CHAPTER TWENTY-FIVE

TRAVELS ABROAD

FERMI TRAVELED OVERSEAS ONLY TWICE IN THE EIGHT YEARS between his return to Chicago in 1946 and his death in 1954. The first trip extended from August through October 1949 and included visits to Basel, Switzerland, and Lake Como in the Italian Alps for a series of conferences and ended with a series of lectures in Rome and Milan. The second trip was to attend two summer schools held during 1954, one in the French Alps and the other at a villa along Lake Como. Once again, given the lack of private diaries and personal letters, one can only speculate why he returned to Europe so infrequently. He was certainly busy at Chicago and spent his summers preoccupied with classified research at Los Alamos. In fact, before he left for Europe in 1949, he spent much of the summer at Los Alamos, involved in the Super and other classified research projects. He may have felt that taking a chunk of time to spend in Europe, in the era prior to easy and convenient air travel, was simply not worth it. A more interesting possibility is related to the classified nature of his research. When he lived and worked in Rome, he had an easy and completely open professional relationship with all his colleagues and could speak to them about his work. Even after the war was over, so much of his work was still classified that he must have struggled to censor his conversations with physicists like Amaldi with whom he was once so close. Amaldi clearly felt the struggle, too, and it may have been partly responsible for his insistence, in the bylaws of CERN, drawn up in the late 1940s, that the new multinational European lab would never engage in classified research.

Whatever the reason, the trips to Europe enabled Fermi to catch up with old friends and discuss unclassified work he was doing in Chicago on the origins of cosmic rays and pion-proton scattering.

AT THE 1949 BASEL CONFERENCE, THE SUBJECT WAS HIGH-ENERGY particle physics. The list of almost two hundred attendees was impressive. Along with Fermi, a host of Italians attended, including groups from Rome, Florence, and Milan. A group of Germans also attended, including Heisenberg and his partner in the German atomic weapons program, Walther Bothe. Other notables included Pauli, Frisch, Placzek, Segrè, Pontecorvo, Alfven, Rabi, Schwinger, Meitner, Kronig, Rosenfeld, Telegdi, and Racah. Fermi was not one of the scheduled presenters in Basel, but he attended presentations on experimental methods, particle theory, and QED. Fermi also swam a mile in the Rhine River, a bracing experience even in the summer. His old friend Bruno Pontecorvo joined him.

Lake Como was Fermi’s next stop. He had fond memories of the 1927 Como conference, so this was a particularly emotional way for Fermi to return to his native land. He was especially pleased to be greeted at the station by many of his old friends, some of whom he had not seen in a decade. The topic of the conference was cosmic-ray physics. Fifty-odd papers were presented. Major physicists from around the world were in attendance, and Fermi’s Italian colleagues were there in force: Amaldi, Segrè, Pontecorvo, Occhialini, Piccioni, Bernardini, and Wataghin were among the many Italian physicists who came to present work and renew their friendships with Fermi. A whole new generation of physicists came as well, eager to see their legendary compatriot in the flesh. It was a heady time for Enrico and Laura, who were delighted to see old friends. Fermi took on the challenge of playing Pontecorvo in tennis during breaks in the sessions. Segrè records pleasure in watching Fermi try hard, without success, to beat the athletic and handsome Pisan.

The Fermis moved on to Rome, where a lecture series had been planned by the newly revitalized Accademia dei Lincei, under the directorship of Fermi’s old Roman mentor and promoter, the mathematician Guido Castelnuovo. Castelnuovo had arranged for Fermi to present six lectures in Rome and another three in Milan. The lectures covered a wide range of topics, at varying levels of sophistication.

The time in Rome also provided an opportunity to see relatives. The Fermis visited the old Capon home in Via dei Villini, where Laura’s eleven-year-old nephew, Giorgio Capon, remembers meeting his illustrious uncle for the first and only time. Giorgio’s parents expected him to be “seen and not heard” in the presence of Enrico and Laura. Giorgio, who went on to become a respected physicist in his own right, found his famous uncle unpretentious and engaging. Fermi also met with his sister Maria, and the two presumably had some form of reconciliation over Enrico’s role in the Manhattan Project. When the lectures were finished at the end of October 1949, the Fermis departed for Chicago. Rome was no longer their home. They were, for better or worse, Americans, and upon their return they settled back into their normal life in Chicago.

THE SECOND TRIP TO EUROPE, IN THE SUMMER OF 1954, COVERED slightly different territory. They traveled with Giulio, who had just finished a relatively happy year at Oberlin. Laura and Enrico decided to bring him along to see the sights and enjoy the fresh mountain air.

