by Gino Segrè
Fermi decided to use his scholarship in Göttingen. Curiously enough, his stay there was neither especially happy nor productive. Although Fermi was not treated badly during his eight months in Göttingen, there is no indication of his having been perceived as especially promising or of his having formed any connection with Werner Heisenberg, his contemporary and a rising star there.
Fermi was surely made conscious of the low esteem in which German physicists held physics research in Italy. According to a close colleague, Fermi had felt the Germans “were very conscious of their capacity, of their preparation, of their ability. All others were coming to learn from them. And it was true. But they tried to make a point of this, to stress the point.” This bothered the proud young man.
The lonely twenty-two-year-old Fermi wrote Persico with some irony about Göttingen, including a comical sketch of the German perception of atomic scattering and a portrait of a prototypical Göttingen woman physicist. Both were uncomplimentary. He assured Persico that given the woman’s looks, there was no danger of his being summoned as best man for a wedding.
Both the foci and the ethos of Göttingen physics were unappealing to Fermi. He always pursued a physical picture rather than the mathematical formalism prevalent in Göttingen. In this respect, it’s interesting to compare Fermi to three other budding theoretical physics geniuses who were his contemporaries. Unlike Fermi’s, the talent of those three was immediately recognized in Göttingen. In addition to Heisenberg (b. 1901), there were Wolfgang Pauli (b. 1900) and Paul Dirac (b. 1902).
By 1930, all four prodigies had done Nobel Prize–caliber work, were established professors, and were attracting younger physicists from around the world to their respective centers in Leipzig, Zurich, Cambridge, and of course Rome. The four often worked on similar problems, and sometimes even on the same ones, but in markedly dissimilar ways. Each had a characteristic style, a reflection of his personal strengths and predilections. It may seem strange that style plays such an important role in theoretical physics, since science’s results are often portrayed in an impersonal manner. But human passions and special abilities shape its achievements as much as they do in other endeavors.
Pauli and Heisenberg had been Sommerfeld’s students together in Munich and in successive years were assistants of Born’s in Göttingen. Dirac had been educated at Cambridge, hardly the physics backwater that Italy was. Unlike the other three, Fermi was self-taught. In addition, Fermi considered himself an experimentalist as well as a theorist, combining action with concepts.
The three others, in contrast to Fermi, were exclusively grounded in theory. Dirac wanted mathematical elegance and beauty to be his guide. He was known for his quirkiness, often brusquely answering questions with “Yes” or “No” or “That is not a question.” Heisenberg almost failed his doctorate exam because he enraged the committee’s experimental physicist by being unable to explain how a storage battery worked. As for Pauli, he prided himself on the so-called Pauli Effect, which said that a key piece of machinery would always break when he entered the room.
One cannot imagine any of these stories being told about Fermi. He operated easily in both the theoretical and experimental spheres. Years later, when asked how he had entered the experimental field, he laughed and said, “I could never learn to stay in bed late enough in the morning to be a theoretical physicist.”
While effectively bridging experiment and theory, Fermi also had his limits. He would not make the intellectual leaps that Heisenberg became known for or formulate one of Dirac’s aesthetic mathematical marvels. Nor was he as famously critical as Pauli. But nobody could grasp all the interconnected aspects of a problem and reach a conclusion the way he could, nobody was able to significantly probe as many areas of physics as he was, and nobody could estimate orders of magnitude of physical phenomena as surely and as quickly as he could.
All in all, Fermi did appreciate the contributions of the German community of theoretical physicists. As a pragmatist, he was cognizant that they were unlikely to follow the Italian scientific literature. Accordingly, Fermi adopted the procedure of publishing key articles in either German or English. For reasons of national pride, he usually submitted a parallel version to Italian journals.
Returning from Germany to Italy in late summer of 1923, Fermi found his interest turning increasingly to statistical mechanics, a subject that would allow him a deeper understanding of thermodynamics, the study of heat. Thermodynamics had been one of the great triumphs of nineteenth-century science, its laws a cornerstone of physics and chemistry. But since thermodynamics is confined to macroscopic quantities, a number of individuals in the second half of the nineteenth century began to seek its underpinnings in the microscopic objects that make up the macroscopic state. They asked such questions as “What does thermal equilibrium mean, and how is it achieved? What does temperature really measure, and how does disorder come about?”
