He was famously taciturn; so much so that fellow students invented a unit called the dirac to represent the smallest imaginable amount of conversation, one word per hour.
He was also famously scruffily dressed. I used to cite him as an example whenever people came up with the dictum "Dress smart, think smart."
I was inspired to read this book having read the brilliant The Fly in the Cathedral by Brian Cathcart which explores the background to Cockcroft and Walton splitting the atom. The Strangest Man is a stunning biography. Not only does Farmelo manages to make quantum physics accessible, at least in its generalities; not only does he describes the intoxicating excitement of the early days of discovery with Heisenberg and Einstein and Schrodinger, when Gottingen University was one pole and Bohr's Copenhagen the other; but he also charts the dreadful consequences of the Second World War, when Schrodinger had to hide in Dublin having initially endorsed Nazism, when Dirac's best friend Kapitza was kept in Moscow by Stalin, always fearing that Beria might arrest him and have him killed, when Heisenberg was working for the Nazis and Bohr was in occupied Denmark, and Dirac's sister, an Englishwoman married to a Jew, was in occupied Amsterdam. Then there are the days of McCarthyism when Dirac's left wing politics had him banned from America while his friend Oppenheimer, who had led the atom bomb project, had his security clearance revoked.
And in particular, this biography centred on the human that was Dirac, the survivor of a horrible childhood in which his life and that of his mother who became a slave in her own home and Dirac's brother who killed himself, and Dirac's sister who gave up on life to stay quietly at home until Dirac managed to free her to go to University were all the victims of a terrible father, a bully, an adulterer, a tax cheat, and a man who tried in vain to understand the difficult stuff that his brilliant son was doing.
Then comes Dirac's marriage to a lively tempestuous woman, the polar opposite of the taciturn man he himself was. He acquired two step-children (his step-daughter disappeared in America, her car found abandoned) and fathered two children of his own. His marriage had its rocky patches. They were too different. And he must have struggled not to be like his own father. But the marriage survived.
This was a stunning portrait of a brilliant mind. Read it!
August 2016; 438 pages
There is a BBC Radio 4 In Our Time programme about Paul Dirac; it was broadcast on 5th March 2020
Dirac had a dreadful childhood. His father was a disciplinarian teacher who bullied his family. Paul was made to eat dinner with his father and to speak only French (his father was Swiss); he was often sick. Paul's elder brother Felix committed suicide (which devastated the father so he was loving if a bully); his sister stayed at home after being schooled and did nothing; the mother became an unpaid servant for the father, kept on a pittance (although he was clearly a lot richer than he admitted) and was told by him after thirty years of marriage that he had never loved her; she then discovered he had been having at least one long term affair. In short, the father was a nasty piece of work.
Paul was forced to study engineering at Bristol University; he was two years younger than the other students; having graduated Bristol arranged for him to take a maths degree and skip the first year. But he almost never got to Cambridge because his father was unwilling to find the necessary money for Paul to afford to live. It was only once he got to Cambridge as a graduate student that he started to fill in some of the huge holes in his knowledge, partly by taking extra geometry classes on Sunday afternoon in the Arts School when, apart from him and the other students having tea and being taught, and a few cleaners, the building was "as lifeless as a museum at midnight". (p 72)
He cultivated a straight-talking, straight-writing, plain English prose style following George Orwell's dictum that "Good prose is like a windowpane." (p 75)
Even Dirac was subject to failing to see when he was on the trail of something. When he first met de Broglie's idea that a particle such as an electron could act like a wave he "carried out some initial calculations but put the work aside after concluding that he had done nothing worth publishing. Having sniffed the scent of an important problem, he had then lost it; but he would soon return." (p 81)
His first breakthrough was recognising that the rather complex maths in Heisenberg's first formulations of quantum theory, being non-commutative, reminded him of Poisson's brackets: "Fifty two years later, he remembered, 'The idea first came in a flash, I suppose, and provided of course some excitement'" (p 86) Brackets were important to Dirac. Having invented a new mathematical notation for quantum physics which involved two halves of a bracket (which he called the bra and the ket) he later told a discussion at high table in St John;s on neologisms that "I invented the bra". Being taciturn he then relapsed into silence for the rest of the meal. (p 326)
