Physics Faces

Paul Adrien Maurice Dirac  (1902-1984)

 “P.A.M. Dirac was a gifted mathematical inventor who saw how quantum mechanics rises from classical mechanics, yet transcends it. Dirac did not know of the Bohr atom when he arrived at Cambridge in 1923; yet he quickly began contributing to the mathematical structure demanded by quantum phenomena, discovering the connection between the Poisson bracket and the commutator of Heisenberg”s matrix representation of observables. Then, with careful attention to its classical antecedent, Dirac found the equation governing the evolution of the matrix elements which had eluded Heisenberg in the operator ihdA/dt = [A,H]. He then went on to discover spinors in describing the relativistic electron and antimatter implied by the quantum in relativistic space-time. Dirac conceived the many-time formulation of relativistic quantum mechanics and laid the foundations of the Feynman path integral thereby opening the way to quantum electrodynamics. Newton synthesized the foundations of classical mechanics. In fitting kinship, Dirac, who did the equivalent for quantum mechanics, filled the chair at Cambridge held by Newton.”

From: The Shaggy Steed of Physics by David Oliver, Springer-Verlag, 1994.

Dirac in about 1930

Dirac in about 1960

From: Dirac: A Scientific Biography  by Helge Kragh, Cambridge Univ. Press, 1990, pg 72.

 “Dirac’s introversive style and his interest in abstract theory were rather foreign to the scientists at the University of Wisconsin. They recognized his genius but had difficulties in comprehending his symbolic version of quantum theory. The Americans also found him a bit of a strange character. A local newspaper, the Wisconsin State Journal, wanted to interview the visiting physicist from Europe and assigned this task to a humorous columnist known as ‘Roundy’. His encounter with Dirac is quoted here in extenso because it not only reveals some characteristic features of Dirac’s personality but also is an amusing piece of journalism:

 ‘I been hearing about a fellow they have up at the U. this spring – a mathematical physicist, or something, they call him – who is pushing Sir Isaac Newton, Einstein and all the others off the front page. So I thought I better go up and interview him for the benefit of the State Journal readers, same as I do all the other top notchers. His name is Dirac and he is an Englishman. He has been giving lectures for the intelligensia of the math and physics department – and a few other guys who got in by mistake.

 So the other afternoon I knocks at the door of Dr. Dirac’s office in Sterling Hall and a pleasant voice says, “Come in.” And I want to say here and now that this sentence “come in” was about the longest one emitted by the doctor during our interview. He sure is all for efficiency in conversation. It suits me. I hate a talkative guy.

 I found the doctor a tall youngish-looking man, and the minute I see the twinkle in his eye I knew I was going to like him. His friends at the U. say he is a real fellow too and good company on a hike – if you can keep him in sight, that is.

 The thing that hit me in the eye about him was that he did not seem to be at all busy. Why if I went to interview an American scientist of his class – supposing I could find one – I would have to stick around an hour first. Then he would blow in carrying a big briefcase, and while he talked he would be pulling lecture notes, proof, reprints, books, manuscripts, or what have you, out of his bag. But Dirac is different. he seems to have all the time there is in the world and his heaviest work is looking out the window. If he is a typical Englishman it’s me for England on my next vacation!

 Then we sat down and the interview began. “Professor,” says I, “I notice you have quite a few letters in front of your last name. Do they stand for anything in particular?”

 “No.” says he.

 “You mean I can write my own ticket?”

 “Yes,” says he.

 “Will it be all right if I say that P. A. M. stands for Poincare Aloysius Mussolini?”

 “Yes,” says he.

 “Fine,” says I, “We are getting along great! Now doctor will you give me in a few words the low-down on all your investigations?”

 “No,” says he.

 “Good,” says I. “Will it be all right if I put it this way – ‘Professor Dirac solves all the problems of mathematical physics, but is unable to find a better way of figuring out Babe Ruth’s batting average’?”

 “Yes,” says he.

 “What do you like best in America?” says I.

 “Potatoes,” says he.

 “Same here,” says I. “What is your favorite sport?”

 “Chinese chess,” says he.

 That knocked me cold! It sure was a new one to me! Then I went on: “Do you go to the movies?”

 “Yes,” says he.

 “When?” says I.

 “In 1920 – perhaps also 1930,” says he.

 “Do you like to read the Sunday comics?”

 “Yes,” says he, warming up a bit more than usual.

 “This is the most important thing yet Doctor,” says I. “It shows that me and you are more alike than I thought. And now I want to ask you something more: They tell me that you and Einstein are the only two real sure-enough high-brows and the only ones who can really understand each other. I won’t ask you if this is straight stuff for I know you are too modest to admit it. But I want to know this – Do you ever run across a fellow that even you can’t understand?”

 “Yes,” says he.

 “This will make great reading for the boys down at the office,” says I. “do you mind releasing to me who he is?”

 “Weyl,” says he.

 The interview came to a sudden end just then for the doctor pulled out his watch and I dodged and jumped for the door. But he let loose a smile as we parted and I knew that all the time he had been talking to me he was solving some problem no one else could touch.

 But if that Professor Weyl ever lectures in this town again I sure am going to take a try at understanding him! A fellow ought to test his intelligence once in a while.’