by American Prometheus: The Triumph;Tragedy of J. Robert Oppenheimer
Even after Lawrence married, Oppie was a frequent dinner guest, invariably bringing orchids for Ernest’s wife, Molly. When Molly gave birth to their second son, Ernest insisted on naming the boy Robert. Molly acquiesced, but over the years she grew to think of Oppenheimer as somewhat faux, a man whose elaborate affectations betrayed a certain shallowness of character. Early in her marriage, she did not come between the two friends; but later, when circumstances changed, Molly would push her husband to see Oppie in a different light.
Lawrence was a builder—and he had the fundraising skills to realize his ambitions. In the months before meeting Oppenheimer, he had conceived the notion of building a machine capable of penetrating the so far unassailable nucleus of the atom, which existed, he quipped, “like a fly inside a cathedral.” And not only was the nucleus tiny and elusive, it was also protected by a skin called the Coulomb barrier. Physicists estimated that it would take a stream of hydrogen ions, propelled with the potential of perhaps a million volts, to penetrate it. Generating such levels of high energy seemed an impossibility in 1929; but Lawrence conceived of a way around the impossible. He suggested that a machine could be built that used relatively small 25,000-volt potential to accelerate protons back and forth in an alternating electric field. By means of vacuum tubes and an electromagnet, the ion particles might then be accelerated by the electric field to greater and greater speeds along a spiral path. He was not sure how big an accelerator had to be to penetrate an atom’s nucleus—but he was convinced that with a large enough magnet and a big enough circular chamber, he could break the million-volt mark.
By early 1931, Lawrence had built his first crude accelerator, a machine with a small 4.5-inch chamber within which he generated 80,000-volt protons. A year later, he had an eleven-inch machine that produced million-volt protons. Lawrence now dreamed of building ever bigger accelerators, machines weighing many hundreds of tons and costing tens of thousands of dollars. He coined a new name for his invention, the “cyclotron,” and persuaded the president of the University of California, Robert Gordon Sproul, to give him an old wooden building adjacent to LeConte Hall, the physics building that sat high on the upper end of Berkeley’s beautiful campus. Lawrence named it the Berkeley Radiation Laboratory. Theoretical physicists around the world soon realized that what Lawrence had created in his “Rad Lab” would allow them to explore the innermost reaches of the atom. In 1939, Lawrence won the Nobel Prize for physics.
Lawrence’s relentless drive for ever larger and more powerful cyclotrons epitomized the trend toward the kind of “big science” associated with the rise of corporate America in the early twentieth century. Only four industrial laboratories existed in the country in 1890; forty years later there were nearly one thousand such facilities. In most of these labs a culture of technology, not science, was supreme. Over the years, theoretical physicists like Oppenheimer, devoted to pure “small” science, would find themselves alienated from the culture of these big labs, which were often devoted to “military science.” Even in the 1930s, however, some young physicists couldn’t stand the atmosphere. Robert Wilson, a student of both Oppenheimer and Lawrence, decided to leave Berkeley for Princeton, having concluded that the science associated with these big machines was “an activity that epitomized team research at its worst.”
Building cyclotrons with eighty-ton magnets required large sums of money. But Lawrence was adept at enlisting financial support from such Berkeley regents as oil entrepreneur Edwin Pauley, banker William H. Crocker and John Francis Neylan, a national power broker who happened to be William Randolph Hearst’s chief counsel. In 1932, President Sproul sponsored Lawrence for membership in San Francisco’s elite Bohemian Club, a fraternity of California’s most influential businessmen and politicians. The members of the Bohemian Club would never have thought to welcome Robert Oppenheimer; he was Jewish and too otherworldly. But the Midwestern farm boy Lawrence slipped effortlessly into this elite society. (Later, Neylan got Lawrence into the even more exclusive Pacific Union Club.) Gradually, as Lawrence repeatedly took the money of these powerful men, he found himself also sharing their conservative, anti–New Deal politics.
