Einstein on the Run Read online

  Comment by Einstein in The Evolution of Physics: The Growth of Ideas from the Early Concepts to Relativity and Quanta, 1938

  Even as he crossed the Atlantic Ocean in October 1933, Einstein busied himself with trying to help other refugees from Nazi Germany. Writing to the Academic Assistance Council in London on 14 October from on board ship to express his satisfaction at the Albert Hall event and the substantial funds it had raised, he brought to the council’s attention the names and details of three deserving Jewish academics: a professor of paediatrics now in Holland, a psychiatrist still in Berlin and a physician in Zurich. The psychiatrist, Otto Juliusburger – a friend who had treated Einstein’s nephew – wanted to emigrate to Palestine and found a clinic there, Einstein noted, but he had been financially ruined by the German government. If the council were to contact him, he added, it should on no account mention who had suggested Juliusburger’s name, because this move would be highly dangerous for him if he were somehow associated with Einstein. (Juliusburger eventually left Berlin at the last minute, in 1941, with Einstein’s help and financial support, and died in New York in 1952 at an advanced age.)

  About a month after he reached Princeton, he wrote again to Lindemann on the same subject. It was ‘hardly justifiable’, he said, that he should continue to receive payments from Christ Church, given the current emergency. Might the college offer the money from his annual stipend – £400 per annum for the years 1932–37 – to another foreign scholar in distress?

  Lindemann replied on 6 December, after discussion with some colleagues, that such an arrangement would probably be possible. ‘On the other hand, we should be very sorry if you abandoned your connections with the college.’ He hoped that Einstein would come to stay in Oxford for as long as possible during the summer of 1934, ‘especially since Belgium cannot be particularly attractive in the present circumstances’. Then he added, obviously thinking of what he regarded as Einstein’s political naïveté (including perhaps the speech at the Albert Hall?):

  I trust you are enjoying America and have not been pestered too much by people who want to exploit you for political ends. I gather in Germany scarcely any of these demonstrations do any good. On the contrary, any activities abroad are made an excuse to intensify the campaign against the Jews remaining. In these matters politicians, even the most well meaning, unless they know the situation in Germany, are apt to be unsafe guides to follow.

  Einstein replied quickly, but made no commitment to visit Oxford during the following year. As for politics in the United States, he wrote: ‘I have voiced my opinion much less than it may seem, since the press makes a great deal of fuss over me without my intending it or wishing it.’ But then he significantly qualified this observation: ‘All the same I am of the opinion that a conscientious person who has a certain amount of influence cannot in times like the present keep completely silent, since such silence can lead to wrong interpretation which is undesirable in the present circumstances.’

  Here was a hint of what would keep Einstein from returning to Europe. If the American press oppressed him, how much more oppressive would be the European press, given his uniquely symbolic role in opposing the increasing barbarity of Nazism? While he could cope with one Albert Hall meeting, a series of such events would have been a very different and much more stressful matter. Nor would he have a hideaway to retreat to and think about science, away from the pressure of political and media events; an Oxford college, even Christ Church, was far from being such a retreat. So he declined offers of hospitality in England in mid-1934 from both Lindemann and, separately, Locker-Lampson, who was equally keen on Einstein’s return for his own, entirely non-scientific reasons.

  Nothing came of Lindemann’s hopes for another Einstein visit to Oxford. In early May, Einstein officially informed the dean of Christ Church that he would not visit the college that summer and hoped that his stipend might be used in whole or in part to pay one or more distinguished foreign scientists to give brief lecture courses during the term. If this suggestion were agreeable, then the dean might consult Lindemann, and also Erwin Schrödinger, who was then in Oxford, to find out which scientists were available. ‘I need scarcely tell you how much I regret my inability to see once more my many friends at Christ Church but I hope to be more fortunate on some future occasion.’ And in January 1935, he told Lindemann that he would not visit that year either, ‘because if I come to Oxford I must also go to Paris and Madrid and I lack the courage to undertake all this’. He said almost the same thing, around the same time, to his musical friend Elisabeth, Queen of Belgium: ‘Sometimes I think back nostalgically to beautiful past hours; they tempt me to make a journey to Europe. But so many obligations would await me there that I cannot summon the courage for such an undertaking.’ No doubt, in addition to the demands of anti-Nazi politics, Einstein also had in mind his reluctance to deal with intractable family matters in Europe, in particular the psychiatric illness of his younger son, Eduard, looked after by his ex-wife Mileva. He did not accompany his wife Elsa when she returned to Paris in May 1934 to watch her elder daughter, Ilse, die – despite his fondness for his stepdaughter.

