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the mathematical framework surrounding his quarks, and SLAC theorists thought of themselves as trying to generalize these tools to smaller distances, higher energies. At accelerators like SLAC, most of the thinking focused on the simplest reactions—two particles in, two particles out—although most of the actual collisions produced enormous flashes of many more particles. Experimenters wanted the most precise possible data, and precision was impossible in these bursts of detritus. Feynman chose a different point of view. He introduced a formalism in which one could look at the distributions of twenty or fifty or more particles. One did not have to be able to measure the momentum of each particle; in effect one could sum over all the possibilities. A Stanford theorist, James D. Bjorken, had been thinking along similar lines. An electron hits a proton; an electron comes out, along with a burst of immeasurable fragments. The emerging electron was a common factor. Bjorken decided to set aside the miscellaneous spray and simply plot the distribution of the energies and angles of the emerging electrons, averaged over many collisions.

He isolated a remarkable regularity in the data, a phenomenon he called “scaling”—the data looked the same at different energy scales. He did not know just how to interpret this. He had a variety of guesses, most framed in the language of current algebra. When Feynman arrived, Bjorken happened to be away; Feynman saw the graphed data without hearing a clear explanation of its origin. He suddenly recognized it, however, and he calculated long into the evening. It could be viewed as a graph of his pancake theory, the theory he had been toying with all summer on his own.

He had decided to cut through the incalculable swarming muddle of proton pieces by positing a mysterious new constituent that he called a parton, a name based inelegantly on the word part. (Finally he had an entry of his own in the Oxford English Dictionary.) Feynman made almost no assumptions about his partons except two: they were pointlike, and they did not interact meaningfully with one another but floated freely about inside the proton. They were an abstraction—just the kind of unobservable entity that physicists hoped not to have to fall back on—yet they were tantalizingly visual in spirit. They were pegs on which to hang a field theory of the old, manageable sort, with wave functions and calculable probability amplitudes. By analogy, quantum electrodynamics had its partons, too: the bare electrons and photons.

Feynman showed that collisions with these hard nuggets inside the proton would produce the scaling relations in a natural manner, unlike collisions with the puffy whole proton. He chose not to decide what quantum numbers they did or did not carry, and he most emphatically decided not to worry one way or the other about whether his partons were the fractionally charged quarks of Gell-Mann and Zweig.

By the time Bjorken returned, he found the theory group awash in partons. Feynman buttonholed him. He had idolized Feynman ever since taking an old-fashioned, historically organized quantum electrodynamics course at Stanford. “When Feynman diagrams arrived,” he said, “it was the sun breaking through the clouds, complete with rainbow and pot of gold. Brilliant! Physical and profound!” Now here was Feynman in the flesh, explaining Bjorken’s own theory to him with a new language and a new visual image. As he could instantly see, Feynman’s essential insight was to place himself once again in the electron, to see what the electron would see at light speed. He would see the protons flashing toward him—and they were therefore flattened relativistically into pancakes. Relativity also slowed their internal clocks, in effect, and, from the electron’s point of view, froze the partons into immobility. His scheme reduced the messy interaction of an electron with a fog of different particles to a much simpler interaction of an electron with a single pointlike parton emerging from the fog. Bjorken’s scaling pattern flowed directly from the