by James Gleick
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 still 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 all 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. You told me that Block might be right. And you don’t do a damn thing about it. You should write it up, for crying out loud, when you have something like this. She also reminded him that he had mentioned an idea for a universal theory of weak interactions—tying together beta decay and the strange-particle decays based on the weak force—and urged him, finally, to see where it would lead.
In its classic form, beta decay turns a neutron into a proton, throwing off an electron and another particle, a neutrino—massless, chargeless, and hard to detect. Charge is conserved: the neutron has none; the proton carries + 1 and the electron – 1. Analogously, in the meson family, a pion could decay into a muon (like a heavy electron) and a neutrino. A good theory would predict the rates of decay in such processes, as well as the energies of the outgoing particles. There were complications. The spins of the particles had to be reconciled, and for the massless neutrinos, especially, problems of handedness arose in calculating the appropriate spins. So the new understanding of parity violation immediately changed the weak-interaction landscape—for Feynman, for Gell-Mann, and for others.
In sorting the various kinds of particle interactions, theorists had created a classification scheme with five distinct transformations of one wave function into another. In one sense it was a classification of the characteristic algebraic techniques; in another, it was a classification of the types of virtual particles that arose in the interactions, according to their possible spins and parities. As shorthand, physicists used the labels S, T, V, A, and P, for scalar, tensor, vector, axial vector, and pseudoscalar. The different kinds of weak interaction had evident similarities, but this classification scheme posed a problem. As Lee pointed out at the 1957 Rochester meeting, most experiments on beta decay had demonstrated S and T interactions, while the new parity-violation experiments tended to suggest that meson decay involved V and A. Under the circumstances, the same physical laws could hardly be at work.
In reading Lee and Yang’s preprint for the meeting—Joan had ordered him, for once, to sit down like a student and go through it step by step—Feynman saw an alternative way of formulating the violation of parity. Lee and Yang described a restriction on the spin of the neutrino. He liked the idea enough to mention it from the audience during five minutes cadged from another speaker. He went far back into the origins of quantum mechanics—back not only to the Dirac equation itself but beyond, to the Klein-Gordon equation that he and Welton had manufactured when they were MIT undergraduates. Using path integrals, he moved forward again, deriving—or “discovering”—an equation slightly different from Dirac’s. It was simpler: a two-component equation, where Dirac’s had four components. “Now I asked this question,” Feynman said:
Suppose that historically [my equation] had been discovered before the Dirac equation? It has absolutely the same consequences as the Dirac equation. It can be used with diagrams the same way.
The diagrams for beta decay, of course, added a neutrino field interacting with the electron field. When Feynman made the necessary change to his equation, he found:
Of course I can’t do that because this term is parity unsymmetric. But——beta decay is not parity symmetric, so it’s now possible.
There were two difficulties. One was that he came out with the opposite sign for the spin: his neutrino would have to spin in the opposite direction from Lee and Yang’s prediction. The other was that the coupling in his formulation would have to be V and A, instead of the S and T that everyone knew was correct.
Gell-Mann, meanwhile, had also thought about the problem of creating a theory for weak interactions. Nor were Feynman and Gell-Mann alone: Robert Marshak, who had put forward the original two-meson idea at the Shelter Island conference in 1947, was also leaning toward V and A with a younger physicist, E. C. G. Sudarshan. That summer, with Feynman traveling in Brazil, Marshak and Sudarshan met with Gell-Mann in California and described their approach.
Feynman returned at the end of the summer determined, for once, to catch up with the experimental situation and follow his weak-interaction idea through to the end. He visited Wu’s laboratory at Columbia, and he asked Caltech experimenters to bring him up to date. The data seemed a shambles—contradictions everywhere. One of the Caltech physicists said that Gell-Mann even thought the crucial coupling could be V rather than S. That, as Feynman often recalled afterward, released a trigger in his mind.
I flew out of the chair at that moment and said, “Then I understand everything. I understand everything and I’ll explain it to you tomorrow morning.”
They thought when I said that, I’m making a joke… . But I didn’t make a joke. The release from the tyranny of thinking it was S and T was all I needed, because I had a theory in which if V and A were possible, V and A were right, because it was a neat thing and it was pretty.
Within days he had drafted a paper. Gell-Mann, however, decided that he should write a paper, too. As he saw it, he had his own reasons for focusing on V and A. He wanted the theory to be universal. Electromagnetism depended on vector coupling, and the strange particles favored V and A. He was unhappy that Feynman seemed to be thoughtlessly dismissing his ideas.