  ESTABLISHMENT AT PRINCETON AMONG FELLOW EUROPEAN EXILES

  Thus did Einstein’s last institutional link with England, and with Europe as a whole, fade away. But at the same time, of course, Europe came to Einstein in America, in the shape of numerous Jewish fellow refugees and non-Jewish visitors to the Institute for Advanced Study. In fact, Einstein’s closest human interactions in America were almost exclusively with Europeans, not native-born Americans, until his death in 1955. As noted by an influential English-born physicist, Freeman Dyson, who knew Einstein at Princeton in 1948 and later settled in the United States: ‘He had gone through the ritual of naturalisation, but he remained an alien spirit in America.’ In fact, Einstein retained his Swiss citizenship when he became a United States citizen in 1940. Despite his admiration for the principles of American democracy, Dyson’s summary comment feels true. After all, in late 1939, following the outbreak of war in Europe, Princeton University’s freshmen chose Hitler, for the second year running, as ‘the greatest living person’ in the annual poll of their class conducted by the Daily Princetonian. (The German leader received ninety-three votes in the poll; Einstein twenty-seven votes; and Neville Chamberlain, the British prime minister, fifteen votes.) Certainly, Einstein never gave expression to any deep gratitude, or even love, towards America, as he did towards England in 1933.

  By way of example of his continuing European Jewish affiliations, he collaborated with Leopold Infeld and Banesh Hoffmann on general relativity, to create the important Einstein–Infeld–Hoffmann equations of motion, published in 1938. Infeld was a Polish-born physicist who left Poland for Cambridge in 1933, and later came to Princeton as a Polish refugee without any academic position, where his excellent command of English enabled him to co-write The Evolution of Physics with Einstein and survive financially on the royalties from sales of the book. Hoffmann was a British-born son of Polish immigrants, educated at the University of Oxford, who earned his doctorate at Princeton University, settled at the City University of New York as a mathematician, and later wrote Albert Einstein: Creator and Rebel with Einstein’s secretary, Dukas.

  Einstein in his study at Princeton, 1951. On the wall is a portrait of Mahatma Gandhi, of whom Einstein said: ‘Generations to come, it may well be, will scarce believe that such a one as this ever in flesh and blood walked upon this earth.’ Other walls carried portraits of Isaac Newton, Michael Faraday and James Clerk Maxwell. Much of Einstein’s time in Princeton was spent alone at home, working on physics, despite his active involvement with American Cold War politics.

  Hoffmann had an irresistible anecdote about Einstein in Princeton caught in the act of thinking about physics, accompanied by Infeld and himself:

  Whenever we came to an impasse the three of us had heated discussions – in English for my benefit, because my German was not too fluent – but when the ar
gument became really intricate Einstein, without realising it, would lapse into German. He thought more readily in his native tongue. Infeld would join him in that tongue, while I struggled so hard to follow what was being said that I rarely had time to interject a remark till the excitement died down.

  When it became clear, as it often did, that even resorting to German did not solve the problem, we would all pause, and then Einstein would stand up quietly and say, in his quaint English, ‘I vill a little t’ink’. So saying he would pace up and down or walk around in circles, all the time twirling a lock of his long, greying hair around his forefinger. At these moments of high drama Infeld and I would remain completely still, not daring to move or make a sound, lest we interrupt his train of thought. A minute would pass in this way and another, and Infeld and I would eye each other silently while Einstein continued pacing and all the time twirling his hair. There was a dreamy, far-away, and yet sort of inward look on his face. There was no appearance at all of intense concentration. Another minute would pass and another, and then all of a sudden Einstein would visibly relax and a smile would light up his face. No longer did he pace and twirl his hair. He seemed to come back to his surroundings and to notice us once more, and then he would tell us the solution to the problem and almost always the solution worked.

