The Pope of Physics

by Gino Segrè

  He also began writing for the Periodico di Matematiche, a journal aimed at keeping secondary school teachers abreast of recent developments in physics and mathematics. Fermi’s early articles in the Periodico demonstrated his dazzling ability to explain what had been achieved and what still needed to be answered.

  Because of Fermi’s rising prominence, he felt responsible for keeping the Italian general public informed. Physicists, chemists, and other scientists were aware that new developments were taking place in atomic physics, but what bearing did they have on everyday life? In a long piece entitled La Fisica Moderna (Modern Physics) that Fermi wrote in 1930, he tried to provide an answer. He began with the rhetorical question “What practical consequences have been or might be derived from such a great increase in our knowledge of matter’s intimate structure?”

  His reply, still valid, is that it usually takes years, if not decades, for applications of fundamental new insights to be developed. But Fermi reassured readers “that the work of scientists is not distancing itself from life, losing itself in the pursuit of abstruse and purely abstract ideas.” And he was right in that as well.

  Fermi had an ulterior motive in accepting many of these writing commitments. They allowed him to earn money to supplement his relatively modest professor’s salary, about ninety dollars a month. Though a man of simple tastes, he was aiming to have the kind of upper-middle-class way of life many of his colleagues enjoyed. A few years earlier, as a young bachelor, he had slept in a freezing room adjacent to the Florence Physics Institute; that was no longer acceptable for a married man with a growing professional reputation. Fermi now strove for a lifestyle that included a comfortable residence, interesting vacations, a housemaid, and occasional entertaining.

  This was the mode of living that Laura had grown up with and expected to continue. Her dowry allowed them to purchase an apartment but they had no savings. Conservative by nature, they both also hoped to have a little nest egg if something unexpected and untoward were to occur. As Laura wrote, “Enrico felt that we needed more, not to lead an extravagant existence, but to acquire a sense of security and to be prepared for emergencies.”

  Fermi thought of a strategy for achieving greater security. He would, with Laura’s help, write a physics textbook for Italian high schools. In 1928 he had published a book, Introduzione alla Fisica Atomica (Introduction to Atomic Physics), but it didn’t make any money. A high school textbook might be different. There was no such text in Italian that Fermi thought adequate. With this book, students would learn physics in a new way, not having to consult obscure texts as he had been forced to do.

  Laura and Enrico set to work on the textbook after their honeymoon, a trip that mixed romance and physics. The passionate husband could not stop sharing his infatuation with his trade; as Laura correctly deduced, “I was to learn physics, all there is to know about physics.” By and large, Fermi dictated the book’s contents to Laura. If she didn’t understand what her husband was saying, she would interrupt. This would often evoke the response “It’s obvious,” which would then lead Laura to reply that it wasn’t obvious at all. Cooperation had its limits.

  Working on the book mostly during vacations, Laura and Enrico adopted a program of writing six pages a day. This meant that the five-hundred-page text took almost two years to complete. Laura opined that it “was mediocre prose [but] it still served its purpose of bringing economic returns for many years.” That income would not be needed after all. By the time the book was published, the Fermis had acquired a far more lucrative funding stream. Unexpectedly, it was thanks to Mussolini.

  Since the mid-1920s, Il Duce had wanted to establish a prestigious Italian academy that would bring together prominent scholars and artists. Such an institution already existed: the Accademia dei Lincei. Originally founded in 1603, the Lincei had not taken its modern form until 1870, when Rome became the capital of Italy. The new Italian government had then provided the Accademia with a distinguished residence by purchasing the beautiful Palazzo Corsini on the banks of the Tiber. But the Lincei was too independent for Mussolini’s taste. It took stands that were not always pleasing to Il Duce.

  Mussolini wanted an academy whose actions on the cultural front would be in line with Fascist doctrines, one in which Italy’s very recent past would be glorified. He also wanted to personally select its members. Accordingly, in January 1926, he announced the formation of the Royal Italian Academy. It would take him three years to assemble the funding for its support and for the annual awarding of four Mussolini Prizes.