Before the tension between them rose higher, their department head, Robert Bacher, stepped in and asked them to write a joint paper. He preferred not to see rival versions of the same discovery coming out of Caltech’s physics group. Colleagues strained to overhear Feynman and Gell-Mann in the corridors or at a cafeteria table, engrossed in their oral collaboration. They stimulated each other despite the characteristic differences in their language: Feynman offering what sounded like you take this and it zaps through here and you come out and pull this together like that, Gell-Mann responding with you substitute there and there and integrate like so… . Their article reached the Physical Review in September, days before Marshak presented his and Sudarshan’s similar theory at a conference in Padua, Italy. Feynman and Gell-Mann’s theory went further in several influential respects. It proposed a bold extension of the underlying principles beyond beta decay to other classes of particle interactions; it would be years before experiment fully caught up, showing how prescient the two men had been. It also introduced the idea that a new kind of current—analogous to electrical current, a measure of the flow of charge—should be conserved; new extensions of the concept of current became a central tool of high-energy physics.
Feynman tended to recall that they had written the paper together. Gell-Mann sometimes disdained it, complaining particularly about the two-component formalism—a ghastly notation, he felt. It did bear Feynman’s stamp. He was applying a formulation of quantum electrodynamics that went back to his first paper on path integrals in 1948; Gell-Mann allowed him to remark fondly, “One of the authors has always had a predilection for this equation.” Yet it could hardly have been Feynman who wrote that their approach to parity violation “has a certain amount of theoretical raison d’être.” Evident, too, was Gell-Mann’s drive to make the theory as unifying and forward-looking as possible. The discovery was esoteric compared to other milestones of modern physics. If Feynman, Gell-Mann, Marshak, or Sudarshan had not made it in 1957, others would have soon after. Yet to Feynman it was as pure an achievement as any in his career: the unveiling of a law of nature. His model had always been Dirac’s magical discovery of an equation for the electron. In a sense Feynman had discovered an equation for the neutrino. “There was a moment when I knew how nature worked,” he said. “It had elegance and beauty. The goddamn thing was gleaming.” To other physicists, “Theory of the Fermi Interaction,” barely six pages long, shone like
a beacon in the literature. It seemed to announce the beginning of a powerful collaboration between two great and complementary minds. They took a distinctive kind of theoretical high ground, repeatedly speaking of universality, of simplicity, of the preservation of symmetries, of broad future applications. They worked from general principles rather than particular calculations of dynamics. They made clear predictions about new kinds of particle decay. They listed specific experiments that contradicted their theory and declared that the experiments must therefore be wrong. Nothing could have more strikingly declared the supremacy of the theorists.
Toward a Domestic Life
The two-piece “bikini” bathing suit, named after the tiny Pacific atoll that was blasted by atomic and hydrogen bombs through the forties and fifties, had not yet taken over the beaches of the United States in 1958, but Feynman saw one, blue, on the sand of Genève-Plage, and laid his beach towel down nearby. He was visiting Geneva for a United Nations conference on the peaceful uses of atomic energy. He was preparing to give a summary talk in his own name and Gell-Mann’s, telling the assembly:
We are well aware of the fragility and incompleteness of our present knowledge and of the manifold of speculative possibilities… . What is the significance or the pattern behind all these interrelated symmetries, partial symmetries, and asymmetries?
The yearly Rochester conference had also changed venue for the occasion, and he discussed the weak-interaction theory, impressing listeners with the body language he used to demonstrate the appropriate spins and handednesses. He had just turned forty. It was spring, and the young woman in the blue bikini volunteered that Lake Geneva was cold. “You speak English!” he said. She was Gweneth Howarth, a native of a village in Yorkshire, England. She had left home to see Europe by working as an au pair. That evening he took her to a nightclub.
The violation of parity had reached newspapers and magazines briefly. For readers who looked to science for a general understanding of the nature of the universe, the fall of left-right symmetry may have been the last genuinely meaningful lesson to emerge from high-energy physics, circumscribed though it was in the domain of certain very short-lived particle interactions. By contrast, though the universal theory of weak interactions commandeered the attention of theorists and experimenters a year later, the replacement of S and T with V and A made no ripple in the cultural consciousness. By then the American public was busy anyway, assimilating the most shocking scientific development of the 1950s, the piece of news establishing once again in the public mind the truism that science is power.