  So here we were, with the magic performed triumphantly and the solution sometimes was so simple we could have kicked ourselves for not having been able to think of it by ourselves. But that magic was performed invisibly in the recesses of Einstein’s mind, by a process that we could not fathom. From this point of view the whole thing was completely frustrating. But, from the more immediately practical point of view, it was just the opposite, since it opened a way to further progress and without it we should never have been able to bring the research to a successful conclusion.

  As Infeld subsequently observed: ‘The clue to the understanding of Einstein’s role in science lies in his loneliness and aloofness. In this respect he differs from all other scientists I know.’ Perhaps Dirac, whom Infeld knew in Cambridge, could be regarded as ‘the nearest to Einstein, although the difference between them is still great’.

  NUCLEAR FISSION AND THE ATOMIC BOMB

  Probably the best-known European Jewish refugee to work with Einstein in America was the Hungarian-born physicist Leo Szilard. Having moved from post-war Hungary to study in Berlin, he got to know Einstein in the early 1920s and together they designed and patented an Einstein–-Szilard refrigerator pump in 1927, which was later used for the circulation of liquid sodium coolant in nuclear reactors. With the advent of the Nazi regime, Szilard moved to England in 1933, became involved with the fledgling Academic Assistance Council, and took a job at St Bartholomew’s Hospital studying the use of radioactive istopes for medical treatments. While in London – after reading a newspaper article on atomic energy by Rutherford and supposedly just after waiting for a traffic light not far from the British Museum to go green so that he could step off the kerb – Szilard conceived, on 12 September 1933, the idea of the nuclear chain reaction, which would prove so crucial in the atomic bomb project. In 1938, fearing an imminent war with Germany, he emigrated to the United States, where he once again came in contact with Einstein.

  In July 1939, Szilard became concerned by reports that German physicists were investigating nuclear fission, very likely with a view to making a bomb. He – accompanied by another Hungarian émigré physicist, Eugene Wigner, a future Nobel laureate – decided to drive out from New York and interrupt Einstein at his summer house in rural Long Island, in order to ask him to intervene politically. It was so tricky to find the address in Peconic, however, that they were about to give up and return to New York when Szilard thought of asking a young boy where Professor Einstein lived. The boy got into their car and took them to him.

  Talking to Einstein, Szilard was surprised to discover that he had not considered the possibility of a nuclear chain reaction. That is, the idea of one neutron bombarding a uranium atom, causing it to fission and release two neutrons, which then cause two uranium atoms to fission, producing four neutrons, and so on – and very quickly a concatenation of neutrons and an explosion of atomic energy. ‘I never thought of that!’ Szilard recalled Einstein’s saying when he told him that Enrico Fermi (a recent physicist refugee from Mussolini’s Italy) had just achieved a nuclear chain reaction in his New York laboratory. But as usual Einstein was quick to see the scientific implications of the new idea. And he instinctively shared his visitors’ fear that the Nazis might build the bomb first. ‘He was willing to assume responsibility for sounding the alarm even though it was quite possible that the alarm might prove to be a false alarm,’ said Szilard. ‘The one thing most scientists are really afraid of is to make fools of themselves. Einstein was free from such a fear and this above all is what made his position unique on this occasion.’

  By 2 August, the threesome had finalised what would become a historic letter from Einstein to President Franklin Roosevelt. Its most dramatic paragraph read as follows:

  This new phenomenon [a nuclear chain reaction] would also lead to the construction of bombs, and it is conceivable – though much less certain – that extremely powerful bombs of a new type may thus be constructed. A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory.

  But Einstein advised that such bombs might possibly turn out to be too heavy to be transported in aircraft.

  Einstein’s letter was personally delivered to the president through a trusted intermediary after a considerable delay – by which time war had broken out in Europe. Roosevelt responded promptly, but it took well over two years (and another reminder to Roosevelt from Einstein in 1940), plus the Japanese attack on the United States in December 1941, before the Manhattan Project to build the bomb got fully under way.

