Diz’s parents hadn’t wanted her to pursue her scientific ambitions, either, her mother preferring that she go after a teaching degree and her father that she find herself a husband. But from the start, Diz had no intention of fitting into the passive role expected of women at the time.
Diz’s research was considered top-notch. Her PhD dissertation, which she had completed at the University of Chicago while Fermi was there, involved neutron-scattering experiments, and this work had, of course, come to the attention of the Manhattan Project’s officials, who quickly hired her to work on the selection of a neutron reflector surrounding the core of the atomic bomb. Once she and Al arrived at Los Alamos, they managed to ingratiate themselves into the community, most especially with Oppenheimer. And it was there that she pioneered a method to speed up the explosive growth of the chain reaction that powered the bomb.
As she worked on her experiments, she felt very removed from her university days, when she was just a girl crossing the halls of the University of Chicago, one of the few women in the physics department. She often reflected about how far she had come, further than her parents had ever imagined, further than they had ever wished for her.
chapter fifteen
The Professor and the Apprentice
Initially, Leona Woods did not realize the impact Fermi would have on her life, either on a professional level or on a scientific one. At the Met Lab in Chicago, he taught her not only the scientific theories that would propel her to become one of the most important figures of the Manhattan Project but also the essence of how to deal with the other scientists, how to move along with scientific changes, and how to handle the humiliations that were part of everyday living inside the laboratories. She became an assistant, a colleague, and a friend.
Although she was a self-confident young woman, when she started working with Fermi and his colleagues she suffered a momentary bout of self-doubt, especially when she began associating with them on a more informal level, something Fermi wanted her to do. They often played the game Murder, and at one point she observed, “I shrank into the corner and listened with astonishment to these brilliant, accomplished, famous, sophisticated people shrieking and poking and kissing each other in the dark like little kids.” They surprised her and they amused her. But they also appeared a little more human.
She soon discovered that Fermi did not believe, as most Americans did, that people were born with equal mental abilities. He had worked with a wide variety of personalities, he told her one day, and had noticed how different people were at a fundamental level. There were internal differences, he’d learned, no matter how hard people tried to pretend otherwise. The idea that anyone could become anything they wished if they simply tried hard enough, he imagined to be only wishful thinking, perhaps an American invention to give hope to those who had none. No amount of hard work would allow a person to become anything more than their nature had set them up to be. The predisposition for greatness usually showed up early on. As it had in him, he was not too humble to add.
Leona herself was not a humble young woman. She had realized from a young age that her intellect was exceptional and that it separated her from her peers. Listening to Enrico Fermi and his theories on greatness, she was often struck by the feeling that he might be correct.
Both Leona and Fermi were friends with Herbert Anderson, and it was Herbert who had helped solidify their friendship outside the laboratory. Soon after she started working at the lab, Leona began to spend time with Anderson and Fermi after work. Each evening, they escaped their laboratories and headed outside. Fermi was a powerful swimmer, whose notion of a good time included a few laps in the waters of Lake Michigan. This was usually done every day between five and six o’clock. She swam with them during the spring and summer, but when the colder weather arrived, she had a hard time keeping up with Fermi. So did his wife, Laura, who disliked the activity. He’d jump off the rocks from Promontory Point, swim a few laps, then walk back to the laboratory, accompanied by Anderson.
Fermi had initially arrived in Chicago without his wife and children, who were then settled in New Jersey. He had found housing for a short while in an apartment just around the corner from International House, where several professors and quite a few students, including Leona, were then living.
Eventually Laura Fermi joined her husband in September 1942, bringing along their children, Nella and Giulio. They rented a large house on University Avenue, and the children were soon enrolled in school, where they thrived, to Fermi’s obvious delight. Greatness, he told Leona, was also hereditary.
Sometimes their swims in the lake were followed by the large meals Laura would always prepare. It was during these suppers that Leona learned about the Fermis’ life in Italy and about their leaving Rome. Their home in New Jersey had been bought with a portion of the Nobel Prize money, chosen because it possessed a big basement. Fermi had dug a deep hole in the basement floor and buried a good chunk of what was left of their savings. He had come to fear that now, because they were considered enemy aliens, someone might come in the middle of the night and take away what they owned or kick them out of the country that had so graciously welcomed them. Fear had pursued him in Italy, and while he was not as afraid in the United States, anxiety had now become a part of his persona.
While Fermi was an exceptional instructor at the university, he was first and foremost a physicist. He went nowhere without his slide rule, which he kept at the ready safely tucked in his breast pocket, his mind seemingly spinning a hundred ideas per minute. He had an office where he liked to work on his theories, initially doing so on his own, then sharing the results with his colleagues. When Leona joined the team, he got into the habit of calling on her in her tiny office, not far from his, to come join him, and together they pored over the day’s calculations. It was not unusual for them to stay up late talking physics and performing experiments. Sharpened pencil in hand, or with screeching chalk on a blackboard, Leona probably spent more hours with him than his wife did.
