Dirac grew up in Bristol, where he was a contemporary of the actor Cary Grant, then known as Archie Leach, although the two didn't know each other. His father was Swiss and taught French; he was a difficult man and Dirac himself attributed his own reserve and taciturnity to his upbringing, although it will doubtless occur to many readers of this book that he may have been autistic, something that Farmelo considers in a chapter at the end of the book.
In Bristol, Dirac trained as an engineer, but he won a scholarship to Cambridge, where he flourished and achieved fame as a theoretical physicist. He eventually held the chair of Lucasian Professor of Mathematics, a post once occupied by Isaac Newton. He was recognised as one of the principal founders of quantum theory. Farmelo makes a good job of explaining his ideas in so far as this is possible without using mathematics, which is perhaps not very far—Dirac himself always refused to do this. For Dirac, what mattered most was mathematical beauty in an equation; experimental verification was relatively quite unimportant. But mathematical beauty is not something that can be conveyed in words.
In fact, we learn of the importance of Dirac's work mainly through the comments of other physicists, including Heisenberg, Bohr, Oppenheimer and Einstein, all of whom recognised his central importance in the field. In 1933 he shared the Nobel Prize for physics with Schrödinger. But theoretical physics is a young man's game. By the time that Dirac was in his early thirties he had largely completed his original work. But this doesn't mean that his life after this age lacked interest. He travelled a good deal, especially in Russia; he loved the country and one of his closest friends was Russian, although he was never a Communist. But perhaps the most unexpected event in his later life was his marriage in 1937 to Manci, a Hungarian widow who already had two children—Dirac later had two of his own.
Dirac and his wife were diametrically opposite in character. She was an extreme extrovert who hated life in Cambridge, which he loved; after he retired she persuaded him to move to America to take an appointment at Florida State University. Later in life he told a friend that it had been a mistake to marry a woman who needed contact with other people so much. Still, the marriage endured; Dirac was deeply attached both to his stepchildren and to his own two children, although these relationships were eventually marked by tragedy.
Farmelo has given us a fine biography; completely different in content and tone from what I had expected but certainly fascinating. Dirac's strange character emerges most clearly, I think, in some the anecdotes Farmelo relates.
One of these concerns Dirac's literal-mindedness. At the end of a lecture in which Dirac had written a number of equations on the blackboard, the moderator asked the audience if there were any questions. A man held up his hand and said that he hadn't understood one of the equations Dirac had written. Dirac remained silent for long time. 'There is a question about one of your equations, Professor,' the moderator said.at last. 'It wasn't a question, it was a comment,' Dirac replied.
Another delightful remark was cherished by Oppenheimer, who occasionally wrote verse in his spare fime, something that puzzled Dirac. found puzzling.
'I don't see how you can work on physics and write poetry at the same time,' he remarked during one of their works. 'In science, you want to say something nobody knew before, in words everyone understands. In poetry, you are bound to say something that everybody knows already in words that nobody can understand.'
13-06-2021