The logic behind these questions can be applied to other arenas. Knowing the size of a city, the total number of its inhabitants, and their average age tells a great deal, but it is not sufficient for planning traffic patterns. A well-oiled machine may work perfectly, but it is only by understanding its components and how it is assembled that one can truly appreciate its functioning. Asking for analogous explanations from thermodynamics led physicists to questions of probability, a topic that would continue to interest Fermi throughout his career.
Fermi’s fascination with thermodynamics and statistical mechanics was absorbing him, but he still had no job. Fortunately Corbino came to the rescue once again, arranging for him to teach a mathematics course for chemists and biologists at the University of Rome. At least he would receive a salary, even if not a generous one. Fermi was frugal and still living at home. His material needs were met, although he felt intellectually isolated. Other than his friend Persico, who had remained in Rome as Corbino’s assistant, only mathematicians seemed to grasp the meaning of his research.
As in Pisa, there were many more mathematics chairs than physics ones in Rome. Four of the occupants had considerable international reputations. None was more distinguished than Vito Volterra, the most senior of the four, but Guido Castelnuovo, Federico Enriques, and Tullio Levi-Civita were not far behind. They welcomed Fermi enthusiastically, recognized his talents, and anticipated what he might contribute to advancing Italian physics.
Beyond being embraced in an academic circle, Fermi discovered that the mathematicians also formed a tight-knit social circle, and he was invited to be part of it. The group provided him for the first time with a community of peers. Their families and those of their close friends typically gathered together on Saturday night, usually at the Castelnuovos’, for far-ranging discussions on everything from scientific advances to local gossip.
Other than being great mathematicians, Volterra, Castelnuovo, Enriques, and Levi-Civita had another common trait, one that would come to have a significant impact on Fermi’s life. They were all Jews. This might seem a remarkable coincidence for a country that had only some forty thousand Jews, approximately a tenth of one percent of the total Italian population of forty million. It wasn’t altogether accidental.
Ghetto walls had been torn down in the middle of the nineteenth century and Jews had finally been allowed full access to university life. Education had always been valued in Jewish culture, and young Jews stood out in a country where more than half of the children over the age of ten were still illiterate. Furthermore, mathematics, if only as an aid to becoming merchants, bankers, and doctors, had been a customary subject for Jews to study. They would frequently select mathematics or related fields once universities were open to them.
The beginning of the twentieth century was a time of great pride for Italian Jews. After centuries of being shuttered away in ghettos, they were fully integrated citizens of a new nation. By and large, they became extraordinarily patriotic. Large synagogues were built in Italy’s major cities, replacing the hidden rooms in unmarked buildings wher
e worship had previously been held. And when war was declared in 1915, Jews rushed to enlist. Volterra, then fifty-five years old, had enlisted as a lieutenant in the Army Corps of Engineers and set to work calculating artillery trajectories.
Sadly, those feelings of patriotism would erode in the 1920s and eventually turn to scorn as Jews saw their homeland reject them by aligning itself with Hitler’s racist tenets. And Fermi’s newfound colleagues in mathematics were among the first to feel the yoke of anti-Semitism.
6
THE SUMMER OF 1924
As spring approached in 1924, Fermi was worried about his mother’s health. She had suffered from a number of pulmonary ailments and recently spent time in a sanatorium. By April, all attempts to save her were failing.
In anticipation of enjoying their retirement in a peaceful setting, Fermi’s parents had purchased land a few miles northeast of Rome in a housing development intended for government employees. They were building a small dwelling there, but it wasn’t expected to be ready until the fall of 1924. It was looking as if Fermi’s mother would not live to see it completed. She died on May 8, having just turned fifty-three. Afterward Fermi seldom spoke of her, and when he did, it was mainly to praise her organizational skills. Her lingering depressions and favoritism for her deceased child had made her emotionally unavailable to him, more notable for her managerial and technical capabilities than her maternal ones.