He loved the United States, Fermi often told Leona, but he worried about his wife. He had wanted to leave Italy for some time, but it was only when he won the Nobel Prize that the opportunity to do so had presented itself. And Columbia University had stepped up. While he had been happy for the chance at a new life, Laura had not been happy about leaving Rome. She had a large family in Italy and an equally large group of friends. She loved Rome, which she believed was the center of the world, the Eternal City, with the most fascinating, wonderful people. It had not helped Fermi’s cause that Laura came from a privileged family that had always provided for and doted on her. It was only the threat on their lives that had finally pushed her to agree to leave.
Laura had been a student at the University of Rome, where she studied electrical engineering. But after meeting Enrico, she gave up on those endeavors for the sake of marriage. And she never regretted it.
Those who came to know Laura Fermi in America wondered why she had bothered with a university course at all. She never asked her husband’s colleagues any questions, nor did she seem interested in her husband’s work or the projects that he was involved in at the University of Chicago. She didn’t talk about politics or the war in Europe. Her conversations revolved around the children, their schoolwork and afternoon activities, food, olive oil, and good wine. While that was the impression she liked to give, in reality she was a deep thinker, as people would eventually find out—a woman who kept her feelings to herself rather than divulge them to others in the way she had come to expect from most Americans.
Fermi was a busy man and had the habit of withdrawing completely when working out a problem, holing up in his office and hardly communicating with anybody until he had cracked the answer. Taking little notice of anyone around him, he barely ate or drank, and Laura Fermi was aware of this. She let him be.
Laura had learned English at a very young age, so that when she arrived in the United States she spoke the language better than her husband did, a m
atter that irritated Fermi, as for a time he had difficulty communicating, and people complained of not being able to understand him.
Enrico had discovered the field of radioactivity in summer 1919, at the age of seventeen, when he read the laboratory notes of physician Ernest Rutherford. He wrote summaries of Rutherford’s papers in his notebooks and studied them in depth, soon realizing that in Italy the subject was hardly ever discussed. By the time Fermi was twenty, he could also read scientific papers in German, which was very useful, given that much of the work in radioactivity was being done in Germany. He attended the graduate program at Pisa and in 1926 took part in a competition for a professorship being held by the University of Rome. He won, thus becoming the youngest professor the university had ever had.
His own experiments on the bombardment of matter with neutrons started in 1934. Those experiments were performed alongside his students and colleagues, and he published dozens of articles about them. But the experiments ended when his Rome laboratory broke up and he moved to the United States, his colleagues scattering across Europe. However, he still hoped to carry on that work in America, he initially told Leona while working in Chicago, together with his new faithful associates.
chapter sixteen
Chicago Pile-1
In scientific circles in the United States and the world over, not all scientists were thrilled with the idea of using science as a means for developing a bomb. Many hoped that some sort of technical glitch would prevent a chain reaction from happening, and in turn would prevent the building of an atomic weapon. But Enrico Fermi wished the opposite, and one night in December 1942, he conducted an experiment beneath the stands of the University of Chicago’s stadium to prove once and for all that it could be done, that his hopes could be realized.
Arthur Compton had originally wanted the test to take place in an area about twenty miles southwest of Chicago, in the Argonne Forest, named for the Forest of Argonne in France, where the United States troops had fought during World War I. The forest was heavily wooded with oak trees and had a log cabin that had once housed a Girl Scout club. The site was a pretty one, with trees flanking a lake that iced over in the winter; colorful flowers shooting up from the ground every spring and summer; and foliage changing hues as the summer days ended. Construction for the experiment started in earnest and continued at a frantic pace. However, by the time the scientists had collected enough graphite and uranium for the chain reaction, construction had not been completed. This posed a problem, as speed and efficiency were required. So it was decided that the experiment should be tried a little closer to home. The University of Chicago’s Stagg Field was chosen as the spot; its stands, in the underbelly of the stadium, would have to work.
Compton agreed that Stagg Field’s double squash court would be a suitable site. Despite its being in the middle of a stadium at the University of Chicago, and the university itself being in the center of a populated area, they did not expect trouble. Compton initially wondered if they should ask the president of the university for permission, but he didn’t think it was necessary. No one, aside from them, needed to know about their doings.
On November 4, they prepared the double squash court under the west stands of Stagg Field. The layers of the graphite matrix were to be the supporting graphite for four- by six-inch timbers, which were carefully laid out. They performed this work very slowly and carefully, and by November 20, they had added a fifteenth layer of graphite.
Within each layer a hole was left for a zip rod, a long wooden stick wrapped in cadmium that would absorb neutrons. The rod was meant to be pulled out and dropped in with the help of a rope. If the rope snapped, the rod would fall and stop the chain reaction. If the rod was pulled out and held for a moment just before the pile started up again, or if it was let go, gravity would do the job and the rod would fall back into the pile. Walter Zinn, another scientist in Fermi’s laboratory, was in charge of this whole operation, and he felt the weight of responsibility.
In addition to the zip rod, another wooden stick encased in cadmium had been added that could be manipulated by hand. There was an emergency bell that would ring if the boron trifluoride counters and ion chambers rose to a potentially dangerous level.