By contrast, Oppenheimer had a laissez-faire attitude toward the role of money in his own research. When one of his graduate students wrote him for help in raising money for a particular project, Oppie replied whimsically that such research, “like marriage and poetry, should be discouraged and should occur only despite such discouragement.”
On February 14, 1930, Oppenheimer finished writing a seminal paper, “On the Theory of Electrons and Protons.” Drawing on Paul Dirac’s equation on the electron, Oppenheimer argued that there had to be a positively charged counterpart to the electron—and that this mysterious counterpart should have the same mass as the electron itself. It could not, as Dirac had suggested, be a proton. Instead, Oppenheimer predicted the existence of an “anti-electron—the positron.” Ironically, Dirac had failed to pick up on this implication in his own equation, and he willingly gave Oppenheimer the credit for this insight—which soon impelled him, Dirac, to propose that perhaps there existed “a new kind of particle, unknown to experimental physics, having the same mass and opposite charge to an electron.” What he was very tentatively proposing was the existence of antimatter. Dirac suggested naming this elusive particle an “anti-electron.”
Initially, Dirac himself was not at all comfortable with his own hypothesis. Wolfgang Pauli and even Niels Bohr emphatically rejected it. “Pauli thought it was nonsense,” Oppenheimer later said. “Bohr not only thought it was nonsense but was completely incredulous.” It took someone like Oppenheimer to push Dirac into predicting the existence of antimatter. This was Oppenheimer’s penchant for original thinking at its best. In 1932 the experimental physicist Carl Anderson proved the existence of the positron, the positively charged antimatter counterpart to the electron. Anderson’s discovery came fully two years after Oppenheimer’s calculations suggested its theoretical existence. A year later, Dirac won his Nobel Prize.
Physicists around the globe were racing to solve the same set of problems, and the competition to be first was fierce. Oppenheimer proved to be a productive dilettante in this race. Working with a small number of students, he still managed to skip from one critical problem to another just in time to publish a short letter on a particular topic a month or two ahead of the competition. “It was amazing,” recalled one Berkeley colleague, “that Oppenheimer and his group essentially got something on all these problems, about the same time as the competition.” The result might not be elegant or even particularly accurate in all the details—others would have to come along and clean up his work. But Oppenheimer invariably had the essence. “Oppie was extremely good at seeing the physics and doing the calculation on the back of the envelope and getting all the main factors. . . . As far as finishing and doing an elegant job like Dirac would do, that wasn’t Oppie’s style.” He worked “fast and dirty, like the American way of building a machine.”
In 1932, Ralph Fowler, one of Oppie’s former teachers from Cambridge, England, visited Berkeley and had a chance to observe his old student. In the evenings, Oppie persuaded Fowler to play his particularly complicated version of tiddlywinks for hours on end. Some months later, at a time when Harvard was trying to recruit Oppenheimer away from Berkeley, Fowler wrote that “his work is apt to be full of mistakes due to lack of care, but it is work of the highest originality and he had an extremely stimulating influence in a theoretical school as I had ample opportunity of learning last fall.” Robert Serber agreed: “His physics was good, but his arithmetic awful.”
Robert did not have the patience to stick with any one problem very long. As a result, it was frequently he who opened the door through which others then walked to make major discoveries. In 1930 he wrote what would become a well-known paper on the infinite nature of spectral lines using direct theory. A splitting of the line in a spectrum of hydrogen suggested a small difference in the energy levels of tw
o possible states of the hydrogen atom. Dirac had argued that these two states of hydrogen should have precisely the same energy. In his paper, Oppenheimer disagreed, but his results were inconclusive. Years later, however, an experimental physicist, Willis E. Lamb, Jr., one of Oppenheimer’s doctoral students, resolved the issue. The so-called “Lamb shift” correctly attributed the difference between the two energy levels to the process of self-interaction—whereby charged particles interact with electromagnetic fields. Lamb won a Nobel Prize in 1955, in part for his precise measurement of the Lamb shift, a key step in the development of quantum electrodynamics.