Nevertheless Fermi felt the loss and that summer looked for consolation in the beauty of the mountains, specifically in the Dolomite peaks and valleys that lie north of Venice and south of the Austrian border. The spectacular scenery drew him to the region and he also found congenial company, since many of the distinguished Rome mathematicians vacationed there with their families. Eager to continue taking the brilliant young physicist under their wings, they were happy to have him join them. Fermi could discuss algebraic geometry with them and also take long hikes with their children, in their twenties, closer in age to him.
The death of Fermi’s mother coincided with another death, one the whole country was focused on. It was the murder of Giacomo Matteotti, an overtly antifascist socialist deputy, which for many was a watershed in Italy’s march toward totalitarianism. On the thirtieth of May 1924, Matteotti had delivered an impassioned speech in Parliament denouncing the fraud in recent elections and the intimidation of opponents by Fascist brigades. At its conclusion he had declared, “I have finished my speech, now prepare the speech for my funeral.” Many feared his prediction would come true.
On the sixteenth of June, Matteotti’s body was discovered in a shallow grave about twenty miles from Rome. He presumably had been stabbed while trying to escape after being kidnapped. It remained murky whether his murder had been ordered directly by Mussolini, but it was a consequence of the climate Mussolini and his fellow Fascists had created during their two years of controlling the country.
Despite the unrest sparked by Matteotti’s murder, opposition to Mussolini was divided. The king was weak, ineffective, and not inclined to criticize the man he had named as his prime minister. Mussolini, emboldened, made his move on the third of January 1925. Appearing before the Chamber of Deputies, he challenged its members to impeach him, adding, “Italy wants tranquility and hardworking calmness. We will provide this with love, if possible, by force if it is necessary. You can be sure that the whole situation will be made clear within the next forty-eight hours.” Applause broke out, a clarion call for the country to turn into a totalitarian regime. Mussolini began referring to himself as Il Duce, foreshadowing a similar move by a man to the north who became known as Der Führer.
Dissent was no longer tolerated. In November 1926, a party tribunal was constituted and a special police force was formed. The Organization for Vigilance and Repression of Anti-Fascism, or OVRA, with several thousand members, began to permeate all levels of society. It would become a model for Germany’s Gestapo and Russia’s NKVD, though fortunately for Italy it never achieved the levels of ruthlessness and efficiency of the latter two.
Fermi seemed oblivious to politics. His views were very close to those Rasetti held, described thus by the latter in a 1982 interview: “In the first few years, in 1922, Fascism didn’t seem so bad. In fact a large class of Italians welcomed it, because the Communists were very powerful and disorganized all industrial production, disorganized the railway traffic. So at that time Mussolini seemed a fairly reasonable dictator. The first act that really disgusted the more reasonable people was the Matteotti murder, which happened in 1924.” Fermi was among those “more reasonable people.”
How had Italy, a nation with a healthy democratic tradition, come to this point? The country had suffered in World War I, and not only from loss of life. Profiteering during the war had angered many returning veterans; the difficulties they were encountering in finding employment had further exacerbated the situation. The warnings of a national disaster were in place. Inflation was rising, industrial strikes were breaking out, landowners were afraid of reforms that would threaten their agrarian holdings, the army was unhappy, and the king was indecisive. Taking advantage of a government that seemed powerless, Mussolini, both cunning and ruthless, inserted himself into the mix. With a flair for propaganda and bombastic oratory, he was above all an opportunist, willing to change his position in whatever way suited his ambitions.
The Fascist Party, established in 1919, initially gained little traction, but as discontent rose, the accompanying fear of a left-wing takeover grew stronger; Mussolini exploited the desire for what he would later call “tranquility and hardworking calmness.” He organized squadrons of thugs armed with clubs, their aim supposedly that of keeping the peace. And because he was financed by the right wing, Mussolini’s hold increased.
