Pandora's Keepers (2 page)

Now, several years later, Hahn had followed Noddack’s suggestion and did some careful chemistry. Common uranium has 92 protons (positively charged particles) and 146 neutrons, a total of 238 particles in its nucleus. By Fermi’s logic, transuranic elements would contain more of both. To Hahn’s astonishment, he found barium instead. Barium has a much lighter nucleus than uranium: 56 protons and 82 neutrons—a total of 138 particles. Hahn was puzzled. How could a uranium nucleus be split in half by a slow neutron of very low energy? It was as if a thick steel girder had been cleaved by a rubber band.

Rather than publish his findings immediately, Hahn wrote his former colleague Lise Meitner, a brilliant theoretical physicist who had been forced to leave the Kaiser Wilhelm Institute for Sweden a few months earlier because of her Jewish ancestry. Hahn asked her for assistance in interpreting the unexpected results.

Hahn’s letter reached Meitner at the seaside resort of Göteborg, where she had gone with her visiting nephew Otto Frisch, another brilliant theoretical physicist up from Copenhagen to be with his aunt during her first holiday in exile. When she read Hahn’s letter to him, Frisch disagreed and almost refused to listen. When his aunt persisted, he suggested they go for a walk, she on foot, he on skis. It must have been a strange sight: the diminutive sixty-year-old Meitner trudging through the snowy woods outside Göteborg alongside her thirty-four-year-old nephew on skis, both struggling to make sense of Hahn’s letter. Like all other physicists of the time, they assumed heavy nuclei could not be split in two. Could that assumption be wrong? They now began to question it. Using Danish physicist Niels Bohr’s “liquid drop” model of the atomic nucleus as their theoretical guide, Meitner and Frisch reasoned that the stresses on a heavy uranium nucleus triggered by neutron bombardment could make it wobble like a perturbed drop of water and eventually split it into two smaller, lighter nuclei. This might explain Hahn’s strange discovery.

Meitner and Frisch then went one fateful step further in their interpretive speculation. Using Albert Einstein’s famous formula for the conversion of matter into energy (E = mc
²
, an enormous number),
^*
they calculated the energy that would be released when splitting apart or “fissioning” the nucleus of a uranium atom. The figure was staggering: 200 million electron volts of energy. Two hundred million electron volts is not a large amount of energy—only about enough to nudge a speck of dust—but it is an awesome, almost unimaginable amount of energy from a single, tiny atom. And in just one gram of uranium there is an astounding number of atoms: about 2,500,000,000,000,000,000,000.

As he stood in Wigner’s infirmary room, these details struck Leo Szilard like a thunderbolt. What Szilard had dimly imagined for years—yet vaguely dreaded—had been found. Fissioned uranium released a million times more energy than dynamite, which was the most explosive force known at that time. Such energy might be harnessed into a terrible weapon of mass destruction. Such a weapon in the hands of Hitler and the Nazis would give them an instrument with which to enslave the world. This seemed an all-too-plausible danger because Germany had some of the best scientific brains in the world—like Otto Hahn—and the industrial capacity to do the job. Suddenly, a dramatic melancholy fell upon Szilard.

The discovery of fission spread among the other physicists like wind across a field of wheat. Hungarian physicist Edward Teller was looking forward to seeing Szilard at the Third Annual Conference on Theoretical Physics in Washington, D.C., where Teller had sought refuge as a professor at George Washington University after fleeing Nazi persecution four years earlier. The participants at the Washington conference would include Bohr, who was coming from his world-famous institute in Copenhagen, and Fermi, who had been awarded the Nobel Prize the month before for his research on neutrons.

Bohr himself had learned of fission from Otto Frisch just before leaving Copenhagen. “How could we have missed it all this time?” he exclaimed in utter astonishment. When Bohr’s ship docked in New York two weeks later, he took the train to Washington and arrived at the home of Russian physicist George Gamow, the conference organizer and a colleague of Teller’s, late in the afternoon on the day before the conference began. An hour later Gamow phoned Teller in great agitation. “Bohr says uranium splits,” he told Teller. That was all of Gamow’s message. It was enough. Teller understood what fission might mean.

Bohr opened the conference the next morning by announcing the discovery. It escaped few, if any, that the atom had been split in Nazi Germany. Teller glanced across the auditorium at Fermi as Bohr spoke. Fermi’s wife was a Jew, and he had become uneasy about remaining in Mussolini’s Italy, an ally of Hitler’s Germany. Leaving everything behind, Fermi had taken his family out of Italy the month before when he left to accept the Nobel Prize. They had used the prize money to travel on to New York, where Fermi was settling in as a professor at Columbia University.

Fermi had learned of fission a few days before the conference began from I. I. Rabi, his colleague on the physics faculty at Columbia who himself had picked up the news at Princeton while his friend Szilard was there. A short time later Rabi saw Fermi standing at his large office window on the top floor of Pupin Hall high above the Columbia campus, looking down the length of Manhattan’s grid of skyscrapers crisscrossed by streets teeming with pedestrians and taxis. Fermi cupped his hands as if he were holding nothing larger than a ball. “A little bomb like that,” he said simply, “and it would all disappear.”
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Hans Bethe, who also attended the Washington conference, had fled Nazi Germany the same year as Teller. He pondered the consequences of fission on the long train ride back to Cornell University in upstate New York after the conference. Bethe realized that atomic bombs were now theoretically possible, though he did not believe they were even remotely feasible. The task of making an atomic bomb was simply too big and too difficult from a technical and engineering point of view. There was simply no way, Bethe was convinced, to produce fissionable uranium even in amounts as small as a millionth of a gram; a kilogram of fissionable uranium was far beyond the reach of science, he thought.

