THE PERIOD BETWEEN EARLY 1935, WHEN FERMI SUBMITTED HIS long report on slow neutrons to the Royal Society in London, and November 1938, when he left Italy for good, was marked more by a consolidation of knowledge rather than by any new, revolutionary discoveries. In part this reflects a natural cycle in scientific inquiry, particularly for people like Fermi who, having made a significant discovery, tried to understand everything about that discovery before moving on to other research interests. In part, though, it reflects the increasingly political environment in Italy under fascism, culminating in the Italian aggression against Ethiopia and the gradual slide from domination over Nazi Germany to a humiliating subservience to the regime in Berlin. It also reflects developments in the Roman academic world that complicated Fermi’s situation and worked to restrain his own research agenda.
THE WORK ON SLOW NEUTRONS CONTINUED UNABATED. SEVERAL members of the team moved on, a natural result of professional pressures and opportunities. Segrè was offered a position at the University of Palermo in Sicily, where Corbino had done some of his early research in physics, and from the summer of 1935 onward was no longer a fixture at Via Panisperna. Next to leave was Bruno Pontecorvo, who moved to Paris in 1936 to work with the Joliot-Curies. D’Agostino returned to his job with Trabacchi at about this time, as well. Fermi continued to work with Rasetti and Amaldi, and together the three of them did exhaustive research on slow-neutron bombardment. Of the twenty-one papers Fermi published between the submission to the Royal Society in March 1935 and his departure from Italy in December 1938, only three focused on matters unrelated to slow neutrons: eulogies for Corbino, Rutherford, and Marconi, in that order. Of particular scientific importance, at least in retrospect, was a series of papers on the diffusion of neutrons in matter. These papers became a foundation for work done in the United States in 1939 and 1940, when Fermi began to explore the possibility of controlled fission reactions. Nothing the team discovered as they repeated experiment after experiment was as significant or as exciting as the original discovery of slow neutrons, but that did not matter to Fermi. His instinct for thoroughness drove him to complete these measurements in spite of—or perhaps because of—the deteriorating political situation. Burying himself in work was natural for him, but it also provided an escape from a thoroughly depressing political landscape.
Elsewhere in the world of physics, the main development in this period came not from Europe but, interestingly, from Japan. Until 1935, there were no satisfactory theories as to how a nucleus with many protons held together, despite the electrostatic repulsion of positively charged particles with each other. Something was holding protons and neutrons together in a tightly bonded mass at the center of the atom. The nature of the force was still a mystery.
At the moment Fermi was preparing the 1935 report on slow neutrons for the Royal Society, a Japanese physicist named Hideki Yukawa proposed a quantum field theory to explain how the nucleus is held together against electromagnetic repulsion. As part of the theory he proposed the existence of a massive particle, which he called a “mesotron,” which would act as a sort of glue to bind the protons and neutrons within the nucleus. In the history of scientific nomenclature, the mesotron’s story is particularly confusing. Its name was soon shortened to meson. Then it was called a pi-meson, and Fermi, in a typical attempt to find a catchy name for a new particle, shortened the name to “pion,” a label that stuck. Most of the work on Yukawa’s theory would have to wait until after World War II, when particle accelerators became powerful enough to produce pions as a product of bombarding nuclei with high-energy protons. For his theory of nuclear forces, Yukawa won the 1949 Nobel Prize.
Fermi played a major role in these pion studies after the war, but if he was aware of the theory as early as 1935, he certainly understood that the equipment at his disposal was completely inadequate to meaningfully explore Yukawa’s ideas about the atomic nucleus. He was, under the circumstances, compelled to continue his neutron studies, hoping for the day when he would have access to a powerful cyclotron particle accelerator.
THE INTERNATIONAL SITUATION AND THE GROWING RELATIONSHIP between Mussolini and Hitler certainly had an impact on events at Via Panisperna.
