Genius: The Life and Science of Richard Feynman

by James Gleick

For Feynman the most surprising—and oppressive—offer came from the Institute for Advanced Study, Einstein’s institute in Princeton, in the spring. Oppenheimer had now been named as the institute’s director, and he wanted Feynman. H. D. Smyth, Feynman’s old chairman at Princeton, wanted him, too, and the two institutions had sounded him out about a special joint appointment. His anxiety about failing to live up to such expectations was reaching a peak. He experimented with various tactics to break his mental block. For a while he got up every morning at 8:30 and tried to work. Looking in the mirror one morning as he shaved, he told himself the Princeton offer was absurd—he could not possibly accept, and furthermore he could not accept the responsibility for their impression of him. He had never claimed to be an Einstein, he told himself. It was their mistake. For a moment he felt lighter. Some of his guilt seemed to lift away.

A few days later he was eating in the student cafeteria when someone tossed a dinner plate into the air—a Cornell cafeteria plate with the university seal imprinted on one rim—and in the instant of its flight he experienced what he long afterward considered an epiphany. As the plate spun, it wobbled. Because of the insignia he could see that the spin and the wobble were not quite in synchrony. Yet just in that instant it seemed to him—or was it his physicist’s intuition?—that the two rotations were related. He had told himself he was going to play, so he tried to work the problem out on paper. It was surprisingly complicated, but he used a Lagrangian, least-action approach and found a two-to-one ratio in the relationship of wobble and spin. That was satisfyingly neat. Still, he wanted to understand the Newtonian forces directly, just as he had when he was a sophomore taking his first theory course and he provocatively refused to use the Lagrangian approach. He showed Bethe what he had discovered.

But what’s the importance of that? Bethe asked. It doesn’t have any importance, he said. I don’t care whether a thing has importance. Isn’t it fun? It’s fun, Bethe agreed. Feynman told him that was all he was going to do from now on—have fun.

Sustaining that mood took deliberate effort, for in truth he had given up none of his ambition. If he was floundering, so were far more distinguished theoretical physicists, commi...

“I am engaged now in a general program of study—I want to understand (not just in a mathematical way) the ideas of all branches of theor. physics,” he wrote. “As you know I am now struggling with the Dirac Equ.” Despite what he told Bethe, he did make a connection between the axial wobble of a cafeteria plate and the abstract quantum-mechanical notion of spin that Dirac had so successfully incorporated in his electron.

Spin was a problem for Feynman’s theory as he had left it in his Princeton thesis. The quantity of action in ordinary mechanics contained no such property. And his theory would be useless if he could not apply it to a spinning, relativistic electron—the Dirac electron. Among the obstacles blocking his path, this was one of the heaviest. No wonder his eye might have been drawn to things that spun—a cafeteria plate, for example, wobbling in a split-second trajectory. His next step was peculiar and characteristic. He reduced the problem to a skeleton, a universe with just one dimension (or two: one space and one time). This universe was merely a line, and in it a particle could take just one kind of path, back and forth, reversing direction like a crazed insect. Feynman’s goal was to begin with the method he had invented at Princeton—the summing of all possible paths a particle could take—and see whether he could derive, in this one-dimensional world, a one-dimensional Dirac equation.

Feynman did have an extraordinary affinity for his friends’ children. He would entertain them with gibberish, or with juggling tricks, or with what sounded to Dyson like a one-man percussion band. He could enthrall them merely by borrowing someone’s eyeglasses and slowly putting them on, taking them off, and putting them on. Or he would engage them in conversation. He once asked Henry Bethe, “Did you know there are twice as many numbers as numbers?” “No, there are not!” Henry said. Feynman said he could prove it. “Name a number.” “One million.” Feynman said, “Two million.” “Twenty-seven!” Feynman said, “Fifty-four,” and kept on countering with the number that was twice Henry’s, until suddenly Henry saw the point. It was his first real encounter with infinity. For

“It is wrong to think that the task of physics is to find out how nature is,” said Bohr. “Physics concerns only what we can say about nature.” This had always been true. Never before, though, had nature so pointedly rubbed physicists’ noses in it.

