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

Assuming that a particle’s decay conserved parity, a physicist had to believe that the tau and the theta were different. Intuitions were severely tested. Sometime after

the Rochester conference ended, Abraham Pais wrote a note to himself: “Be it recorded here that on the train back from Rochester to New York, Professor Yang and the writer each bet Professor Wheeler one dol ar that the theta- and tau-meson are distinct particles; and that Professor Wheeler has since col ected two dol ars.”

Everyone was making bets. An experimenter asked Feynman what odds he would give against an experiment testing for the unthinkable, parity violation, and Feynman was proud later that he had offered a mere fifty to one. He actual y raised the question at Rochester, saying that his roommate there, an experimenter named Martin Block, had wondered why parity could not be violated. (Afterward Gel -

Mann teased him mercilessly for not having asked the question in his own name.) Someone had joked nervously about considering even wild possibilities with open minds, and the official note taker recorded:

Pursuing the open mind approach, Feynman brought up a question of Block’s: Could it be that the

[theta] and [tau] are different parity states of the same particle which has no definite parity, i.e. , that parity is not conserved. That is, does nature have a way of defining right- or left-handedness uniquely?

Two young physicists, Chen Ning Yang and Tsung Dao Lee, said they had begun looking into this question without reaching any firm conclusions. So desperately did the participants dislike the idea of parity violation that one scientist proposed yet another unknown particle, this time one that departed the scene with no mass, no charge, and no momentum—just carrying off “some strange space-time transformation properties” like a sanitation worker carting away trash. Gel -Mann rose to suggest that they keep their minds open to the possibility of other, less radical solutions.

Discussion continued until, as the note taker put it, “The

chairman”—Oppenheimer—“felt that the moment had come to close our minds.”

But in Feynman’s tentative question the answer had emerged. Lee and Yang undertook an investigation of the evidence. For electromagnetic interactions and strong interactions, the rule of parity conservation had a real experimental and theoretical foundation. Without parity conservation, a wel -entrenched framework would be torn apart. But that did not seem to be true for weak interactions. They went through an authoritative text on beta decay, recomputing formulas. They examined the recent experimental literature of strange particles. By the summer of 1956 they realized that, as far as the weak force was concerned, parity conservation was a free-floating assumption, bound neither to any experimental result nor to any theoretical rationale. Furthermore, it occurred to them that Gel -Mann’s conception of strangeness offered a precedent: a symmetry that held for the strong force and broke down for the weak. They quickly published a paper formal y raising the possibility that parity might not be conserved

by

weak

interactions

and

proposing

experiments to test the question. By the end of the year, a team led by their Columbia col eague Chien Shiung Wu had set one of them up, a delicate matter of monitoring the decay of a radioactive isotope of cobalt in a magnetic field at a temperature close to absolute zero. Given an up and down defined by the alignment of the magnetic coil, the decaying cobalt would either spit out electrons symmetrical y to the left and right or would reveal a preference. In Europe, awaiting the results, Pauli joined the wagerers: he wrote Weisskopf, “I do not believe that the Lord is a weak left-hander, and I am ready to bet a very large sum that the experiments wil give symmetric results.”

Within ten days he knew he was wrong, and within a year Yang and Lee had received one of the quickest Nobel Prizes ever awarded. Although physicists stil did not

understand it, they appreciated the import of the discovery that nature distinguished right from left in its very core.

Other symmetries were immediately implicated—the correspondence between matter and antimatter, and the reversibility of time (if the film of an experiment were run backwards, for example, it might look physical y correct except that right would be left and left would be right). As one scientist put it, “We are no longer trying to handle screws in the dark with heavy gloves. We are being handed the screws neatly aligned on a tray, with a little searchlight on each that indicates the direction of its head.”

Feynman made an odd presence at the high-energy physicists’ meetings. He was older than the bright young scientists of Gel -Mann’s generation, younger than the Nobel-wielding senators of Oppenheimer’s. He neither withdrew from the discussions nor dominated them. He showed a piercing interest in the topical issues—as with his initial prodding on the question of parity—but struck younger physicists as detached from the newest ideas, particularly in contrast to Gel -Mann. At the 1957 Rochester conference it occurred to at least one participant that Feynman himself should have applied his theoretical talents to the question he had raised a year earlier, instead of leaving the plum to Yang and Lee. (The same participant noticed a revisionists’ purgatory in the making: theorists from Dirac to Gel -Mann “busy explaining that they personal y had never thought parity was anything special,”

and experimenters recal ing that they had always meant to get around to an experiment like Wu’s.) Publicly, Feynman was as serene as ever. Privately, he agonized over his inability to find the right problem. He wanted to stay clear of the pack. He knew he was not keeping up with even the published work of Gel -Mann and other high-energy physicists, yet he could not bear to sit down with the journals or preprints that arrived daily on his desk and piled up on his shelves and merely read them. Every arriving

paper was like a detective novel with the last chapter printed first. He wanted to read just enough to understand the problem; then he wanted to solve it his own way. Almost alone among physicists, he refused to referee papers for journals. He could not bear to rework a problem from start to finish along someone else’s track. (He also knew that when he broke his own rule he could be devastatingly cruel.

He summarized one text by writing, “Mr. Beard is very courageous when he gives freely so many references to other books, because if a student ever did look at another book, I am sure he would not return again to continue reading Beard,” and then urged the editor to keep his review confidential—“for Mr. Beard and I are good personal friends.”) His persistently iconoclastic approach to other people’s work offended even theorists whom he meant to compliment. He would admire what they considered a peripheral finding, or insist on what struck them as a cockeyed or baroque alternative viewpoint. Some theorists strived to col aborate with col eagues and to set a tone and an agenda for whole groups. Gel -Mann was one. Feynman seemed to lack that ambition—though a generation of physicists now breathed Feynman diagrams. Stil , he was frustrated.

He sometimes confided in his sister, Joan, who had begun a career in science herself, getting a doctorate in solid-state physics at Syracuse University. She was stil living in Syracuse, and Feynman visited her when he went to Rochester. He complained to her that he could not work.

She reminded him of al the recent ideas that he had shared with her and then refused to pursue long enough to write a paper. You’ve done it again and again , she said.