I enjoyed Graham Farmelo’s recent article on Paul Dirac—and his book, The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom (Basic Books, 2009; reviewed in Physics Today, December 2009, page 52). Jeremy Bernstein has also recently written an interesting piece about Dirac. 1  

My experience is that Dirac was concise rather than reticent, and always friendly, if somewhat dry. I attended Dirac’s course on quantum mechanics at Cambridge University in 1950. I was a neophyte physicist then, still weak on theory. I found the text hard to follow, but Dirac invoked some interesting sidelines—for example, that Maxwell’s four equations reduce to one if you use spinor algebra. He appeared to me to be very old. Thin and stooped, he would lean over his narrow lectern until we were convinced that both he and it would fall over, though they never did.

Dirac was notoriously precise about his lectures. Victor Weisskopf used to tell the famous joke about Dirac’s answering questions after he’d given a lecture. One student said, “I don’t understand that second equation, Professor Dirac.” Dirac remained silent. “Aren’t you going to answer the question?” asked Weisskopf. “That was not a question, that was a statement,” said Dirac.

I religiously copied the notes Dirac would write on the board, even though I rarely understood them. Many years later he visited me here in the States. I took out those notes, and then, miraculously, they made sense.

Many tales are told of Dirac’s absent-mindedness. Here is a particular favorite, from when his wife, Eugene Wigner’s sister, was pregnant. A student, seeing him wandering about distractedly, asked him what was the matter. “Oh,” said Dirac, “Wigner’s sister is having a baby.”

Farmelo’s book discusses the strange demise in 1958 of the Kapitza club (page 381), a group formed in 1922 by Peter Kapitza to discuss recent research. However, it held one final meeting in 1966 with Kapitza, Dirac, and John Cockcroft present. All evidence of the del squared V, a similar club of the era, has apparently vanished. I would be happy to learn what happened, since in my opinion, the most important discoveries of the time were discussed more in those two clubs than in seminars.

Am. J. Phys.