Intuition was not just visual but also auditory and kinesthetic. Those who watched Feynman in moments of intense concentration came away with a strong, even disturbing sense of the physicality of the process, as though his brain did not stop with the gray matter but extended through every muscle in his body. A Cornell dormitory neighbor opened Feynman’s door to find him rolling about on the floor beside his bed as he worked on a problem. When he was not rolling about, he was at least murmuring rhythmically or drumming with his fingertips. In part the process of scientific visualization is a process of putting oneself in nature: in an imagined beam of light, in a relativistic electron.

In seeking to analyze his own way of visualizing the unvisualizable he had learned an odd lesson. The mathematical symbols he used every day had become entangled with his physical sensations of motion, pressure, acceleration ... Somehow he invested the abstract symbols with physical meaning, even as he gained control over his raw physical intuition by applying his knowledge of how the symbols could be manipulated.

When I start describing the magnetic field moving through space, I speak of the E- and B- fields and wave my arms and you may imagine that I can see them. I’ll tell you what I see. I see some kind of vague, shadowy, wiggling lines ... and perhaps some of the lines have arrows on them—an arrow here or there which disappears when I look too closely.... I have a terrible confusion between the symbols I use to describe the objects and the objects themselves.

In mid-1947 friends of Feynman persuaded him—threats and cajoling were required—to write for publication the theoretical ideas they kept hearing him explain. When he finally did, he used no diagrams. The result was partly a reworking of his thesis, but it also showed the maturing and broadening of his command of the issues of quantum electrodynamics. He expressed the tenets of his new vision with an unabashed plainness. For some physicists this would be the most influential set of ideas Feynman ever published.

Sealing the paradox, quantum mechanically, is a conclusion that one cannot escape: that each electron “sees,” or “knows about,” or somehow goes through both slits. Classically a particle would have to go through one slit or the other. Yet in this experiment, if the slits are alternately closed, so that one electron must go through A and the next through B, the interference pattern vanishes. If one tries to glimpse the particle as it passes through one slit or the other, perhaps by placing a detector at a slit, again one finds that the mere presence of the detector destroys the pattern.

He plainly admitted that his reformulation of quantum mechanics contained nothing new in the way of results, and he stated even more plainly where he thought the merit lay: “There is a pleasure in recognizing old things from a new point of view. Also, there are problems for which the new point of view offers a distinct advantage.” (For example, when two particles interacted, it became possible to avoid the laborious bookkeeping of two different coordinate systems.) His readers—and at first they were few—found no fancy mathematics, just this shift of vision, a bit of physical intuition laid atop a foundation of clean, classical mechanics.

Feynman’s path-integral view of nature, his vision of a “sum over histories,” was also the principle of least action, the principle of least time, reborn. Feynman felt that he had uncovered the deep laws that gave rise to the centuries-old principles of mechanics and optics discovered by Christiaan Huygens, Pierre de Fermat, and Joseph-Louis Lagrange. How does a thrown ball know to find the particular arc whose path minimizes action? How does a ray of light know to find the path that minimizes time? Feynman answered these questions with images that served not only for the novel mysteries of quantum mechanics but for the treacherously innocent exercises posed for any beginning physics student. Light seems to angle neatly as it passes from air to water. It seems to bounce like a billiard ball off the surface of a mirror. It seems to travel in straight lines. These paths—the paths of least time—are special because they tend to be where the contributions of nearby paths are most closely in phase and most reinforce one another. Far from the path of least time—at the distant edge of a mirror, for example—paths tend to cancel one another out. Yet light does take every possible path, Feynman showed. The seemingly irrelevant paths are always lurking in the background, making their contributions, ready to make their presence felt in such phenomena as mirages and diffraction gratings.