During these years, Oppenheimer wrote important, even seminal, papers on cosmic rays, gamma rays, electrodynamics and electron-positron showers. In the field of nuclear physics, he and Melba Phillips calculated the yield of protons in deuteron reactions. Phillips, an Indiana farm girl, born in 1907, was Oppenheimer’s first doctoral student. Their calculations on proton yields became widely known as the “Oppenheimer-Phillips process.” “He was an idea man,” recalled Phillips. “He never did any great physics, but look at all the lovely ideas that he worked out with his students.”
Physicists today agree that Oppenheimer’s most stunning and original work was done in the late 1930s on neutron stars—a phenomenon astronomers would not actually be able to observe until 1967. His interest in astrophysics was initially sparked by his friendship with Richard Tolman, who introduced him to astronomers working at Pasadena’s Mt. Wilson Observatory. In 1938, Oppenheimer wrote a paper with Robert Serber titled “The Stability of Stellar Neutron Cores,” which explored certain properties of highly compressed stars called “white dwarfs.” A few months later, he collaborated with another student, George Volkoff, on a paper titled “On Massive Neutron Cores.” Laboriously deriving their calculations from slide rules, Oppenheimer and Volkoff suggested there was an upper limit—now called the “Oppenheimer-Volkoff limit”—to the mass of these neutron stars. Beyond this limit they would become unstable.
Nine months later, on September 1, 1939, Oppenheimer and a different collaborator—yet another student, Hartland Snyder—published a paper titled “On Continued Gravitational Contraction.” Historically, of course, the date is best known for Hitler’s invasion of Poland and the start of World War II. But in its quiet way, this publication was also a momentous event. The physicist and science historian Jeremy Bernstein calls it “one of the great papers in twentieth-century physics.” At the time, it attracted little attention. Only decades later would physicists understand that in 1939 Oppenheimer and Snyder had opened the door to twenty-first-century physics.
They began their paper by asking what would happen to a massive star that has begun to burn itself out, having exhausted its fuel. Their calculations suggested that instead of collapsing into a white dwarf star, a star with a core beyond a certain mass—now believed to be two to three solar masses—would continue to contract indefinitely under the force of its own gravity. Relying on Einstein’s theory of general relativity, they argued that such a star would be crushed with such “singularity” that not even light waves would be able to escape the pull of its all-encompassing gravity. Seen from afar, such a star would literally disappear, closing itself off from the rest of the universe. “Only its gravitation field persists,” Oppenheimer and Snyder wrote. That is, though they themselves did not use the term, it would become a black hole. It was an intriguing but bizarre notion—and the paper was ignored, with its calculations long regarded as a mere mathematical curiosity.
Only since the early 1970s, when the technology of astronomical observation caught up with theory, have numerous such black holes been detected by astronomers. At that time, computers and technical advances in radio telescopes made black-hole theory the centerpiece of astrophysics. “Oppenheimer’s work with Snyder is, in retrospect, remarkably complete and an accurate mathematical description of the collapse of a black hole,” observed Kip Thorne, a Caltech theoretical physicist. “It was hard for people of that era to understand the paper because the things that were being smoked out of the mathematics were so different from any mental picture of how things should behave in the universe.”
Characteristically, however, Oppenheimer never took the time to develop anything so elegant as a theory of the phenomenon, leaving this achievement to others decades later. And the question remains: Why? Personality and temperament appear to be critical. Robert instantly saw the flaws in any idea almost as soon as he had conceived it. Whereas some physicists—Edward Teller immediately comes to mind—boldly and optimistically promoted all of their new ideas, regardless of their flaws, Oppenheimer’s rigorous critical faculties made him profoundly skeptical. “Oppie was always pessimistic about all the ideas,” recalled Serber. Turned on himself, his brilliance denied him the dogged conviction that is sometimes necessary for pursuing and developing original theoretical insights. Instead, his skepticism invariably propelled him on to the next problem.5 Having made the initial creative leap, in this case to black-hole theory, Oppenheimer quickly moved on to another new topic, meson theory.