The beachball-sized aluminum sphere called Sputnik began orbiting the earth on October 4, 1957. Its unexpected presence overhead and the insouciant beep-beep-beep played again and again on American radio and television broadcasts set off a wave of anxiety like nothing since the atomic bomb itself. (Feynman arrived at a picnic that evening in the biologist Max Delbrück’s backyard with a small gray radio receiver that looked as if he had built it himself. He called for an extension cord, tuned the receiver quickly, held up a finger to demand silence, and grinned as the beeps played out over the crowd.) “Red Moon over U.S.,” said Time magazine, immediately announcing “a new era in history” and “a grim new chapter in the cold war.” Newsweek called it “The Red Conquest”—with “all the mastery that it implies in the affairs of men on earth.” Why had the United States established no comparable space program? A worried-looking President Eisenhower said at a news conference, “Well, let’s get this straight. I am not a scientist.” The director of the American Institute of Physics seized the occasion to say that unless his country’s science education caught up with the Soviet Union’s, “our way of life is doomed.” That message was heard: Sputnik produced a rapid new commitment to the teaching of science. Magazines focused new attention on American physicists. Among the younger generation, Time singled out Feynman—
Curly-haired and handsome, he shuns neckties and coats, is an enormously dedicated adventurer … became fascinated with samba rhythms … playing bongo drums, breaking codes, picking locks …
and Gell-Mann—
he formulated the “Strangeness Theory,” i.e. assigned physical meanings to the behavior of newly discovered particles. At CalTech Gell-Mann works closely with Feynman on weak couplings. At the blackboard the two explode with ideas like sparks flying from a grindstone, alternately slap their foreheads at each other’s simplifications, quibble over the niceties.
But the physicist who received most of the public’s attention that fall was Edward Teller. He was in tune with the cold war. Sputnik led him to declare—though there was evidence to the contrary—“Scientific and technical leadership is slipping from our hands.” A direct Soviet attack on the United States was possible, but he saw an even greater threat. “I do not think this is the most probable way in which they will defeat us,” he said. He predicted that the Soviet Union would gain a broad technological dominance over the free world. “They will advance so fast in science and leave us so far behind that their way of doing things will be the way, and there will be nothing we can do about it.”
With the winter’s excitement barely waning—the Reader’s Digest had now faced into the wind with an article titled “No Time for Hysteria”—a State Department official let Caltech know that the department would appreciate a presentation at the Geneva conference in the name of both Feynman and Gell-Mann, to balance the expected Soviet scientific presence there. Feynman acquiesced, although the mixing of propaganda and science disturbed him.
He declined to let the State Department make his hotel reservation; he found a walk-up room in an establishment called, in English, Hotel City. It reminded him of the flophouses he had known in Albuquerque and on his cross-country trip with Freeman Dyson. He had hoped to bring a woman with whom he had been having a sporadic and tempestuous yearlong love affair—the wife of a research fellow. She had accompanied him on a trip the summer before, when he was working on weak interactions. Now she agreed to meet him afterward in England but refused to come to Geneva. Instead, he met Gweneth Howarth on the beach.
She told him she was making her way around the world. She was twenty-four years old, the daughter of a jeweler in a town called Ripponden. She had worked as a librarian for a salary of three pounds weekly and then as a yarn tester at a cotton mill before deciding life in the backwaters of Yorkshire was too dull. She let Feynman know that she had two current boyfriends, a semiprofessional miler from Zurich, always in training, and a German optician from Saarbrücken. He immediately invited her to come to California and work for him. He needed a maid, he said. He would sponsor her with the immigration authorities and pay her twenty dollars a week. It seemed to her that he was not behaving like a forty-year-old; nor like other Americans she had met. She said she would consider it, and an unusual courtship began.
“I’ve decided to stay here after all,” she wrote him that fall. One of the boyfriends, Johann, had decided to marry her—out of jealousy, she suspected—
so you see what a good turn you did for me… . we talked for hours and hours, planning our life together. We shall probably start married life living in one room… . Were you really expecting me to come? … You’ll just have to get married again, or find a nice solid middle-aged housekeeper so people won’t gossip.
His love affairs were going badly, meanwhile. That same week a letter arrived from the other woman, making it clear that their relationship was over. She demanded money—five hundred dollars—“I will be frank, the chances of your getting it all back within a year are nil.” She had asked for money before, saying that she needed it for an abortion, but now she said that that had been a ruse. His money had actually gone for furniture and house painting.
You were too much of the “playboy.” But I was both embarrassed & intrigued by the effects that your girl friends had on you when they called you in my presence. Sometimes you left the phone, shaking & foaming at the mouth… . I recognized a baseness in you and was frightened that you too
k my love and affection for you cheaply, and so I wanted to compensate against that horrible feeling.
