The Age of Radiance

by Craig Nelson

  Fermi worked in the Institute of Physics, which was on a small hill in the middle of Rome, surrounded by a sea of traffic but very quiet on that little hill. There were trees, ponds, a nice garden, a fountain—really quite an oasis in the hectic traffic of Rome. Fermi was twenty-nine years old when I got there. He was a full professor since he published Fermi’s Statistics at the age of twenty-five.

  I had studied with [Arnold Sommerfeld, one of the cofounders of quantum mechanics], and Sommerfeld’s style was to solve problems exactly. You would sit down and write down the differential equation. And then you would solve it, and that would take quite a long time; and then you got an exact solution. And that was very appropriate for electrodynamics, which Sommerfeld was very good at, but it was not appropriate at all for nuclear physics, which very soon entered all of our lives.

  Fermi did it very differently. . . . He would sit down and say, “Now, well, let us think about that question.” And then he would take the problem apart, and then he would use first principles of physics, and very soon by having analyzed the problems and understood the main features, very soon he would get the answer. It changed my scientific life. It would not have been the same without having been with Fermi; in fact I don’t know whether I would have learned this easy approach to physics which Fermi practiced if I hadn’t been there. . . .

  Fermi seemed to me at the time like the bright Italian sunshine. Clarity appeared wherever his mind took hold. . . . Depending on how we count, Fermi training led to ten, eleven, or twelve Nobel Prizes. I estimate the probability that an existing Nobel Prize winner in physics “gives birth” to another winner is less than 1/10. So if this is purely random, the probability of one winner giving birth to ten other winners would be one-tenth to the tenth power or one in 10 billion, which is essentially impossible.

  Physics seemed to infuse Fermi’s every waking moment, as American physicist Phil Morrison remembered from his time with Enrico: “I want to mention the ‘Fermi Questions.’ Fermi was the first physicist to my knowledge who enjoyed doing physics out loud walking through the hall. . . . As we walked, the sounds of our footsteps reflected off the high surface—wood, no acoustic treatment—and seemed to bounce throughout. And he said, ‘How far do you think our footsteps can be heard in this building?’ And then he began to tell me what the yield of sound would be from the impulse, how far that would go, how you have to worry about the wood conduction and the air passage. And pretty soon, by the end of the hall, he had [an answer]. It was a fast calculation. Sounded very reasonable. And when I tried to recalculate it, I got something like the same result—slowly and looking at the numbers over and over again. This was my idea of a Fermi Question: Turn every experience into a question. Can you analyze it? If not, you’ll learn something. If you can, you’ll also learn something.”

  At that moment in the nuclear science of the 1930s, there was a whole series of astonishing new questions to answer. Inspired by Fred Joliot and Irène Curie’s revelations, those who’d taken an interest in radioelements began to focus on the atom’s nucleus as the source of uranic powers. This was a difficult proposition, as physicist Amir Aczel noted, since “if an atom were the size of a bus, than the nucleus would be the dot on the letter i in a newspaper story read by a passenger on the bus.” Hitting that dot on the letter i would make Enrico Fermi a laureate. His efforts began in 1934, when he combined the Joliot-Curie method of artificial irradiation with Chadwick’s neutron discovery and his own theory of the weak force to imagine a tiny, uncharged particle that would not be waylaid on its path to crashing into an atom’s nucleus. Neutrons fired in the right way, Fermi believed, should be able to excite radiation and produce isotopes—subatomic variations of elements—on just about any member in good standing of the periodic table. Hans Bethe: “Fermi organized a group to do this—of course, his old collaborators and friends, but they added d’Agostino, who was a chemist, and most importantly, Trabacchi, who was a biophysicist in charge of the biophysics in the Department of Health of the City of Rome. He had a very precious possession, namely one gram of radium. And radium produces all the time radon, a gas, which can easily be separated because it escapes from the radium, and then you can expose any sample you want to the alpha rays from radon.” Emilio Segrè: “Radon plus beryllium sources were prepared by filling a small glass bowl with beryllium powder, evacuating the air, and replacing the air with radon. Rasetti was vacationing in Morocco so Fermi, Amaldi, and Segrè got to work. Fermi did a good part of the measurements and calculations; Amaldi did the electronics; and I secured the substances to be irradiated, the sources, and the necessary equipment.”

