Kai Bird & Martin J. Sherwin

by American Prometheus: The Triumph;Tragedy of J. Robert Oppenheimer

  The new physics was, to be sure, highly controversial. When Max Born sent Albert Einstein a copy of Heisenberg’s 1925 paper on matrix mechanics, an intensely mathematical description of the quantum phenomenon, he explained somewhat defensively to the great man that it “looks very mystical, but is certainly correct and profound.” But after reading the paper that autumn, Einstein wrote Paul Ehrenfest that “Heisenberg has laid a big quantum egg. In Göttingen they believe in it. (I don’t.)” Ironically, the author of the theory of relativity would forever believe the Knabenphysik incomplete if not profoundly flawed. Einstein’s doubts were only heightened when in 1927 Heisenberg published his paper on the central role of uncertainty in the quantum world. What he meant was that it is impossible to determine at any given moment both an entity’s precise position and its precise momentum: “We cannot know, as a matter of principle, the present in all its details.” Born agreed, and argued that the outcome of any quantum experiment depended on chance. In 1927, Einstein wrote Born: “An inner voice tells me that this is not the true Jacob. The theory accomplishes a lot, but it does not bring us closer to the secrets of the Old One. In any case, I am convinced that He does not play dice.”

  Obviously, quantum physics was a young man’s science. The young physicists in turn regarded Einstein’s stubborn refusal to embrace the new physics as a sign that his time had passed. A few years down the road, Oppenheimer would visit Einstein in Princeton—and he came away distinctly unimpressed, writing his brother with cocky irreverence that “Einstein is completely cuckoo.” But in the late 1920s, the boys from Göttingen (and Bohr’s Copenhagen) still had hopes of recruiting Einstein to their quantum vision.

  The first of Oppenheimer’s papers written at Göttingen demonstrated that quantum theory made it possible to measure the frequencies and intensities of the molecular band spectrum. He had become obsessed with what he called the “miracle” of quantum mechanics precisely because the new theory explained so much about observable phenomena in a “harmonious, consistent and intelligible way.” By February 1927, Born was so impressed with Oppenheimer’s work on the application of quantum theory to transitions in the continuous spectrum that he found himself writing S. W. Stratton, the president of the Massachusetts Institute of Technology: “We have here a number of Americans. . . . One man is quite excellent, Mr. Oppenheimer.” For sheer brilliance, Robert’s peers ranked him with Dirac and Jordan: “There are three young geniuses in theory here,” reported one young American student, “each less intelligible to me than the others.”

  Robert got into the habit of working all night and then sleeping through a good part of the day. Göttingen’s damp weather and poorly heated buildings wreaked havoc on his delicate constitution. He walked around with a chronic cough which friends attributed to either his frequent colds or his chain-smoking. But in other respects, life in Göttingen was pleasantly bucolic. As Hans Bethe later observed of this golden age in theoretical physics, “. . . life at the centers of the development of quantum theory, Copenhagen and Göttingen, was idyllic and leisurely, in spite of the enormous amount of work accomplished.”

  Oppenheimer invariably sought out those young men with growing reputations. Others could not help but feel they had been snubbed. “He [Oppenheimer] and Born became very close friends,” Edward Condon said rather peevishly years later, “and saw a great deal of each other, so much so, that Born did not see much of the other theoretical physics students who had come there to work with him.”

  Heisenberg passed through Göttingen that year and Robert made a point of meeting the brightest of Germany’s young physicists. Just three years older than Oppenheimer, Heisenberg was articulate, charming and tenacious in argument with his peers. Both men possessed original intellects and knew it. The son of a professor of Greek, Heisenberg had studied with Wolfgang Pauli at the University of Munich, and later he had done postdoctoral work with both Bohr and Born. Like Oppenheimer, Heisenberg had a way of using his intuition to cut to the root of a problem. He was an oddly charismatic young man, whose sparkling intellect commanded attention. By all accounts, Oppenheimer admired Heisenberg and respected his work. He could not have known then that in the years ahead they would become shadowy rivals. Oppenheimer would one day find himself contemplating Heisenberg’s loyalty to wartime Germany and wondering whether the man was capable of building an atomic bomb for Adolf Hitler. But in 1927, he was building on Heisenberg’s discoveries in quantum mechanics.