Years later, Robert’s friends and peers in the world of physics, who generally agreed that he was brilliant, would ruminate on why he never won a Nobel Prize. “Robert’s own knowledge of physics was profound,” recalled Leo Nedelsky. “Perhaps only Pauli knew more physics and knew it more profoundly than Robert.” And yet, winning a Nobel, like much in life, is a matter of commitment, strategy, ability, timing, and, of course, chance. Robert had a commitment to doing cutting-edge physics, to attacking problems that interested him; and he certainly had the ability. But he did not have the right strategy—and his timing was off. Finally, the Nobel Prize is a distinction awarded to scientists who achieve something specific. By contrast, Oppenheimer’s genius lay in his ability to synthesize the entire field of study. “Oppenheimer was a very imaginative person,” recalled Edwin Uehling, a postdoctoral student who studied under him during the years 1934–36. “His knowledge of physics was extremely comprehensive. I am not sure that one should say that he didn’t do Nobel Prize–quality work; but it just didn’t happen to lead to that kind of result which the Nobel Prize committee regarded as exciting.”
“The work is fine,” Oppenheimer wrote to Frank in the autumn of 1932. “Not fine in the fruits but the doing. . . . We have been running a nuclear seminar, in addition to the usual ones, trying to make some order out of the great chaos. . . .” While Oppenheimer was a theorist who knew how incompetent he was in the laboratory, he nevertheless stayed close to experimentalists like Lawrence. Unlike many European theorists, he appreciated the potential benefit from close collaboration with those who were involved in testing the validity of the new physics. Even in high school, his teachers had noted his gift for explaining technical things in plain language. As a theorist who understood what the experimentalists were doing in the laboratory, he had that rare quality of being able to synthesize a great mass of information from disparate fields of research. An articulate synthesizer was exactly the kind of person needed for building a world-class school of physics. Some physicists have suggested that Oppenheimer possessed the knowledge and resources to publish a comprehensive “bible” of quantum physics. By 1935, he certainly had the material for such a book at hand. His basic lectures explaining quantum mechanics were so popular on campus that his secretary, Miss Rebecca Young, had his lecture notes mimeographed and sold them to students. The proceeds were used for the physics department’s petty cash fund. “Had Oppenheimer gone one step further and compiled his lectures and papers,” argues one colleague, “his work would have made one of the finest textbooks on quantum physics ever written.”
ROBERT HAD PRECIOUS LITTLE TIME for diversions. “I need physics more than friends,” he confessed to Frank in the autumn of 1929. He managed to go horseback-riding once a week in the hills overlooking San Francisco Bay. “And from time to time,” he wrote Frank, “I take out the Chrysler, and scare one of my friends out of all sanity by wheeling corne
rs at seventy. The car will do seventy-five without a tremor. I am and shall be a vile driver.” One day he crashed his car while recklessly racing the coast train near Los Angeles; Robert escaped unscathed but for a moment he thought his passenger, a young woman named Natalie Raymond, was dead. Actually, Raymond had only been knocked unconscious. When Julius found out about the accident, he gave her a Cézanne drawing and a small Vlaminck painting.
Raymond was a beautiful woman in her late twenties when she met Oppenheimer at a Pasadena party. “Natalie was a dare-devil, an adventurer, as was Robert to some extent,” wrote a mutual friend. “This may have been the common ground of their natures. Robert grew up (or did he?), Natalie less so.” Robert called her Nat, and they saw quite a bit of each other in the early 1930s. Frank Oppenheimer described her as “quite a lady,” and Robert himself wrote Frank after seeing her at a New Year’s Eve party: “Nat has learned to dress. She wears long graceful things in gold and blue and black, and delicate long earrings, and likes orchids, and even has a hat. To the vicissitudes and anguishes of fortune which have brought this change to her I need say nothing.” After spending an evening with her at Radio City Music Hall listening to a “most marvelous” Bach concert, he wrote Frank, “The last days were impregnated with Nat; her always new & always moving miseries.” She even spent part of the summer of 1934 with Robert and others at Perro Caliente. But the relationship ended when she moved to New York to work as a free-lance book editor.