The Strangest Man

by Graham Farmelo

  53 Interview with Dirac, AHQP, 6 May 1963, p. 4. Another example of the kind of neat tricks that engineers use and that Dirac read about as an engineering student is featured in the appendix to one of his set textbooks (Thomälen, 1907).

  54 The two books that Dirac used to study stress diagrams were Popplewell (1907) (see especially Chapter 5) and Morley (1919) (see especially Chapter 6).

  55 Dirac (1977: 113).

  56 The ‘spoilsport’ taught Dirac in the autumn of 1920. Dirac’s reports are in Dirac Papers, 1/10/16 (FSU).

  57 Interview with Dirac, AHQP, 6 May 1963, p. 13. Dirac’s lack of a qualification in Latin was not a bar to his admission to postgraduate study at Cambridge, but it would have made him ineligible to study there as an undergraduate.

  58 Warwick (2003: 406 n.); Vint (1956).

  59 Letter from Charles Dirac, 7 February 1921, STJOHN.

  60 Dirac took the examination on 16 June 1921. The examination papers are in Dirac Papers, 1/10/11 (FSU).

  61 Letter from Dirac to the authorities at St John’s College, 13 August 1921, STJOHN.

  62 Boys Smith (1983: 23). A much higher estimate of the amount needed to live as a student in Cambridge at the time is given in Howarth (1978: 66): about £300.

  63 Letter from Charles Dirac, 22 September 1921, STJOHN.

  64 Unsigned letter from St John’s College to Charles Dirac, 27 September 1921, STJOHN. The signatory concludes his letter: ‘Perhaps before deciding [what to do] you would be so kind as to let me know the sum total of means that he would have at his disposal, I could then better advise what he can do.’

  Chapter four

  1 Interview with Dirac, AHQP, 6 May 1963, p. 9.

  2 Recollections of Dirac’s first term in the mathematics class are from the testimony of E. G. Armstead in a letter to Richard Dalitz. The lecturer concerned was Horace Todd.

  3 Dirac (1977: 113); interview with Dirac, AHQP, 6 May 1963, p. 10.

  4 Interview with Dirac, AHQP, 1 April 1962, p. 3.

  5 It is likely that Dirac learned this subject from Projective Geometry by G. B. Matthews (1914), published by Longmans, Green and Co. This book apparently meant a lot to him as it was one of the few books from his youth that he kept until his death. His copy is kept in his private library, stored in the Dirac Library, Florida State University.

  6 Dirac studied four courses in pure mathematics: ‘Geometry of Conics; Differential Geometry of Plane Curves’, ‘Algebra and Trigonometry; Differential and Integral Calculus’, ‘Analytical Projective Geometry of Conics’ and ‘Differential Equations, Solid Geometry’. See Bristol University’s prospectus for 1922–3, BRISTU.

  7 Dirac studied four courses in applied mathematics: ‘Elementary Dynamics of a Particle and of Rigid Bodies’, ‘Graphical and Analytical Statics; Hydrostatics’, ‘Dynamics of a Particle and of Rigid Bodies’ and ‘Elementary Theory of Potential with Applications to Electricity and Magnetism’. See Bristol University’s prospectus for 1922–3, BRISTU.

  8 Testimony of Norman Jones (who attended the Merchant Venturers’ School from 1921 to 1925) to Richard Dalitz in the 1980s. Private communication from Dalitz.

  9 Interview with Dirac, AHQP, 1 April 1962, p. 8, and 6 May 1963, p. 10.

  10 The inclusion of the lectures on special relativity can be deduced from the presence of examination questions on the subject. See Dirac Papers, 1/10/15 and 1/10/15A (FSU).