  That spring, prompted by a remark from Heisenberg, Robert became interested in using the new quantum theory to explain, as he put it, “why molecules were molecules.” In very short order, he found a simple solution to the problem. When he showed Professor Born his notes, the older man was startled and very pleased. They then agreed to collaborate on a paper, and Robert promised that while he was in Paris for Easter, he would write up his notes into a first draft. But Born was “horrified” when he received from Paris a very spare, four- or five-page paper. “I thought that this was about right,” Oppenheimer recalled. “It was very light of touch and it seemed to me all that was necessary.” Born eventually lengthened the paper to thirty pages, padding it, Robert thought, with unnecessary or obvious theorems. “I didn’t like it, but it was obviously not possible for me to protest to a senior author.” For Oppenheimer, the central new idea was everything; the context and the academic window dressing were clutter that disturbed his acute aesthetic sense.

  On the Quantum Theory of Molecules was published later that year. This joint paper containing the “Born-Oppenheimer approximation”—in reality, just the “Oppenheimer approximation”—is still regarded as a significant breakthrough in using quantum mechanics to understand the behavior of molecules. Oppenheimer had recognized that the lighter electrons in molecules travel with a much greater speed than the heavier nuclei. By integrating out the higher frequency electron motions, he and Born were then able to calculate the “effective wave-mechanical” phenomena of nuclear vibrations. The paper laid the foundation for developments more than seven decades later in high-energy physics.

  Late that spring, Robert submitted his doctoral thesis, the heart of which contained a complicated calculation for the photoelectric effect in hydrogen and X rays. Born recommended that it be accepted “with distinction.” The one fault he noted was that the paper was “difficult to read.” Nevertheless, Born recorded that Oppenheimer had written “a complicated paper and he did it very well.” Years later, Hans Bethe, another Nobel laureate, observed that “[i]n 1926 Oppenheimer had to develop all the methods himself, including the normalization of wave functions in the continuum. Naturally, his calculations were later improved upon, but he correctly obtained the absorption coefficient at the K edge and the frequency dependence in its neighborhood.” Bethe concluded: “Even today this is a complicated calculation, beyond the scope of most quantum mechanics textbooks.” A year later, in a related field, Oppenheimer published the first paper to describe the phenomenon of quantum mechanical “tunneling,” whereby particles literally are able to “tunnel” through a barrier. Both papers were formidable achievements.

  On May 11, 1927, Robert sat down for his oral examination and emerged a few hours later with excellent grades. Afterwards one of his examiners, the physicist James Franck, told a colleague, “I got out of there just in time. He was beginning to ask me questions.” At the last moment, the university’s authorities discovered to their indignation that Oppenheimer had failed to register formally as a student—and so they threatened to withhold his degree. He was finally awarded his doctorate only after Born interceded and falsely told the Prussian Ministry of Education that “economic circumstances render it impossible for Herr Oppenheimer to remain in Göttingen after the end of the summer term.”

  That June, Professor Edwin Kemble happened to be visiting Göttingen and soon wrote a colleague: “Oppenheimer is turning out to be even more brilliant than we thought when we had him at Harvard. He is turning out new work very rapidly and is able t
o hold his own with any of the galaxy of young mathematical physicists here.” Curiously, the professor added, “Unfortunately, Born tells me that he has the same difficulty about expressing himself clearly in writing which we observed at Harvard.” Oppenheimer had long since become an extremely expressive writer. But it was also true that his physics papers were usually brief to the point of being cursory. Kemble thought Robert’s command of language was indeed remarkable, but that he became “two different people” when talking about physics and about any other general topic.

