The Strangest Man

by Graham Farmelo

  41 For a full account of Rutherford’s campaign to secure Kapitza’s release, see Badash (1985), notably Chapter 2. See also Kojevnikov (2004: Chapter 5).

  42 Letter from Dirac to Anna Kapitza, 19 December 1934, copy held by Alexei Kojevnikov.

  43 Dirac wrote of his vacation, without mentioning Manci, to Max Newman in a letter written on 13 January 1935 (Newman archive, STJOHN). The story of the alligator, which Gamow named Ni-Nilich, is related in letters from Dirac to Manci on 2 February, 29 March, 22 April and 2 May 1935 and in the letter from Manci to Dirac on 5 April 1935 (DDOCS). See also the letter from Gamow to Dirac, 25 March 1935, Dirac Papers, 2/3/1 (FSU).

  44 Letter from Dirac to Anna Kapitza, 14 March 1935, copy held by Alexei Kojevnikov.

  45 Letter from Rutherford to Bohr, 28 January 1935, Rutherford archive, UCAM.

  46 Gardiner (1988: 240–8).

  47 Gardiner (1988: 241).

  48 Gardiner (1988: 242).

  49 Kragh (1996: Chapter 2).

  50 ‘Lemaître Follows Two Paths to Truth’, New York Times, 19 February 1933.

  51 Letter from Dirac to Manci, 2 February 1935 (DDOCS).

  52 Dirac had heard Lemaître speak at the Kapitza Club in about 1930. Dirac commented on this in a note he wrote on 1 September 1971: ‘There was much discussion about the indeterminacy of quantum mechanics. Lemaître emphasised his opinion that he did not believe God influenced directly the cause of atomic events’: Dirac Papers, 2/79/2 (FSU).

  53 Letter from Dirac to Manci, 2 March 1935 (DDOCS).

  54 Letter from Dirac to Manci, 2 May 1935 (DDOCS). Schnabel gave the concert on 7 March 1935.

  55 Letter from Dirac to Manci, 10 March 1935 (DDOCS).

  56 Letter to Dirac from Manci, 28 March 1935 (DDOCS).

  57 Letter from Dirac to Manci, 29 March 1935 (DDOCS).

  58 Letter from Dirac to Manci, 2 May 1935 (DDOCS).

  59 Letter from Dirac to Manci, 9 May 1935 (DDOCS).

  60 Letter to Dirac from Manci, 30 May 1935 (DDOCS).

  61 Letter to Dirac from Manci, 4 March 1935 (DDOCS).

  62 Letter from Dirac to Manci, 9 April 1935 (DDOCS).

  63 Badash (1985: 29).

  64 Badash (1985: 31).

  65 Letter from Kapitza to his wife, 13 April 1935, quoted in Boag et al. (1990: 235).

  66 Letter from Kapitza to his wife, 23 February 1935, quoted in Boag et al. (1990: 225).

  67 Letter from Kapitza to his wife, 23 February 1935, quoted in Boag et al. (1990: 225, 226).

  68 Kojevnikov (2004: 107).

  69 Letter from Dirac to Manci, 2 May 1935 (DDOCS).

  70 Lanouette (1992: 151); see also letter from Dirac to Anna Kapitza, 31 May 1935, copy held by Alexei Kojevnikov.

  71 Letter from K. T. Compton to the Soviet Ambassador, 24 April 1935, copy held by Alexei Kojevnikov.

  72 Letter from Dirac to Anna Kapitza, 27 April 1935, copy held by Alexei Kojevnikov.

  73 ‘Embassy Occupied by Troyanovsky’, New York Times, 7 April 1934.

  74 Letter from Dirac to Anna Kapitza, 27 April 1935, copy held by Alexei Kojevnikov.

  75 Letter from Dirac to Anna Kapitza, 27 April 1935.

  Twenty

  STALIN: You, Mr Wells, evidently start out with the assumption that all men are good. I, however, do not forget that there are many wicked men.