  11 The term ‘non-commuting’ was introduced by Dirac later in the 1920s.

  12 Cahan (1989: 10–24); Farmelo (2002a: 7–12).

  13 Letter from Hassé to Cunningham, 22 March 1923, STJOHN.

  14 Interview with Dirac, AHQP, 6 May 1963, p. 14. During Dirac’s first visit to Cambridge, he had met Cunningham.

  15 Warwick (2003: 466, 467, 468, 493 and 495).

  16 Stanley (2007: 148); see also Cunningham (1970: 70), STJOHN.

  17 Letter from Ebenezer Cunningham to Ronald Hassé, 16 May 1923, and letter from Dirac to James Wordie, 21 July 1923, STJOHN. The grant from the Department of Science and Industrial Research was technically a maintenance allowance for research. Wordie became Dirac’s tutor in his early years in Cambridge. Postcard from Dirac to his parents, 25 October 1926 (DDOCS).

  18 Dirac often spoke to close friends of the significance of this gesture by his father. Among those to attest to this: Kurt Hofer in an interview on 21 February 2004, Leopold Halpern in an interview in February 2006 and Nandor Balázs in an interview on 24 July 2002.

  Chapter five

  1 Gray (1925: 184–5).

  2 Boys Smith (1983: 10).

  3 See contemporary issues of the Cambridge students’ magazine The Granta; for exam ple, the poem ‘The Proctor on the Granta’, 19 October 1923.

  4 Boys Smith (1983: 20).

  5 Dirac kept the lodging accounts for the digs where he stayed as a student. See Dirac Papers, 1/9/10 (FSU). Dirac’s landlady at 7 Victoria Road was Miss Josephine Brown, and he resided with her from October 1923 to March 1924. From April to June 1924, he stayed at 1 Milton Road. In his final postgraduate year, he lived at 55 Alpha Road.

  6 College records attest that he took his meals there: his bill for food in college during his first term was £8 17s 0d, about the same as other students who ate there (STJOHN). The bill from Miss Brown includes no charges at all for either ‘cooking’ or ‘food supplied’.

  7 From documents in STJOHN. A typical example of a menu that Dirac would have been offered is the following, served on 18 December 1920: ‘Hare soup / Boiled mutton / Potatoes, mashed turnips, carrots au beurre / Pancakes / Ginger mould / Hot and cold pie / Anchovy eggs’. He will not have gone hungry.

  8 Interview with Monica Dirac, 7 February 2003.

  9 Interview with Mary Dirac, 21 February 2003. Dirac’s words were ‘give myself courage’.

  10 Interview with John Crook, 1 May 2003.

  11 Boys Smith (1983: 7).

  12 See contemporary issues of the Cambridge students’ magazine The Granta.

  13 Werskey (1978: 23).

  14 Snow (1960: 245). See also Dirac (1977: 117).

  15 Needham (1976: 34).

  16 Stanley (2007: Chapter 3), especially pp. 121–3; Earman and Glymour (1980: 84–5).

  17 Hoyle (1994: 146).

  18 de Bruyne, N. in Hendry (1984: 87).

  19 This description is taken mainly from Snow (1960), and from Cathcart (2004: 223).

  20 Wilson (1983: 573).

  21 Oliphant (1972: 38).

  22 Mott (1986: 20–2); Hendry (1984: 126).

  23 Oliphant (1972: 52–3).

  24 Carl Gustav Jung introduced the words ‘extrovert’ and ‘introvert’ into the English language in 1923.

  25 ‘Naval diary, 1914–18. Midshipman’, by Patrick Blackett, pp. 80–1. Text kindly supplied by Giovanna Blackett.

  26 Nye (2004: 18, 24–5).

  27 Boag et al. (1990: 36–7); Shoenberg (1985: 328–9).

  28 Boag et al. (1990: 34).

  29 Chukovsky’s first book, Crocodile, was published in 1917. I am indebted to Alexei Kojevnikov for this information. Chadwick later recalled Kapitza’s first explanation of the nickname: when discussing his work with Rutherford, Kapitza was always afraid of having his head bitten off. (Chadwick papers, II 2/1 CHURCHILL). Chadwick dismissed other explanations (e.g. Boag et al. 1990:11).