  It was a good thing these physicists were young and in shape, as this turned out to be a multistage investigation requiring a great deal of sprinting. Bombarding beryllium with radon produced neutrons, which Fermi and his team would in turn use to irradiate as many elements as they could get, to dramatically extend the Joliot-Curie findings of man-made radiance. Making neutrons from radon-charged beryllium, however, triggered their homemade version of Geiger counters that would be used to measure whether they’d succeeded in creating isotopes, making it look as though everything was already radioactive (Geigers weren’t yet commercially available, so every scientist working on radiation crafted his or her own). To keep this from affecting their results, Fermi and his grad students would bombard the test element with their neutrons in one room, then run the irradiated subject to the other end of the hall to measure it with the counters. Bethe: “The experimenters had to run as fast as they could along the second-floor corridor from the exposure place to the counter. . . . I believe Fermi had the record of time of running from one place to another. There was a visit one time from a very dignified Spanish physicist, who wanted to see His Excellency Fermi, and he was shown a man in a very dirty lab coat, running like mad along the corridor.”

  They began at the beginning, with the periodic table’s slot number one—hydrogen—and proceeded up the grid: oxygen, lithium, beryllium, boron, carbon. Nothing worked. Even with Trabacchi’s precious seed as a source, they could find no induced radiance. Element after element failed, then failed again, then again and again . . . until they got to fluorine. From then on, the success rate was incredible: out of sixty elements tested, forty could be alchemized into radioactive isotopes. Joliot-Curie’s quirk of happenstance had been turned by the Fermi team into a scientific procedure.

  When Fermi’s team bombarded uranium, their chemical tests showed its nucleus capturing the neutrons, spitting out photons of gamma radiation, and becoming heavier, turning into an isotope with an atomic number (in protons) of 93 and an atomic weight (in protons and neutrons) of 239—an element that had not yet been discovered. Would this be as epochal as the Curies’ discovery of radium? The Nobel committee thought so, as did the Fascists. But Fermi wasn’t absolutely sure since the chemistry needed for proof was inconsistent. Even so, on October 22, 1934, a professional’s intuition would trigger the discovery of a fundamental ingredient in the birth of nuclear power. “One day, as I came to the laboratory, it occurred to me that I should examine the effect of placing a piece of lead before the incident neutrons,” Fermi remembered. “Instead of my usual custom, I took great pains to have the piece of lead precisely machined. I was clearly dissatisfied with something: I tried every excuse to postpone putting the piece of lead in its place. When finally with some reluctance I was going to put it in its place, I said to myself: ‘No, I do not want this piece of lead here; what I want is a piece of paraffin.’ It was just like that with no advance warning, no conscious prior reasoning. I immediately took some odd piece of paraffin and placed it where the piece of lead was supposed to have been. About noon everyone was summoned to watch the miraculous effects of the filtration by paraffin. At first I thought the counter had gone wrong because such strong activities had not appeared before.”

  Hans Bethe: “Neutron research led to many surprises. It turned out that if you (as I remember it from the tales, since I was
n’t there) put the sample on top of a wooden table, the radioactivity was stronger than if you put it on top of a marble table. Of course, everything in Rome was of marble, if it wasn’t of wood. And so, I guess they got the idea that maybe different surroundings might make a difference, and so instead of using a lead box around the sample, they decided to use a paraffin box. And the paraffin box was tremendously effective. The radioactive count increased about 100-fold with most of the elements. That was a great surprise, of course. And Fermi, having discovered that in the morning, went to lunch, and over lunch he decided what was the reason for it. . . . The hydrogen, which was in paraffin and in wood, would slow down the neutrons.” The slowing down made neutrons more likely to collide with neighboring nuclei, and more likely to sustain a chain reaction. Laura Fermi: “Physics was comprehensible, as long as atoms were small planetary systems and discoveries could be made in goldfish ponds . . . like the discovery of slow neutrons. . . . Back in the laboratory after their siesta, the group decided to test Fermi’s theory using the most abundant hydrogenated substance at hand; and so they plunged neutron source and target in the goldfish pond at the back of the old physics building. Lo and behold! Fermi was right. Water too increased the radioactivity in the target by many times.”

