Work at Argonne required new routines for everyone. Fermi could no longer walk the half mile or so to his lab. Argonne was some twenty miles southwest of Hyde Park, along fabled US Route 66, and the drive, with Baudino at his side, took the better part of an hour. The hour-long drive drew the two men—opposites in so many ways—close together. Fermi might have initially resisted the idea of a bodyguard as unnecessary, but they soon became friends. Occasionally, Baudino lent a helping hand, stacking graphite bricks or moving blocks of paraffin. Libby, Anderson, and Marshall, who normally slept in a primitive dorm on the lab site, sometimes rode with their boss when they needed to get into town, and they discussed the day’s objectives as they drove through the cornfields and prairie land between the city and their new workplace. Fermi got to know the vast fertile plains that make up the American heartland. He was fascinated by the landscape, which was so very different from what he was used to in Italy.
Laura adjusted well to the new environs. Chicago was different from New York, and she liked her new home. She enjoyed socializing with the growing group of physicists and their spouses at the Met Lab—a very social group, even under the constraints of official secrecy. The party she hosted on the evening of December 2, 1942, was but one of many she hosted during this period. The Fermis did not drink very much at all—when they had wine, it was always with a bit of water added—but they served alcohol to their guests. They enjoyed playing party games like charades, which Enrico took very seriously. Old friends like the Ureys and Mayers made Laura feel even more at home. Laura also got along well with Leona Libby, although one senses Laura was a bit jealous Enrico was spending more time with this attractive twenty-three-year-old than he was with his own wife. During a snowstorm, Leona was a passenger in Fermi’s car as he drove home from the lab late at night. When Leona suggested they might have to stop the car and sleep there overnight, Fermi objected, saying that it might harm his reputation. The young woman, by now married to John Marshall and pregnant with his child, suggested that perhaps she should be worried about her reputation and because she wasn’t, why should he be? He asserted with characteristic confidence that his reputation was more important and they drove on. Unspoken, perhaps, was his concern over what Laura might have said the next morning.
Leona’s pregnancy posed some problems at Argonne. The health and safety officers assigned there would certainly have prohibited her from working at the new pile if they had known. She was, however, able to persuade those around her to keep the secret and wore baggy clothes to hide the pregnancy. Zinn apparently never knew or if he knew he never let on. Fermi became convinced he might have to perform midwife duty at the lab some nine months on, given the twenty-seven miles between Argonne and the Chicago hospital where Leona and John planned to have their baby (why exactly he didn’t expect John, who worked there every day, to perform these duties if necessary is not clear). Fermi even researched what he would be required to do. Fortunately for everyone involved, including Laura, it never came to that and the Marshalls had their first child at the hospital.
As she settled into life in Chicago, Laura also devoted time to the children. By this time, Nella was twelve years old and Giulio was almost seven. They were both enrolled in the famous Lab School established in 1896 by American educator John Dewey. The school, founded on progressive principles of child development and education, was somewhat less permissive than Nella’s New York school. Giulio was unhappy, but Nella adjusted well—perhaps because she was older and her temperament was better suited to the more structured program. Also, Giulio was upset that he was taken away from his friends in New Jersey without sufficient explanation. It was a resentment he carried with him throughout his life.
SOME OF THE NEW MEMBERS OF THE ARGONNE TEAM HAD HEARD of Fermi’s extraordinary abilities but were now witnessing them for the first time and were suitably impressed. One of the most important of these was an experimental physicist named Luis Alvarez, a student of Compton at Chicago in the early 1930s. Alvarez’s work in those days was the stuff of Chicago legend by the time Fermi arrived. After getting his degree, Alvarez left Chicago to join Lawrence’s team at Berkeley, doing a series of important experiments at the cyclotron. At the beginning of the war, Alvarez worked in England and at MIT on the development of radar, and in the summer of 1943 he arrived at Argonne, climbing on top of CP-2 and working with Libby to design and build new instruments, something at which he was particularly adept.
