Frequently he would climb down into the ravine to the Omega site, working with King, Anderson, Hinton, and others on the water boiler. He also now had responsibility for Teller and the Super. Teller had mastered the fusion equations that were required for the work, but no one could figure out how to keep the assembly of fission and fusion devices together long enough to produce a true fusion explosion. These and other less vital, but still pressing, technical issues preoccupied Fermi at work. But Los Alamos was not just about work.
Even with the punishing work schedule at Los Alamos, Sundays were for leisure, and Fermi took active advantage of them. The surrounding Jemez Mountains were ideal for long, strenuous hikes with his colleagues and friends. As in his youth, he would plan out the excursion, lead it, and walk ahead of most of the others. Geoffrey Chew, a twenty-year-old physicist from George Washington University who worked in the Theoretical Division, was a tall, athletic young man. He recalls that he was one of the few who could keep up with Fermi. He doesn’t recall talking physics at all or in fact talking about much of anything except the beautiful austere Southwestern landscape. During the winter it snowed on the Jemez range, giving Fermi an opportunity to go skiing. He was joined by some of his former European colleagues who had learned to ski when they were young, notably Hans Bethe and Niels Bohr.
Fermi eagerly ventured off-site in other directions as well and explored the Bandelier forest, about ten miles southwest of the Los Alamos mesa, where old Pueblo Indian ruins could be found at the end of long, inspiring hikes. He also tried to pick up the art of trout fishing in the many streams at the base of the ravines surrounding the mesa. To the amusement of those who had labored to learn the difficult skill of fly fishing, he insisted on using live bait, usually worms, arguing that it was more humane to give fish live bait for their final meal. Segrè once pressed him on this and Fermi explained he could not see the point of fly fishing. Segrè patiently lectured Fermi on how it was harder to catch a trout with a fly lure, that it took real skill to put the fly down on the stream in such a way as to fool the fish into thinking it was an insect. Fermi grinned and said, with only mild irony, “I see, so it’s a battle of wits!”
FIGURE 19.1. Fermi skiing with colleagues in the mountains around Los Alamos. Courtesy of Los Alamos National Laboratory.
The social life at Los Alamos was also active. In general, those with white badges—the several hundred scientists who were cleared to know anything and everything about the project—socialized among themselves, and those with blue badges—everyone else—socialized among themselves. It was easier that way. The white badge parties were frequent and lively. Sometimes they were held at the cramped apartments of the scientists, although the Oppenheimers, who lived on Bathtub Row, also hosted parties in their more spacious digs. Sometimes there were grander affairs, held either at Fuller Lodge, a larger log cabin–style structure that served as the white badge mess hall, or even at the much larger general mess hall for the entire community. Neither Enrico nor Laura were big drinkers, but they enjoyed these parties and hosted many of their own, at which they led guests in the types of parlor games Enrico always tried to win.
Chew tells the story of one party he and his young wife hosted, which the Fermis attended. Chew suggested a party game involving the passing of a scissors around a circle; you passed it “closed” if your legs were crossed and “open” if your legs were not crossed. A few people knew the secret, while others had to guess as they watched. Round and round the scissors went and with each cycle Fermi grew more and more agitated because he could not guess the rule. Laura picked up the rule fairly early, and finally, sensing her husband’s growing frustration, she leaned over and explained it to him. He was so upset that the two made excuses and left the party early. The Chews were mortified, but the incident seemed to have no lasting effect. After the war Chew went to Chicago and was one of Fermi’s graduate students.
