Born 
was to live until 1970). For long periods 
these letters were the only link between 
them. Whether they are commiserating 
over the plight of German Jews in exile, 
or delighting in the plays and poems of 
Born's wife Hedwig, or exchanging sharp 
and often witty comments about their 
scientific colleagues, the two men reveal 
throughout the essential warmth and 
generosity of their personalities. As 
Bertrand Russell writes in his foreword: 
'In an age of mediocrity and moral pygmies, 
their lives shine with an intense beauty. 
Something of this is reflected in their 
correspondence, and the world is richer 
for its publication'.