The morning of the test was frigid. Leona and Fermi stepped outside the slightly snow-covered grounds of the university buildings and onto the field, icy particles crunching beneath their feet. She held on to a thick pile of papers with Fermi’s calculations and plans depicting the experiments reaching the critical points. Everything had been well thought out, with each person knowing his or her assignments. They made sure to have nearby a vat of concentrated nitrate solution, which could be used to douse the graphite pile in case of emergency, stopping the chain reaction. However, despite all their preparations, they felt agitated, as they knew that if the experiment worked, the repercussions would be historic.
Everyone was there as Leona, in a fairly loud voice, began to read the counts of the boron trifluoride counter: “Two, two, three, one.” It was the manner of counting Enrico Fermi had designated, in ten-second intervals, and which she had memorized.
No one spoke in the darkness. Leona could hear her own teeth chattering from the cold, although she guessed the rattling was also partly due to the excitement. There was nothing normal about the situation, and they knew it. To quiet their nerves, some of them counted backward.
George Weil, one of the scientists present, pulled out the last control rod, plucking it out foot by foot, as Fermi had instructed him to do. Fermi, at that particular moment, was on the stands above them, watching the whole operation and making additional calculations on the spot, while Leona kept watch on the monitors.
Those present felt their anxiety growing by the minute, until finally Walter Zinn released the rope, the rod falling into the reactor, and the control rod was pushed in, the intensity of the neutrons dropping quickly. The chain reaction was thus stopped. Then it was started again, and everything operated normally. December 2, 1942, would go down in history as the first time a chain reaction had occurred. Sure, the spark had been only enough to power a lightbulb, but that was not important. What was important was the fact that it had worked.
Leona had spent two months beneath the stands of Stagg Field preparing for the first chain reaction, and its success made her giddy. Fermi had instructed her to read everything she could about the latest developments on plutonium production reactors; she had also prepared the counters for the graphite piles. Now her work had come to fruition. She felt giddy with pride.
Leona and the others started locking every control mechanism and turning off the power supply. They were about to don their overcoats to walk back to the laboratories when Eugene Wigner, another scientist in the Fermi group, who was carrying a bottle of Chianti wine, stopped them. Given that Fermi was Italian, Wigner thought Chianti a fine choice to commemorate the occasion. He had also found some minuscule paper cups, and in those he managed to pour some wine for the nearly two dozen people present. Each person then signed his or her name on the bottle.
Eugene Wigner later wrote: “The success of the experiment, its accomplishment, had a deep impact on us. For some time we had known that we were about to unlock a giant; still, we could not escape an eerie feeling when we knew we had actually done it. We felt as, I presume, everyone feels who has done something he knows will have very far-reaching consequences which he cannot foresee.”
Leona and Fermi returned to the university’s laboratory, their feet echoing loudly on the frozen ground, the temperature having dropped below zero. They said little. Leona didn’t know what Fermi was thinking, and she didn’t want to ask; however, she could speculate. She imagined his thoughts were just as heavy as hers. “Of course, the Germans have already made a chain reaction because we have,” she told herself, “and they have been ahead until now. When do we get as scared as we ought to and work harder?” No one knew how far the Germans were in their own development of the bomb, but just like every other sci
entist, Leona feared that the Americans were falling behind. However, she didn’t share these thoughts with Fermi. Arriving near the laboratory, they went their separate ways.
Completing the experiment beneath the stands at the University of Chicago had seemed like a good idea. Fermi had decided to use several neutron-absorbing cadmium rods. As he slowly inserted those into the pile, the fission chain reaction stopped. If he wanted to get it started again, he needed to pull out a rod again—this action was performed very, very slowly.
Of his success, Fermi had this to say: “The first pile had no device built in to remove the heat provided by the reaction, and it was not provided with any shield to absorb the radiations produced by the fission process. For these reasons, it could be operated only at the nominal power which never exceeded two hundred watts. [Two hundred watts will illuminate a couple of lightbulbs.] It proved, however, two points: that the chain reaction with graphite and natural uranium was possible, and that it was very easily controllable.”
In mid-1942, Zinn and his assistants removed the graphite-and-uranium assembly from beneath the stands of Stagg Field and transferred them to the Argonne Forest, which was still a forested lot when they began dismantling the original pile. Along with the pile went pertinent instruments, pliers, files, and whatever else was needed or that Leona Woods had managed to steal from other departments.
The scientists felt a lot of pressure at Argonne. The new pile was now nicknamed CP-2; the new laboratory contained a large machine shop for construction, a chemistry shop for experiments, and a long room that worked as an office. The two-story dormitories were two wide-open spaces that were not used efficiently, Leona thought, as one was the domain of all the men involved in the project, and the other one was entirely her own, as she was the only woman on staff. Between the two dormitories was a bathroom with a shower and a toilet, which they all shared, to her despair. The men were not a tidy bunch, especially when they did their laundry and hung it in the bathroom. John Marshall made a habit of taking his damp underwear into Leona’s dormitory, where there was more space. On the first floor of the dormitories were the offices of Enrico Fermi and Walter Zinn.
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