Einstein on the Run Read online

  Never in all my life shall I forget the wonderful change which took place in Einstein’s face at that moment. The light came back into his eyes, and his whole face seemed transfigured with joy and delight when it came home to him in this way that, no matter how badly he had been treated by the Nazis, both he himself and his undoubted genius were at any rate greatly appreciated at Oxford.

  HERBERT SPENCER LECTURE IN OXFORD

  The psychological strain seems to have expressed itself in Einstein’s scientific thinking as well as his personal behaviour. In his lecture on 10 June, ‘On the method of theoretical physics’ – the German manuscript of which lay on his Christ Church desk at the very time he was writing to Born – he tried to escape from the messy physical reality inherent in experimental physics, including quantum mechanics, and substitute for it the paradise of pure mathematics, which he had been pursuing for some years in his unified field theory, most recently with the help of his calculator, Walther Mayer, in Le Coq. ‘The sanctuary from personal turmoil that Einstein sought in physics may also have coloured the extreme rationalist pronouncements in his Herbert Spencer lecture,’ according to the editors of The Cambridge Companion to Einstein. Opinions consequently differ as to the lecture’s value. One Einstein biographer, Fölsing (who originally trained as a physicist), condemned it as ‘a reckless overestimation of the possibility of understanding nature through mathematics alone – a mistake he would not have been capable of in his most productive years’ (while acknowledging that ‘this faith, though ultimately unproductive, sustained him for decades in his search for the unified field theory’). By contrast, another Einstein biographer, Abraham Pais, a practising physicist who knew Einstein personally over a long period, hailed the lecture as ‘perhaps the clearest and most revealing expression of his mode of thinking’.

  Einstein (front row, second from left) as a guest at a political debate at the Oxford Union, June 1933. In the second row, third from left, is Michael Foot, then a student at the university, who later became leader of the Labour Party in Britain. Einstein did not speak in the debate, which was about British politics and did not refer to Germany. After a brief stay in Oxford, he left the city, never to return.

  Theoretical physics had always been Einstein’s sanctuary, as he revealed on several occasions during his life, including his ‘Autobiographical notes’ written for his seventieth birthday in 1949, which called theoretical physics a liberation ‘from the chains of the “merely personal”’. Back in 1897, when he was eighteen, while breaking up with his first girlfriend he wrote to her mother:

  Strenuous intellectual work and looking at God’s Nature are the reconciling, fortifying, yet relentlessly strict angels that shall lead me through all of life’s troubles. . . . One creates a small little world for oneself, and as lamentably insignificant as it may be in comparison with the perpetually changing size of real existence, one feels miraculously great and important, like a mole in his self-dug hole.

  And as an adult in 1918, while struggling with wartime privations, divorce and illness that left him bedridden for several months, he made this powerful statement in a speech on the sixtieth birthday of Planck:

  I believe with Schopenhauer that one of the strongest motives that leads men to art and science is escape from everyday life with its painful crudity and hopeless dreariness, from the fetters of one’s own ever shifting desires. A finely tempered nature longs to escape from personal life into the world of objective perception and thought. . . . With this negative motive goes a positive one. Man tries to make for himself in the fashion that suits him best a simplified and intelligible picture of the world; he then tries to some extent to substitute this cosmos of his for the world of experience, and thus to overcome it. This is what the painter, the poet, the speculative philosopher, and the natural scientist do, each in his own fashion. Each makes this cosmos and its construction the pivot of his emotional life, in order to find in this way the peace and security which he cannot find in the narrow whirlpool of personal experience.

  Einstein’s Oxford lecture opened with an uncharacteristically emotional introduction – at least by his unemotional standards – perhaps hinting at his mental state in early June 1933:

  I wish to preface what I have to say by expressing to you the great gratitude which I feel to the University of Oxford for having given me the honour and privilege of delivering the Herbert Spencer lecture. May I say that the invitation makes me feel that the links between this university and myself are becoming progressively stronger?

  Then he thanked three colleagues at Christ Church – a philo-sopher, Gilbert Ryle, a classicist, Denys Page and a physicist, Claude Hurst – ‘who have helped me – and perhaps a few of you – by translating into English the lecture which I wrote in German’. (Oddly, he did not mention a role for Lindemann.) This time at Rhodes House, unlike in May 1931, in Einstein’s first-ever lecture solely in English, the audience did not have to struggle with an unfamiliar language – although Einstein’s inimitably accented English, as he read from the dense translation, might sometimes have appeared to have been a foreign tongue. Nor were there any blackboards chalked with baffling mathematics, to be saved by eager science dons. That said, the lecture, as printed, was demanding enough to challenge any listening physicist or philosopher, not to mention the anonymous correspondent of The Times with the unenviable task of trying to summarise its content for a general readership. (The Times report on 12 June was safely, if unimaginatively, headlined ‘Basic concepts in physics’.)

