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

And he added something new—a diagram, purely schematic, for keeping track of the zigs and zags. The horizontal dimension represented his one spatial dimension, and the vertical dimension represented time.

He successful y negotiated the details of this one-dimensional shadow theory. The spin of his particles implied a phase, like the phase of a wave, and he made some assumptions, only partly arbitrary, about what would happen to the phase each time a particle zagged. Phase was crucial to the mathematics of summing the paths, because paths would either cancel or reinforce one another, depending on how their phases overlapped.

Feynman did not attempt to publish this fragment of a theory, excited though he was by the progress. The chal enge was to extend the theory to more dimensions—to

let the space unfold—and this he could not do, though he spent long hours in the library, for once reading old mathematics.

Shrinking the Infinities

Feynman’s frustration in these first postwar years mirrored a growing sense of impotence and defeat among established theoretical physicists. The feeling, at first private and then shared, remained invisible outside their smal community. The contrast with the physicists’ public glory could hardly have been greater.

The cause was abstruse. The single difficulty at the core of this anguish was a mathematical tendency of certain quantities to diverge as successive terms of an equation were computed—terms that should have been vanishing in importance. Physical y it seemed that the closer one stood to an electron, the greater its charge and mass would appear. The result: the infinities with which Feynman had been struggling since Princeton. It meant that quantum mechanics produced good first approximations fol owed by a Sisyphean nightmare. The harder a physicist pushed, the less accurate his calculations became. Such quantities as the mass of the electron became—if the theory were taken to its limit—infinite. The horror of this was hard to comprehend, and no glimmer of it appeared in popular accounts of science at the time. Yet it was not merely a theoretical knot. A pragmatic physicist eventual y had to

face it. “Thinking I understand geometry,” Feynman said later, “and wanting to fit the diagonal of a five foot square, I try to figure out how long it must be. Not being very expert I get infinity—useless… .”

It is not philosophy we are after, but the behavior of real things. So in despair, I measure it directly—lo, it is near to seven feet—neither infinity nor zero. So, we have measured these things for which our theory gives such absurd answers… .

Experimental yardsticks for the electron were not so easy to come by, and it was a tribute to the original theory of Heisenberg,

Schrödinger,

and

Dirac

that

first

approximations matched any experimental results that the laboratories had produced so far. Better results were on the way, however.

Meanwhile, the scientists contemplating the state of theoretical physics descended into a distinct gloominess; in the aftermath of the bomb, their mood seemed postcoital.

“The last eighteen years”—the period, that is, since the quick birth of quantum mechanics—“have been the most sterile of the century,” remarked I. I. Rabi to a col eague over lunch in that spring of 1947, though Rabi himself was thriving as head of a fruitful group at Columbia.

“Theoreticians were in disgrace”—so it seemed to one especial y precocious student of physics, Murray Gel -

Mann.

“The theory of elementary particles has reached an impasse,” Victor Weisskopf wrote. Everyone had been struggling futilely, he said, especial y since the war, and everyone had had enough of “knocking a sore head against the same old wal .”

Merely a few dozen men in mathematical difficulty—or the generation’s deepest crisis in theoretical physics. It was al the same. Weisskopf was preparing for an unusual gathering. A former president of the New York Academy of Sciences, Duncan MacInnes, had been nursing a conviction that modern-day conferences were growing too unwieldy. Hundreds of people would appear. Speakers were starting to cater to these diffuse audiences by delivering generalized and retrospective talks. As an experiment, MacInnes proposed an intimate meeting restricted to twenty or thirty invited guests, to take place in a relaxed, country-inn setting. With “Fundamental Problems of Quantum Mechanics” as a topic, he managed—though it took more than a year—to draw a select group in early June to an inn cal ed the Ram’s Head, just opening for the summer season on New York’s Shelter Island, between the forks of eastern Long Island. Weisskopf was one of those charged with setting the agenda. Other participants were Oppenheimer, Bethe, Wheeler, Rabi, Tel er, and several representatives of the younger generation, including Julian Schwinger and Richard Feynman.

So two dozen suit-jacketed physicists met on a Sunday afternoon on the East Side of New York and motored across Long Island in a rickety bus. Somewhere along the

way a police escort picked them up, sirens wailing, and a banquet was arranged by a local chamber of commerce official who had been serving in the Pacific when, he felt, the atomic bomb saved his life. A ferry carried them across to Shelter Island, and to some of the physicists there was an air of unreality about it al . When they gathered for breakfast the next morning, they noticed the phrase

“restricted clientele” on the menus and performed a quick head count: their group contained more Jews, they decided, than the inn’s dining room had ever seen. One New York newspaper reporter had come along, and he telephoned his report to the Herald Tribune : “It is doubtful if there has ever been a conference quite like this one… .

They roam through the corridors mumbling mathematical equations, eat their meals amid the fury of technical discussions… .” Island residents, he wrote, are reasonably confused about this sudden descent of science among them. The principal theory is that the scientists are busy making another type of atomic bomb, and nothing could be farther from the truth… .

Quantum mechanics is the never-never land of science, a world in which matter and energy become confused and where al the verities of day-to-day life become meaningless… .

To those sensitive to smal breezes, it was beginning to seem that two of the younger men in particular, Schwinger and Feynman, were engaged in a gestation of fresh ideas.

Schwinger mostly kept his own counsel during these three days. Feynman tried his methods out on a few people; a young Dutch physicist, Abraham Pais, watched him derive results at lightning speed with the help of sketchy pictures that left Pais baffled. On the last morning, after some words by Oppenheimer, Feynman was asked to give the whole group an informal description of his work, and he did, happily. No one real y understood, but he left the memory of

—as one listener recorded in his diary—“a clear voice, great rush of words and il ustrative gestures sometimes ebul ient.”

Above al , however, it was a conference dominated by news from experimenters, and particularly experimenters in the furnace Rabi was stoking at Columbia. The Columbia groups favored techniques that seemed homely and unspectacular in this era of the burgeoning particle accelerator, though their arsenal also included technologies fresh from the wartime Radiation Laboratory, magnetrons and microwaves. Wil is Lamb had just shined a beam of microwaves onto a hot wisp of hydrogen blowing from an oven. He was trying to measure the precise energy levels of electrons in the hydrogen atom. He succeeded—the art of spectroscopy had never seen such precision—and he found a distinct gap between two energy levels that should have been identical. Should have been , that is, according to the clearest existing guide to hydrogen atoms and electrons, the theory of Dirac. That was in April. Lamb had gone to bed thinking about knobs and magnets and a bouncing spot of light from the galvanometer and the clear