  30 Letter from Keynes to his wife Lydia, 31 October 1925, Keynes archive, JMK/PP/45/ 190/3/14 to JMK/PP/45/190/3/16 (KING’S © 2008).

  31 Spruch (1979: 37–8); Gardiner (1988: 240). See also The Cambridge Review, 7 March 1942; Boag et al. (1990: 30–7).

  32 Parry (1968: 113).

  33 Letter from Kapitza to V. M. Molotov, 7 May 1935, translated in Boag et al. (1990: 322).

  34 See Hughes (2003), Section 1.

  35 Childs, W., Scotland Yard, to Chief Constable, Cambridge, 18 May 1923, KV 2/777, UKNATARCHI.

  36 Werskey (1978: 92); Brown (2005: 26, 40).

  37 I am grateful to Maurice Goldhaber for his recollecti
ons of the meetings of the Kapitza Club, moderated by Kapitza, in 1933 and the first two terms of 1934.

  38 Blackett (1955).

  39 Postcard from Dirac, 16 August 1925 (DDOCS).

  40 See, for example, letters to Dirac from his mother, 26 October and 16 November 1925, 2 June 1926, 7 April 1927: Dirac Papers, 1/3/5 and 1/3/6 (FSU).

  41 Ramsay MacDonald’s Labour Government was a minority one, whose survival depended on support from at least one of the other two parties. This partly explains the Government’s moderate agenda.

  42 Letter to Dirac from his mother, 9 February 1924, Dirac Papers, 1/3/3 (FSU).

  43 In one letter, c. 1924, Felix requests a weekly wage of £2 10s 0d. Dirac Papers, 1/6/3 (FSU).

  44 The spelling of the Reverend’s name is not completely clear. His letters to Felix, including one dated 25 September 1923 and another dated 21 September, are in Dirac Papers, 1/6/6 (FSU). I am grateful to Peter Harvey for his advice on the theosophy of Felix’s correspondent and to Russell Webb for pointing out the tone of the Reverend’s letters, from the point of view of a follower of Eastern philosophy.

  45 Interview with Dirac, AHQP, 1 April 1962, pp. 5–6.

  46 Cunningham (1970: 65–6).

  47 Description of Compton is from the article ‘Compton Sees a New Epoch in Science’, New York Times, 13 March 1932.

  48 Einstein (1949), in Schilpp (1949: 47).

  49 Hodge (1956: 53). Details of Dirac’s early mathematical and scientific influences in Cambridge are in the final section of Darrigol (1992).

  50 Cunningham, E., ‘Obituary of Henry Baker’, The Eagle, 57: 81. Dirac (1977: 115–16).

  51 Edinburgh Mathematical Notes, 41, May 1957.

  52 Quoted in Darrigol (1992: 299–300).

  53 Moore (1903: 201); Baldwin (1990: 129–30). Moore’s conception of the role of art in relation to morality is prefigured in Hegel and thence by his successors. Moore adapts this position to the utilitarian scheme that he took over from the Victorian thinker Henry Sidgwick. John Stuart Mill anticipates Moore through the conception of the great value of the ‘higher’ pleasures.

  54 As Budd describes Kant’s conception of the experience of beauty, it was ‘the facilitated play of imagination and understanding, mutually quickened (and so made pleasurable) by their reciprocal harmony’ (2002: 32).

  55 Boag et al. (1990: 133).

  56 Letter from Einstein to Heinrich Zangger, 26 November 1915.

  57 This, and all of Dirac’s publications until the end of 1948, is reproduced in Dalitz (1995).

  58 Interview with Dirac, AHQP, 7 May 1963, p. 7.

  59 Orwell (1946: 10).

  Chapter six

  1 Reference for Dirac by Cunningham, April 1925, provided for Dirac’s application for a Senior Studentship, 1851COMM.

  2 Undated to Dirac from his mother, c. May 1924.

  3 Dirac was in room H7 on the first floor of New Court in Michaelmas (autumn) term. Later, he moved into other rooms: in Lent (winter) and Easter term 1925, he was in New Court room E12; from Michaelmas term in 1927 to Easter term 1930, he was in New Court room A4; in Michaelmas term in 1930, he was in Second Court room C4; from Michaelmas term 1936 to Michaelmas 1937, he was in New Court room I10.