  Mussolini’s choice for the Academy’s location was pointed: Villa Farnesina was directly across the street from the Lincei’s Palazzo Corsini. The villa, a grand early-sixteenth-century building, was a jewel with ground-floor frescoes by Raphael. Mussolini made sure the message to Italy was not lost: his Academy was superior to the Accademia. He provided generous financial support for its members: a university professor would more than double his salary. Artists were similarly compensated. To underscore the Academy’s political connection to the regime, Mussolini scheduled its first meeting on the anniversary of the 1922 March on Rome, the event that marked his ascent to power.

  In March 1929, Mussolini announced the Academy’s first thirty members. The list included composers, artists, and playwrights. It had also appeared likely that a physicist would be appointed. Corbino was the natural choice, but the Academy’s by-laws stipulated that if one was a senator, as Corbino was, he was not eligible for membership. Lo Surdo, the second Rome physics professor, thought he might be named, particularly because he was an ardent Fascist. But much to everyone’s amazement, Fermi was chosen. Given the stipend that came with the nomination and the fact that it was a lifetime position, Fermi’s financial worries were over.

  Corbino had certainly been the force behind Fermi’s selection, but Mussolini must have been pleased to see that Fermi did not hold any expressed antifascist views and was not even a member of the Accademia dei Lincei. Ironically, Fermi would have been a member except for a supposedly accidental lapse by Lo Surdo. Corbino, away on a trip to the United States, had asked him, in his absence, to nominate Fermi. Upon Corbino’s return, Lo Surdo claimed to have forgotten. The truth was almost certainly that he, jealous of Fermi’s success, had tried to keep him out of the Accademia. When Fermi was appointed to the Royal Academy, Corbino must have felt avenged.

  In keeping with Fascism’s bombastic style, the appointed Academicians were required to purchase an elaborate uniform to wear at official gatherings. Complete with cape, silver sword, and plumed hat, this outfit was Mussolini’s creation, an image designed by Il Duce to impress onlookers and ensure that Academicians were conscious of the honor they had been granted. Unpretentious, Fermi found wearing the uniform embarrassing and went to some lengths to avoid being seen in it.

  Though certain occasions could not be avoided, Fermi was probably the only Academician to arrive in a yellow Bébé Peugeot rather than a chauffeured limousine. An oft-told story revolves around his driving the Bébé to a high-powered government meeting. As Fermi—in his undistinguished car—approached guards blocking the access road, he asserted, “I am the driver to His Excellency Fermi. And His Excellency would be very annoyed if you didn’t let me in.” When Fermi recounted the story, he underscored that in both comments he had told the truth.

  More disturbing to Fermi than the Academy’s ostentatious trappings was the obtrusive hand of Fascism in the selection of its members. The rumor spread that Federigo Enriques had been in the initial group of thirty Academy members, but a lesser mathematician had been chosen at the last minute. Was Enriques’s being Jewish the reason, or was it because the mathematician chosen was a Fascist? Government interference was also blatant in the conferring of the Mussolini Prize. In 1931, when Fermi nominated three distinguished mathematicians to choose from, all of whom happened to be Jewish, Il Duce summarily rejected each.

  It is commonly said that there were no serious problems with anti-Semiti
sm under Fascism until Mussolini came under Hitler’s influence in the late 1930s. Mussolini was open about his longtime affair with Margherita Sarfatti, who was Jewish and an ardent promoter of artistic modernism. It does seem more than coincidental, however, that the Royal Academy never had a Jewish member.

  Probably the insidious exclusion of Jews was partially due to a rapprochement between the regime and the Catholic Church. The schism dated back to 1870 when, in the final event of Italian unification, the Papal State was defeated and Rome captured. The Pope refused diplomatic recognition of the nascent Kingdom of Italy and, in turn, Italy did not recognize the Vatican State. The so-called Concordato or Lateran Pacts of February 1929 put an end to that almost-sixty-year hostile stalemate. The Pacts negotiated around this issue with a series of trade-offs. The Vatican was given a large sum of money and gained control over Italian marriage and divorce laws. The government, under Mussolini, recognized Catholicism as the official state religion and mandated religious education in public schools. Considerable benefits had accrued to the Catholic Church. But when Il Duce refused to kneel before the pontiff or kiss his hand, Pius XI began to see the high cost at which they had come. Once Italy was officially made into a Catholic country, Jews—by definition—were marginalized.