In December 1934, skirmishes broke out between Italian and Ethiopian military forces along the border between Italy’s colonial protectorate in Somaliland and Haile Selassie’s ancient independent kingdom. The skirmishes gave Mussolini the excuse he was looking for to launch a dramatic military intervention that would be the fascist regime’s crowning military glory. Threatening to invade Ethiopia, Mussolini whipped his population into frenzied patriotic fervor, at the height of which he called upon all married women to trade in their gold wedding rings for rings of steel. The government’s fiscal state was precarious at the best of times and unable to finance a major military campaign without additional financial reserves. Mussolini understood the power of public ritual and made sure that women throughout the country offered up their nuptial gold in public ceremonies that had the dual purposes of raising the country’s gold reserves and pushing war patriotism to a fevered pitch. Even Laura Fermi was impressed with the outpouring of devotion to the cause and offered up the gold ring Enrico had bought for her in 1928.
Mussolini’s increasingly aggressive stance lost the support of Britain and France at the League of Nations and thrust him into the arms of the one major power that would support him—Nazi Germany.
During the run-up to hostilities, the atmosphere at Via Panisperna was deeply affected. Segrè noted an inexplicable anxiety among his colleagues during the spring and mentioned it to Fermi. Fermi told him to go to the institute library and consult a large book in the middle of a table in the library. It was a world atlas and it opened up without effort to the well-thumbed pages on which were displayed the countries of the Horn of Africa. Segrè may have been oblivious, but clearly Fermi was not. He certainly discussed international events with Corbino, who as a member of the Senate was thoroughly informed of the government’s thinking on the subject. In the summer of 1935, Fermi went to the United States to attend the summer session at Ann Arbor, leaving Laura behind, and again was struck by how attractive the United States was as a place to work. At this point, the main thing keeping him from accepting a job in the United States was Laura’s refusal to leave Italy.
He spent the next two summers in the United States, as well. In 1936, George Pegram, head of the Columbia physics department, invited him to give a series of summer lectures on thermodynamics. The results, compiled later that year into a short book, are a model of clarity and simplicity and still worth reading for anyone interested in a brief but pithy introduction by one of the true masters of the field. While there, Fermi received an offer from Pegram to join the faculty on a permanent basis, but knowing of Laura’s resistance to leaving her beloved Rome, he politely declined. In 1937, he spent the summer in California, lecturing at Berkeley, where he spent time with the inventor of the cyclotron, Ernest Lawrence, as well as with a German-trained American theorist named J. Robert Oppenheimer. He also lectured at Stanford University, where he renewed his friendship with a young Swiss experimentalist named Felix Bloch. Bloch had completed a post-doc in Rome in 1932 and soon after, with Hitler’s rise to power, left Europe for Stanford.
Bloch and Fermi drove back across the United States together from California to New York, during which time they found the ubiquitous Burma Shave billboards greatly amusing: “At crossing roads don’t trust to luck / The other car may be a truck! Burma Shave.” Bloch accompanied Fermi back to Rome and joined Laura and Enrico on a trip to the country home in Tuscany in a new, more elegant car than the bébé Peugeot that served as the Fermis’ first car. The highway was now lined with billboards displaying menacing yet faintly ridiculous fascist slogans authored by Mussolini himself: “Mussolini is always right!” “To win is necessary. But to fight is more necessary.” Fermi and Bloch passed the time by converting these to Burma Shave slogans: “Mussolini is always right. Burma Shave!” The amusement they found in this subversive humor was, of course, short lived. Bloch returned to California and Fermi stayed behind, trying to stay out of trouble under an increasingly delusional fascist regime.
The Tuscan villa Laura’s aunt and uncle owned was the Fermi family’s summer refuge, and Enrico would join Laura and the children whenever he returned from his summer stints in the States. There they would spend the last few weeks of the summer enjoying the relative tranquility with Nella and Giulio, still young children. In the Tuscan countryside they could escape the constant barrage of fascist propaganda that Mussolini pumped out in an effort to keep the nation together under his increasingly erratic and paranoid rule. Whether they argued over the possibility of a move to the United States remains unrecorded, although it would be odd if the subject did not come up at least occasionally. Still, Laura refused to consider leaving Rome and Tuscany behind.