  4 Letter from Dirac to Max Newman, 13 January 1935, Newman archive in STJOHN.

  5 Letter to Dirac from his mother, undated, c. November 1924, Dirac Papers, 1/3/3 (FSU).

  6 Letter from ‘Technical Manager’ (unnamed) at W & T Avery Ltd, 10 January 1925, Dirac Papers, 1/6/3 (FSU).

  7 Interview with Dirac, AHQP, 1 April 1962, p. 5; Salaman and Salaman (1986: 69). I am assuming that the date of Felix’s death on his gravestone, 5 March 1925, is correct; on his death certificate, the date of his death is given as the day after.

  8 Letter to Dirac from his Auntie Nell, 9 March 1925, Dirac Papers, 2/1/1 (FSU).

  9 Express and Star (local paper in Much Wenlock), 9 March 1925; Bristol Evening News, 27 March 1925.

  10 Interview with Mary Dirac, 21 February 2003; interview with Monica Dirac, 7 February 2003. In an interview with Leopold Halpern, 18 February 2003, Halpern commented that Dirac found the suicide of Felix too painful to talk about.

  11 Bristol Evening News, 9 March 1925.

  12 Bristol Evening News, 10 March 1925.

  13 Dirac often remarked on this. His feelings are recorded in Salaman and Salaman (1986: 69). His close friend Leopold Halpern also mentioned that Dirac had mentioned this to him, quite independently (interview on 18 February 2002).

  14 Letter to Dirac from his mother, 4 May 1925, Dirac Papers, 1/3/4 (FSU). Dirac always mentioned this when he opened his heart to friends and even mentioned it to his children.

  15 Flo wrote her poem ‘In Memoriam. To Felix’ on 5 March 1938. The poem is in Dirac Papers, 1/2/12 (FSU).

  16 Letter to Dirac from his mother, 22 March 1925, Dirac Papers, 1/3/4 (FSU).

  17 Death cerificate of Felix Dirac, registered 30 March 1925.

  18 Interview with Leopold Halpern, 18 February 2003.

  19 Interview with Christine Teszler, 22 January 2004.

  20 The problem that Dirac addressed was: if light consists of photons, as Compton had argued, how would these particles be affected by collisions with electrons swirling around on the surface of the Sun?

  21 Mehra and Rechenberg (1982: 96).

  22 Dirac (1977: 118).

  23 C. F. Weizsächer, in French and Kennedy (1985: 183–4).

  24 Pais (1967: 222). Pais gives a vivid description of Bohr’s strange oratory, noting ‘Bohr’s precept never to speak more clearly than one thinks.’

  25 Letters from Bohr to Rutherford, 24 March 1924 and 12 July 1924, UCAM Rutherford archive.

  26 Elsasser (1978: 40–1).

  27 In his AHQP interview on 1 April 1962 (p. 9) and in an interview on 26 June 1961 (Van der Waerden 1968: 41), Dirac says he was not present, whereas elsewhere he says he was there (Dirac 1977: 119).

  28 Heisenberg recalls his experience at the Kapitza Club, and of staying with the Fowlers, in the BBC Horizon programme ‘Lindau’, reference 72/2/5/6025. The recording was made on 28 June 1965, in Dirac’s presence.

  29 The application is held by the 1851COMM.

  30 Letter to Dirac from his mother, with a contribution from his father, June 1925, in Dirac Papers, 1/3/4 (FSU). The application was advertised in the Times Higher Education Supplement, his mother says.

  31 This proof copy is in Dirac Papers, 2/14/1 (FSU).

  32 An English translation of this paper, together with other key papers in the early history of quantum mechanics, are reprinted in Van der Waerden (1967).

