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

Feynman found that a system of equations in which advanced and retarded waves were combined half and half seemed to withstand every objection.

Waves forward and backward in time. Wheeler and Feynman tried to work out a consistent scheme for the interactions of particles, and they embroiled themselves in paradoxes of past and future . A particle shakes; its influence spreads outward like waves from a stone thrown into a pond. To make their theory symmetrical, they also had to use inward-traveling waves-implying action backward in time.

They found that they could avoid unpleasant paradoxes because these normal and time-reserved waves ("retarded" and "advanced") canceled each other out-but only if the universe was arranged so as to guarantee that all radiation would be absorbed somewhere, sometime. A beam of light traveling forever into infinite, empty space, never striking an absorber, would foil their theory's bookkeeping.

Thus cosmologists and philosophers of time continued to consider their scheme long after it had been supplanted in the mainstream of quantum theory.

He described it to his graduate student friends and chal enged them to find a paradox he could not explain his way through. For example, could one design a mechanism with a target that would shut a gate when struck by a pel et, such that the advanced field closed the gate before the pel et arrived, in which case the pel et could not strike the target, in which case the advanced field would not close the gate after al … He imagined a Rube Goldberg contraption that might have come straight from Wheeler’s old book of ingenious

mechanisms

and

mechanical

devices.

Feynman’s calculations suggested that the model was surprisingly immune to paradox. As long as the theory relied on probabilities, it seemed to escape fatal contradictions. It did not matter where the absorber was or how it was shaped, as long as there were absorbing particles off at some distance in every direction. Only if there were “holes” in the surrounding layer, places where

radiation could go forever without being absorbed, could the advanced effects make trouble, arriving back at the source before they had been triggered.

Wheeler had his own motive for pursuing this quixotic theory. Most physicists were now persuaded that the atom embodied at least three irreconcilably different particles, electrons, protons, and neutrons, and cosmic rays were providing intimations of several more. This proliferation offended Wheeler’s faith in the ultimate simplicity of the world. He continued to cherish a notion so odd that he was reluctant to discuss it aloud, the idea that a different kind of theory would reveal everything to be made of electrons after al . It was crazy, he knew. But if electrons were to be the ultimate building blocks, their radiative forces would have to provide the key, in ways that the standard theory was not prepared to explain. Within weeks he began pressing Feynman to write a preliminary paper. If they were going to make grand theories, Wheeler would make sure they publicized the work properly. Early in 1941 he told Feynman to prepare a presentation for the departmental seminar, usual y a forum for distinguished visiting physicists, in February. It would be Feynman’s first professional talk. He was nervous about it.

As the day approached, Wigner, who ran the col oquiums, stopped Feynman in the hal . Wigner said he had heard enough from Wheeler about the absorber theory to think it was important. Because of its implications for cosmology he had invited the great astrophysicist Henry Norris Russel . John von Neumann, the mathematician, was also going to come. The formidable Wolfgang Pauli happened to be visiting from Zurich; he would be there. And

though Albert Einstein rarely bestirred himself to the col oquiums, he had expressed interest in attending this one.

Wheeler tried to calm Feynman by promising to field questions from the audience. Wigner tried to brief him. If Professor Russel appears to fal asleep during your talk, Wigner said, don’t worry—Professor Russel always fal s asleep. If Pauli appears to be nodding, don’t assume he agrees—he nods from palsy. (Pauli could be ruthless in dismissing work he considered shal ow or flimsy: “ ganz falsch ,” utterly false—or worse, “ not even false.”) Feynman prepared careful y. He col ected his notes and put them into a brown envelope. He entered the seminar room early and covered the blackboard with equations. While he was writing, he heard a soft voice behind him. It was Einstein.

He was coming to the lecture and first he wondered whether the young man might direct him to the tea.

Afterward Feynman could remember almost nothing: just the trembling of his hand as he pul ed his notes from the envelope and then a feeling that his mind put itself at ease by concentrating on the physics and forgetting the occasion and the personalities. Pauli did object, perhaps sensing that the use of advanced potentials merely invoked a sort of mathematical tautology. Then, politely, Pauli said, “Don’t you agree, Professor Einstein?” Feynman heard that soft Germanic voice again—so pleasant, it seemed—saying no, the theory seemed possible, perhaps there was a conflict with the theory of gravitation, but after al the theory of gravitation was not so wel established …

The Reasonable Man

He suffered spel s of excessive rationality. When these struck it was not enough to make progress in his scientific work, nor to rectify his mother’s checkbook, nor to recompute his own equivocal balance sheet (eighteen dol ars for laundry, ten dol ars to send home … ), nor to lecture his friends, as they watched him repair his bicycle, on the sil iness of believing in God or the supernatural.

During one occurrence he wrote out an hourly schedule of his activities, both scholarly and recreational, “so as to efficiently distribute my time,” he wrote home. When he finished, he recognized that no matter how careful he was, he would have to leave some indeterminate gaps—“hours when I haven’t marked down just what to do but I do what I feel is most necessary then—or what I am most interested in—whether it be W.’s problem or reading Kinetic Theory of Gases, etc.” If there is a disease whose symptom is the belief in the ability of logic to control vagarious life, it afflicted Feynman, along with his chronic digestive troubles.

Even Arline Greenbaum, sensible as she was, could spark flights of reason in him. He grew concerned about the potential for emotional disputes between husbands and wives. Even his own parents fought. He hated the battles and the anger. He did not see why two intel igent people, in love with each other, wil ing to converse openly, should get caught in arguments. He worked out a plan. Before revealing it to Arline, however, he decided to lay it out for a physicist friend over a hamburger at a diner on the Route 1

traffic circle. The plan was this. When Dick and Arline disagreed intensely about a matter of consequence, they

would set aside a fixed time for discussion, perhaps one hour. If at the end of that time they had not found a resolution, rather than continue fighting they would agree to let one of them decide. Because Feynman was older and more experienced (he explained), he would be the one.

His friend looked at him and laughed. He knew Arline, and he knew what would real y happen. They would argue for an hour, Dick would give up, and Arline would decide.

Feynman’s plan was a sobering example of the theoretical mind at work.

Arline was visiting more and more often. They would have dinner with the Wheelers and go for long walks in the rain. She had the rare ability to embarrass him: she knew where his smal vanities were, and she teased him mercilessly whenever she caught him worrying about other people’s opinions—how things might seem . She sent him a box of pencils emblazoned, “Richard darling, I love you!