THE ITALY FERMI RETURNED TO IN THE FALL OF 1935 WAS ON WAR footing, and in October Mussolini decided to act, launching a full-scale invasion of Ethiopia. The Italian victory, inevitable though it was, took some seven months to secure and involved Italian use of chemical weapons against a poorly equipped Ethiopian military. Mussolini had his military victory, but little did he appreciate that its price would be ever-increasing reliance on economic, military, and diplomatic support from the ever more powerful Nazi regime in Berlin. Once the dominant member of the fascist club, Mussolini now found himself playing number two to an increasingly powerful and bellicose Hitler.
To avoid the stress of the daily headlines and the constant war propaganda, Fermi and Amaldi drove themselves at an even more aggressive pace. Weekend jaunts to the beach or the mountains became less frequent, and the easy camaraderie, the occasional pranks and jokes that defined the early years of the Rome School became difficult to maintain. “Physics as soma,” Amaldi later called it, using the term from Aldous Huxley’s 1932 Brave New World, which described a drug that induced a zombie-like state. It was their way of avoiding having to think about the increasingly troubling direction of the Italian regime.
Physics in Rome was no longer pure fun. Indeed, for Fermi, who had found unalloyed enjoyment in physics since his early youth, physics would not delight him again for at least a decade. Even then, in the aftermath of World War II and his own role in ending it, physics was never again for him the entirely carefree delight that characterized his early career.
WHEN FERMI RETURNED TO ROME IN 1936, THE FASCIST REGIME had built him a brand new institute.
In the early 1930s, Mussolini decided to bring all the disparate departments of the University of Rome together to one location, a relatively open area south of the old medical center, northeast of Rome’s Termini railroad station.
The building that would house the physics department, designed by one of Mussolini’s favorite architects, Giuseppe Pagano, was a functional, horizontal, five-story building, faced with glazed mustard-colored brick, far better suited to its purpose than the old rabbit warren on Via Panisperna. Never particularly sentimental, Fermi did not miss the old lab and appreciated the convenience of the new campus, a short bicycle ride from home and an easy lunchtime commute.
The team continued to disperse. The brilliant Ettore Majorana, who speculated presciently on some of the fundamental characteristics of neutrinos, received a position at the University of Naples in 1937, notably without having to enter a competition. He then disappeared without a trace the following year, on a boat ride from Palermo to Naples. The mystery of what happened to him remains unsolved but has been the subject of continuing conjecture to this day. Although new Italian students were admitted to the physics program at the University of Rome, including Oreste Piccioni and Eugene Fubini, the flow of post-docs and more senior visitors from the United States and Europe slowed, in large part because of political tensions and the flight of Jewish scientists from Germany and Austria to safe havens in the United States, the United Kingdom, and Canada. They were going to places like New York and Berkeley and London, not to fascist Rome, irrespective of the special treatment accorded Fermi and his team. In 1927, Italy could attract great European and American scientists to an international conference in Como. By 1931, however, some invitations to the Rome conference were discreetly declined owing to reservations about the character of the fascist regime. By 1937, doubts about the regime had vanished and, even if he had tried, Fermi would have found it difficult to attract the best international minds.
The biggest blow to Fermi and the dwindling Rome team was Corbino’s relatively sudden death from pneumonia in January 1937. Of all the people Fermi had encountered in his professional career in Italy, Corbino was clearly the most important and certainly one of the most extraordinary. In the early 1930s the regime required almost every academic in Italy to take an oath of allegiance to the Fascist Party. Corbino notably did not comply and, unlike Fermi, he never joined the Fascist Party. Corbino’s judgment, administrative genius, and seniority protected him. He identified Fermi as his star understudy early on, believing that the twenty-three-year-old would be able to push Italy into the forefront of international physics. Fermi never disappointed him, and the only serious recorded conflict between the two—when Corbino made his premature speech in 1934 regarding the discovery of transuranic elements—was quickly smoothed over. Corbino was more than Fermi’s boss. He was the younger man’s mentor, protector, and father figure, even standing in for Fermi’s late father at Fermi’s 1928 wedding. The sudden and unexpected loss of Corbino dealt a serious blow not only to Fermi but to the group as a whole.
