Genius (15 page)

Developing a theory for reflection by multiple-layer thin films was not so different for Feynman from math team in the now-distant past of Far Rockaway. He could see, or feel, the intertwined infinities of the problem, the beam of light resonating back and forth between the pair of surfaces, and then the next pair, and so on, and he had a giant mental kit bag of formulas to try out. Even when he was fourteen he had manipulated series of continued fractions the way a pianist practices scales. Now he had an intuition for the translating of formulas into physics and back, a feeling for the rhythms or the spaces or the forces that a given set of symbols implied. In his senior year the mathematics department asked him to join a team of three entrants to the nation’s most difficult and prestigious mathematics contest, the Putnam competition, then in its second year. (The top five finishers are named as Putnam Fellows and one receives a scholarship at Harvard.) The problems were intricate exercises in calculus and algebraic manipulation; no one was expected to complete them all satisfactorily in the allotted time. In some years the median has been zero—more than half the entrants fail to solve a single problem. One of Feynman’s fraternity brothers was surprised to see him return home while the examination was still going on. Feynman learned later that the scorers had been astounded by the gap between his result and the next four. Harvard sounded him out about the scholarship, but he told them he had already decided to go elsewhere: to Princeton.

His first thought had been to remain at MIT. He believed that no other American institution rivaled it and he said so to his department chairman. Slater had heard this before from loyal students whose provincial world contained nothing but Boston and the Tech, or the Bronx and the Tech, or Flatbush and the Tech. He told Feynman flatly that he would not be allowed back as a graduate student—for his own good.

Slater and Morse communicated directly with their colleagues at Princeton in January 1939, signaling that Feynman was something special. One said his record was “practically perfect,” the other that he had been “the best undergraduate student we have had in the Physics Department for five years at least.” At Princeton, when Feynman’s name came up in the deliberations of the graduate admissions committee, the phrase “diamond in the rough” kept materializing out of the wash of conversation. The committee had seen its share of one-sided applicants but had never before admitted a student with such low scores in history and English on the Graduate Record Examination. Feynman’s history score was in the bottom fifth, his literature score in the bottom sixth; and 93 percent of those who took the test had given better answers about fine arts. His physics and mathematics scores were the best the committee had seen. In fact the physics score was perfect.

Princeton had another problem with Feynman, as the head of its department, H. D. Smyth, made clear to Morse. “One question always arises, particularly with men interested in theoretical physics,” Smyth wrote.

Is Feynman Jewish? We have no definite rule against Jews but have to keep their proportion in our department reasonably small because of the difficulty of placing them.

By March no word had come and Slater was concerned enough to write Smyth again, collegially: “Dear Harry … definitely the best undergraduate we have had for a number of years … first-rate both in matters of scholarship and personality …” The recommendation was formal and conventional, but in a handwritten postscript that would not appear on the carbon copies Slater got to the point: “Feynman of course is Jewish …” He wanted to assure Smyth there were mitigating circumstances:

… but as compared for instance with Kanner and Eisenbud he is more attractive personally by several orders of magnitude. We’re not trying to get rid of him—we want to keep him, and privately hope you won’t give him anything. But he apparently has decided to go to Princeton. I guarantee you’ll like him if he does.

Morse, too, reported that Feynman’s “physiognomy and manner, however, show no trace of this characteristic and I do not believe the matter will be any great handicap.”