  Two years later, Mussolini further tightened his control over Italy. In the fall of 1931, the government announced that all of Italy’s university professors would be required to sign a loyalty oath professing allegiance and devotion to king, country, and the Fascist regime. Again, this disproportionately affected Jews. Although Jews made up 0.1 percent of Italy’s population, approximately 10 percent of university professors were Jewish. If one counted only those academics in the fields of science, mathematics, and medicine, the percentage of Jewish professors was much higher.

  Of the more than twelve hundred and fifty professors at the time, only a dozen refused to sign the oath, among them the mathematician Vito Volterra. Some who took the oath justified their actions by reasoning that their places would just be filled by Fascist loyalists. Others maintained that it would be better to oppose the system from within. Many claimed the oath was a simple formality that meant nothing.

  Fermi was not asked to take the oath, since he had already joined the Fascist Party a few days after his nomination to the Royal Academy. Although it was not a requirement for his appointment, it was an expectation. Fermi had been happy to oblige, since politics meant little to him. Physics is what mattered, and as long as he could pursue his research without undue interference, the rest did not concern him—an attitude shared by the other Boys as well.

  Fermi’s apolitical stance and desire to avoid clashes with the Fascist regime were well known. Enrico Persico, by now a professor of physics in Turin and nicknamed Prefetto di Propaganda Fede (Prefect of Propaganda for the Faith) by the Boys because of his success in spreading the quantum gospel, was aware of this. In a letter to Fermi recommending that he hire as his assistant Giancarlo Wick, a bright twenty-two-year-old Turin theorist, Persico alerted him to Wick’s professed antifascism. Fermi’s response was that he had no prejudices about political views but preferred having no public expressions of antifascism.

  Wick, not a radical, was willing to curtail his political activities. He even took the oath of loyalty to the regime in 1937, when he became a professor. But in 1951, when the University of California regents asked all faculty members to swear they were not and had never been Communists, Wick resigned his Berkeley professorship rather than do so. Although he had in fact never been a Communist, Wick remarked to a friend, “I had once to take such an oath in Italy for mere survival reasons and I always regretted it.” He never wanted to be in that position again.

  12

  CROSSING THE ATLANTIC

  Ignoring the increasingly repressive political atmosphere in Rome, the Boys of Via Panisperna concentrated their energies on physics and were successfully making their mark. Edoardo Amaldi, Emilio Segrè, and Ettore Majorana had published—with a boost from Fermi—their respective first articles by 1928. They, as well as Rasetti, began to think of expanding their horizons. The prized Rockefeller Foundation fellowships, instituted in 1923, were becoming more widely available, and the Boys thought obtaining one might be a good vehicle for advancement.

  Fermi had been the first Italian physicist to win a Rockefeller fellowship and had subsequently studied in Leiden. A few years later, Rasetti was awarded one. It would have been natural for Rasetti to go to one of the Northern European physics centers. Instead, always the most adventurous of the Boys, Rasetti was determined to see America, in particular the Wild West. He opted to spend the fellowship year at Pasadena’s California Institute of Technology, familiarly known as Caltech.

  The United States was not yet the physics powerhouse it would soon become thanks in large part to the efforts of a dynamic mix of individuals, some fully American-trained, such as Arthur Compton and Ernest Lawrence, and others who had studied in Europe, such as J. Robert Oppenheimer, Linus Pauling, and Isidor Rabi. That mix was further enriched by a number of European scientists who had emigrated. To them, America was a land of promise and a refuge from totalitarian regimes. It was to become home.