Some of the bigger parties involved square dancing, which was an entirely new experience for the Fermi family. Bernice Brode, the wife of physicist Robert Brode, who developed the fuse mechanisms for the first fission weapons, was one of the leaders of the square dance group, which met frequently throughout the period. In later years she recalled that when the Fermi family initially came to the sessions where she and others taught newcomers, they just sat and watched, presumably terrified at the thought they might have to execute these complex dance patterns. Eventually, Laura and Nella joined in, but Enrico still sat on the sidelines, studying the moves:
He said in his mild and reasonable voice he would let me know when he was ready to join a square, and one could almost see his mind watching and remembering. Then one evening he came up to me and said, “Well, I think I am ready now, if you will be my partner.” He offered to be head couple, which I thought most unwise for his first venture, but I could do nothing about it, and the music began. He led me out on the exact beat, knew exactly each move to make and when. He never made a mistake then or thereafter. I wouldn’t say he enjoyed himself, for he was so intent on not making a mistake, which the best of us did all the time. Although I congratulated him, I also kidded him and admonished him to relax and have fun. He laughed tolerantly, but I knew he could continue to dance with his brains instead of his feet.
He eventually learned to enjoy square dancing, so much so that it became a feature of the many parties hosted by the Fermis in Chicago after the war.
BY MARCH 1945, THE PLUTONIUM PRODUCTION REACTORS AT Hanford were producing at full speed, the giant facilities at Oak Ridge were enriching uranium on an industrial scale, and shipments were arriving at Los Alamos with increasing frequency. Much work had been accomplished regarding critical mass in uranium, most notably the famous “tickling the dragon” experiments that took place alongside the water boiler in the Omega site. A subcritical slug of enriched uranium was dropped through another subcritical block of enriched uranium with a hole bored through it just large enough to accommodate the slug being dropped. For a brief instant the whole apparatus was supercritical, not quite long enough to explode, but long enough to give high confidence that estimates of U-235 critical mass were accurate.
The implosion device, however, required more work. One critical experiment consisted of carefully controlled implosions of aluminum spheres. The configuration of the high-explosive charges around the sphere, designed by Kistiakowsky’s team guided by the calculations of Bethe’s Theoretical Division, proved sufficiently promising to begin manufacturing a sphere of plutonium metal. To the consternation of Robert Bacher, who headed the group responsible for weapons physics, Fermi’s attention turned now to the issue of the “initiator,” the device that would provide the fast neutrons at exactly the moment of criticality. Bacher was a respected experimentalist who would go on to a long and distinguished career after the war. Fermi and Bacher had enormous mutual respect, but Bacher felt that Fermi was becoming a bit of a nuisance. Fermi had been playing with a number of different initiator concepts, all of which Bacher considered hare-brained. In later years, Bacher, who remained friendly with Fermi in spite of his annoyance over the initiator issue, described it this way:
I think Fermi began to be very worried about the fact that this terrific thing that he’d sort of been the father of was going to turn into a great big weapon. I think he was terribly worried about it.… I think he [Fermi] was worried about the whole project, not just the initiator. But focusing on the initiator was the one thing that he thought he could look at. The thing really might not work.
And I think he also felt an obligation to take something that was as hare-brained as this was and try to find a way in which it really wouldn’t work. So he did look into every sort of thing, and I think every second day or so for a period, I’d see him and he’d come up or he’d see Hans [Bethe] and come up with a new reason why the initiator wouldn’t work.
Perhaps, as Bacher surmised, Fermi finally understood the enormity of the project and was looking for ways to demonstrate that the problem was
impossible to solve. Or perhaps Fermi was struggling with the admittedly difficult technical problem of how to get enough neutrons out of the initiator to create a full explosive chain reaction before the initiator was destroyed. Regardless, Bacher and Oppenheimer decided to give the initiator assignment to Niels Bohr and his son Aage, who arrived as residents of the mesa during late 1943/early 1944. Bacher believed Fermi would accept a design approved by the Bohrs, and he was right. The Danish father and son team thought about the problem for a few days and came up with an elegant solution, dubbed “the urchin,” a spherical version of the original neutron sources that Fermi had used in Rome that would sit inside the plutonium sphere and would be triggered under the enormous pressure of the implosion, releasing between ten and one hundred neutrons before being destroyed. Those neutrons would be sufficient to initiate a full explosive fission throughout the plutonium sphere. Fermi, confronted with this elegant solution, conceded that it would probably work.