  At this time, during 1941, Infeld – who had now emigrated from the United States to Canada – happened to publish an autobiography, Quest. He wrote presciently: ‘Very few of the younger generation of physicists are seriously interested in the problems with which Einstein occupies his life. Most of them work in close contact, gathering material, searching for theories, often of a provisional character, to fit the tremendous richness of experimental data in the realm of nuclear physics’ – a situation that did not remotely resemble that of solitary young physicist-cum-lighthouse-keepers as fantasised by Einstein in his Albert Hall speech in 1933.

  Indeed, Einstein had nothing directly to do with the actual making of the atomic bomb – unlike Szilard and Wigner, who both joined the Manhattan Project. While he was responsible for deriving the equation E = mc2, which he published in 1905, at that time he had absolutely no vision of its use in weaponry. ‘It is true that this equation plays an important role in nuclear physics, but to say this made possible the construction of weapons is like saying that the invention of the alphabet caused the Bible to be written,’ remarked Abraham Pais. In July 1939, when Szilard met him, Einstein was clearly out of touch with nuclear physics. Despite his letters to Roosevelt, during the Manhattan Project in 1942–45 Einstein was not given a security clearance by the army authorities (probably because of his alleged Communist sympathies) – although he did receive clearance from the naval authorities to work on the theory of explosions – and was kept officially unaware of the project’s technical progress right up to the bombing of Hiroshima and Nagasaki in August 1945. So Einstein was certainly not the ‘father’ of the atomic bomb, as strongly implied on a famous cover of Time magazine in 1946, although there is a case for calling him the bomb’s ‘grandfather’. But after 1945, once he came to know that the German scientists (including Heisenberg) had achieved no significant progress in building an atomic bomb, Einstein strongly regretted his encouragement of Roosevelt; and for the remainder of his life he was relentlessly opposed to the spread of nuclear weapons.

  As well as receiving visitors from Europe, Einstein al
so kept in contact by letter with those who remained there. His correspondents included Elisabeth, Queen of Belgium, Murray in Oxford, two old friends from Zurich days, Besso and Solovine, and among the major physicists living outside the Third Reich, Born in Britain (Cambridge and Edinburgh) and Schrödinger in Ireland (Dublin).

  FRIENDSHIP AND DEBATE WITH MAX BORN ACROSS THE ATLANTIC

  The most illuminating of these exchanges was undoubtedly that with Born – most famously, Einstein’s 1926 remark to Born about God not playing dice with the universe – covering the period 1916–55, beginning in wartime Germany and continuing after the last personal meeting between Einstein and Born in 1932. Thereafter, they were divided by the Atlantic Ocean. (Born arrived in England in 1933 just after Einstein’s departure, and never visited the United States after 1933.) Like Einstein, Born abandoned his German citizenship, becoming a British citizen just days before the outbreak of war in 1939, in Edinburgh, where he had been appointed a professor of physics at the uni-versity in 1936. His son and two daughters married and settled down in the new country. But unlike Einstein, Born returned to Germany in 1954 on his retirement, and died in his native land. Their letters range from analysis of quantum mechanics to debate over the German threat to peace, including some fundamental disagreements about physics, politics and life in general, which at times led to long periods of silence between them. Nonetheless, Born, who edited the letters after Einstein’s death with the addition of an extensive commentary, concluded the collection with the comment: ‘With his death, we, my wife and I, lost our dearest friend.’

  It was published after Born’s own death as The Born–Einstein Letters in 1971, with prefatory material by two Nobel laureates: a foreword by Bertrand Russell and an introduction by Heisenberg, both of whom had known Born and Einstein personally, if from very different angles. Then it appeared in a second edition in 2005, the centenary of special relativity, with a new preface jointly written by Diana Kormos Buchwald, general editor of the Einstein Papers Project, and Kip Thorne, a leading expert on the astrophysical implications of general relativity. They focused on the history of Einstein’s scientific ideas over a century, and how ‘many of his scientific concerns at the time continue to engage modern physics’. For instance, the Einstein–Infeld–Hoffmann equations of 1938 – ‘Einstein’s greatest contribution to relativity after 1920’ – and also gravitational waves, predicted by Einstein from general relativity in 1916, which were finally confirmed to exist in 2016 by a team including Thorne (for which he shared a Nobel prize in 2017).