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

Final y he managed to move forward, promising that al would be made clear in due course. As always, he made a point of lecturing without notes, and nearly al of his

point of lecturing without notes, and nearly al of his presentation was formal, deriving one equation after another. His talk became a marathon, lasting late into the afternoon. Bethe noticed that the formal mathematics silenced the critics, who raised questions only when Schwinger tried to express plainly physical ideas. He mentioned this to Feynman, suggesting that he, too, take a mathematical approach to his presentation. Fermi, glancing about at his famous col eagues, noticed with some satisfaction that one by one they had let their attention drift away. Only he and Bethe managed to stay with Schwinger to the end, he thought.

Then it was Feynman’s turn. He was uneasy. It seemed to him that Schwinger’s talk, though a bravura performance, had not gone wel (but he was wrong—everyone, and crucial y Oppenheimer, had been impressed). Bethe’s warning made him reverse his planned presentation. He had meant to stay as closely as possible to physical ideas.

He did have a mathematical formalism, as private though not as intricate as Schwinger’s, and he could show how to derive his rules and methods from the formalism, but he could not justify the mathematics itself. He had reached it by trial and error. He knew it was correct, because he had tried it now on so many problems, including al of Schwinger’s, and it worked, but he could not prove that it worked and he could not connect it to the old quantum mechanics. Nevertheless he took Bethe’s advice and began with equations, saying, “This is a mathematical formula which I wil now show you produces al the results of quantum mechanics.”

He had always told his friends that once he started talking about physics he did not care who his audience was. One of his favorite stories was about Bohr, who had singled him out at Los Alamos as a young man unafraid to dispute his elders. Bohr had consulted Feynman privately there from time to time, often through his physicist son, Aage. Stil , he had never ful y warmed to Feynman, with his overeager, American, working-class style. Now Bohr waited, at the end of a long day, in this formidable audience of twenty-six men. Not even at Princeton, when he lectured to Einstein and Pauli, had Feynman stood before such a concentration of the great minds of his science. He had created a new quantum mechanics almost without reading the old, but he had made two exceptions: he had learned from the work of Dirac and Fermi, both now seated before him. His teachers Wheeler and Bethe were there. So were Oppenheimer, who had built one bomb, and Tel er, who was building the next. They had known him as a promising, fearless young light. His thirtieth birthday was seven weeks away.

Schwinger himself was hearing Feynman’s theory for the first time. He thought it intel ectual y repulsive, though he did not say so (and afterward they cordial y compared techniques and found themselves in nearly perfect agreement). He could see that Feynman was offering a patchwork of guesses and intuition. It struck him as engineering, al I-beams and T-beams. Bethe interrupted once, sensing that the audience was numbed with detail, and tried to return Feynman to fundamentals. Feynman

explained his path integrals, an alien idea, and his positrons moving backward in time, even more disturbing.

Tel er caught the apparent infringement of the exclusion principle and refused to accept Feynman’s unrigorous justification. It struck Feynman that everyone had a favorite principle or theorem and he was violating them al . When Dirac asked, “Is it unitary?” Feynman did not even know what he meant. Dirac explained: the matrix that carries one from the past to the future had to maintain an exact bookkeeping of total probability. But Feynman had no such matrix. The essence of his approach was a view of past and future together, with the freedom to go forward or backward in time at wil . He was getting almost nothing across. Final y, as he sketched diagrams on the blackboard—schematic trajectories of particles—and tried to show his method of summing the amplitudes for different paths, Bohr rose to object. Had Feynman ignored the central lesson of two decades of quantum mechanics? It was obvious, Bohr said, that such trajectories violated the uncertainty principle. He stepped to the blackboard, gestured Feynman aside, and began to explain. Wheeler, taking notes, quickly jotted, “Bohr Has Raised The Question As To Whether This Point Of View Has Not The Same Physical Content As The Theory Of Dirac, But Differs In A Manner Of Speaking Of Things Which Are Not Wel -Defined Physical y.” Bohr continued for long minutes.

That was when Feynman knew he had failed. At the time, he was in anguish. Later he said simply: “I had too much stuff. My machines came from too far away.”

There

Was

Also

Presented

(by

Feynman) …

Wheeler had arranged as rapid a news service as the available technology permitted. On his first day back in Princeton he pressed his graduate students into service as scribes. They reproduced his notes page by page onto mimeograph blanks and printed dozens of copies, turning their forearms magenta. For months this samizdat document served as the only available introduction to the new Schwingerian covariant quantum electrodynamics.

Only a few pages were devoted to Feynman, with his

“alternative formulation” and curious diagrams. Dyson read the Wheeler notes avidly. Bethe had tried to get him an invitation to Pocono (“you can imagine that I was highly pleased and flattered,” Dyson wrote his parents), but Oppenheimer refused to consider someone whose current caste was student.

Feynman himself was assigned the task of writing a nontechnical account of the Pocono meeting for a new trade journal for physicists, Physics Today —anonymously, he hoped. He explained renormalization à la Schwinger, concluding:

A major portion of the conference was spent in hearing and discussing these results of Schwinger.

(((One conferee put it: “We did not have time to

(((One conferee put it: “We did not have time to discuss a great deal, for we had to take time out to learn some physics.” He was referring to this work of Schwinger.)))

There was also presented (by Feynman) a theory in which the equations of electrodynamics are artificial y altered so that al quantities including the inertia of the electron turn out finite. The results of this theory are in essential agreement with those of Schwinger, but they are not as complete.

In the same runner-up vein Feynman was asked to help select a winner for a new prize the National Academy of Sciences was awarding for “an outstanding contribution to our knowledge of the nature of light.” When Schwinger saw Feynman’s name on the list of judges, he inferred correctly that the prize was meant for him. What was quantum electrodynamics about, if not light, in al its many dresses?

No one had been more definitively impressed by Schwinger,

and

unimpressed

by

Feynman,

than

Oppenheimer. Awaiting him back in Princeton was a startling confirmation of Schwinger’s theory, in the form of a letter from a Japanese theorist, Shin’ichirō Tomonaga, whose claim to glory began with the words: “I have taken the liberty of sending you copies of several papers and notes …”

Japan’s physicists had just begun making significant contributions to the international community in the 1930s—

it had been Hideki Yukawa at Kyōto University who first proposed that a massive, short-lived, undiscovered particle