Bacher was not a psychiatrist and it is difficult in any case to speculate on Fermi’s inner life, given his profound reticence. Yet Fermi may well have been experiencing some deep level of psychic stress. He had climbed on board the Manhattan Project express train early on and had helped stoke the engine for more than five years. In fact, he was the best coal man the train had and that train was now bearing down on its destination. Perhaps somewhere deep inside, he was feeling a growing sense of panic that he was responsible for launching a physics project that would result in terrible consequences. Of course, it might also have reflected a concern that the project on which his advice and judgment and physics expertise largely relied might fail in the end, with unimaginable personal embarrassment for him. We have seen a certain reluctance all along, in his expressions of doubt that the project would work, in his lukewarm presentation to the military in March 1939, and in his decision not to spend the summer of that year devoted to fission, that fateful summer when his erstwhile colleague, Leo Szilard, petitioned Einstein to write a letter to FDR urging work on fission weapons. Now, in early 1945, his mind latched on to the idea that the initiator could not in principle be made to work. If this were true, then the United States would not be able to make nuclear weapons, but then neither would the Germans. If this were true, a lot of money would have been spent demonstrating that the demonic device was technically impossible. The fact that Bohr and his son came up with an initiator that would work in some subtle way let Fermi off the hook, but it left the project intact. Fermi would have one last chance to try and stop the express train from reaching its destination, but for now, at least, he stopped fighting it and returned to supporting it.
THE WAR WITH GERMANY EFFECTIVELY ENDED IN LATE APRIL 1945; on May 2, the Soviet flag flew over the Reichstag. The Allies’ most important European enemy had been comprehensively defeated and with it, the fear that Heisenberg and his colleagues would beat the Allies to the atomic bomb.
The Germans had come nowhere near building an atomic weapon, though, as Jeremy Bernstein conclusively demonstrates, they tried hard to do it. Their decision initially to pursue a heavy water model doomed the project from the start. Heisenberg later encouraged suggestions that he had deliberately chosen that route knowing that it would delay the project, but the consensus today among historians is that this explanation was somewhat self-serving. In addition, when the Germans turned to graphite moderation, the graphite they used was filled with impurities that altered the material’s ability to serve as a moderator. To cap it off, they grossly overestimated the critical mass of uranium. In the end, they were never even able to achieve a self-sustaining chain reaction.
THE END OF THE WAR IN EUROPE PROFOUNDLY CHANGED THE NATURE of the Manhattan Project. In the eyes of many of the scientists involved, including Fermi, the main justification for the project had evaporated. Germany had lost the race to build the first nuclear weapon. Looking to the future, no one took seriously the threat of a possible Japanese atomic bomb. Groups of scientists at the Met Lab, most importantly James Franck and Leo Szilard, now believed that the Manhattan Project should be slowed or altogether stopped, and that certainly the bomb, if developed, should not be dropped on Japan. The scientists at Los Alamos were aware of the growing discomfort of the Chicago scientists and some of them expressed misgivings as well.
Thinking within the political and military leadership, however, was not tending in the same direction. Groves wanted to push the weapon through to completion, believing it was a quick way to end the war against Japan and also wanting to measure the weapon’s effectiveness. Those few around the new president, Harry Truman, who knew about the project—most notably, Secretary of War Henry Stimson—shared Groves’s perspective. So did the president himself, who only learned of the project the day he assumed office.
Against this background, Secretary of War Henry Stimson called four key scientists to Washington in late May: Arthur Compton, Fermi, Lawrence, and Oppenheimer. They were to advise the “Interim Committee,” newly established to provide the president with high-level political and strategic advice on the future of the whole nuclear project. Members of the Interim Committee, chaired by Stimson, included a small group of the government’s highest level civilian and military leadership.
The meeting, held at Stimson’s Pentagon office, started around ten o’clock in the morning, continued over lunch, and ended late in the afternoon. Compton later recalled the meeting for his memoir. The conversation covered the current status of the project, estimates of the weapon’s effectiveness, whether, and if so when, and how to let the Soviets know of the project, how to manage the still secret technology in the postwar world, and, most importantly, how to use the weapon to end the war with Japan.
