Inside the Centre: The Life of J. Robert Oppenheimer (24 page)

The non-deterministic, probabilistic nature of quantum mechanics provided Born with an intriguing answer to the general question regarding the physical reality described by its equations, allowing him to decide between the particle-like ‘quanta’ described by the mathematics of Heisenberg and Dirac and the waves described by Schrödinger’s differential equations. Basically, he came down on the side of regarding electrons as particles, while providing an ingenious explanation for why Schrödinger’s wave mechanics ‘worked’. Schrödinger believed that the success of his wave functions showed that de Broglie was right – electrons
are
waves – and his problem was to explain why, in countless experiments (including the original experiments of J.J. Thomson back in the 1890s), electrons seemed to behave like particles. For Born, it was the other way round; electrons
were
particles (or at least discrete ‘quanta’) and what required explanation was why they
seemed
to behave like waves. His answer to this last question invoked the probabilistic nature of quantum theory that he had demonstrated in his analysis of collisions. The waves of de Broglie and Schrödinger, Born argued, had no physical reality. Rather, they were
probability waves. What they described was the probability of an electron being in a particular place at a particular time. Quantum mechanics, according to Born, is unable to say definitely whether an electron is or is not at a particular place at a particular time; it can only say what the odds are that it is here or there. And this is not because of the limitations of our knowledge; it is an inherent feature of physical reality, linked to its non-deterministic nature. This ‘statistical interpretation of quantum mechanics’, as it became known, was quickly adopted by other leading physicists, most notably Heisenberg and Bohr (who famously defended it against Einstein on numerous occasions), and it was for discovering it that Born was awarded the Nobel Prize, though oddly not until 1954, more than twenty years after the same honour had been awarded to de Broglie, Heisenberg, Schrödinger and Dirac.
^fn22

Though Born had already sent his paper to the
Zeitschrift
, it had not yet been published when he came to Cambridge to deliver his talk to the Kapitza Club on 29 July 1926. When it was published, in September 1926, a footnote had been added, acknowledging the importance of Oppenheimer’s paper on the two-body problem. For a twenty-two-year-old research student who had not yet completed a PhD thesis, this was a significant feather in his cap. Born was evidently very impressed with Oppenheimer. In the second week of August, Born returned to England to read a paper at the annual meeting of the British Association for the Advancement of Science, which that year was held in Oxford. The paper, entitled ‘Physical Aspects of Quantum Mechanics’, was Born’s most direct statement yet on the question of how, in the light of quantum mechanics, we are to understand physical reality, and was responsible for spreading his idea of probability waves to theoretical physicists in Britain. When the paper was published in
Nature
the following year, it carried the following acknowledgement: ‘Translated by Mr Robert Oppenheimer. The author is very much obliged to Mr Oppenheimer for his careful translation.’

By the summer of 1926, then, Oppenheimer had not only established himself as a promising young theorist; he had become a collaborator with the person who at that time was leading the effort of the international community of physicists to understand the extraordinary world of quantum mechanics. He had, in fact, positioned himself where he
had wanted to be: at the ‘centre’ of theoretical physics. His year at Cambridge had allowed him to achieve this, partly because it had enabled him to see that, in 1926, the centre of theoretical physics was not Cambridge, but Göttingen. The person to work with was not Ernest Rutherford, or even Niels Bohr, but rather Max Born. Accordingly, on 18 August 1926, a week after the meeting at Oxford, Oppenheimer wrote to Raymond Priestley, asking for permission to spend the following year at Göttingen, under the supervision of Born, who, Oppenheimer informed Priestley, was ‘particularly interested in the problems at which I hoped to work’. Reflecting on his decision to leave Cambridge for Göttingen, Oppenheimer later said that, though he ‘had very great misgivings about myself on all fronts’, he still felt determined to pursue his inclination to become a theoretical physicist: ‘Here was something I felt just driven to try.’

He may have had misgivings, but he must also have known that, in pursuing this inclination, he had every chance of meeting with success. He had never stood any chance of impressing the ‘tutors & the dukes’ of British high society, he would never have been invited to Garsington or to Pontigny, and he would never be described (as Blackett had been by I.A. Richards) as ‘a young Oedipus’, but he
had
succeeded in impressing one of the foremost quantum physicists in the world – an achievement that brought him not just near the centre of theoretical physics, but right inside it.

