Leonard Mlodinow

Feynman's Rainbow
by Leonard Mlodinow

IN A GRAY CEMENT building on the olive tree-lined Caltech campus on California Boulevard in Pasadena, a thin man with longish hair steps into his modest office. Some students, on this planet less than one-third as long as the professor has been, stop in the hallway and stare. No one would say a word if he didn't come to the office this day, but nothing could keep him away, especially not the surgery, the effects of which he would no longer allow to ruin his routine.

Outside, bright sun bathes the palm trees, but it is no longer the withering sun of the summer. The hills rise, brown now giving way to green, their vegetation reborn with the coming of the more hospitable winter season. The professor might have wondered how many more cycles of green and brown he would live to witness; he knew he had a disease that would kill him. He loved life, but he believed in natural law, and not in miracles. When his rare form of cancer was first discovered in the summer of 1978, he had searched the literature. Five-year survival rates were generally reported to be less than 10 percent. Virtually no one survived ten years. He was into his fourth.

Some forty years earlier, when he was almost as young as the students currently around him, he had sent a series of papers to the prestigious journal Physical Review. The papers contained odd little diagrams, which constituted a new way of thinking about quantum mechanics, less formal than the standard mathematical language of physics. Though few seemed convinced of his new approach, he thought how amusing it would be if some day that journal would be full of his diagrams. As it turned out, the method they reflected proved to be not only correct and useful, but revolutionary, and on that day late in 1981, in the Physical Review, his diagrams were ubiquitous. They were about as famous as diagrams get. And he was about as famous, at least in the world of science, as scientists get.

The professor has been working on a new problem the past couple of years. The method he worked out in his student days had been wildly successful when applied to a theory called quantum electrodynamics. That is the theory of the electromagnetic force that governs, among other things, the behavior of the electrons that orbit the nucleus of the atom. These electrons impart to atoms their chemical properties and their spectral properties (the colors of light they emit and absorb). Hence the study of these particular electrons and their behavior is called atomic physics. But since the professor's student days physicists had made great progress in a new field called nuclear physics. Nuclear physics looks beyond the electronic structure of atoms to the potentially much more violent interactions of the protons and neutrons within the nucleus. Though protons are subject to the same electromagnetic force that governs the behavior of the atomic electrons, these interactions are dominated by a new force, a force that is far stronger than the electromagnetic force. It is called, fittingly, the "strong force."

To describe the strong force a grand new theory had been invented. The new theory had some mathematical similarities to quantum electrodynamics, and it was given a name that reflected these similarities- quantum chromodynamics (despite the root, chromo, it has nothing to do with color as we know it). In principle quantum chromodynamics provided a precise quantitative description of protons, neutrons, and related particles and how they interact-how they might bind to each other, or behave in collisions. But how do we extract descriptions of these processes from the theory? The professor's approach applied in principle to this new theory but practical complications arose. Though quantum chromodynamics had had certain triumphs, for many situations neither the professor nor anyone else knew how to use his diagrams- or any other method-to extract accurate numerical predictions from the theory. Theorists couldn't even calculate the mass of the proton-a very basic quantity that had long ago been accurately measured by the experimentalists.

The professor thinks, perhaps, that with the months or years he has left on earth he'll play around with the problem of quantum chromodynamics, considered one of the most important of its day. To create the "Feynman's Rainbow" and will he needs for his effort, he tells himself that everyone else who had for so many years unsuccessfully attacked this problem lacked certain qualities that he possesses. What they are he, Richard Feynman, isn't sure: an oddball approach, perhaps. Whatever those qualities are, they had served him well-he had one Nobel Prize, but might arguably have deserved two or three when you considered all the wide-ranging and important breakthroughs he had made in his career.

Meanwhile, in 1980, several hundred miles north in Berkeley, a much younger man had sent off a couple papers with his own new approach to solving some of the old mysteries of atomic physics. His method offered answers to some difficult problems, but there was a catch. The world he explored in his imagination was one in which space has an infinite number of dimensions. It is a world with not just up/down, right/left, and forward/backward, but also a countless array of other directions. Could you really say anything useful about our three-dimensional existence by studying a universe like that? And could the method be extended to other areas of study, such as the more modern field of nuclear physics? It would turn out that it is promising enough that this student received a beginning faculty appointment at Caltech, and an office down the hall from Feynman.

The night after receiving that offer of employment, I remembered lying in my bed half my life earlier, wondering what it would be like the next day, my first day in junior high. More than anything else, as I recall, I was worried about gym and showering in front of all those other boys. What I was really worried about was ridicule. I would be exposed, too, at Caltech. In Pasadena there would be no faculty advisor, no mentor, just my own answers to the hardest problems the best physicists could think of. To me, a physicist who didn't produce brilliant ideas was one of the living dead. At a place like Caltech, he would also be shunned, and soon unemployed.

Did I have it or didn't I? Or was I asking the wrong question? I started talking to the thin, dying professor with long hair in an office down the hall. What the old man told me is the subject of this book.

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