  Born was disheartened to see Oppenheimer depart. “It’s all right for you to leave, but I cannot,” he told him. “You have left me too much homework.” A parting gift from Robert to his mentor was a valuable edition of LaGrange’s classic text Mécanique Analytique. Decades later, long after he had been forced to flee Germany, Born wrote Oppenheimer: “This [book] has survived all upheavals: revolution, war, emigration and return, and I am glad that it is still in my library, for it represents very well your attitude to science which comprehends it as a part of the general intellectual development in the course of human history.” By then Oppenheimer had long eclipsed Born in notoriety—although not in scientific achievement.

  Göttingen was the scene of Oppenheimer’s first real triumph as a young man coming of age. Becoming a scientist, Oppenheimer later remarked, is “like climbing a mountain in a tunnel: you wouldn’t know whether you were coming out above the valley or whether you were ever coming out at all.” This was particularly so for a young scientist on the cusp of the quantum revolution. More of a witness to this upheaval than a participant, he nevertheless demonstrated that he had the raw intellect and motivation to make physics his life’s work. In nine short months he had combined real academic success with a renewal of his personality and his own sense of worth. The profound emotional inadequacies that only a year before had threatened his very survival had been trumped by serious achievements, and the confidence that flowed from them. The world now beckoned.

  CHAPTER FIVE

  “I Am Oppenheimer”

  God knows I’m not the simplest person, but compared to Oppenheimer, I’m very, very simple.

  I. I. RABI

  BY THE END OF HIS YEAR IN GÖTTINGEN, Oppenheimer was showing unmistakable signs of homesickness. In his casual remarks about things German he sounded like a chauvinistic American. Nothing in Germany could compare to the desert landscapes of New Mexico. “He’s too much,” complained a Dutch student. “According to Oppenheimer, even the flowers seem to smell better in America.” He threw a party at his apartment the night before leaving, and among many others, the lovely, dark-haired Charlotte Riefenstahl came to say good-bye. Robert made a point of giving her the pigskin satchel she had admired when they had first met. She kept it for the next three decades, calling it “The Oppenheimer.”

  After a quick side trip with Paul Dirac to Leiden, Robert sailed for New York from Liverpool in mid-July 1927. It felt good to be home. He had not only survived, he had triumphed, bringing back a hard-earned doctorate. Among theoretical physicists, it was known that young Oppenheimer had firsthand knowledge of the latest European breakthroughs in quantum mechanics. Barely two years after graduating from Harvard, Robert was a rising star in his field.

  Earlier that spring, he had been encouraged to take a Rockefeller Foundation–funded postdoctoral fellowship awarded by the National Research Council to promising young scientists. He had accepted, and decided to spend the fall term at Harvard before moving to Pasadena, California, where he had been offered a teaching post at the California Institute of Technology (Caltech), a leading center of scientific research. So, even as he unpacked his bags at the Oppenheimer home on Riverside Drive, Robert knew that his immediate future was set. In the meantime, he had six weeks to become reacquainted with his fifteen-year-old brother, Frank, and to visit with his parents.

  To his regret, Julius and Ella had decided to sell the Bay Shore house the previous winter. But as his sailboat, the Trimethy, was still temporarily moored near the house, Robert took Frank out, as he had so many times in the past, for a wild sail along the Long Island coast. In August the brothers joined their parents for a short vacation on Nantucket. “My brother and I,” Frank recalled, “spent most of the days painting with oils on canvas the dunes and grassy hills.” Frank worshipped his brother. Unlike Robert, he was good with his hands and loved tinkering with things, taking apart electric motors and watches and putting them back together. Now, at the Ethical Culture School, he too was gravitating toward physics. When Robert had left for Harvard, he had given Frank his microscope, and Frank had used it one day to look at his own sperm. “Never having heard of sperm,” Frank said, “it was really a marvelous discovery.”