^fn17
T.S. Eliot and Bertrand Russell.

^fn18
It is impossible to tell how much of this story is true. Can one believe that Oppenheimer deliberately dropped his suitcase, intending it to hit the woman? Did he really kiss her? And, perhaps most improbably of all: can one really imagine him travelling third-class?

^fn19
An alpha particle, as Rutherford was the first to establish, is a helium nucleus. It is (we now know, though this was not known before the discovery of neutrons in 1932) made up of two protons and two neutrons. What Rutherford and the physicists of the 1920s knew about alpha particles/helium nuclei was that they had an atomic weight of 4 and that they, like all nuclei, were positively charged. Chiefly, however, alpha particles were associated in the minds of the scientists of this period with what Rutherford had christened ‘alpha radiation’, which occurs when a radioactive element such as radium decays. The radioactive decay simply is the emission of alpha particles. As these particles include two protons, the decayed radium (atomic number 88) turns into radon (atomic number 86), and then, successively, into polonium (84) and lead (82).

^fn20
Nitrogen has atomic number 7, so that when it absorbs a proton it becomes element number 8 – i.e. oxygen.

^fn21
It is indicative of the attitude towards theoretical physics at Cambridge during this period that Fowler’s official position was college lecturer in mathematics.

^fn22
As far as I know, no authoritative answer has been given as to why it took so long to award Born the Nobel Prize. Jeremy Bernstein has speculated that it is because, in 1933, when Heisenberg, Dirac and Schrödinger were honoured, it would have been natural to have included Born and Jordan, but Jordan was a member of the Nazi Party and unacceptable. Therefore the committee had to wait until they had a reason for giving it to Born alone. This might explain why Born did not receive the prize in 1933, but it hardly explains why he had to wait a further twenty-one years.

IN THE STARKEST
contrast to his arrival in Cambridge just a year earlier, Oppenheimer arrived in Göttingen in the summer of 1926 in a state of almost unrestrained self-confidence. As Max Born put it, Oppenheimer seemed ‘conscious of his superiority’. In his autobiography Born complains several times about Oppenheimer’s arrogance, without appearing to recognise the central role he himself had played in nurturing it. Whereas at Cambridge, Oppenheimer arrived having been rejected by the leading physicist there, at Göttingen he arrived having been
invited
by the leading physicist there, who made no secret of the fact that he was extremely impressed with, and indeed a little intimidated by, Oppenheimer’s intelligence.

Though apparently unaware of what it revealed, Born tells a story that perfectly conveys the role he played in allowing, even encouraging, Oppenheimer to be ‘conscious of his superiority’. The story concerns Born’s most famous paper, ‘The Quantum Mechanics of Collision Processes’, the one that he read to the Kapitza Club in July 1926, when he first met Oppenheimer. Born says that when he finished writing the paper, he showed it to Oppenheimer in order for him to check the difficult and involved calculations it contained. This must have been, I think, in August 1926, when Born returned to England to read the paper that Oppenheimer translated to the British Association for the Advancement of Science at Oxford. Born had by then received the proofs of ‘The Quantum Mechanics of Collision Processes’ from the
Zeitschrift für Physik
, and it is presumably these proofs that he showed to Oppenheimer. What would immediately have struck Oppenheimer, and boosted his confidence enormously, was the footnote Born added to the paper at the proof stage drawing attention to the importance of Oppenheimer’s work on the two-body problem. Born, who was self-critical to a fault, says that he asked Oppenheimer to check the calculations because ‘I was never
very good at long calculations and always made silly mistakes.’ All his students knew this, he says, but Oppenheimer ‘was the only one frank and rude enough to say it without joking’. For, after he had checked the paper, Oppenheimer returned it to Born, saying, with an astonished expression: ‘I couldn’t find any mistake – did you really do this alone?’ ‘I was not offended,’ Born insists. ‘It actually increased my esteem for his remarkable personality.’