When Oppenheimer was having a nervous breakdown at the Cavendish he tried to poison his teacher, Blackett, by leaving him an apple laced with chemicals. (p 97) Shades of Snow White and Alan Turing! When he defended his PhD thesis to examiners Franck and Born Franck later said: "I'm glad that is over. He was on the point of questioning me." (p 133)
Even Albert Einstein struggled "to understand his [Dirac's] peculiar combination of logic and intuition" telling a friend "This balancing on the dizzying path between genius and madness is awful." (p 114)
He hypothesised the positron (which he called an anti-electron; a later suggestion from California was 'oreston' because Electra's brother was Orestes) because he "followed the logic of Sherlock Holmes: 'When you have eliminated all which is impossible then whatever remains, however improbably, must be the truth.'" (p 187) (Doyle 1926, The Adventure of the Blanched Soldier). We are still in a world where the imbalance of matter over anti-matter of just one part in a billion after the Big Bang cannot really be explained but "without that imbalance, the matter and anti-matter formed at the beginning of time would have annihilated each other immediately, so that the entire universe would only ever have amounted to a brief bath of high-energy light. Matter would, in that case, never have had an opportunity to discover anti-matter." (p 434)
Farmelo quotes Stephen Spender talking about young Germans after the great inflation: "their aims were to live from day to day; and to enjoy to the utmost everything that was free: sun, water, friendship, their bodies." (p 121)
The big band (OK, that's a typo, but it sounds so much better than the big bang) theory of the universe was first proposed by a Belgian cleric, the Abbe Lemaitre "who believed that the Bible teaches not science but the way to salvation" (p 261)
Despite a long bachelorhood lasting beyond thirty, Dirac flirted with Gamow's wife Rho and later got involved with Wigner's sister, Hungarian born Manci, who became his wife (although he described her as "Wigner's sister" even after the wedding. They had a long courtship conducted often by letter. When she complained he didn't answer her questions he numbered her letters and wrote a table of (often brutally) honest responses leading her to complain that some of the questions he had now answered were rhetorical! (p 262) As he grew closer to marriage his parents' relationship fell apart. His father told his mother he had not loved her for thirty years (predating Dirac's birth) and his mother discovered that his father had been engaging in long-term affairs (after he died she also discovered that he had been systematically cheating the taxman so he wasn't just miserly with her). But Dirac's marriage to Manci, though often tempestuous (at least on her part, he greeted her moods with indifference which must have infuriated her even more) did last. "She once snapped at him when he was eating his dinner, 'What would you do if I left you?' only for him to reply - after a half-minute pause - 'I'd say "Goodbye dear"'" (p 366)There is a photo of him on the beach at Brighton on his honeymoon in his suit "pencils still protruding from the pocket of his jacket" (p 284)
He was intrigued by the coincidental ratios of force strengths to one another and to the dimensions of the Universe and hypothesised that this might be because the strength of gravity is inversely proportional to the age of the Universe (which would explain why it is expanding but rather upsets the standard estimates of such things as the age of the Earth). (p 290)
He became Fred Hoyle's supervisor "partly because he was amused at the prospect of a relationship between a supervisor who did not want a student and a student who did not want a supervisor" (p 295)
He disliked the idea of electrons as point sources because that would involve infinities in such things as electric field strengths. But I would have thought that quantum mechanics does not allow points; they are forbidden by Heisenberg; a particle that was a point would have an infinite momentum,
He believed mathematical beauty was more important than experimental evidence.
As he got older he was more often challenged by "the drawn sword of youth". (p 321) As Oscar Wilde said in 1887 "In America, the young are always ready to give those who are older than themselves the full benefit of their inexperience." (p 332)
During the Second World War he worked on the separation of the fissile U-235 isotope from its chemically identical and much more abundant non-fissile U-238; he invented a series of methods including centrifuges. (p 321)
After Einstein's death, Dirac became "the most famous loner in theoretical physics, an elderly rebel with a cause that no one else could quite understand." (p 355) He then developed a primitive version of string theory.
Page references refer to the 2010 Faber and Faber paperback edition