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

physicist, so like Feynman and yet so unlike him, who would control his destiny for the next three years, J. Robert Oppenheimer.

Soon after Feynman’s trip to Columbia bearing uranium, these men made their final decision on Princeton’s adventure with the isotron. On the recommendation of Lawrence, nominal y in charge of al electromagnetic separation research, they closed the Princeton project down. Operational y the calutron seemed a ful year ahead, and money had to be committed as wel to the more conventional diffusion approach, with pumps and pipes instead of magnets and fields, the atoms drifting in random trajectories, at ever-so-slightly different speeds, through many miles of metal barriers pricked with bil ions of microscopic holes. Wilson was stunned. He thought the committee was acting not just hastily but hysterical y. To his senior col eagues it seemed that Wilson had lost to the personal strength and promotional skil of his former mentor Lawrence. Smyth and Wigner both felt privately that, given a ful er trial, the isotron might conceivably have shortened the war. “Lawrence’s calutron simply used raw brute force to pry the beam a little way apart,” a younger team member said. “Our method was elegant .” Blown up to the scale needed for mass production—thousands of giant machines

—the isotron promised a yield many times greater.

Feynman had produced detailed calculations for the design of a vast manufacturing plant, with isotrons working in a

“cascade” of increasing purity. He took into account everything from wal -scrapings to uranium that would be lost in workers’ clothing. He conceived arrays of several thousand machines—yet that proved a modest scale, in

light of the later reality.

For Feynman one legacy of the Princeton effort was the friendship with Olum, a friendship, like many that fol owed, intel ectual y rich and emotional y unequal. Encounters with Feynman left marks on a series of young physicists and mathematicians, in the glare of a bright light, out-thought for the first time in their lives. They found different ways of adapting to this new circumstance. Some subordinated their own abilities to his and accepted his occasional bantering abuse in exchange for the surprising pleasure that came with his praise. Some found their self-image enough changed that they abandoned physics altogether.

Olum himself eventual y returned to mathematics, where he was more comfortable. He worked with Feynman throughout the war and then Feynman drifted away. They met only a few times in the next forty years. Olum thought of his old friend often, though. He was president of the University of Oregon when he heard of Feynman’s death.

He realized that the young genius he had met at Princeton had become a part of him, impossible to extricate. “My wife died three years ago, also of cancer,” he said.

… I think about her a lot. I have to admit I have Dick’s books and other things of Dick’s. I have al of the Feynman lectures and other stuff. And there are things that have pictures of Dick on them. The article in Science about the Challenger episode. And also some of the recent books.

I get a terrible feeling every time I look at them. How could someone like Dick Feynman be dead? This

great and wonderful mind. This extraordinary feeling for things and ability is in the ground and there’s nothing there anymore.

It’s an awful feeling. And I feel it—— A lot of people have died and I know about it. My parents are both dead and I had a younger brother who is dead. But I have this feeling about just two people. About my wife and about Dick.

I suppose, although this wasn’t quite like childhood, it was graduate students together, and I do have more

—— I don’t know, romantic, or something, feelings about Dick, and I have trouble realizing that he’s dead.

He was such an extraordinarily special person in the universe.

Finishing Up

Absent from Princeton’s nuclear effort was John Wheeler.

He had already departed for Chicago, where Enrico Fermi and his team at the Metal urgical Laboratory—that enigmatic laboratory employing no metal urgists—were driving toward the first nuclear reactor. They intended to use less-than-bomb-grade uranium to produce slow fission.

In the spring of 1942 Chicago was the place where it was easiest to gain a sense of what the future held. Wheeler knew how deeply his former student was mired in the isotope-separation work. In March he sent Feynman a message. It was time to finish his thesis, no matter how many questions remained open. Wigner—who was also more and more a part of the Chicago work—agreed that

Feynman had accomplished enough for his degree.

Feynman heard the warning. He requested a short leave from the isotron project. Even now he did not feel quite ready to write, especial y under such pressure. Later he remembered spending the first day of his leave lying on the grass, guiltily looking at the sky. Final y, writing with fountain pen in his fast adolescent scrawl, he fil ed sheaves of scratch paper—but paper was expensive, so he used the stationery of the Lawrencian , the Lawrence High School newspaper (Arline Greenbaum, editor in chief) or surplus order forms of G. B. Raymond & Company, sewer pipe, flue linings, etcetera, of Glendale, Long Island. He had now thoroughly assimilated Wheeler’s revolutionary attitude, the stance that declared a break with the past. When the quantum mechanics of Max Planck was applied to the problem of light and the electromagnetic field, he wrote,

“great difficulties have arisen which have not been surmounted satisfactorily.” Other interactions, with more recently discovered particles, were creating similar difficulties, he pointed out: “Meson field theories have been set up in analogy to the electromagnetic field theory. But the analogy is unfortunately al too perfect; the infinite answers are al too prevalent and confusing.” So he disposed of the field—at least the old idea of the field as a free medium for carrying waves. The field is a “derived concept,” he wrote.

“The field in actuality is entirely determined by the particles.” The field is a mere “mathematical construction.”

Just as radical y, he deprecated the wave function of Schrödinger, the now-orthodox means of describing the ful state of a quantum-mechanical system at a given time. It was practical y useless, after al , when the interaction of

particles involved a time delay. “We can take the viewpoint, then, that the wave function is just a mathematical construction, useful under certain conditions”—no, “certain particular conditions … but not general y applicable.”

He also took pains to leave his col aboration with Wheeler decisively behind. He wanted his thesis to be his own; he may already have sensed that the absorber theory in itself was leading toward a quirky dead end. It was his conception of the principle of least action that now consumed him. Wheeler-Feynman had been only a starting point, he wrote. It happened to provide most of the

“il ustrative examples” that would fil out the thesis. But he declared that his least-action method “is in fact independent of that theory, and is complete in itself.”

When he was done, the first part of the thesis looked deceptively old-fashioned. It worked out some nearly textbook equations for the description of mechanical systems, such as springs, coupled together by means of another oscil ator. Then this intermediate oscil ator disappeared. A stroke of mathematical ingenuity eliminated it. A shorthand calculation appeared, very much like the classical Lagrangian. Soon the ground shifted, and the subject was quantum mechanics. The classical machinery of the first part turned into something quite modern. Where there had been two mechanical systems coupled by an oscil ator, now there were two particles interacting through the medium of an oscil ating field. The field, too, was now eliminated. A new quantum electrodynamics arose from a blank slate.