Alvarez was never a modest man, so his report of an early encounter with Fermi is particularly instructive. He joined a conversation in the Argonne cafeteria with Fermi, the Marshalls, and Herb Anderson, who were discussing how neutrons might obey a law of refraction similar to those of X-rays. Fermi commented that he could not remember the exact formula for X-ray refraction. Alvarez pointed out that it was contained in the classic textbook on X-ray diffraction written by Compton and Allison. Alvarez had seen a copy of the textbook on a desk next door and offered to get it. Fermi told him not to bother—he would derive it.
Alvarez goes on to describe Fermi’s performance:
As a student of Compton’s I had thought long and deeply about X-rays, but I had never seen the refractive-index formula derived from basic principles. Enrico wrote James Clerk Maxwell’s classic electromagnetic field equations on the blackboard and then in six separate steps derived the formula. The most remarkable aspect of this tour de force was that Enrico worked through his derivation line by line at a constant rate, as if he were copying it out of a book. That night at home I reproduced it and was quite pleased with myself. If one step was easy enough to allow me to go faster than he did, the next was so difficult that I could never have managed it alone. But Enrico worked the difficult steps at exactly the same rate he worked the easy ones.
In time, the two of them became good friends. Alvarez, back at Berkeley after the war, would occasionally call Fermi to ask for recent graduate students for post-doc positions at Berkeley and Fermi would happily oblige.
Increasingly, young American physicists who encountered Fermi for the first time were impressed by his ability to work his way through thorny problems. Many of the brilliant physicists of Alvarez’s generation—about ten years younger than Fermi—had never worked closely with people of Fermi’s European peer group, the Heisenbergs and Diracs of the physics world. The closest many of them had come to this group was Oppenheimer at Berkeley, who in the late 1920s brought European-style theoretical physics back to the United States. To see one of the quantum pioneers at work must have been quite inspirational. Increasingly, young American physicists were exposed directly to Fermi and shared Alvarez’s sense of awe.
That awe was not confined to the younger generation. At Fermi’s memorial service in 1954, Sam Allison recalled that on a train ride to Hanford, Compton decided to make small talk with Fermi. He remarked to Fermi that during his time in the Andes pursuing cosmic-ray studies his watch did not keep good time. “I thought about this considerably,” Compton explained, “and finally came to an explanation that satisfied me. Let’s hear your discourse on the subject.” Fermi immediately pulled pencil, paper, and slide rule from his pocket and after a few minutes came up with an answer that explained the phenomenon and even predicted the amount of the watch’s inaccuracy. Compton’s look of wonder was something that Allison, Compton’s long-time collaborator, would never forget.
INCREASINGLY, FERMI’S ATTENTION WAS DRAWN TO PROBLEMS ARISING in the planning and construction of the reactors. The first major plutonium reactor, known as X-10, was rising at Oak Ridge, with three objectives: to determine how fast plutonium could be produced, to develop the chemistry to separate plutonium from the other by-products of controlled uranium fission, and to provide small samples of plutonium to determine its suitability for use in a fission weapon. Fermi’s old friend Emilio Segrè, now at Berkeley, but soon to relocate to Los Alamos, would be one of the key scientists researching this latter issue.
The construction was a helter-skelter affair
, with engineers working round the clock from the sketchiest of drawings. Based at Argonne, Fermi provided guidance and advice on scientific and technical questions. Eventually, the enormous cube took shape atop a small hill at Oak Ridge. It looked more like CP-2 than CP-1, but there was a difference. It was built so that, after the reactor had been running for an appropriate length of time, the uranium rods could be easily removed and placed in acid baths to initiate the extraction of plutonium. A large cube of graphite, twenty-four feet on each side, it had 1,260 long channels bored into one face. Into these channels rods of uranium metal would be inserted. Along a perpendicular face, channels were drilled to accept cadmium safety rods, which were attached to a mechanized system to pull them out or reinsert them as conditions required. Designed to run hot, at one thousand kilowatts (one megawatt), to produce enough plutonium to study in a relatively short amount of time, it required a cooling system that neither CP-1 nor CP-2 had. The system chosen was air cooling. Air flow supplied by motorized fans circulated air in and around the channels for the uranium rods. At the intended power level, radiation from the pile became an important safety issue, so engineers encased the pile in concrete shielding seven feet thick, creatively formulated to retain water even after curing so that it would be more effective at slowing down any excess neutrons escaping from the pile.