Not even at Princeton, when he lectured to Einstein and Pauli, had Feynman stood before such a concentration of the great minds of his science. He had created a new quantum mechanics almost without reading the old, but he had made two exceptions: he had learned from the work of Dirac and Fermi, both now seated before him. His teachers Wheeler and Bethe were there. So were Oppenheimer, who had built one bomb, and Teller, who was building the next. They had known him as a promising, fearless young light. His thirtieth birthday was seven weeks away.

It was his sum-over-histories theory of physics that claimed his passion. As Dyson saw, it was a grand vision and a unifying vision—too ambitious, he thought. Too many physicists had already stumbled in pursuit of this grail, including Einstein, notoriously. Dyson—more than anyone who heard Feynman at Pocono or attended his occasional seminars at Cornell, more even than Bethe—was beginning to see just how far Feynman sought to reach.

It was essential to his view of things that it must be universal. It must describe everything that happens in nature. You could not imagine the sum-over-histories picture being true for a part of nature and untrue for another part. You could not imagine it being true for electrons and untrue for gravity. It was a unifying principle that would either explain everything or explain nothing.

The Feynman diagram: “The fundamental interaction.” It is a space-time diagram: the progress of time is shown upward on the page. If one covers it with a sheet of paper and then draws the paper slowly upward: • A pair of electrons—their paths shown as solid lines—move toward each other. • When (6) is reached, a virtual photon is emitted by the right-hand electron (wiggly line), and the electron is deflected outward.

Feynman noted that it is arbitrary to think of the photon as being emitted in one place and absorbed in the other: one can say just as correctly that it is emitted at (5), travels backward in time, and is then (earlier) absorbed at (6). The diagram is an aid to visualization. But it serves physicists mainly as a bookkeeping device. Each diagram is associated with a complex number, an amplitude that is squared to produce a probability for the process shown.

There was a grammar of permissible diagrams, corresponding, as Dyson had emphasized, to the permissible mathematical operations. Still, the diagrams could grow arbitrarily complicated, virtual particles appearing and disappearing in an intricate, recursive mesh.

Even so, physicists would shortly find themselves agonizing over pages of diagrams resembling catalogs of knots. They found it was worth the effort; each diagram could replace an effective lifetime of Schwingerian algebra.

Feynman diagrams seemed to depict particles, and they had sprung from a mind focused on a particle-centered style of visualization, but the theory they anchored—quantum field theory—gave center stage to the field. In a sense the paths of the diagrams, and the paths summed in the path integrals, were the paths of the field itself.

South America was on his mind. He had gone so far as to study Spanish. Pan American Airways had opened the continent to American tourists on a large scale, jumping from New York to Rio de Janeiro in thirty-four hours for roughly the price of the fortnight-long ocean voyage,

Words about words: Feynman despised this kind of knowledge more intently than ever, and when he returned to the United States he found out again how much it was a part of American education, a mind-set showing itself not just in the habits of students but in quiz shows, popular what-should-you-know books, and textbook design. He wanted everyone to share his strenuous approach to knowledge. He would sit idly at a café table and cock his ear to listen to the sound sugar made as it struck the surface of his iced tea, something between a hiss and a rustle, and his temper would flare if anyone asked what the phenomenon was called—even if someone merely asked for an explanation. He respected only the not-knowing, first-principles approach: try sugar in water, try sugar in warm tea, try tea already saturated with sugar, try salt ... see when the whoosh becomes a fizz. Trial and error, discovery, free inquiry.

He resented more than just the hollowness of standardized knowledge. Rote learning drained away all that he valued in science: the inventive soul, the habit of seeking better ways to do anything. His kind of knowledge—knowledge by doing—“gives a feeling of stability and reality about the world,” he said, “and drives out many fears and superstitions.” He was thinking now about what science meant and what knowledge meant.