  After the Fermi team announced that bombarding uranium produced short-lived transuranics—an array of isotopic variants that, to the inexperienced radiochemists of the time, appeared to be innumerable—the University of Rome experiments were taken up by the Joliot-Curie team in Paris, and by Lise Meitner and Otto Hahn in Berlin. Racing to uncover uranium’s secrets, the three labs appeared to generate more and more transuranes, with ever more half-life decays. The method used by modern science, especially within a focused group such as this—sending details of experiments and results to each other, publishing findings as soon as possible, colluding and at the same time rapaciously competing to be first with a groundbreaking discovery—would in the web argot of the next century be called hive mind, a collective effort of human brainpower that would create far more than any one person or team could achieve alone. Scientists have been hive-minding, it turns out, since the Royal Academy began publishing during the Enlightenment.

  By the end of 1935, however, the ragazzi Corbino were undone, with Rasetti at Columbia, Segrè at Palermo, Pontecorvo in France, and the atmosphere in Italy relentlessly gloomy as the country prepared for war in Ethiopia and the limitations brought by globally imposed sanctions. Only Amaldi and Fermi remained in the department of physics’ garden monastery.

  The phone call Enrico and Laura were waiting for that night of November 10, 1938, would affirm his decision to abandon their relatives, their friends, their heritage, the Eternal City, which Laura loved with such a passion, their extremely comfortable life, and the whole of their worldly possessions (including a lemon-yellow Peugeot Bébé convertible with celluloid windows and a hand crank for emergency start-ups, which were frequent). The family would immediately flee, as resident aliens, to the United States. Laura’s most significant previous American experience had been in joining her husband when he taught summer school in Michigan, and regardless of the many charms of Ann Arbor, it was not Rome. During one visit coinciding with America’s Prohibition, the university’s chemistry department had to bury the alcohol it used for experiments to keep it from being stolen and drunk. Enrico, however, regularly discussed emigrating to the USA. Coming back from one semester accompanied by the Swiss physicist Felix Bloch, the two noted how superior the Burma Shave billboards in Michigan had been compared to Mussolini’s Fascist exhortations along the Roman highways.

  But that was one of the few jovial moments outside the lab. In 1936, a month after Hitler occupied the Rhineland, Enrico thought it prudent to supply each member of his family with a gas mask. He wasn’t being fearful, just pragmatic. Nella Fermi: “For the most part, my father had very little to do with us when we were children, and I think it’s too simple to say that he was too busy with his work and that he had no time for my brother and me. I think he was certainly absorbed in his work, but beyond that, he was a man of reason, and he was a physicist through and through. And he could not relate to us on an emotional level, so it wasn’t until we were old enough (and I quote from him) ‘to talk to’ that he could approach us, and that he could approach us on his own level. With adult hindsight I am convinced that it wasn’t that he lacked emotions but that he lacked the ability to express them.”

  Depending on the phone call, Laura and her children would immediately be deserting the culture and refinement of Europe, the magnificence of Rome, and a life of wealth and status, for some backwoods of hillbillies on the other side of the globe. A third-generation Italian cosmopolite, Sra. Fermi felt she could never fit in over there. Her English was rudimentary schoolgirl; her husband’s came from reading Jack London novels. He loved everything about America. She thought otherwise.

  Signore Fermi met Signorina Capon when he was twenty-two, and already so prominent as to hold a professorship. She was a mere sixteen. It was a Sunday in the spring of 1924, and a group of friends were taking the air in the countryside of suburban Rome, in a meadow adjoining the fork where the Aniene meets the Tiber. He was dressed in a black suit and black bowler, still in mourning over the death of his mother; yet, he decided that they should all play soccer.