Arthur Compton, a Nobel Prize-winning physicist at the University of Chicago who personally knew most of those at the Washington conference, learned of fission while at the McDonald Observatory in the Davis Mountains of West Texas. Could a chain reaction of splitting uranium atoms occur? he wondered. The amount of energy released by such a chain reaction, according to his quick calculations, was enormous. Here was something of great importance, thought Compton, and also of great danger.

Ernest Lawrence, Compton’s former graduate student and now a successful and ambitious professor of physics at the University of California, Berkeley, grasped the larger meaning of fission at once. Its military potential—which many physicists such as Bethe considered insurmountable—seemed like a heroic challenge to him. “This uranium business is certainly exciting,” he wrote Fermi within weeks.
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Lawrence was determined to do what he could to make sure that if an atomic bomb was possible, America would get it first.

Working at the blackboard in his office, Lawrence’s charismatic Berkeley colleague Robert Oppenheimer tried at first to prove that fission could not happen. Within a week, however, Oppenheimer the theoretician had decided that it could and that additional neutrons would be released. Within another week there was a crude drawing on his blackboard of a bomb. Oppenheimer wrote to a colleague that a ten-centimeter cube of uranium “might very well blow itself to hell.”
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Nine physicists. Colleagues and friends. For the European refugees among them, the 1930s had been a decade of indelible scarification. When Nazism first began to spread like a malignant cancer, they had felt secure in their ivory towers, hoping that Hitler was not really a problem or, if he was, that he would go away. They felt no urgency because they believed politics was not a physicist’s concern, much less a physicist’s responsibility. But the rise of Hitler made politics personal, even for cloistered physicists. The world they knew and the scientific values they cherished were being destroyed, and that deeply painful but inescapable fact became increasingly difficult, and finally utterly impossible, for them to ignore. They wanted to preserve that world and those values. That was the fundamental thing that moved them. But one by one they had realized that if they were to stay in Europe, there would be no future. Deep down, they sensed that the world as they’d known it had only a little more time to run. So they packed what they could and brought their heavy accents and heavy wool suits to a New World that welcomed them.

For the native-born Americans they met in labs and university offices, the 1930s had marked an education in the troubling realities of a world more interconnected and complex than they had thought. American physicists had believed that the United States was insulated and invulnerable, separated as it was by a vast ocean from the misfortunes, follies, and crimes of Europe. This was a sentiment that most of their isolationist countrymen shared in the 1930s. But the experience of their refugee brethren, and their own knowledge of what fission portended, made them imagine, and confront, an ominous future.

“Science can solve every problem”—this was an article of faith among them, physics a pure and lofty calling. They had a detached preference for objective facts over subjective values. Raising moral considerations was not their professional style. Their aim had been to understand the world, not change it. But with the announcement of Hahn’s breakthrough, that would change. What followed would be a tale of unrivaled brilliance and unintended folly. It would also be a tragedy in the deepest and most fundamental sense. For had the atomic scientists not pursued fission, they would have been untrue to their nature and aspirations as physicists; yet having done so, they would be haunted by their quest. It is a sobering paradox not lost on the atomic scientists themselves. “Taken as a story of human achievement, and human blindness,” Robert Oppenheimer observed late in his life, it is “among the great epics.” And the epic begins with the shadow that the discovery of fission cast over the idyllic world of physics in the 1930s. Hahn had split more than an atom. After his discovery, there would always be a before and an after. Out of little things come big things—but nobody, not even the nine men who would go on to build the bomb, had any idea just what was to come.

PART I

A FEARSOME
GRAIL

CHAPTER 1

Exodus

A
NYONE WHO DID
physics before the discovery of fission could remember what that world was like. Pre-fission physics was a beautiful, intimate subject that simmered with purpose. It was attractive, awe-inspiring, and deeply satisfying. Physicists worked in an atmosphere of intellectual and emotional excitement. Things were new, there were surprises, they were turning corners. Physics had no object other than satisfying the human spirit of intellectual adventure. Through every experiment and theory coursed an aesthetic pleasure and the moral uplift of pursuing the truth. More than other scientists, physicists prided themselves that their science did not have any practical use.

Physics was a personal undertaking. A physicist enjoyed autonomy. He chose what work to do. His subject for research was his own. Physicists viewed their work as a calling, as an enlargement of their lives, not just as a career. It meant something to them personally, in the same sense that art or literature did to others. The study of physics was noble, enlightening, and constructive, a model of how life should be lived. And the scientific method was an anchor of predictability and precision in a chaotic and uncertain world. Nature was profound, yet its secrets could be unlocked. The joy of insight, physicist Victor Weisskopf once said, was “a sense of involvement and awe, the elated state of mind that you achieve when you have grasped some essential point. It [was] akin to what you feel on top of a mountain after a hard climb or when you hear a great work of music.”
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