It has been said that at lunch in Fuller Lodge one could see as many as eight or ten Nobel Prize-winners eating at the same time (Rabi, Lawrence, Fermi, Bloch, Bohr, Chadwick, and others). Their interests were wide because physics has more definite and obvious central problems than mathematics, which splits into many almost independent domains of thought. They considered not only the main problem — the construction of an atomic bomb and related physical questions about phenomena that would attend the explosion — the strictly project work — but also general questions about the nature of physics, the future of physics, the impact of nuclear experiments on the technology of the future, and contrastingly its influence on the future development of theory. Beyond this, I remember very many after-dinner discussions about the philosophy of science, and of course on the world situation, from daily progress on the war fronts to prospects of victory in the months to come.
The intellectual quality of so many interesting persons and their being constantly together was unique. In the entire history of science there had never been anything even remotely approaching such a concentration. The radar project in Cambridge, Massachusetts, proceeding at the same time, had some of these characteristics, but without the same intensity. It was more technological perhaps, and did not touch as many fundamental questions of physics.
Who were some of the luminaries of this fantastic assembly? Von Neumann, Fermi, Bethe, Bohr, Feynman, Teller, Oppenheimer, O. R. Frisch, Weisskopf, Segré, and many more. I have already tried to sketch the personalities of some of them and can describe a few more.
I first met Fermi when he arrived at Los Alamos, a few months after us, after the Chicago pile had been successfully completed. I remember sitting at lunch in Fuller Lodge before his arrival with six or seven people, including von Neumann and Teller. Teller said, "It is quite certain now that Enrico will arrive next week." I had learned earlier that Fermi was referred to as "the pope" because of the infallibility of his pronouncements. So immediately I intoned: "Annuncio vobis gaudium maximum, papam habemus," which is the classical way cardinals announce the election of a pope on the balcony overlooking St. Peter's Square, after the white smoke comes out of the chimney in the Vatican. Johnny, who understood, explained this reference, and the allusion was applauded by the entire table.
Fermi was short, sturdily built, strong in arms and legs, and rather fast moving. His eyes, darting at times, would be fixed reflectively when he was considering some question. His fingers often nervously played with a pencil or a slide rule. He usually appeared in good humor, with a smile almost perpetually playing around his lips.
He would look at a questioner in an inquiring way. His conversation included many questions rather than expressions of opinion. His questions were formulated in such a way, however, that it was clear which way Fermi's beliefs or guesses went. He would try to elucidate other persons' thoughts by asking questions in a Socratic manner, yet more concretely than in Plato's succession of problems.
Sublimated common sense characterized his thoughts. He had will power and control; and not obstinacy but persistence in following a line, all the while looking very carefully at possible ramifications. He would not neglect the opportunities that presented themselves, often by chance, from random observations in scientific work.
Once when we discussed another physicist, he characterized him as too systematically obstinate. Yet he also told me that he liked to work very systematically in an orderly fashion in order to keep everything under control. At the same time he had decided in his youth to spend at least one hour a day thinking in a speculative way. I liked this paradox of a systematic way of thinking unsystematically. Fermi had a whole arsenal of mental pictures, illustrations, as it were, of important laws or effects, and he had a great mathematical technique, which he used only when necessary. Actually it was more than mere technique; it was a method for dissecting a problem and attacking each part in turn. With our limited knowledge of introspection this cannot be explained at the present time. It is still an "art" rather than a "science." I would say that Fermi was overwhelmingly rational. Let me explain what I mean: the special theory of relativity was strange, irrational, seen against the background of what was known before. There was no simple way to develop it through analogies with previous ideas. Fermi probably would not have tried to develop such a revolution.
I think he had a supreme sense of the important. He did not disdain work on the so-called smaller problems; at the same time, he kept in mind the order of importance of things in physics. This quality is more vital in physics than in mathematics, which is not so uniquely tied to ''reality." Strangely enough, he started as a mathematician. Some of his first papers with very elegant results were devoted to the problem of ergodic motion. When he wanted to, he could do all kinds of mathematics. To my surprise, once on a walk he discussed a mathematical question arising from statistical mechanics which John Oxtoby and I had solved in 1941.
Fermi's will power was obvious, even to the extent of controlling his impulsive gestures. In my opinion, he deliberately avoided volatile Latin mannerisms, and perhaps by a conscious decision controlled gesticulations and avoided exclamations. But Enrico smiled and laughed very readily.
In all activities, scientific or otherwise, he had a mixture of semi-logical whimsical humor about common-sense points of view. When he played tennis, for instance, if he lost four games to six, he would say: "It does not count because the difference is less than the square root of the sum of the number of games." (This is a measure of purely random fluctuations in statistics.)
He loved political discussions, and he loved trying — not too seriously — to foresee the future. He would ask people in a group to write down what they thought would happen, and put it in a sealed envelope to be opened a couple of months later. On the whole he was very pessimistic about the long-range outlook politically, concluding that humanity is still foolish and would destroy itself one day.
He could be also quite a tease. I remember his Italian inflections when he would taunt Teller with statements like: "Edward-a how com-a the Hungarians have not-a invented anything?" Once Segré, who was very fond of fishing on weekends in the streams of the Los Alamos mountains, was expounding on the subtleties of the art, saying that it was not easy to catch trout. Enrico, who was not a fisherman, said with a smile, "Oh, I see, Emilio, it is a battle of wits."
In conversations with friends about the personalities of others, he tried to be entirely detached and objective, allowing little of personal or subjective opinions or feelings to surface. About himself, he had tremendous self-assurance. He knew that he had the touch as well as luck on top of his supreme common sense, enormous mathematical technique, and knowledge of physics.
Enrico was fond of walking; several times we walked all the way from Los Alamos down the walls of a canyon and along a stream to the Bandelier National Monument. It was a walk of seven or eight miles during which we had to cross the stream more than thirty times. The walk lasted several hours, and we discussed many subjects.