  ‘A Conversation between Stalin and [H. G.] Wells’,

  New Statesman, 27 October 1934

  Moscow was beckoning again. For the following four months, Dirac’s diary was empty, and he was determined to spend most of that time with Kapitza. Dirac knew that the secret police read his letters to Anna Kapitza and that he would probably be followed when he was in Moscow. He told her, ‘If anyone follows me around in Moscow he will get some long walks.’1

  Dirac and Tamm had intended to spend the summer hiking and climbing together in the Caucasus, and Dirac hoped to see one of the allegedly productive factories and the new Dneproges hydroelectric power station, one of the proudest achievements of Soviet engineering. But when Anna Kapitza asked Dirac to cancel the trip in order to support her husband, Dirac shelved his plans and declared himself to be at the service of her and her husband: ‘I am ready for anything.’2 He travelled to Moscow via Berkeley, where Oppenheimer found that Dirac was as tight-lipped as ever about physics. Two of Oppenheimer’s students were elated when he told them that their British guest was prepared to hear their ideas about quantum field theory, which built on his work. During their fifteen-minute presentation, Dirac said nothing. Afterwards, the students braced themselves for his perceptive comments, but there was an agonisingly long silence, eventually broken by Dirac when he asked them, ‘Where is the post office?’ The students offered to take him there and suggested that he could tell them what he thought of their presentation. Dirac told them, ‘I can’t do two things at once.’3

  On the afternoon of 3 June 1935, Dirac waved goodbye to Oppenheimer and boarded the Japanese MS Asuma Bura.4 He settled into his private cabin and prepared to sail through the mist to San Francisco – catching sight of the half-constructed Golden Gate Bridge – and then on to Japan, China and the USSR. Manci, meanwhile, was lounging around in Budapest, awaiting the arrival of her first car, a six-cylinder Mercedes Benz bought for her by her father.5 She had persuaded Dirac to visit her in Budapest at the end of his trip. Her complaints that he didn’t respond to her questions drew another tabulated response:

  Have you played ping-pong with pretty girls? With one pretty girl. Most of the passengers were Japanese, and Japanese girls do not play ping-pong.

  Have you flirted? No. She was too young (15 years old). But you ought not to mind if I did. Should I not make the most of what you taught me?

  Why were you so derisive? I am sorry, but I cannot help it at times.6

  Six weeks after he had set sail from the USA, Dirac arrived in Moscow railway station. Even he, with his Gandhian indifference to his surroundings, must have been struck by the contrast between the fresh, early summer air of Princeton and the stench of rotten eggs that hung over the Soviet capital. It was no longer the city that he had seen four years before but a reeking, overcrowded metropolis. The playwright Eugene Lyons described the ‘viscous ooze of [Moscow’s] dung-coloured people, not ugly but incredibly soiled, patched, drab; the odour and colour of ingrained poverty, fetid bundles, stale clothes’.7 Dirac stayed there only briefly: he had arranged to spend most of his time in the more agreeable ambience of the Kapitzas’ dacha (summer home) in the village of Bolshevo, thirty-five miles south of the city. Kapitza was looking forward to seeing his English friend, though the tone of his comments to his wife indicates that he did not fully reciprocate the intensity of Dirac’s affection. But a day after Dirac’s arrival, Kapitza appeared to have changed his mind. He wrote to her:

  [We] came here with Tamm and have been walking, boating and talking ever since. I haven’t had such a pleasant time with anyone up to now. Dirac treats me so simply and so well that I can feel what a good and loyal friend he is. We talk about all sorts of things and this has been very refreshing. […] Dirac’s arrival has revived my memories of the respect and reputation I enjoyed in Cambridge […]8

  The two friends relaxed together for almost three weeks. Kapitza’s abject morale had not improved when he heard that the Soviet authorities had, for unknown reasons, sent ‘Dimus’ Ivanenko into exile.9 It was a familiar story, though no one dared to question Stalin’s policy in public. Kapitza was considering giving up physics and changing the subject of his research to physiology so that he could work with Russia’s most senior scientist, the elderly but still active Ivan Pavlov. Within the modest compass of Dirac’s verbal skills, he tried to lift Kapitza’s spirits, and in return Kapitza – evidently knowing nothing of Dirac’s friendship with Manci – tried to fix him up with a young girl they met, a good-looking, English-speaking language student. Dirac did not respond.

  During his stay, he met the Trinity College physiologist Edgar Adrian and other
British colleagues asked by Rutherford to assess Kapitza’s situation and his psychological state. The Soviet Government supported this visit, presumably to demonstrate their flexibility. But, by the time Adrian and his colleagues met with Kapitza, the die was cast: Kapitza had been forbidden to return to Cambridge, and it remained only to secure the best terms for him to work in his new institute. When Dirac left Moscow at the beginning of September, he knew that he had lost his first diplomatic battle; he would have to become accustomed to living in Cambridge without the man he thought of as his closest friend.

