Odd man out

<strong>The Strangest Man: the Hidden Life of Paul Dirac, Quantum Genius</strong>

Graham Farmelo

In 1971, when Florida State University offered a post to Paul Dirac, then 68 years old, the grumbling of some academic staff was silenced by a ­senior physicist. "To have Dirac here," he said, "would be like the English faculty recruiting Shakespeare." Some years later, at the unveiling of a memorial to Dirac in Westminster Abbey, Stephen Hawking paid him a tribute that was only a little less grand, declaring him to be "probably the greatest British theoretical physicist since Newton".

Shakespeare and Newton clearly have better PR, for just a quarter of a century after his death Dirac is all but unknown outside the world of physics. Even in Britain, where he was born (in Bristol) and lived those first 68 years of his life, few people recognise his name. Far better known are his friends and rivals such as Werner Heisenberg, Erwin Schrödinger and Niels Bohr, and yet when Dirac was at the peak of his powers those men held him in awe.

Perhaps the most perverse thing about this is that Dirac was anything but dull. So intriguing and surprising was he, in fact, that whenever his scientific contemporaries got together in the Twenties and Thirties they liked nothing better than to talk of him. A description survives of ­afternoon tea at Bohr's institute in Copenhagen one day in 1932, when the entire conversation was devoted to Dirac stories, with each participant trying to top the last.

This was because Paul Dirac, as Bohr remarked and the title of this book reminds us, was the strangest man. If asked a question at the end of a lecture he was perfectly capable of delivering most of his talk again, word for word. This was not perversity: he had decided upon the best way to express his idea and saw no reason to depart from it. If a query took the form of a statement, such as "I don't understand so-and-so", he did not feel called upon to respond at all.

At high table in his Cambridge college he could go for weeks without speaking, and offered one-word answers to even the most carefully crafted opening gambits. A casual comment about the weather was likely to draw from him a terse meteorological correction.

But he was not just a man of few words: he had a peculiarly literal, analytical take on the world. Asked once, at an exhibition, which of two Impressionist paintings he preferred, he replied: "I like that, because the degree of inaccuracy is the same all over." On another occasion he is said to have watched a woman knitting for a few minutes and then explained to her another way of doing it. "Of course," she replied indignantly, "that is called purl." She did not realise that Dirac had just deduced purl from first principles.

So, a revered, Nobel-winning scientist, but in an extremely challenging field - the "Dirac equation" of 1928 transformed the understanding of electrons and pointed the way to the existence of antimatter - and an eccentric, but of the reclusive, difficult kind; not the most obvious material, you might think, for a readable biography.

How wrong can you be? Graham Farmelo, once a theoretical physicist himself and now a specialist in science communication, has produced a marvellously rich and intimate study which, if anything can do it, should finally get people talking about this great 20th-century Briton the way he deserves to be talked about.

Few who knew Dirac would have expected much evidence about the private man to have survived, or even to have been committed to paper in the first place, yet Farmelo is able to lead us through his often-troubled life with a fullness of detail that might even satisfy a psychoanalyst.

We meet the father, a Swiss-born schoolteacher revealed as a deceitful, hypocritical bully, and the clinging, needy mother, and the older brother who took his own life - plenty there, it seems, to explain a certain taciturnity. And we also meet the teachers, textbooks and ideas of his youth, and discover that what seemed an oddity- that Dirac's first degree was in engineering - makes perfect sense in the evolution of a mind that would bring fresh tools to theoretical physics.

We also come to understand Dirac's superficially improbable 45-year marriage to the bubbly, tempestuous Margit "Manci" Wigner - and we gain along the way two lovely new anecdotes. First, when he suspected he might be falling in love, Dirac did what academics are supposed to do: he read a book on the subject: George Bernard Shaw's Getting Married. And second, when Manci complained that he dodged her questions about feelings in their love letters, he methodically broke the questions down into numbered grids (reproduced in the text) and answered them one by one.

All this and mind-blowing science too, equally fluently delivered. As with Einstein, Dirac was at his dazzling best for just a few years, in his case straddling the Twenties and Thirties. But, again like Einstein, he would make important contributions long after that, across a variety of fields; and he was especially eloquent on the need for important equations to be, as he put it, beautiful.

Perhaps Farmelo's greatest service to Dirac's memory, though, lies in the final, brave passages of the book, where he unpicks his subject's lifelong hatred for, and fury against, his own father. Farmelo does not believe this was justified, for all the father's nasty ways.

Dirac's problem, if problem it was, did not begin with a tortured childhood, but before that, for Farmelo argues convincingly that he was autistic. To the casual reader, seeing the description of the man above, that may not be surprising, but the implications are fascinating.

In the 21st century we are learning to think afresh about autism, and in the context of Dirac perhaps we should be grateful for it. He saw things that even Heisenberg and Schrödinger were unable to see; and although we can put that down, in part, to a fortuitously well-suited education, he surely also owed it to a brain tuned to unusually deep concentration and to the visualisation of numbers and patterns. That which made Dirac strange may also have given the world a genius.

Brian Cathcart is the author of "The Fly in the Cathedral" (Penguin, £7.99)