FIGURE 18.1. The author at the control panel of the X-10 reactor at Oak Ridge. Photo by Susan Schwartz.
The Oak Ridge pile went operational on November 4, 1943, less than a year after the first pile in Chicago. It was a tremendous achievement and, in recognition of this, Compton and Fermi traveled to Oak Ridge to witness the event. They were sleeping in when they were awakened before dawn—apparently with some glee—by the crews loading the uranium fuel, who were ahead of schedule. The pile went critical at five o’clock that morning. Soon it was producing plutonium, which was transported by courier—on a commercial flight—to Los Alamos for study by Segrè. Segrè’s discoveries regarding these samples, which were often just a few milligrams in size, would alter the entire course of the Manhattan Project.
For the time being, however, the success of the Oak Ridge pile must have given great satisfaction to the Chicago physicists and to DuPont’s leadership, especially Crawford Greenewalt, who had come to worship Fermi. Seaborg’s chemical separation unit next door would soon give Groves and the civilian leadership confidence to start an all-out effort to build industrial-scale plutonium production reactors at Hanford.
DURING LATE 1942 AND EARLY 1943, WORK UNDER OPPENHEIMER at Berkeley continued to focus on issues relating to the use of U-235 for a fission bomb; all signs pointed to the conclusion that fast neutrons would cause that particular isotope of uranium to split. This was progress for the project, because fast neutrons would be the only way the energy locked in the uranium nucleus could be released in the short time required to create an explosion. Gifted with an ability to read people and situations quite accurately, Oppenheimer charmed the blunt anti-intellectual Army general. He did not spend a lot of time regaling Groves with meditations on high culture. Instead, he evinced a complete confidence that, with the scientific team at his disposal, he could deliver the goods. Groves agreed and selected Oppenheimer as the scientific director of the effort to design and build the actual weapons once sufficient materials were produced.
The story of how Oppenheimer persuaded Groves to designate a mesa about twenty miles northwest of Santa Fe, New Mexico, the site of a boys’ boarding school called Los Alamos, as the site—code-named Site Y—for the technical effort to design and build the bombs is told elsewhere. Fermi attended the first organizational meetings Oppenheimer held there in April 1943, along with a stellar cast of scientists, including Rabi, Bethe, Segrè, and many other old friends. Fermi’s presence was eagerly anticipated. A senior group of scientists were lunching at Fuller Lodge, the canteen for the high-level scientists, and Teller assured them that Fermi would be arriving within the week. Stanislaw Ulam, a Polish mathematician who in later years was credited with a major breakthrough in the development of the hydrogen bomb, intoned “Annuncio vobis gaudium maximum, papam habemus.” To the bewildered group, John von Neumann, Ulam’s brilliant Hungarian colleague who played a central role at Los Alamos over the next few years, translated the Latin used by the church to announce the election of a new pope: “I announce to you with greatest joy that we have a new Pope.” The group knew of Fermi’s nickname in Rome and burst into applause. They had been looking forward to Fermi’s arrival and loved Ulam’s allusion.
When the entire group was assembled at Los Alamos, they discussed a “primer” on bomb design prepared by Oppenheimer student and collaborator Rob Serber, the result of the Berkeley theoretical group’s months of study and debate. Oppenheimer began to plan a division of labor, which he was able to sustain until late summer 1944, when events forced reorganization. This was Fermi’s first exposure to the magnificent wilderness of the New Mexican portion of the Rio Grande valley. Over countless millennia, the river ground out the valleys the scientists now hiked in and explored. The wilderness around Los Alamos was like nothing Fermi had ever experienced, and when Norris Bradbury, the first postwar director of Los Alamos, invited Fermi back for a number of summers after the war, it was not a hard sell for the inveterate outdoorsman.
The April 1943 meetings at Los Alamos were the first time all the senior scientists came together to discuss the design and construction of the bomb. In later years Oppenheimer recalled that Fermi seemed taken aback by the enthusiasm of many in the group. “I believe your people actually want to make a bomb,” Oppenheimer reported Fermi commenting to him. “I remember his voice sounded surprised,” Oppenheimer added. Fermi, like Szilard, understood the gravity of the challenge they were facing and, though he understood it might be necessary, especially because the Germans were known to be pursuing nuclear weapons on their own, he did not share the majority’s enthusiasm.