  The final stage of his trip was an antidote to his disappointment: he was to visit Manci in Budapest. She was living with her children in an apartment in what had been Archduke Frederick’s house, a short stroll from her parents’ sumptuous residence opposite Count Batthyány Park. This was a world of plenty – fine food, exquisitely cut clothes, attentive servants and private concerts in the living room. Dirac’s modest origins in Bishopston were part of another world. Manci took her material comforts for granted, but she was unhappy and longed to get away from her parents, who must have been taken aback by the arrival on their doorstep of an unkempt Englishman who knew hardly a word of Hungarian. They knew next to nothing about him and surely cannot have expected that their feisty, outspoken daughter would choose such a diffident man. But they liked him and could see that Manci and Dirac clicked during their nine days together, driving around the city in her new car, sightseeing and soaking in the famous indoor public baths.10 When he returned to Cambridge, he wrote to Manci: ‘I felt very sad when leaving you and still feel that I miss you very much. I do not understand why this should be, as I do not usually miss people when I leave them. I expect you spoil me too much when I am with you.’11

  Manci was making progress. But three weeks later, her heart sank when she read the final entry in Dirac’s latest table of unanswered questions: to her query ‘Do you miss me a little?’, he responded, ‘Sometimes.’12

  When Dirac returned to England in the early autumn of 1935, the country was still disfigured by unemployment and worried by Hitler’s aggressive rearmament, Mussolini’s sabre-rattling in East Africa and Japan’s occupation of Manchuria. ‘I would like to kill the politicians of middle Europe,’ Manci fumed.13 Dirac was soon back in his Cambridge routine, but the thrill had gone. Although he had not given up on quantum electrodynamics, he seemed to be getting nowhere. Dirac thought a revolution was needed and probably wondered whether he, now thirty-three, might be too old to be one of its leaders.

  Rutherford had negotiated a deal that involved moving almost every item of Kapitza’s equipment to the Institute for Physical Problems, enabling him to resume all his experiments there. Anna had made Dirac a guardian of the Kapitzas’ sons, and he took his duties seriously, taking the boys out at the weekends for rides in his crumbling car and organising his first fireworks display for them on 5 November.14 These were good times for Dirac, but he was preparing for yet more loneliness: the Blacketts had left for London, Chadwick for Liverpool, Walton for Dublin, and now the Kapitzas were about to depart for good. Dirac was not the self-sufficient eremite that many people believed him to be: he needed new companionship, and he knew it. Manci was eager to oblige, but he was wary of her forwardness, as he showed when she telephoned him one night late in November as he was preparing to go to bed.15 She thought he would be delighted to receive an unexpected call from her but he was angry and shaken. The college telephone system was arranged so that the porters heard their stilted conversation, as he explained to her in a brusque note. Surely it was sufficient to communicate only by letter, he wrote, with all the warmth of a tax inspector. She swiftly replied, making clear what she thought of his secretiveness: ‘ridiculous’.16

  Incidents like that rattled him: could he live with someone who had so little sympathy with his need for privacy? He will have had no wish to be party to a disastrous marriage, like his parents’, which he had seen in all its unpleasantness two months before, during another rain-soaked visit to Bristol.17 Charles and Flo were living out their marriage contract in an unwinnable endgame of squabbles and recriminations. Divorce was out of the question for the born-again Catholic Charles, but when he read his copy of George Bernard Shaw’s Getting Married, he may well have sympathised with the author’s recommendation: ‘Make divorce as easy, as cheap, and as private as marriage.’18 Flo would probably have welcomed a divorce, but the shame would have been too much for her. So they both remained unhappily shackled to each other, with nothing to look forward to except more arguments. Flo told her son that her pleasures were limited to taking long walks on the Downs, sitting alone in the parks and attending meetings of the new Bristol Shiplovers’ Society. ‘I have made an awful mess of my life somehow,’ she wrote, adding that she blamed herself: ‘What we sow, we reap.’19

  Dirac’s mother appears to have had no more than a passing interest in his work, but his father struggled hard to understand it. Charles looked through the journals in the library, searching for readable accounts of quantum theory, hoping to absorb some of their content by writing out paragraphs of difficult technical prose, verbatim. He kept a record of his findings in a small, red notebook, on whose front cover he had written a two-inch-high letter P.20 The desultory references and notes inside are heart-rending records of a keen but confused amateur, unable to make any headway in a subject he longed to understand. Charles had written, in his rheumatic hand, some of the most complimentary comments about his son, highlighting some of the most generous ones: ‘Dirac stands out amongst his contemporaries in this field for his originality.’ Apart from a summary of one of Crowther’s articles on ‘New Particles’, Charles had not tracked down any of the lively and accessible accounts of quantum mechanics by Eddington or any of the other accomplished popularisers. It seems that his son was giving him no help at all.