In the streets of Rio he discovered a taste for the Third World and especially for the music, the slang, and the art that was not codified in books or taught in school—at least not American schools. For the rest of his life he preferred traveling to Latin American and Asia. He soon became one of the first American physicists to tour Japan and there, too, headed quickly for the countryside.

Brazilian samba was an African-Latin slum-and-ballroom hybrid, played in the streets and nightclubs by members of clubs facetiously called “schools.” Feynman became a sambista. He joined a local school, Os Farçantes de Copacabana, or, roughly, the Copacabana Burlesquers—though Feynman preferred to translate farçantes as “fakers.” There were trumpets and ukuleles, rasps and shakers, snare drums and bass drums. He tried the pandeiro, a tambourine that was played with the precision and variety of a drum, and he settled on the frigideira, a metal plate that sent a light, fast tinkle in and around the main samba rhythms, the mood shifting from explosive abstract jazz to shameless pop schmaltz. At first he had trouble mastering the fluid wrist torques of the local players, but eventually he showed enough competence to win assignments on paid private jobs. He thought he played with a foreign accent that the other musicians found esoteric and charming. He played in beach contests and impromptu traffic-stopping street parades. The climactic event in the yearly samba calendar was Rio’s carneval in February, the raucous flesh-celebrating festival that fills the nighttime streets with Cariocas half naked or in costume.

Now that quantum electrodynamics had been solved, no single problem seemed as universally compelling. Most theoretical physicists turned convoy fashion toward the smaller atomic distances and smaller time scales at which new particles appeared. They were driven in part by the logic of the past century’s history: each new step inward toward the atom’s core had brought not just new revelations but also a new simplification. The periodic table of elements had once served as a powerful unifying scheme; now it seemed more like a taxonomical catalog, itself unified by the deeper principles revealed by the quest inside the atom. A rhetoric was appearing in popular writing about physics by physicists and journalists: catchwords were fundamental and constituents of matter and building blocks of nature and innermost sanctum of matter. The phrases were seductive. Other kinds of science sought laws of nature, but a kind of priority seemed to belong to the search for elementary units.

The year before, Schrieffer had listened intently as Feynman delivered a pellucid talk on the two phenomena: the problem he had solved, and the problem that had defeated him. Schrieffer had never heard a scientist outline in such loving detail a sequence leading to failure. Feynman was uncompromisingly frank about each false step, each faulty approximation, each flawed visualization.

This particle’s ephemerality made it less consequential in the everyday world of tables and chairs, chemistry and biology, than on this exciting frontier: it typically vanished after a lifetime of a tenth of a millionth of a billionth of a second. This qualified as a short time by 1950 standards. Yet standards were changing. Within a few years particle tabulations would list this fleeting entity in the category of STABLE.

It also required not just honesty, but a sense that honesty required exertion.

“I think if he had not been so quick people would have treated him as a brilliant quasi-crank, because he did spend a substantial amount of time going down what later turned out to be dead ends,” said Sidney Coleman, a theorist who first knew Feynman at Caltech in the fifties.

Feynman continued to refuse to read the current literature, and he chided graduate students who would begin their work on a problem in the normal way, by checking what had already been done. That way, he told them, they would give up chances to find something original.

Nor could one measure imagination as certain psychologists try to do, by displaying a picture and asking what will happen next. For Feynman the essence of the scientific imagination was a powerful and almost painful rule. What scientists create must match reality. It must match what is already known. Scientific creativity, he said, is imagination in a straitjacket. “The whole question of imagination in science is often misunderstood by people in other disciplines,” he said. “They overlook the fact that whatever we are allowed to imagine in science must be consistent with everything else we know....” This is a conservative principle, implying that the existing framework of science is fundamentally sound, already a fair mirror of reality.

Feynman said, “Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there.”