He was, however, capable of coming up with rather brutal and ruthless ideas for winning the war. A letter from Oppenheimer to Fermi dated mid-1943 survives, commenting on an idea being considered by the two physicists for massive radiation poisoning of the German civilian population. How the idea arose is not clear, because Fermi’s side of the correspondence has never been found, but it is clear that both Oppenheimer and Fermi were open to considering a range of ideas to end the war quickly. Fermi might not have been enthusiastic about these ideas, but he probably considered it an obligation to think them through anyway.
Fermi returned to Chicago after the April 1943 meetings and continued his CP-2 experiments and his consultations with DuPont over the construction of the plutonium production reactors until August 1944, when he finally moved to Los Alamos. In the interim, Oppenheimer and others at Los Alamos continued to consult with him on a variety of problems, and he traveled to Los Alamos on several occasions, but his home base remained Chicago.
WHAT FERMI MADE OF OPPENHEIMER, DURING THOSE INITIAL April 1943 meetings or later, is hard to divine. He made only the occasional, brief comment to close colleagues. Yet even the casual observer would have noted the differences between the two physicists. Oppenheimer was the product of a highly cultured upbringing on Manhattan’s Upper West Side. The son of assimilated and wealthy German-Jewish parents, he attended the exclusive Ethical Culture School and then Harvard, where he distinguished himself in a wide range of disciplines. He then studied at Cambridge University under J. J. Thomson—the man who discovered the electron—and took his doctoral degree with Max Born at Göttingen. Oppenheimer was a man of the world, well read, conversant on art, history, and philosophy. He felt right at home at Göttingen, where a few years previously young Fermi felt an outcast. He was a prodigious theoretician who contributed to the quantum theory of his generation. At Berkeley he developed a reputation as a stern, even cruel, taskmaster, someone who occasionally took delight in ridiculing hapless graduate students or post-docs who were guilty of an error in calculation. One might accept C. P.
Snow’s judgment that Oppenheimer would have traded his entire career to have made just one discovery of the magnitude of Fermi’s three great contributions and yet still respect Oppenheimer’s achievements as a physicist of high caliber. Certainly, he had the respect of his colleagues at Berkeley and, increasingly, those of the growing Manhattan Project for which he now found himself in a leadership role.
The contrast with Fermi was striking. Fermi was neither well-rounded nor interested in high culture. He came from a distinctly middle-class background and never felt the need to rise above that. He could be socially charming, but in a more informal way. Everyone who knew him commented on the surprise they first felt when they met the legendary genius and discovered he was extraordinarily approachable, even diffident.
Fermi also found Oppenheimer’s style of physics more than a bit foreign. In 1940, he had traveled to Berkeley to give the Hitchcock Lectures, and in his spare time sat in on a lecture by an Oppenheimer acolyte. Later he confided to Segrè:
Emilio, I am getting rusty and old. I cannot follow the highbrow theory developed by Oppenheimer’s pupils anymore. I went to their seminar and was depressed by my inability to understand them. Only the last sentence cheered me up; it was, “and this is Fermi’s theory of beta decay.”
By 1943 Fermi was a legend, even before his colleagues began to appreciate the beta decay paper of 1934. Many things contributed to the legend: his landmark discoveries, his single-minded commitment to physics at the highest level, his astonishing ability to work his way through complex problems, his ability to simplify those problems in ways that facilitated understanding by those less gifted than he. He could be blunt, even dismissive if he believed someone was wrong, and his fondness for teasing those closest to him could be irritating, but he was never deliberately cruel. Physicists presenting new research knew they were in trouble if Fermi interrupted and said, “Excuse me, but there is something here I do not understand.” That was enough to convey his belief that the speaker was wrong. He had already won a Nobel Prize, something about which Oppenheimer may have had a bit of envy. He had also been in on the very start of the project that was now under Oppenheimer’s guidance.
The Last Man Who Knew Everything Page 26