Fermi wrote a eulogy for Corbino that not only focused on his scientific achievements but also touched on his important character traits, reflecting the debt Fermi felt for Corbino’s help and support. Fermi acknowledged Corbino’s influence on his career with his method of radically simplifying the study of apparently complex phenomena. The two physicists shared this love of simplicity, reflecting a conviction that the beauty of the discipline lay in its ability to describe complexity through the elucidation of simple underlying relationships. In their long and fruitful relationship, surely Corbino learned this from Fermi as much as Fermi did from Corbino.
The loss of his mentor and friend was compounded by the elevation of Lo Surdo to director of the institute. Fermi would not have sought this post, an administrative one with little advantage in terms of pursuing research, but it must have rankled Fermi that Corbino’s political opponent in the world of Rome physics would now run the institute that Fermi called home. To make matters worse, Marconi—head of the CNR and a strong supporter of Fermi and his team—died several months later. The early part of 1937 was not a happy time for Fermi.
MEANWHILE, ITALY AND GERMANY GREW EVER CLOSER, WITH Germany increasingly the dominant partner. During a May 1938 state visit to Rome, Hitler received a hero’s welcome. A new railway station, Ostiense, was built for the arrival of the German dictator. Street lamps were torn down and replaced with lamps topped with Nazi eagle iconography. Mussolini prepared an elaborate welcome, and Hitler seemed pleased with the reception. On a grand tour of the city, the two leaders passed through the beautiful central park of Rome, the Villa Borghese. The Fermis’ nanny was walking with young Giulio at the time, and the event seemed to register in the mind of the three-year-old. A few years later he would, rather innocently, step up to the defense of the two dictators while at elementary school in Chicago, causing not inconsiderable consternation for his parents, who were keenly sensitive about their immigrant status and their privileged position in the war effort.
The Villa Borghese was a short walk from the new Fermi home. In early 1938, the Fermis made a decision to upgrade their living accommodations. The old apartment on Via Belluno was not small by Roman standards, but the family could afford a nicer one, with Enrico’s double salaries from the university and the Reale Accademia, not to mention royalties from Enrico’s textbook and Laura’s independent income from her family. Perhaps at the urging of Laura’s close friend Ginestra Amaldi, the Fermis found an apartment on an elegant side street called Via Lorenzo Magalotti, less than a block from the Amaldis’ home and a short walk from the Villa Borghese, and moved there in May 1938. The upper-middle-class neighborhood was leafy and quiet, with expensive apartment buildings and small villas lining the Via dei Parioli, where the Amaldis had moved not long before. On Via Magalotti, the apartment was fitted out with a green marble-lined bathroom. Laura loved it. “It satisfied my ambitions of grandeur,” she later recalled, “which had been rising as Enrico’s position had steadily grown better.… I felt rich, well established, and firmly rooted in Rome.”
The timing speaks to Fermi’s thoughts regarding potential emigration. In spite of everything, in early 1938 the family had no immediate plans to leave Rome. Events over the next two months would, however, radically change the family’s calculations.
HITLER HAD BEEN PRESSING MUSSOLINI FOR SOME TIME TO CRACK down on the ancient and assimilated community of Italian Jews. Under the Nazi regime, Hitler had been able to carry out an increasingly aggressive anti-Semitic social policy in Germany, first excluding Jews from professional positions at universities and hospitals and banks and law firms and then broadening the restrictions, limiting the ownership of property and greatly reducing their rights as citizens of the Third Reich. Worse was soon to come.