  At the end of that summer, Robert was pleased to hear that Charlotte Riefenstahl had accepted a teaching post at Vassar College. When, in September, her boat arrived in New York harbor, he was at dockside to meet her. Traveling with her were two other triumphant Göttingen alumni— Samuel Goudsmit and George Uhlenbeck—with Uhlenbeck’s new wife, Else. Oppenheimer knew both men as accomplished physicists. Together, Goudsmit and Uhlenbeck had discovered the existence of electron spin in 1925. Robert spared no expense in serving as their host in New York.

  “We all got the real Oppenheimer treatment,” Goudsmit recalled, “but it was for Charlotte’s benefit really. He met us in this great chauffeur-driven limousine, and took us downtown to a hotel he had selected in Greenwich Village.” Over the next few weeks, he escorted Charlotte all over New York, taking her to all his old haunts, from the city’s great art galleries to the most expensive restaurants he could find. Charlotte protested, “Is the Ritz really the only hotel you know?” And as an indication of how serious were his intentions, he introduced Charlotte to his parents at the spacious apartment on Riverside Drive. But though Charlotte admired Robert and was flattered by his attentions, she sensed that he was emotionally unavailable. He evaded all her attempts to get him to talk about his past. She found the Oppenheimer home stifling and overprotective, and the couple began to drift apart. Charlotte’s teaching position at Vassar kept her out of New York—and Oppenheimer’s fellowship required his presence at Harvard. Charlotte eventually returned to Germany; in 1931 she married Robert’s Göttingen classmate Fritz Houtermans.

  BACK AT HARVARD THAT AUTUMN, he renewed his friendship with William Boyd, who was in Cambridge finishing his doctorate in biochemistry. Robert confided in him about his troubled year at Cambridge. Boyd was not surprised; he had always thought of Robert as an emotionally taut young man who could nevertheless handle his troubles. Poetry was still a passion with Robert, and when he showed Boyd a poem he had written, his friend encouraged him to submit it to Harvard’s literary magazine, Hound and Horn. It appeared in the June 1928 issue:

  CROSSING

  It was evening when we came to the river

  with a low moon over the desert

  that we had lost in the mountains, forgotten,

  what with the cold and the sweating

  and the ranges barring the sky.

  And when we found it again,

  In the dry hills down by the river,

  half withered, we had

  the hot winds against us.

  There were two palms by the landing;

  The yuccas were flowering; there was

  a light on the far shore, and tamarisks.

  We waited a long time, in silence.

  Then we heard the oars creaking

  and afterwards, I remember,

  the boatman called to us.

  We did not look back at the mountains.

  J. R. Oppenheimer

  New Mexico was calling to Robert. He desperately missed that “low moon over the desert” and the sheer physical sensations—“the cold and the sweating”—that had made him feel so alive during his two summers out West. He could not plausibly do cutting-edge physics in New Mexico—but he had accepted a position at Caltech in Pasadena at least partly bec
ause it was near the desert he loved. At the same time, he also wanted to be free of Harvard and that “separate prison” that had confined him for so long. Part of his recovery from the crisis of the previous year had come from the recognition that he needed a new beginning. Corsica, Proust and Göttingen had afforded him that new beginning; remaining at Harvard now would seem too much like a step backwards. So, shortly after Christmas 1927, Robert packed his bags and moved to Pasadena.

  California suited him. After only a few months he was writing Frank: “I have had trouble getting time to work, for Pasadena is a pleasant place, and hundreds of pleasant people are continually suggesting pleasant things to do. I am trying to decide whether to take a professorship at the University of California next year, or go abroad.”

  Despite his teaching duties at Caltech and Pasadena’s distractions, Oppenheimer published six papers in 1928, all of them on various aspects of quantum theory. His productivity was all the more remarkable in that late the same spring his doctor decided that his persistent cough might be a symptom of tuberculosis. After attending a seminar on theoretical physics at Ann Arbor, Michigan, in June, Robert headed for the dry mountain air of New Mexico. Earlier that spring he had written his brother Frank, now nearly sixteen years old, suggesting that the two of them “might knock around for a fortnight on the desert” sometime that summer.