On the eve of the Second World War institutional anti-Semitism remained a barrier in American science, and a higher barrier for graduate schools than colleges. At universities a graduate student, unlike an undergraduate, was as much hired as admitted to a department; he would be paid for teaching and research and would be on a track for promotion. Furthermore, graduate departments considered themselves responsible to the industries they fed, and the industrial companies that conducted most research in the applied sciences were largely closed to Jews. “We know perfectly well that names ending in ‘berg’ or ‘stein’ have to be skipped,” the chairman of Harvard’s chemistry department, whose name was Albert Sprague Coolidge, said in 1946. Admissions quotas had been imposed broadly in the twenties and thirties, with immigrant children seeking admission to college in greater numbers. The case against Jews rarely had to be articulated. It was understood that their striving, their pushiness, smelled of the tenement. It was unseemly. “They took obvious pride in their academic success… . We despised the industry of those little Jews,” a Harvard Protestant wrote in 1920. Thomas Wolfe, himself despising the ambition of “the Jew boy,” nevertheless understood the attraction of the scientific career: “Because, brother, he is burning in the night. He sees the class, the lecture room, the shining apparatus of gigantic laboratories, the open field of scholarship and pure research, certain knowledge and the world distinction of an Einstein name.” It was also understood that a professor needed a certain demeanor to work well with students; that Jews were often soft-spoken and diffident or, contradictorily, so brilliant as to be impatient and insensitive. In the close, homogenous university communities, code words were
attractive
or
nice
. Even the longtime chairman of J. Robert Oppenheimer’s department at the University of California at Berkeley, Raymond T. Birge, was quoted as saying of Oppenheimer, “New York Jews flocked out here to him, and some were not as nice as he was.”

Feynman, as a New York Jew distinctly uninterested in either the faith or the sociology of Judaism, did not give voice to any awareness of anti-Semitism. Princeton did accept him, and from then on he never had occasion to worry about the contingencies of academic hiring. Still, when he was at MIT, the Bell Telephone Laboratories turned him down for summer jobs year after year, despite recommendations by William Shockley, Bell’s future Nobel laureate. Bell was an institution that hired virtually no Jewish scientists before the war. Birge himself eventually had an opportunity to hire Feynman for Berkeley: a frustrated Oppenheimer was recommending him urgently, but Birge put off a decision for two years, until it was too late. In the first case anti-Semitism may have played the deciding role; in the second case perhaps a smaller role. If Feynman ever suspected that his religion might have shifted the path of his career, he declined to say so.

Forces in Molecules

Thirteen physics majors completed senior theses in 1939. The world of accumulated knowledge was still small enough that MIT could expect a thesis to represent original and possibly publishable work. The thesis should begin the scientist’s normal career and meanwhile supply missing blocks in the wall of organized knowledge, by analyzing such minutiae as the spectra of singly ionized gadolinium or hydrated manganese chloride crystals. (Identifying the telltale combinations of wavelengths emitted by such substances still required patience and good experimental technique, and science seemed to be engendering new substances as fast as spectroscopists could analyze them.) Seniors could devise new laboratory instruments or investigate crystals that produced electrical currents when squeezed. Feynman’s thesis began as a circumscribed problem like these. It ended as a fundamental discovery about the forces acting within the molecules of any substance. If it bore little connection to his greater work that followed—and Feynman himself dismissed it as an obvious result that he should have written in “half a line”—it nevertheless found its way into the permanent tool kit of the physics of solids.

Although he did not know it, his quantum-mechanics professor, Morse, had recommended in his junior year that the department graduate him a year early. The suggestion was turned down, and Slater himself became Feynman’s thesis adviser. Slater proposed a problem that at first seemed not much deeper than most senior theses. The question could almost have come from a physics and chemistry handbook: Why does quartz expand so little when heated? Compared to metals, for example, why is its coefficient of expansion so small? Any substance expands because heat agitates its molecules—heat is the agitation of its molecules—but in a solid the details of the expansion depend on the actual molecular layout. A crystal, with its molecules in a regular geometrical array, can expand more along one axis than another. Typically scientists would represent a crystalline structure with a Tinkertoy model, balls stuck on rods, but real matter is not so rigid. Atoms may be more or less locked in an array, or they may swing or float more or less freely from one place to another. Electrons in a metal will swarm freely about. The color, the texture, the rigidity, the frangibility, the conductivity, the softness, the taste of a substance all depend on the local habits of atoms. Those habits in turn depend on the forces at work within a substance—forces both classical and quantum mechanical—and when Feynman began his thesis work those forces were not well understood, even in quartz, the most common mineral on earth.