To Hitler’s increasing annoyance, Mussolini had done nothing of the sort. Though he remained a virulent and violent Italian nationalist, his views on the Jewish population in Italy were complex and not entirely negative. The beautiful Margherita Sarfatti, one of the ideological drivers of Italian fascism, was Jewish. She served as Mussolini’s confidante, biographer, muse, and mistress for well over a decade. Jewish families were considered in every sense Italian, as well they might have been, given that their presence in Rome predated the unification of the country by some two thousand years. Ironically, many Jews wholeheartedly supported the fascist regime. Many, like Laura Fermi’s family, hardly viewed themselves as Jewish in any but a remote ethnic sense of the term. They were Italians first and foremost. Laura had readily acceded to Enrico’s request to raise the children as Catholics.
While he was the senior partner in the relationship, Mussolini was easily able to fend off Hitler’s demands for him to crack down on Italy’s Jews, but by 1938 il Duce realized this was no longer possible, or at least no longer worth the trouble. In July, the regime issued new racial policies, followed in September by promulgation of laws that began to restrict Jewish access to jobs and positions, to places at universities, and to the financial and real estate markets. The news came as a shock to the Fermi family, who followed these events by radio in the quiet of the Tuscan countryside. It was during discussions over the balance of this anxious summer that Laura finally gave way to Enrico’s persistent requests and agreed to move to the United States.
They assumed, correctly as it turned out, that they were under surveillance by the fascist secret police. Fermi was one of the very few figures of international prominence in fascist Italy, and Mussolini would, Fermi knew, take extraordinary measures to keep him in Rome. Indeed, every time Fermi went abroad he had to apply for permission to do so, under the watchful eye of Mussolini’s domestic and foreign spies, and clearly his wife’s unwillingness to travel with him to the United States ensured his ultimate return to Rome. Fermi’s file with the fascist political police, though not very large, indicates that he had been under surveillance for some time, at least since 1932. Now Laura and the children were going to come with him. He would need to be discreet.
Fermi drafted letters to several American universities, explaining that the circumstances that had held him in Italy no longer applied and inquiring whether a position might be available. Together, Laura and Enrico drove north from Tuscany into the Alps and dropped each letter in a different rural post box. They hoped that they would evade detection by the regime, and they were right. We do not know the names of all the universities queried, but we do know that George Pegram at Columbia, who had offered him a faculty position two years before, replied quickly and unreservedly. Given Fermi’s prior travels in the States, we might surmise that the University of Michigan, Stanford, and Berkeley were among the others. By this time, his good friend Hans Bethe had been at Cornell for three years, and it is certainly possible he also sent a letter there. In any event, Fermi decided to accept the offer from Columbia and began to plan for departure in the first quarter of 1939. This gave Fermi some time to quietly sort out his affairs at home and leave his research program in safe hands. The cover story would be that he was taking a six-month sabbatical. He hoped that the Italian authorities would believe him.
It remains an open question as to whether the racial laws promulgated beginning in September 1938 would have affected Laura. In deference perhaps to his own ambivalence, Mussolini incorporated an opt-out provision in the racial laws. One could apply to the regime for exemption from the laws, a provision designed for Jewish families who had proven useful to the regime and upon whom the regime relied for prestige and legitimacy. Laura’s father, Admiral Capon, applied on behalf of his whole family and his application was accepted in early 1939, meaning that Laura could have returned to Italy at any time during the Mussolini years without endangering herself or her family. Things changed, however, when Mussolini fell in 1943 and the Germans effectively took direct control over much of Italy. Jews, including Laura’s father, were rounded up systematically and sent off to concentration camps, where many, including Admiral Capon, perished.
Certainly, Italy’s increasing isolation and closer alignment with Germany troubled Fermi and constrained his work. Fermi was a vital part of an international community, but that community was vital for him as well, and he knew that isolation from this community would inevitably damage his ability to stay at the cutting edge of the field. He also was never able to obtain the funding he felt he needed and deserved for the experimental research program he envisioned in Rome. After Corbino’s sudden death, that funding became ever more problematic. These factors, as much as the racial laws, would have weighed on him. In short, there were, by mid-1938, many reasons for Fermi to leave Italy.
In mid-October 1938, however, a conversation in Copenhagen changed his carefully laid plans.