Feynman seemed to hoard shadow pools of ignorance, seemed to protect himself from the light like a waking man who closes his eyes to preserve a fleeting image left over from a dream. He said later, “Maybe that’s why young people make success. They don’t know enough. Because when you know enough it’s obvious that every idea that you have is no good.” Welton, too, was persuaded that if Feynman had known more, he could not have innovated so well.

“Would I had phrases that are not known, utterances that are strange, in new language that has not been used, free from repetition, not an utterance which has grown stale, which men of old have spoken.” An Egyptian scribe fixed those words in stone at the very dawn of recorded utterance—already jaded, a millennium before Homer.

Are the latter-day Mozarts not being born, or are they all around, bumping shoulders with one another, scrabbling for cultural scraps, struggling to be newer than new, their stature inevitably shrinking all the while?

The power of genius may lie, as Merton suggests, in the ability of one person to accomplish what otherwise might have taken dozens. Or perhaps it lies—especially in this exploding, multifarious, information-rich age—in one person’s ability to see his science whole, to assemble, as Newton did, a vast unifying tapestry of knowledge. Feynman himself, as he entered his forties, prepared to undertake this very enterprise: a mustering and a reformulating of all that was known about physics.

He owned neither a radio nor a television. He carried pens in a standard slip-in shirt-pocket protector. He taught himself to keep keys, tickets, and change always in the same pocket so that he would never have to give them an instant’s thought.

He felt well acquainted with the essence of evaluating experiments—as he said, “understanding when a thing is really known and when it is not really known.” He could see at once how the centrifuge worked and how ultraviolet absorption would show how much DNA remained in a test tube. Biology was messier—things grew and wiggled, and he found it difficult to repeat experiments as exactly as he wished. He focused on a particular mutation of the T4 virus called rII.

Tools for directly examining the genetic sequence, letter by letter, base pair by base pair, did not exist. But by painstakingly crossing the idiot r’s with the original virus, Feynman was able to show that his second guess was correct: two mutations, situated close to each other on the gene, were interacting. Furthermore, he showed that the second mutation had the same character as the first; it was another rII mutation. He had discovered a new phenomenon, mutations that suppressed each other within the same gene. Friends of his in the laboratory called these “Feyntrons” and tried to persuade him to write up his work for publication. Elsewhere, discovered independently, the phenomenon came to be called intragenic suppression. Feynman could not explain it.

The difficulty, from an experimentalist’s perspective, was that gravity was so weak compared to the other forces. A bare handful of electrons can create a palpable electromagnetic force, while it takes a mass as great as the earth to create the gravity that draws a leaf from a tree. The orders of magnitude separating these forces strain the imagination and cause immense mathematical difficulties for theorists trying to reconcile them. The difference is 1042, a number that defied even Feynman’s ability to find illustrative analogies. “The gravitational force is weak,” he said at one conference, introducing his work on quantizing gravity. “In fact, it’s damned weak.” At that instant a loudspeaker demonically broke loose from the ceiling and crashed to the floor. Feynman barely hesitated: “Weak—but not negligible.”

Feynman’s path integrals might prove to be more than a method, more than an equivalent alternative formulation: “the real foundation of quantum mechanics and thus of physical theory.”

Nanotechnologists, partly inspired and partly crackpot, made tiny silicon gears with carefully etched teeth and displayed them proudly in their microscopes; or imagined tiny self-replicating robot doctors that would swim through one’s arteries. They thought of Feynman as their spiritual father, although he himself never returned to the subject.

If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.

The course was a magisterial achievement: word was spreading through the scientific community even before it ended. But it was not for freshmen.

As the course wore on, attendance by the kids at the lectures started dropping alarmingly, but at the same time, more and more faculty and graduate students started attending, so the room stayed full, and Feynman may never have known he was losing his intended audience.

This was the world according to Feynman. No scientist since Newton had so ambitiously and so unconventionally set down the full measure of his knowledge of the world—his own knowledge and his community’s.