  The physics started with some typically Einsteinian humour. He ironically reprimanded himself for claiming more authority for his remarks to come than perhaps he should:

  If you wish to learn from the theoretical physicist anything about the methods which he uses, I would give you the following piece of advice: don’t listen to his words, examine his achievements. For to the discoverer in that field, the constructions of his imagination appear so necessary and so natural that he is apt to treat them not as the creations of his thoughts but as given realities.

  This statement may seem to be designed to drive my audience away without more ado. For you will say to yourselves, ‘The lecturer is himself a constructive physicist; on his own showing therefore he should leave the consideration of the structure of theoretical science to the epistemologist.’

  Having openly voiced this subtle objection, Einstein further warned his listeners that his personal view of the past and present of theoretical physics was bound to be coloured by what he was currently trying to achieve and hoped to achieve in the future – an implicit reference to his ongoing work on the unified field theory (which he would briefly mention later in the lecture). ‘But this is the common fate of all who have adopted the world of ideas as their dwelling-place. He is in just the same plight as the historian, who also, even though unconsciously, disposes events of the past around ideals that he has formed about human society.’

  Then Einstein got to grips with the relationship in physics between pure theory, that is the free inventions of the human mind, and the data of experience, that is our observations of physical reality. ‘We honour ancient Greece as the cradle of western science,’ he initially reassured his audience, many of whom were no doubt classically trained. ‘She for the first time created the intellectual miracle of a logical system, the assertions of which followed one from another with such rigour that not one of the demonstrated propositions admitted of the slightest doubt – Euclid’s geometry.’ Thinking of his own boyhood, he added: ‘The man who was not enthralled in youth by this work was not born to be a scientific theorist.’

  Yet, for science to comprehend reality, more than Greek thought was required, he reminded his audience:

  Pure logical thinking can give us no knowledge of the world of experience; all knowledge about reality begins with experience and terminates in it. Conclusions reached by purely rational processes are, so far as reality is concerned, entirely empty. It was because he recognised th
is, and especially because he impressed it upon the scientific world, that Galileo became the father of modern physics and in fact of the whole of modern natural science.

  Newton, ‘the first creator of a comprehensive and workable system of theoretical physics’, agreed with Galileo’s view, Einstein continued.

  [He] still believed that the basic concepts and laws of his system could be derived from experience; his phrase ‘hypotheses non fingo’ can only be interpreted in this sense. In fact, at the time it seemed that there was no problematical element in the concepts of space and time. The concepts of mass, acceleration and force, and the laws connecting them, appeared to be directly borrowed from experience. Once this basis is assumed, the expression for gravity seems to be derivable from experience; and the same derivability was to be anticipated for the other forces.

  However, Newton was aware of certain difficulties:

  One can see from the way he formulated his views that Newton felt by no means comfortable about the concept of absolute space, which embodied that of absolute rest; for he was alive to the fact that nothing in experience seemed to correspond to this latter concept. He also felt uneasy about the introduction of action at a distance. But the enormous practical success of his theory may well have prevented him and the physicists of the eighteenth and nineteenth centuries from recognising the fictitious character of the principles of his system.

  In other words, they did not recognise that the principles were free inventions of the human mind.

  On the contrary, the scientists of those times were for the most part convinced that the basic concepts and laws of physics were not in a logical sense free inventions of the human mind, but rather that they were derivable by abstraction, i.e. by a logical process, from experiments.

  Then Einstein mentioned his own contribution:

  It was the general theory of relativity which showed in a convincing manner the incorrectness of this view. For this theory revealed that it was possible for us, using basic principles far removed from those of Newton, to do justice to the entire range of the data of experience in a manner even more complete and satisfactory than was possible with Newton’s principles. But quite apart from the question of comparative merits, the fictitious character of the principles is made quite obvious by the fact that it is possible to point to two essentially different principles, both of which correspond to experience to a large extent. This indicates that any attempt logically to derive the basic concepts and laws of mechanics from the ultimate data of experience is doomed to failure.

  However, said Einstein,

  [i]f it is the case that the axiomatic basis of theoretical physics cannot be an inference from experience, but must be a free invention, have we any right to hope that we shall find the correct way? Still more – does this correct approach exist at all, save in our imagination? Have we any right to hope that experience will guide us aright, when there are theories (like classical [i.e. Newtonian] mechanics) which agree with experience to a very great extent, even without comprehending the subject in its depths?

  He answered confidently, if controversially: ‘in my opinion there is the correct path and, moreover, that it is in our power to find it’. Then followed the most quoted words in his Herbert Spencer lecture (given below in italics):

  Our experience up to date justifies us in feeling sure that in nature is actualised the ideal of mathematical simplicity. It is my conviction that pure mathematical construction enables us to discover the concepts and the laws connecting them which give us the key to the understanding of the phenomena of nature. Experience can of course guide us in our choice of serviceable mathematical concepts; it cannot possibly be the source from which they are derived; experience of course remains the sole criterion of the serviceability of a mathematical construction for physics, but the truly creative principle resides in mathematics.

