Джеймс Глик - Genius - The Life and Science of Richard Feynman

might act as a “carrier” of the nuclear force, binding protons together in the atom’s core—when the war isolated them utterly. Even with the war’s end, channels to occupied Japan opened slowly. News of the Lamb shift reached Kyōto and Tokyo not through American physicists and not through journals, but from a squib in a newsmagazine.

Tomonaga, a native of Tokyo and a graduate of Kyōto University, a classmate and friend of Yukawa, had been deeply influenced by Dirac; he belonged to a smal group that translated Dirac’s famous textbook into Japanese. In 1937 he traveled to Germany to study with Heisenberg; returning at the war’s onset in 1939, he stopped briefly in New York to visit the World’s Fair. He worked out what he cal ed a “super many time” theory, in which every point in the field had its own clock—a workable notion, he found, despite the seeming absurdity of trying to manipulate infinitely many time variables. In his thoughts on physics he traversed much of the ground covered by his European and American counterparts, but with a far greater sense of solitude, hardly diminished by his time in Germany. He recorded a dark mood in his diary from time to time: After supper I took up my physics again, but at last I gave up. Il -starred work indeed! … Recently I have felt very sad without any reason, so I went to a film… .

Returning home I read a book on physics. I don’t understand it very wel … . Why isn’t nature clearer and more directly comprehensible? … As I went on with the calculation, I found the integral diverged—was infinite.

After lunch I went for a walk. The air was astringently cold… . Al of us stand on the dividing line from which the future is invisible. We need not be too anxious about the results, even though they may turn out quite different from what you expect… .

His occasional emotional desolation paled in light of what faced him in the months after the surrender, when shortages of food and housing overshadowed al else in Japan. He made a home and an office in a battered Quonset hut on the Tokyo University grounds. He furnished it with mats.

Although Oppenheimer knew nothing of Tomonaga’s personal circumstances, he knew what he and his Los Alamos compatriots had wrought on Japan, and he also wished to preserve the internationalism of physics in the face of what suddenly seemed an American hegemony. He could hardly have been better placed to appreciate Tomonaga’s letter—clear evidence that a Japanese physicist had not just matched the essentials of Schwinger’s work but had anticipated it. Tomonaga had not published, and he had not created the entire Schwingerian tapestry, but he had been first. Oppenheimer immediately gave Tomonaga his imprimatur in a letter to each of the Pocono participants. “Just because we were able to hear Schwinger’s beautiful report,” he wrote, “we may better be able to appreciate this independent development.” For Dyson, working in Pocono’s aftermath to understand the new theories, the revelation of Tomonaga’s papers lay in

what seemed a simple beauty. He thought that he now understood Schwinger and that not al Schwinger’s complications were necessary. Graduate students poring over the Pocono notes already suspected this, despite the acclaim their elders were awarding. Later Dyson quoted

“an unkind critic” as having said, “Other people publish to show how to do it, but Julian Schwinger publishes to show you that only he can do it.” He seemed to strive for an exceptional ratio of equations to text, and the prose posed serious chal enges to the Physical Review ’s typesetters.

Schwinger occasional y heard what sounded like carping amid the applause: comments to the effect that he was a soul ess Paganini, al flash and technique instead of music; that he was more mathematician than physicist; that he too careful y smoothed the rough edges. “I gather I stand accused,” Schwinger said later, “of presenting a finished elaborate mathematical formalism from which had been excised al the physical insights that provide signposts to its construction.”

He had removed the signposts. He never liked to show the rough pathways of his thinking, any more than he liked to let his audiences see notes when he lectured. Yet al his mathematical power could not have produced his joining of relativity and quantum electrodynamics if he had lacked the intuition of a physicist. Beneath the formalism lay a profound—and historical y minded—conviction about the nature of particles and fields. To Schwinger renormalization was not just a mathematical trick. Rather it marked a mutation in physicists’ understanding of what a particle

was. His central physical insight, had he expressed it in the compromised language of everyday speech, might have sounded like this:

Are we talking about particles or are we talking about waves? Until now, everyone has thought that their equations — the Dirac equation, for example, which is supposed to describe the hydrogen atom — referred directly to the physical particles. Now, in a field theory, we recognize that the equations refer to a sublevel.

Experimentally we are concerned with particles, yet the old equations describe fields. When you talk about fields, you presume that you can describe, and somehow experience, exactly what goes on at every point in space at every time; when you talk about particles, you merely sample the field with measurements at occasional instants.

A particle is a cohesive thing. We know we have a particle only when the same thing stays there as time goes on. The very language of particles implies phenomena with continuity over space and time. Yet if you make measurements at only disconnected instants, how do you know there is a particle? Experiments probe the field only crudely — they look at large spaces over long times.

The essence of renormalization is to make the transition from one level of description to the next. When you begin with field equations, you operate at a level when

particles are not there from the start. It is when you solve the field equations that you see the emergence of particles. But the properties — the mass and the charge — that you ascribe to a particle are not those inherent in the original equations.

Other people say, “Oh, the equations have divergences, you have to cancel them out.” That is only the form, not the essence of renormalization. The essence lies in recognizing that the theories of Maxwell and Dirac are not about electrons, positrons, and photons but about a deeper level.

Cross-Country with Freeman Dyson

Feynman had a tendency to vanish with the end of the school year, leaving behind a vacuum populated by uncorrected papers, ungraded tests, unwritten letters of recommendation. Often Bethe covered for his lapses in the paperwork of teaching. Stil , June might bring a tirade from Lloyd Smith, the department chairman:

Your sudden departure from Ithaca without completing the grades in your courses, especial y those involving seniors who may thus be prevented from graduating, has caused the Department considerable embarrassment. I have begun to be somewhat apprehensive over what would appear to be

a feeling of indifference concerning the obligations and responsibilities to the University …

Feynman would jot some grades—round numbers, none higher than 85—and then start doodling equations.

This June found him at the wheel of his secondhand Oldsmobile, rushing across the country at a constant 65