  With Bristol’s long tradition of adult education, it was easy for the city’s citizens to find out about new science. Arnold Tyndall, who gave Dirac his first introduction to quantum theory, was a popular performer at the night classes on science organised by the university. During one of his courses, a male student caught the eye of the genial Tyndall. Much older than the other students, he always sat at the front, taking careful notes. At the end of the final lecture, he shuffled up to Tyndall to thank him. ‘I am glad to have heard all this. My son does physics but he never tells me anything about it.’ The student was Charles Dirac.21

  In the early summer of 1935, Betty had finished her French course and had come bottom of her class, taking a third-class honours degree, as Felix had done.22 She wanted to be a secretary and to get out of Bristol as quickly as she could. Charles was now open about his relationship with Mrs Fisher, Flo told Dirac: ‘I wish he would go and live with her, folks are always seeing them about together and tell me […] He has always had someone ever since I’ve been married: Betty says it is French.’23

  Dirac’s mother, preparing to go on another Mediterranean cruise alone, sensed that her daughter was growing away from her. In a few weeks, she would temporarily move to London, not leaving her mother a forwarding address. But first Betty went on an August vacation with her father, keeping their destination secret. They were travelling with a group of Catholic priests on a pilgrimage to Lourdes, in the French Pyrenees, where Charles may, to try to rid himself of his ailments, have bathed in its reputedly miraculous waters. He knew that his daughter would pray for him but that his wife and son were, at best, indifferent to his fate.

  Dirac would probably have been happiest if, like Einstein, he had never supervised a graduate student. It was not until the 1935–6 academic year that Dirac first officially became a research supervisor, taking on two students Born left behind when he moved to Edinburgh to take up a professorship.24 Dirac had almost none of the skills that he had seen in Fowler: the ability to set problems pitched at the right level for his students, to motivate them in lean times and to support them in the early stages of their career. Dirac believed his
only obligation was to point his students towards an interesting theoretical concept and then to look over any work they produced in consequence; it was up to the student to take almost all the initiative. Only the cleverest and most independent-minded students could flourish under such a regime, as the Cambridge authorities knew. Dirac knew it, too, and showed no interest in recruiting apprentices. But several of the finest young minds sought his guidance, including the Indian mathematician Harish-Chandra and the Pakistani theoretician Abdus Salam, both part of a pattern – the great majority of Dirac’s successful students were foreign.

  Dirac encouraged his students to keep abreast of the latest publications in theoretical physics and also to keep an eye on the experimenters’ latest findings. But his faith in the veracity of new experimental results was badly shaken by an incident that began in the autumn of 1935. Dirac heard that the Chicago experimenter Robert Shankland had found evidence that sometimes energy is not conserved, contrary to one of the fundamentals of science: when photons are scattered by other particles, he found the particles’ total energy before the collision is not the same as it is afterwards. Setting aside his preference to be led by mathematics rather than experiment, Dirac smelt an impending revolution and in December wrote to Tamm, spelling out the consequences of Shankland’s findings.25 First, the neutrino would no longer be needed, as Pauli had based his entire argument for its existence on the energy-conservation law. Second, and more important, as Shankland’s experiment involved light, his results might be a hint that energy is not conserved whenever particles collide at speeds close to the speed of light. If so, Dirac pointed out, it would be reasonable to retain the basic theory of quantum mechanics, which applies to comparatively slow-moving particles, though the relativistic extensions of the theory, such as quantum electro-dynamics, would have to be abandoned. A few days later at the Kapitza Club – still meeting despite its founder’s absence – Dirac gave a talk on the implications of Shankland’s results. To most physicists, the experiments looked unreliable, and it seemed wise to wait for the results to be checked independently.26 But Dirac could not wait: in January 1936, he set out the implications of Shankland’s results in a short, equationless article in the journal Nature, addressing his comments to the entire scientific community. If Shankland was right, Dirac said, quantum electrodynamics would have to be abandoned, adding, ‘most physicists will be very glad to see the end of it’.27 Coming from one of the discoverers of relativistic quantum mechanics and field theory, these were striking words. Heisenberg privately dismissed Dirac’s thoughts as ‘nonsense’.28 Einstein did not conceal his glee: ‘I am very happy that one of the real experts now argues for the abandonment of the awful “quantum electrodynamics”.’29 Schrödinger, disillusioned with the conventional interpretation of quantum theory, was pleased that Dirac had apparently joined the malcontents.30 Bohr, who in 1924 had been among the first to suggest that energy might not be conserved in every atomic process, was publicly less critical, though he took Shankland’s results with a pinch of salt.31