  Two years later, the Capons were planning to spend the summer in Chamonix, the French resort shaded by Mont Blanc. But Mussolini’s new monetary policy kept them from being able to get any francs on the foreign exchange, and even Laura’s father, an officer in the Italian navy, could not overcome this setback. Friends recommended the Dolomites instead, and they arrived to find many of Laura’s school chums there for the season, including that acquaintance Enrico Fermi, who was now living with his father, Alberto, and sister, Maria, in Città Giardino, a new suburb reserved for civil servants—Alberto worked for the railroads and sang Verdi arias during his morning shave—not far from that meadow where Enrico and Laura first met.

  On his arrival, Fermi immediately arranged for the group to make a series of hikes and climbs, always using his thumb to measure distances, both on maps and in real life. His great passion besides physics was mountain hiking, and this seemingly odd mix of scholar and athlete would be common among his peers. Niels Bohr was both a famed soccer player in his youth and a Ping-Pong champion as an adult, while Werner Heisenberg spent his lifetime downhill racing, at one point being clocked at an alarming fifty miles an hour. Physicist Valentine Telegdi: “Fermi was completely devoted to physics, and his whole existence centered around it. He appeared to have very few outside interests such as literature or the fine arts. He engaged in sports, e.g., in mountaineering and tennis, but one often got the impression that it was all for mens sana in corpore sano—i.e., to be in the best physical condition for doing physics; it must be added that in sports as well as in parlor games (which he occasionally organized in his home) he liked to win, being fiercely competitive [though he] was totally secure in his own physics talent and almost never displayed jealousy of another. The only exception, as one of his students recalls, was Einstein. More than once Fermi expressed annoyance at the attention Einstein received from the press.” Laura Fermi: “One day that summer I asked Fermi to quiz me and see if I was well prepared for the approaching exam on the two-year physics course. We were at Ostia, and Fermi was sitting cross-legged on the sand, in his bathing-suit, which came up almost to his neck. As he quizzed me, his usual grin faded and his lips tightened. In the end he said: ‘I am sorry, Miss Capon, but you don’t understand a thing.’ What an encouragement!”

  Fermi told his friends that the woman of his dreams would be tall, athletic, blond, with ancestors from the countryside and no thoughts of religion—practically the opposite of Laura, who was descended from urban Romans for many generations, unathletic, and relentlessly brunette. Laura: “Fermi had always said he wanted to do something really exciting and outstanding. Either buy a car or get a wife. So when he b
ought a car I was a little disappointed, although I didn’t have any real idea of getting married. But then he was more extravagant and got both a car and a wife. . . . I remember a sense of not even knowing whether he had asked me to marry him or whether he was posing a theoretical question of what would happen if I got married to somebody and he at the same time would get married to somebody else.”

  On July 19, 1928, they were wed, honeymooning in the Alps, hiking through the shadows of the Matterhorn, which Enrico thought was a perfect opportunity to turn Laura into a physicist . . . but when she refused to accept the mathematical proof that light was electromagnetic radiation of waves and particles, he gave up. Together, though, they wrote a physics textbook for Italian secondary schools, which brought the family income during their lean salad years. Laura: “The next winter was the coldest on record in Rome and we began talking of storm windows. Fermi pulled out his slide rule, calculated the effects of drafts on the inside temperatures, misplaced the decimal point, and we froze all winter.”

  Fermi had wanted to leave Italy ever since the government had passed the Manifesto della Razza on July 14, 1938—the Italian version of the Nazis’ Law for the Restoration of the Professional Civil Service, which prevented Jews from government jobs and meant that, as European higher education was civil service, the Universities of Berlin and Frankfurt had, overnight, lost a third of their professors. Though Fermi and the children were Catholic, Laura was Jewish. As a result of the new decrees, Laura’s father, practically of Roman nobility from his decades in the navy, was dismissed from active duty and placed on reserve. Even so, Laura was convinced that the Razza was a minor legal kerfuffle, a temporary annoyance. Italy’s 1870 nationalist movement had freed Jews from the ghettos and given them full equality; they were now so few in number and so thoroughly assimilated that they were practically invisible. A third of them were Fascist Party members; Mussolini’s own mistress was Jewish. Just after the law was announced, Laura overheard one man on the street ask another, “Now they are sending away the Jews. But, who are the Jews?” Mussolini received a telegram from a Sicilian mayor: “Re: Anti-Semitic Campaign. Send specimen so we can start campaign.”