  In a certain sense, therefore, I hold it to be true that pure thought is competent to comprehend the real, as the ancients dreamed.

  The rest of the lecture was more technical, mentioning some of the mathematical concepts, such as Riemann’s geometry and Dirac’s spinors, that had proved fruitful in general relativity and quantum mechanics, and naming key theoretical contributors to the latter field, such as Born, de Broglie, Dirac, Heisenberg and Schrödinger, during the previous decade. (Bohr, strangely, went unmentioned.) But in his conclusion Einstein made no bones about his by now well-known view of quantum mechanics as being a theory of only transitory significance:

  I still believe in the possibility of giving a model of reality, a theory, that is to say, which shall represent events themselves and not merely the probability of their occurrence. On the other hand, it seems to me certain that we have to give up the notion of an absolute localisation of the particles in a theoretical model. This seems to me to be the correct theoretical interpretation of Heisenberg’s uncertainty principle. And yet a theory may perfectly well exist, which though it is in a genuine sense an atomistic one (and not merely on the basis of a particular interpretation), nevertheless involves no localisation of the particles in a mathematical model. . . . Only if this sort of representation of the atomistic structure be obtained could I regard the quantum problem within the framework of a continuum theory as solved.

  MATHEMATICS, PHYSICS AND REALITY

  Thus, in his Herbert Spencer lecture, Einstein assured his Oxford audience, and by extension the international world of physics, that mathematics, on its own, could provide the basis for understanding nature. He apparently now rejected his own earlier position, as elegantly stated in 1921: ‘As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.’ As evidence of his new belief, he cited his own general theory of relativity, conceived in 1915–16, which he now claimed to have been essentially based on mathematical concepts rather than physical observations – for all its crucial confirmation by British astronomers in 1919. No doubt many theoretical and experimental physicists, especially those working in quantum mechanics, were taken aback and unconvinced by such a bold claim, even coming from Einstein, flying as it did in the face of so much of the history of physics, beginning with Galileo and Newton, that evidently arose from a combination of theory, observation and experiment. But which of them was in a position to contest its validity with general relativity’s world-famous creator?

  Perhaps they should have taken Einstein’s initial humorous warning in Oxford more seriously. Was Einstein himself really the best authority on the origins of his own theory? Maybe not, as he himself had hinted. ‘It was not until several decades later that a team of scholars scrutinised his notebooks and demonstrated that he had developed his theory. They saw clear evidence that he used a two-pronged strategy, involving both mathematics and physical reasoning, right up until he completed the theory, yet he subsequently downplayed the role of physical reasoning,’ writes physicist, historian and Dirac’s biographer Graham Farmelo. ‘Einstein appears to have largely based his new philo-sophy of research on distorted recollections of his work in the final month of his search for the correct field equations of gravity.’ According to an associate of the team, Jeroen van Dongen, ‘Einstein overemphasised the part mathematics had played in his development of his theory of gravity, probably to try to persuade his critical colleagues of the value of his way of trying to find a unified theory of gravity and electromagnetism.’

  Ironically, there was a clear indication of Einstein’s tendency towards such distorted recollection a mere ten days after his Herbert Spencer lecture, in his lecture in Glasgow on 20 June. Speaking at the university in considerable technical detail, for the second time in English, on ‘The Origin of the General Theory of Relativity’, Einstein commented on the dark days of late 1915, after two years of excessively hard work, when he had felt lost. Finally, he recognised certain errors of thought, and ‘after having ruefully returned to the Riemannian curvature, succeeded in linking the theory with the facts of astr
onomical experience’. In other words, general relativity rested not only on mathematical concepts but also on physical – in this case astronomical – observations. He closed the lecture with the following memorable statement:

  In the light of the knowledge attained, the happy achievement seems almost a matter of course, and any intelligent student can grasp it without too much trouble. But the years of anxious searching in the dark, with their intense longing, their alternations of confidence and exhaustion and the final emergence into the light – only those who have experienced it can understand that.

  Little wonder, then, that the origins of general relativity should be an obscure and contentious subject – even to Einstein himself.

  For the wider public, of course, even the basics of relativity remained as perplexing in 1933 as they had been on Einstein’s first visit to England in 1921. Glasgow railway station appeared to supply yet another example of this truth. Einstein arrived there from London apparently a day earlier than was expected. He found himself standing on the platform alone, so to speak, in a large crowd – who were awaiting not Einstein but the Hollywood comedy star Thelma Todd (of Marx Brothers fame), who happened to be on the same train. Fortunately, a local newspaper reporter recognised the professor and telephoned the university authorities, who soon rescued him. According to the Manchester Guardian, however, relativity was at work: ‘Professor Einstein is of all living philosophers the one whose name is most widely known to the multitude – but in the matter of railway station receptions even he could not hope to loom so large as a film star. There are “kinks in fame” as it is estimated by the multitude, even as there are “kinks in space” as it is measured by mathematicians.’