Graham Farmelo's biography about
Paul Dirac

“The Strangest Man”

appeared in January 2009 and was/is a big success. It was translated into several languages.

Logic and precision
Dirac was so unusual in the logic and precision of his interaction with the world, both in and out of physics, that legions of "Dirac stories" have become attached to him and have acquired a life of their own. Often these stories revolve around Dirac saying exactly what he meant and no more. Once when someone, making polite conversation at dinner, commented that it was windy, Dirac left the table and went to the door, looked out, returned to the table and replied that indeed it was windy. It has been said in jest that his spoken vocabulary consisted of "Yes", "No", and "I don't know".

Dirac on Dostoevski
Once Peter Kapitza, the Russian physicist, gave Dirac an English translation of Dostoevski's Crime and Punishment.
"Well, how do you like it?" asked Kapitza when Dirac returned the book.
"It is nice," said Dirac, "but in one of the chapters the author made a mistake. He describes the Sun rising twice on the same day." This was his one and only comment on Dostoevski's novel.

Dirac on ghost
At another time, Dirac was at a meeting in a castle, when another guest remarked that a certain room was haunted: at midnight, a ghost is said to appeared. In his only reported utterance on matters paranormal, Dirac asked: "Is that midnight Greenwich time, or daylight saving time?"

It's not a question
At the quesiton period after a Dirac lecture at the University of Toronto, somebody in the audience remarked: "Professor Dirac, I do not understand how you derived the formula on the top left side of the blackboard."
"This is not a question," snapped Dirac, "it is a statement. Next question, please."

Optimal distance to look at a woman
Being a great theoretical physicist, Dirac liked to theorize about all the problems of daily life, rather than to find solutions by direct experiment. Once, at a party in Copenhagen, he proposed a theory according to which there must be a certain distance at which a woman's face looks its best. He argued that at d = infinite one cannot see anything anyway, while at d = 0 the oval of the face is deformed becaue of the small aperture of the human eye, and many other imperfections (such as small wrinkles) become exaggerated. Thus there is a certain optimum distance at which the face looks its best.
"Tell me, Paul," [Gamow, a Russian physicist] asked, "how close have you seen a woman's face?"
"Oh,"replied Dirac, holding his palms about two feet apart, "about that close."

Dirac discovers purling
Another time, Dirac was watching Anya Kapitza knitting while he was talking physics with Peter Kapitza. A couple of hours after he left, Dirac rushed back, very excited. "You know, Anya," he said, "watching the way you were making this sweater I got interested in the topological aspect of the problem. I found that there is another way of doing it and that there are only two possible ways. One is the one you were using; another is like that. . . . " And he demonstrated the other way, using his long fingers. His newly discovered "other way," Anya informed him, is well known to women and is none other than "purling."

Wigner's sister
Dirac married "Wigner's sister", so known among the physicists because she was the sister of the noted Hungarian theoretical physicist Eugene Wigner. When one of Dirac's old friends, who had not yet heard of the marriage, dropped into his home he found with Dirac an attractive woman who served tea and then sat down comfortably on a sofa. "How do you do!" said the friend, wondering who the woman might be. "Oh!" exclaimed Dirac, "I am sorry. I forgot to introduce you. This is...this is Wigner's sister."
(Later when Gamow questioned Mrs. Dirac on this story, she said that what Dirac actually said was: 'This is Wigner's sister, who is now my wife.')

This result is too beautiful to be false; it is more important to have beauty in one's equations than to have them fit experiment.