Born was at that time a forty-three-year old professor at one of the most distinguished universities in the world, at the height of his career, having, in the preceding few years, published work of fundamental, Nobel Prize-winning importance – work that persuaded brilliant young physicists from all over the world to come to Göttingen to study with him. Oppenheimer, meanwhile, was a twenty-two-year-old student, recently recovered from a severe mental illness, who was entirely unknown to the world at large and whose publications to date numbered just two articles. From the point of view of mathematical competence, Born had taken a PhD in mathematics, examined by David Hilbert, widely recognised as the greatest mathematician of his day, who regarded Born as a student of exceptional mathematical ability. Born was also regarded by his peers in theoretical physics as a scientist whose
greatest strength
was his facility with difficult and esoteric mathematics. Oppenheimer, on the other hand, had not yet taken a PhD in either mathematics or physics, and, though regarded as an undergraduate as someone who, in Percy Bridgman’s words, had ‘much mathematical power’, acknowledged himself that there were significant gaps in his mathematical education. His first published paper had been marred by mathematical errors and throughout his life he would have a reputation among physicists as someone prone to mistakes in mathematical calculations. Objectively, there was no reason whatsoever for Born to look up to Oppenheimer, particularly with regard to his mathematical acumen, nor was there any excuse for Oppenheimer to look down on Born. That, within a month of knowing each other, their relationship developed in a way that made it possible for Oppenheimer to be condescending towards Born about his mathematical competence says a great deal about the personalities of both men; about Born’s insecurities and about Oppenheimer’s ability to, as it were, cast a spell.

Another key to understanding Oppenheimer’s self-assurance at Göttingen, compared to the self-doubts and anxieties he had felt at Cambridge, may lie in the contrast between the two universities themselves. The University of Göttingen, though not the oldest in Germany (Heidelberg, Leipzig and several others pre-date it by hundreds of years), is certainly one of the most prestigious and is commonly held to be Germany’s equivalent to Cambridge (with Heidelberg its equivalent to Oxford). What would have struck Oppenheimer when he arrived in
Göttingen in the summer of 1926, however, are the many ways in which it is very
unlike
Cambridge. These differences are immediately apparent: the University of Göttingen’s oldest and grandest buildings are elegant and graceful, rather than Gothic and ecclesiastical, betraying its origins in the eighteenth-century Enlightenment, rather than in thirteenth-century monastic scholarship. Not being a collegiate university, it has no dons, fellows or high table. It has its own famous and celebrated esoteric rituals (the most famous of which is that PhD students should, on passing their oral examination, be carried by cart to the market square in the centre of town, where they have to kiss the statue of the
Gänseliesel
, the goose girl), but it does not have the weight of 700 years of tradition bearing down upon it.

Moreover, the post-war atmosphere of a defeated nation is very different from that of the victors. At Göttingen in the 1920s one would not have been aware of living in a carefree ‘Jazz Age’ or the ‘Roaring Twenties’; neither was there any parallel to the calculatedly unconventional, self-consciously effete aestheticism that characterised British university life in the post-war period: the world depicted, for example, in Evelyn Waugh’s
Brideshead Revisited
. The atmosphere at Göttingen in the 1920s was emphatically not ‘gay’. Rather, as Oppenheimer later put it, it was ‘bitter, sullen . . . discontent and angry and loaded with all those ingredients which were later to produce a major disaster’. Göttingen was, as this description hints, fertile ground for the then-burgeoning Nazi movement. In 1922, one of the very first branches of the Nazi Party was set up there and three years later, just a year before Oppenheimer arrived, a chemistry student named Achim Gercke, later a key figure in the Nazi movement, began to compile a list of Jewish professors at the university, so that, when the Nazis came to power, they would immediately know whom to expel in the name of racial purity.

The portentous sullenness created by such racial hatred was felt deeply by Oppenheimer, who, after less than a year, was glad to leave Göttingen. And yet, despite all this, for the nine months or so that he was there, Oppenheimer thrived at Göttingen as conspicuously as he had floundered at Cambridge. The anger, the resentment, the increasingly vehement and vicious anti-Semitism, though of course extremely unpleasant, were not, as it turned out, as debilitating or oppressive as the ‘excellence’ at Cambridge had been. At Göttingen, no matter what else he had to endure, he did not have to deal with people who mixed with dukes, who felt comfortable at high table, and who discussed literature and philosophy with internationally renowned French intellectuals. Rather, at Göttingen,
he
was the one who intimidated people with his social, intellectual and cultural pre-eminence, as exhibited by his ostentatious wealth, his mastery of the French language and French poetry, his astonishingly wide-ranging
knowledge and his refined taste in everything from literature to clothes, architecture to hand luggage.