Over lunch, Compton and Lawrence both advocated exploring a demonstration, inviting the Japanese political and military leadership to view an explosion. The thinking was that the experience would be so dramatic that the Japanese would quickly sue for peace. Oppenheimer strongly disagreed. He wanted the bombs to be used against targets in Japan. He could not imagine a demonstration that would be sufficiently dramatic to persuade the recalcitrant Japanese to surrender. Nor did he believe the weapon would be significantly less humane than conventional bombing, which had already leveled Japan’s great cities, including Tokyo, and killed some two hundred thousand people.
Oppenheimer’s opinion counted; however, the political leadership attending were already leaning heavily in favor of using the bomb against Japan, either to end the war quickly or to make subsequent invasion easier. The quickest way to do this, in their opinion, would be to use the bomb in a dramatic fashion against major cities involved in the Japanese military-industrial effort. It was also clear that only one or two bombs would be ready for use in the immediate future and they opposed using one simply for a demonstration. If the Japanese did not respond constructively to the demonstration, perhaps only one weapon would remain in the arsenal. If the demonstration proved to be a dud, that would only make matters worse.
Fermi limited his participation to an estimate of the amount of enriched uranium that would be required for future research after the war—about twenty pounds initially, and half a ton in the next phase of work.
What Stimson thought of Fermi, or Fermi of Stimson, is not recorded. Fermi had been working at the heart of the Manhattan Project since its inception but had never been this close to the highest levels of political power. He had encountered important Americans before, but none of Stimson’s stature. Stimson, a product of Andover and Yale and the ultimate Establishment man, must have been bemused by this short, unprepossessing Italian immigrant with a thick accent who, by all accounts, was essential to the project’s success. As the meeting adjourned, Stimson instructed the scientists to prepare a short report to the Interim Committee with advice on the use of the bomb against Japan. It is unclear why Stimson bothered to do this, because the very next day presidential adviser and future Secretary of State James Byrnes reported to the president the Interim Committee recommendation t
hat the United States drop the bombs on Japanese targets. Stimson may have been concerned about the growing consensus among scientists in Chicago and Los Alamos that the bomb should not be dropped and ordered this report from the nation’s top scientific leaders in order to undercut the developing consensus. As it happened, the four scientists, not knowing of Byrnes’s report to the president, canvassed colleagues at their respective labs. Compton’s job was perhaps the most difficult. He asked James Franck, whose moral authority was respected by most of the scientists at Chicago, to prepare a report. Franck was already concerned about how the bomb might be used in the aftermath of the German surrender. He drafted a letter, eventually signed by Szilard and Seaborg, among others, reflecting the views of many in the Met Lab that either a demonstration use or a decision to keep the very existence of the bomb secret would be preferable to using the bomb against Japan. While still leaning toward the option of a demonstration, Compton did not add his signature. Franck personally brought the letter to Washington and gave it to Stimson. It is not clear whether the four scientists who met with the Interim Committee ever saw a final copy.
Oppenheimer scheduled a meeting in mid-June 1945 at Los Alamos with the other three who had briefed the Interim Committee to continue discussions and to prepare the recommendation that Stimson had requested. The meeting began on June 15, 1945, and produced three reports. One relatively uncontroversial report recommended funding the postwar atomic research at a level of $1 billion annually. The third recommended that the Manhattan Project under Groves be extended for the duration of the war to continue oversight of nuclear technologies. It was the second report, however, that historians remember. It addressed the immediate issue of the bomb’s use. Just 350 words in length and presented under Oppenheimer’s signature on behalf of the four scientists, it recommended that the allies be apprised of US progress in atomic weaponry; noted that, though opinions differed among the scientific community, they themselves leaned toward immediate military use to end the war as quickly as possible; and observed that as scientists they recognized that they had no special competence in the political, social, or military aspects of the issue of atomic weapons.
The Last Man Who Knew Everything Page 29
