Dirac and Feynman, Warsaw, 1962

The Strangest Man: The Hidden Life of Paul Dirac, Quantum Genius By Graham Farmelo, Faber, £22.50

Of all the iconic photographs of scientist duos — Albert Einstein and Niels Bohr, Francis Crick and James Watson, and a host of such pairs — my all-time favourite is the one shot in Warsaw in July 1962. The frame captures Paul Adrian Maurice Dirac and Richard Phillips Feynman, both Nobel- laureates, together during, maybe, a break between the lectures at the third international conference on relativity and gravitation. Feynman is seen passionately explaining something, while Dirac, his back against a pillar of a gothic mansion in a half-reclining posture, is listening to his arguments. Together they make perhaps the oddest twosome in the arcane world of theoretical physics. Feynman, the egregious and boisterous; Dirac, the loner and taciturn. Thanks to two highly popular autobiographies, as well as dozens of bestseller biographies, Feynman is the second most popular figure after Einstein in the genre of pop science. Dirac, the subject of only one ‘scientific biography’ besides a few tomes covering his research, is virtually unknown outside the world of professional physicists.

But it is not merely the contrast either in the behavioural traits or the public fame of these two geniuses that makes the photograph an exceptional one. More to the point is the contradictory attitude with which they pursued their craft. Feynman believed that physicists’ job was to infer theories by investigating the way nature behaved; the more the theories corresponded with experimental results, the better they were. Asked to express the essence of physics, Dirac, on the other hand, chose the epigram: “A physical theory must possess mathematical beauty.” This obsessive emphasis on aesthetics while unravelling the secrets of nature forced him to denounce Feynman’s version of the so-called Quantum Electrodynamics, the theory that describes the interaction of light and matter, although he himself had sown the seeds of the subject. Unbothered by the fact that Feynman’s QED agreed well with experiments, and eventually earned him the Nobel Prize, Dirac argued that it was “mathematically ugly”, and therefore, “not fundamentally true”. No wonder the Physics World magazine, which ran a long article on Dirac’s birth centenary in 2002, printed the photo I am discussing with a caption: “Beauty and the Beast”.

Dirac’s outlook paid rich dividends. But for his insights, quantum mechanics, the nascent physics of the first quarter of the last century, would not have come of age so fast. In 1928, when he was barely 26, he arrived at a formula, now known as the ‘Dirac equation’, combining Einstein’s special relativity with quantum theory. This equation governs most of physics and the whole of chemistry. If Dirac had patented his equation, like some people are patenting human genes, he would have become one of the richest men in the world. Every television set or computer would have paid him royalties.

Behind the Dirac equation was a queer mathematical framework in which a multiplication result depended on the order of the factors, as though 2x3 was not equal to 3x2. Bristol University physicist Michael Berry explains this counter-intuitive phenomenon, saying, “We all know that putting on our socks and then our shoes gives a result different from putting on our shoes and then our socks.”

Asked how he conjured up his famous formula, Dirac replied, “I found it beautiful.” In 1931, this kaleidoscope of beauty helped him ‘see’ what others had had no inkling of: anti-matter — particles that are doppelgängers of those that make up our world. For example, an electron’s anti-particle is a positron; they are the same in every respect, but have opposite electric charges. Carl Anderson, a physicist at Caltech, experimentally detected positron in 1932, and Dirac was awarded the Nobel Prize the next year. Anderson earned it in 1936.

Physicist Freeman Dyson, who worked on the early versions of QED, sums up Dirac’s ingenuity, saying, “His great discoveries were like exquisitely carved marble statues falling out of the sky, one after another.” No wonder some experts infer that his impact on modern physics “may have been greater than that of Einstein”.

A senior research fellow at the Science Museum, London, Graham Farmelo’s homework took him five years before he embarked on writing The Strangest Man. He talked to anyone who had anything to say about his hero. Then, while rummaging through the Dirac archive at the Florida State University, he hit upon an amazing cache: not only letters written to Dirac by such stalwarts like Werner Heisenberg and Erwin Schrödinger, but also those that Florence Dirac, his mother, wrote him once a week for almost 20 years. Farmelo was also lucky to have been given by Monica, Dirac’s younger daughter, 120 private letters between him and his girlfriend, and eventually wife, Manci. The reference notes and bibliography in The Strangest Man extend to 66 pages. The diligence and good luck show in this page-turner of a biography.

Alongside the tale of physics becoming modern at breakneck speed, it treats us to heart-rending details of Dirac’s personal life. We trace the genesis of his extreme reticence. Dirac confessed that he never had a childhood and it’s not difficult to see why. The disciplinarianism of his school-teacher father, Charles Dirac, bordered on brutality. Not only did he see to it that his family received no visitors, but also insisted that his children speak to him only in French. His diktat would split the family during mealtime: while Charles and Paul ate in the front room and talked in French, Florence, Paul’s elder brother, Felix, and his younger sister, Betty, ate in the kitchen and spoke English. Paul grew up with the idea that men and women didn’t speak the same language. As Charles punished Paul for grammatical lapses in French, even denying his requests to go to the toilet, the kid thought it better to keep mum than risk humiliations.

As the gap between the academic abilities of Paul and Felix widened in senior school, Charles made no efforts to conceal his contempt for the latter, eventually vetoing his desire to study medicine and forcing him to take up engineering instead. With Paul not particularly given to empathy towards others, the situation worsened. When both the brothers were in the same city for job or apprenticeship, they would walk past each other without exchanging a word. Felix sought solace in many things, including Buddhism and astrology, but finally consumed potassium cyanide.

One of the letters that Florence wrote to Paul is as revelatory as it is touching. Confiding to him that her husband gives her only eight pounds a year for clothes and everything — worse than a servant’s due — she asks her son if he can send her a few pounds for a diamond ring. “I want one so very much,” she writes, “I could wear it in the evenings & think what a darling you are. It is so monotonous doing house work all day long. I get so fed up with it.”

For all Farmelo’s efforts to unravel Dirac’s psyche, readers may find untenable what he speculates: that Dirac had undiagnosed autism. But for this urge on the part of the author to overdo himself, this book would have been a classic. After all, we should remember that even Einstein was at a loss to explain this enigma of a physicist. “I have trouble with Dirac,” he famously said, “This balancing on the dizzying path between genius and madness is awful.”