'Gell-Mann Opened My Eyes'

Author: JOHN POLKINGHORNE Date: December 15, 1986 I am a subscriber to the “great man” theory of the history of science—the view that it is the insights of the men of genius that actually propel the subject. No doubt there is also a role for those of us who belong to the army of honest toilers, providing the background of expectation and exploitation, but the big ideas come from the big men. The first big man of theoretical physics that I knew was Paul Dirac, whose intellectually elegant lectures initiated me into the mysteries of quantum mechanics. However, Dirac was too austerely remote a figure to have any direct influence on my own attempts at research. I had Kemmer and Salam as my successive Ph.D. supervisors, but my most influential working relationship with a great man came when I went to Caltech as a postdoc and met Murray Gell-Mann. Only a little older than myself, Murray was already a full professor and a world famous physicist. The atmosphere of Cambridge theoretical physics at that time had been very mathematical, and I had temperamentally been much absorbed by that side of the subject. I dare say it was my own narrow-minded fault, but I blush to remember that I was surprised to learn that the p- mesons, whose renormalization properties we had talked about, were actually unstable particles! My work always remained mathematically based, but Gell-Mann opened my eyes to the experimentally led side of theoretical physics and its excitements. He once told me how he himself had early on learned the lesson that it was important to talk to the experimentalists. At the time he was a graduate student and went to a seminar on nuclear physics at which an expert on nuclear structure had explained a long and complicated shell-model calculation, resulting in the conclusion that a particular nuclear level had spin-parity 2+. At the end of the lecture there was a question period, and a rather scruffy character at the back of the room put up his hand. “I'm one of the experimentalists who work down in the basement,” he said. “I've measured the spin-parity of that level and actually it's 1-.” A light came on in Murray's mind that has burned brightly there ever since. He also told me about two sets of lectures he went to at that time, both given by distinguished theoretical physicists. One lecture was beautifully architected in Macaulayesque prose. One went away enthused, but, like a Chinese meal, the lecture had all faded away an hour or two later. The other course was given by Victor Weisskopf. He would write up an equation on the board, look at it, scratch his head, and say, “That must be wrong.” The material of the lecture was, as it were, created by trial and error before one's eyes and in consequence was never forgotten. I also learned something from Gell-Mann that proved of value in other meetings with great men—how to benefit from such encounters. Murray was, and is, fertile and forceful. It was therefore fatal, at least for me, to spend too long in his presence. The strength of his ideas and personality were such that they imposed on you the framework of his thinking, but if you tried to think along exactly the same lines he would always outsmart you, since he thought so much more swiftly and effectively than you did. What you had to do was to take on board the drift of his thinking, his assessment— always so canny and stimulating—of where the action was. Then you had to go away and think about that general subject from your own point of view. Some little, but useful, problem might then emerge, for the tackling of which your own way of 'looking at things might prove apt. It is best for those of modest attainments to be content with crumbs from the rich man's table rather than to attempt to seize a place at the feast itself. As I came to know more great men I perceived that they divided into two classes. One group consisted of the impetuous, erupting with ideas—good, bad and indifferent, and let the dust lie where it settles. One of these volcanic thinkers once said to me, “Publish all your ideas. People will remember those that work and forget those that don't.” I was a young man at the time, but even then it seemed to me to be transparently bad advice. People of that kind of temperament work best if they have in their neighborhood someone of sober and persistent character who can act as a preliminary filter to skim off some of the froth. The other group consists of the cautious. They are conscious of their reputations and of the judgment of history, and they want the record to prove positive throughout. Of course, they also represent the self-critical tradition that is rightly highly valued in science. However, if they work at the frontiers of knowledge, where a certain speculative venturesomeness is an essential part of exploration, they are faced with something of a dilemma. How can one stick one's neck out and still make sure that it doesn't get chopped off? The answer lies—to change the metaphor—in the delicate art of kite flying. Murray Gell-Mann certainly belongs to the camp of the cautious, and he has an enviable record of being right. One of his most important suggestions was that there might be new fractionally charged constituents of matter to which, in a learned joke based on Finnegan's Wake, he gave the name quarks. No one has ever seen a quark, though the cumulative evidence for their existence is now overwhelming and physicists invoke “confinement” to explain why they are not encountered solo, outside the particles they make up. For many years Murray referred to the quarks 'as “presumably mathematical.” This exquisitely chosen phrase always seemed to me to be a message in code. Deciphered it read: “If they aren't there, remember I never said they were; if they are there, remember I thought of them first.” I am very grateful for my year at Caltech and my subsequent meetings and friendship with Murray Gell-Mann. He is never a man to miss a trick at physics or much besides. I remember once showing him a letter he had written me and saying that I would sell it in my old age to raise a little cash. “But don't forget the copyright still belongs to me,” he replied. Polkinghorne, a former physicist, is fellow, dean and chaplain at Trinity Hall, University of Cambridge, Cambridge, UK CB2 1TJ. He is author of The Particle Play (WH. Freeman, 1979).

'Gell-Mann Opened My Eyes'

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