  When Rasetti arrived at Caltech in 1928, he was impressed by the variety and vitality of American science. With his wide range of interests, he became friends with a broad spectrum of its biologists, geologists, and astronomers as well as with the physicists. On his return to Rome he regaled the other Boys with tales of his adventures and of strange customs, such as prohibitions against alcohol and the institution of faculty clubs where one mingled with other professors. He regarded America as a new world, one he urged them to see. Highlighting his affection for the United States, Rasetti imported a Ford Model A, undoubtedly one of the few Model A’s in Rome and certainly the only one on Via Panisperna.

  Rasetti’s research work in California had been noteworthy and served as leverage for his obtaining an Italian professorship. Corbino once again held sway. To ensure that Rasetti was not separated from the other Boys, he managed to have a new physics professorship created in Rome. Rasetti filled it. Fermi began working immediately with him, as they had five years earlier in Florence. Again, Fermi was largely responsible for theory and Rasetti for experiment. This two-year collaboration was the springboard for a book Fermi published in 1934, Molecole e Cristalli (Molecules and Crystals). Translated into several languages, it became a standard text for both physicists and chemists seeking to understand the workings of the still new quantum mechanics.

  As in Florence, Fermi also undertook independent research of deep theoretical significance while he was collaborating with Rasetti, who was focusing on more straightforward experimental projects. Quantum mechanics had shown how an electron interacts with an electric or magnetic field but not how it was able to either emit or absorb electromagnetic radiation. This was the question foremost in Fermi’s mind. A new subject, given the name quantum field theory, was in the process of being invented. Perhaps his own approach would help solve its mysteries.

  Fermi was not the only one trying to advance the new subject. All the young theoretical physics geniuses, Dirac, Heisenberg, Pauli, and Jordan, were attacking the same problems. Fermi was less troubled than the others about conceptual difficulties. Instead, he laid out procedures to follow in an easily accessible fashion and then applied them to solving a number of relevant problems, with particular emphasis on explaining previously puzzling results.

  Fermi’s conclusions on quantum field theory were published in a number of shorter papers and finally summarized in a long pedagogical article. In addition to its methodology, it was notable in being Fermi’s first publication in an American journal, Reviews of Modern Physics. The article’s appearance in 1932 strongly influenced a whole generation of theoretical physicists, including Hans Bethe and Richard Feynman. Both future Nobel laureates considered the article pivotal in their own careers and in understanding field theory, commenting on its “enlightening simpl
icity.” Feynman later wrote, “Almost my entire knowledge of QED (quantum electrodynamics) came from a simple paper by Fermi.”

  Fermi’s decision to publish in an American journal was influenced by the very favorable impression of the country from his first visit. The trip came about because of an invitation by George Uhlenbeck, Fermi’s friend from Rome and Leiden days. Uhlenbeck and his fellow student in Leiden, Sam Goudsmit, had just accepted faculty positions in physics at the University of Michigan.

  Happily ensconced in Ann Arbor, they started a summer school for theoretical physics to bring American students together for a period of two months to hear lectures delivered by a few prominent physicists. Paul Ehrenfest, their Leiden mentor, had already agreed to come. Spurred by happy memories of his time in Leiden and encouraged by Rasetti’s tales of America, Fermi accepted the offer. Laura joined him.

  Neither Enrico nor Laura knew much about the United States. Laura admits she had never heard of the American Civil War and assumed Abraham Lincoln was Jewish, Abraham being a common name given to Jews in Italy. Neither of the Fermis knew English beyond basic communications: Fermi could read physics articles but little else. Their reactions to America diverged sharply. The country had little appeal to Laura, who counted the summer of 1930 as a failure in terms of any potential Americanization. In contrast, Fermi found he liked the United States very much. Within the university’s ivory tower, Fermi was relatively impervious to societal changes and the effects of America’s deepening economic depression. The spontaneity and lack of pretension of Americans is what spoke to him.

  Laura, suffering from what she later admitted was snobbery, was less convinced. She, like many of her European friends, considered Americans uncultured and unrefined. While her husband had a busy life with other physicists, she had few friends and little to do. It is also likely that Laura was afflicted with morning sickness. The Fermis’ first child, their daughter, Nella, was born on January 31, 1931, less than six months after their return to Italy.