Genius_ The Life and Science of Richard Feynman - James Gleick [259]
In the year of Feynman’s death, a pair of experimental physicists introduced a text with the simple declaration, “Fifty years of particle physics research has produced an elegant and concise theory of particle interactions at the subnuclear level.” Particle-physics outsiders could be less generous. Elegant and concise? Why, then, did so many particle masses and other specific numerical parameters have to be fed into the theory, rather than read out? Why so many overlapping fields, so many symmetries broken—it seemed—as necessary to fit the data? Quantum numbers such as color and charm might be elegant simplifications, or they might be last-minute rubber bands applied to joints that had threatened to spring loose. And if theorists explained quark confinement, justifying a kind of particle that could never stand on its own, they surely could explain anything. Was the theory rigged—as one critic put it provocatively, “a contrived intellectual structure, more an assembly of successful explanatory tricks and gadgets … than a coherently expressed understanding of experience”?Although each piece of the theory might have been tested against experiment, the whole theory—the style of theory making—had become resistant to disproof. It was hard to imagine phenomena that could not be explained with a new symmetry breaking, a new quantum number, or a few extra spatial dimensions. Perhaps the spare-parts department of modern physics was so well stocked with ingenious devices that a serviceable engine could now be devised to handle any data the particle accelerators could offer.
This was a harsh critique—not Feynman’s. Still, in another time, Feynman had spoken of the search for the fundamental laws of nature. No longer:
People say to me, “Are you looking for the ultimate laws of physics?” No, I’m not… . If it turns out there is a simple ultimate law which explains everything, so be it—that would be very nice to discover. If it turns out it’s like an onion with millions of layers … then that’s the way it is.
He believed that his colleagues were claiming more success at unification than they had achieved—that disparate theories had been pasted together tenuously. When Hawking said, “We may now be near the end of the search for the ultimate laws of nature,” many particle physicists agreed. But Feynman did not. “I’ve had a lifetime of that,” he said on another occasion. “I’ve had a lifetime of people who believe that the answer is just around the corner.”
But again and again it’s been a failure. Eddington who thought that with the theory of electrons and quantum mechanics everything was going to be simple … Einstein, who thought that he had a unified theory just around the corner but didn’t know anything about nuclei and was unable of course to guess it… . People think they’re very close to the answer, but I don’t think so… .
Whether or not nature has an ultimate, simple, unified, beautiful form is an open question, and I don’t want to say either way.
In the 1980s a mathematically powerful and experimentally untestable attempt at unification emerged in the form of string theory, using stringlike entities wrapped through many dimensions as their fundamental objects. The extra dimensions are supposed to fold themselves out of the way in a kind of symmetry breaking given the name compactification. String theory relies on Feynman’s sum-over-histories method as an essential underlying principle; the theory views particle events as topological surfaces and computes probability amplitudes by summing over all possible surfaces. Feynman kept his distance, sometimes saying that perhaps he was too old to appreciate the new fashion. String theory seemed too far from experiment. He suspected that the string theorists were not trying hard enough to prove themselves wrong. In the meantime he never adopted the rhetoric of GUT’s. It made him uncomfortable. He retreated into the stance that he himself merely solved problems as they came along.
When a historian