The situation was ripe for Mussolini’s ascent. On the twenty-eighth of October 1922, he launched the famous March on Rome, directing black-shirted Fascist squadrons to advance on the capital. The army had been mobilized and could have stopped the marchers, but that might have led to a massacre. Everyone was asking whether the king would sign the order for the army to take action.
Fermi happened to be in Corbino’s office on the morning of that march. Never having given much thought to politics, the twenty-one-year-old Fermi looked to his mentor for guidance. That evening he recounted to his family what Corbino said would happen if the king signed the order for action: “So many young men will die who were only in search of an ideal to worship and found none better than Fascism.” When Fermi had asked what one might hope for if the king avoided the confrontation, Corbino had replied, “A hope? Of what? If the king doesn’t sign, we are certainly going to have a Fascist dictatorship under Mussolini.” Both scenarios were bleak.
The king decided not to sign the order. Instead, on the thirtieth of October he asked Mussolini to form a new cabinet. Three years later the takeover was complete and Fascism firmly implanted. Opponents of the regime were jailed or went into exile. The Gregorian calendar was abandoned in favor of dating years in Roman numerals, year I coinciding with the March on Rome. Mussolini proclaimed the inauguration of a new Roman empire.
Mussolini had proved himself a master in his use of propaganda. He did so in person, in the press, and in newsreels, which were becoming an increasingly popular means of communication. The slogans he mouthed were repeated incessantly. In late 1923, after Mussolini’s utterance “Better a day as a lion than a hundred years as a sheep,” a circus owner offered him a lion cub. Mussolini adopted it as a pet-in-residence. Naming the cub Italia, he made sure newsreels filmed him in his convertible Alfa Romeo driving in the nearby Villa Borghese Park, Italia in his arms. The symbolism of a wild beast tamed by its fearless owner was not lost on the populace.
The political situation gradually entered Fermi’s consciousness, but in 1924 he ignored it. Thinking about career rather than politics, he was planning a three-month stay outside of Italy, supported by a new fellowship. In January 1923, John D. Rockefeller Jr. had founded the Int
ernational Education Board for the purpose of “promotion and advance of education throughout the world.” Part of its mission was to award fellowships to promising young scientists, allowing them to visit active research centers for periods of months to a year. Fermi was the first Italian to receive one.
He chose to use his fellowship in Leiden, the Netherlands, opting to do so because of Paul Ehrenfest, a Leiden physics professor with a lifelong interest in statistical mechanics as well as in quantum theory. In his early forties, the Viennese-born Ehrenfest, a wonderful lecturer and an astute critic, was a close friend of both Bohr and Einstein. He was also known for being personally warm and involved in the lives of his students as well as for a free-ranging intuitive style in research, one that contrasted with the more reserved approach characterizing many other senior theorists, especially those in Göttingen.
After reading a 1923 article by Fermi in the Physikalische Zeitschrift, Ehrenfest wrote him a letter telling him how impressed he was. Ehrenfest also told a young former student of his living in Rome to get in touch with Fermi. George Uhlenbeck, later a well-known theoretical physicist, arrived in Rome to serve as tutor to the Dutch ambassador’s son. He and Fermi, almost exactly the same age, contrasted dramatically in appearance, Uhlenbeck almost a foot taller. But physics, not height, is what mattered. In the course of their meaningful exchanges, the young Dutchman sang the praises of both Ehrenfest and university life in Leiden.
The stay in the Netherlands proved valuable for Fermi. Fermi never voiced why his Leiden experience had been so much happier than his Göttingen one, but always spoke fondly of the Dutch group, their openness and their acceptance of people coming from a different tradition. He was admittedly somewhat taken aback initially by how unceremonious Ehrenfest was in his manner as well as by his sloppy attire. The Jewish mathematicians in Rome were always proper and formal; Fermi described Ehrenfest to Persico as “really very nice and wouldn’t be out of place in a ghetto store for used clothing.” Ehrenfest made it known that he considered Fermi extraordinary even when compared to the best young theoretical physicists of the day. And Ehrenfest knew them all.