  33 Dirac (1977: 119).

  34 Interview with Flo Dirac, Stockholms Dagblad, 10 December 1933.

  35 Darrigol (1992: 291–7).

  36 Dirac (1977: 121).

  37 Letter from Albert Einstein to Paul Ehrenfest, 20 September 1925, in Mehra and Rechenberg (1982: 276).

  38 Dirac (1977: 121–5).

  39 Dirac (1977: 122).

  40 Here, X and Y are mathematical expressions of a type known as partial differentials. What is important is the superficial similarity between the form of the Poisson bracket and the difference AB – BA.

  41 Eddington (1928: 210).

  42 Elsasser (1978: 41).

  43 Reference for Dirac, written by Fowler in April 1925, for the Royal Commission of the Exhibition of 1851, 1851COMM.

  44 Dalitz and Peierls (1986: 147). The student was Robert Schlapp, who was studying under the veteran Sir Joseph Larmor.

  45 Van der Waerden (1960).

  46 Letters from Oppenheimer to Francis Fergusson, 1 November and 15 November 1925; in Smith and Weiner (1980: 86–9).

  47 Bird and Sherwin (2005: 44).

  48 Letter to Dirac from his mother, 16 November 1925 (she repeats the image of ‘the block of ice’ in another letter to Dirac, written on 24 November), Dirac Papers, 1/3/4 (FSU).

  49 Heisenberg later remarked that when he read Dirac’s first paper o
n quantum mechanics, he assumed that its author was a leading mathematician (BBC Horizon programme, ‘Lindau’, reference 72/2/5/6025).

  50 Frenkel (1966: 93).

  51 Born (1978: 226).

  52 Letter to Dirac from Heisenberg, 23 November 1925, Dirac Papers, 2/1/1 (FSU).

  53 All these letters from Heisenberg to Dirac at this time are in Dirac Papers, 2/1/1 (FSU).

  54 Beller (1999: Chapter 1); see also Farmelo (2002a: 25–6).

  Chapter seven

  1 Letter from Einstein to Michel Besso, 25 December 1925, quoted in Mehra and Rechenberg (1982: 276).

  2 Letter from Einstein to Ehrenfest, 12 February 1926, quoted in Mehra and Rechenberg (1982: 276).

  3 Bokulich (2004).

  4 Dirac (1977: 129).

  5 Slater (1975: 42).

  6 Jeffreys (1987).

  7 Bird and Sherwin (2005: 46).

  8 Interview with Oppenheimer, AHQP, 18 November 1963, p. 18.

  9 ‘The Cambridge Review’, ‘Topics of the Week’ on 14 March and 12 May 1926.

  10 Letters to Dirac from his mother, 16 March 1926 and 5 May 1926, Dirac Papers, 1/3/5 (FSU).

  11 Morgan et al. (2007: 83); Annan (1992: 179–80); Brown (2005: 40 and Chapter 6); Werskey (1978: 93–5).

  12 Quoted in Brown (2005: 75).

  13 Wilson (1983: 564–5).

  14 Morgan et al. (2007: 84).

  15 Morgan et al. (2007: 80–90).

  16 Dirac Papers, 2/1/2 (FSU).

  17 This description follows the one given by Kapitza of his Ph. D. graduation ceremony three years before, when the proceedings were the same. See Boag et al. (1990: 168–9).

  18 Letter to Dirac from his mother, 28 June 1926, Dirac Papers, 1/3/5 (FSU).

  19 The Cambridge newspapers reported a wave of heat deaths in July. See the Cambridge Daily News, 15 August 1926, the hottest day in the town for three years.

  20 Dirac had carefully studied a derivation of the radiation spectrum produced by the previously unknown Satyendra Bose, a student in Calcutta. No one had understood quite why his derivation worked. Einstein developed Bose’s ideas to produce a theory that is now named after both men.