An old-fashioned steam engine was regulated by a mechanical governor: a pair of iron balls swinging outward from a spinning shaft. The faster it spun, the farther outward they would swing. But the farther they would swing, the harder they would make it to spin the shaft. Feynman started by imagining some analogous effect in the atoms of quartz, silicon dioxide, a pair of oxygen atoms clinging to each atom of silicon. Instead of spinning, the silicon atoms were vibrating; as the quartz grew warmer, he thought that the oxygen atoms might provide a mechanical force that would pull inward against the increasing agitation of the molecules, thus compensating somehow for the ordinary expansion. But how could the forces within each molecule—forces that varied in different directions—be calculated? No straightforward method seemed to exist.

He had never thought about molecular structure in such detail before. He taught himself everything he could about crystals, their standard arrangements, the geometries and the symmetries, the angles between atoms. It all came down to one unknown, he realized: the nature of the forces pressing the molecules into particular alignments. In its search for fundamental laws ever farther down the hierarchy of sizes, physics had now reached a level where molecular forces should be coming into focus. Scientists could measure how much pressure it took to squeeze quartz a given distance in a given direction. With the still-new technique of X-ray diffraction, they could look at the shadow patterns of a regular crystal and deduce its structure. As some theorists continued to look even deeper toward the atom’s core, others now tried applying the quantum techniques to questions of structure and chemistry. “A science of materials as distinct from matter became possible,” a scholar of structure, Cyril Stanley Smith, who worked with Feynman a few years later as the chief metallurgist on the secret project at Los Alamos, said of this time. From atomic forces to the stuff that feeds our senses—that was the connection waiting to be made. From abstract energy levels to three-dimensional forms. As Smith added epigrammatically, “Matter is a holograph of itself in its own internal radiation.”

Forces or energy—that was the choice for those seeking to apply the quantum understanding of the atom to the workings of real materials. At stake was not mere terminology but a root decision about how to conceive of a problem and how to proceed in calculating.

The conception of nature in terms of forces went back to Newton. It was a direct way of dealing with the world, envisioning firsthand interactions between objects. One exerts a force on another. A distinction between force and energy did not emerge clearly until the nineteenth century, and then, gradually, energy began to take over as the fulcrum of scientists’ thinking. Force is, in modern terms, a vector quantity, with both a magnitude and a direction. Energy is directionless, scalar—meaning that it has a magnitude only. With the rise of thermodynamics energy came to the fore. It began to seem more fundamental. Chemical reactions could be neatly computed as operations designed to minimize energy. Even a ball rolling down a hill—moving from a state of higher to lower potential energy—was seeking to minimize its energy. The Lagrangian approach that Feynman resisted in his sophomore-year physics class also used a minimum of energy to circumvent the laborious calculation of direct interactions. And the law of conservation of energy provided a tidy bookkeeping approach to a variety of calculations. No comparable law existed for forces.

Yet Feynman continued to seek ways of using the language of forces, and his senior thesis evolved beyond the problem Slater had posed. As Feynman conceived the structure of molecules, forces were the natural ingredients. He saw springlike bonds with varying stiffness, atoms attracting and repelling one another. The usual energy-accounting methods seemed secondhand and euphemistic. He titled his thesis—grandly—“Forces and Stresses in Molecules” and began by arguing that it would be more illuminating to attack molecular structure directly by means of forces, intractable though that approach had been considered in the past.

Quantum mechanics had begun with energy for two reasons, he contended. One was that the original quantum theorists had habitually tested their formulas against a single type of application, the calculation of the observed spectra of light emitted by atoms, where forces played no obvious part. The other was that the wave equation of Schrödinger simply did not lend itself to the calculation of vector quantities; its natural context was the directionless measurement of energy.