Their first stop was Paris, where they met up with Stan Ulam and his wife, who happened to be spending the summer in Europe as well. The plan was to drive part of the way south with the Ulams in a plain, rented Fiat, but when the president of Fiat heard—how he heard is unclear—what Fermi was planning, he insisted on offering the use of a free vehicle for the trip, a very zippy eight-speed car that Fermi allowed Ulam to drive around the streets of Paris. Heading south, they stopped at a small inn near Avalon, some 150 miles southeast of Paris, where they had a meal Ulam remembered mainly for the ominous conversation he had with Fermi. They spoke at length about the impact of the Oppenheimer hearings, which, they agreed, would make Oppenheimer a martyr. Ulam knew Fermi had no particular respect for Oppenheimer as a physicist but believed Oppenheimer had been treated badly by the AEC and was irritated that Teller’s testimony had been particularly damaging. Ulam asked Fermi what he thought the future held for Oppenheimer, Teller, and the physics community more generally, and to his astonishment Fermi replied, “I don’t know, I’ll look at it from up there.” He pointed skyward. Later that evening they were discussing the future of particle physics, pion research, and the like, and once again Fermi pointed to the sky and said, “I’ll know from up there.” This struck Ulam as odd. Fermi was only fifty-three years old, and he knew Fermi to be particularly irreligious. It was, Ulam realized later, at least a premonition of impending doom and perhaps a sign that Fermi understood he was quite ill. The next day the two families went their separate ways, the Fermis to the Alps and the Ulams to the Riviera.

Les Houches was a fairly Spartan physics summer school at the base of Mont Blanc in the French Alps. The invitation to lecture there was simply too attractive for Fermi to ignore, combining two of his favorite activities, teaching physics and hiking in the magnificent mountains above the village. When he was not lecturing on a range of advanced topics, he participated in strenuous outdoor activities with younger physicists, including Roy Glauber, a future Nobel Prize winner. Glauber recalls that Fermi was quite active while at Les Houches and was shocked to learn how weak and fatigued Fermi was at Varenna only a few weeks later. He also recalls that the group needed to buy hiking boots for their excursion. Glauber chose the sturdiest, most expensive ones he could find. Fermi, not surprisingly, bought the cheapest ones, of obviously inferior quality. When Glauber gently teased Fermi about this, Fermi replied that the young Glauber would be using his boots a lot longer than Fermi his.

The session at Les Houches ended in mid-July, and the Fermis returned to Italy, to the summer school at the beautiful Villa Monastero in the scenic village of Varenna on Lake Como. Fermi was a star guest at the conference, although other prominent physicists, notably Heisenberg, were there as well. Enrico and Laura stayed at the villa, in the master bedroom of the villa’s former owners. Fermi delivered his talks in a lecture hall now called the Sala Fermi and adorned with a bas-relief sculpture of him. Between sessions, attendees could take walks through the genteel gardens sloping down to the lake, take a refreshing dip in the cool lake, or ride by boat across the lake to Bellagio and elsewhere.

Fermi’s lectures at Varenna focused on his recent pion experiments—their production, their scattering, and the analysis of these interactions within the nucleus. Several of the younger attendees took careful notes, supplemented with tape recordings and very short film clips. By this time, Fermi had spent a year or so digesting the results of his Chicago experiments and some of the questions raised by these results proved extremely fruitful in the years to come. This final paper is perhaps the best single summary of those years of high-energy pion experiments.

FIGURE 25.1. Heisenberg and Fermi enjoy the sunshine at the Villa Monastero, Varenna, in September 1954. Photo by Juan G. Roederer. Courtesy of AIP Emilio Segrè Visual Archives, gift of Juan G. Roederer.

At some point during the Varenna sessions, however, Fermi’s energy began to flag. It was uncharacteristic for him to avoid hikes and strenuous physical activity, but he did so now, noticeably fatigued after exertions that would have been easy for him just a few weeks earlier, climbing in the French Alps. He also began to have trouble swallowing and lost his appetite. The many photographs and film clips that survive from these sessions do not reveal his discomfort, but we can be sure that by the time the conference ended, he knew something was very wrong.

AFTER VARENNA, THE FERMIS MET UP WITH THE AMALDIS AT THE small resort village of San Cristoforo, near Trento, in the Italian Alps, where the two families rented a villa for several weeks. Persico joined them there. Giulio Fermi and Ugo Amaldi, Edoardo and Ginestra’s son, met and got to know each other a bit. There were still walks and hikes, but it was increasingly apparent to everyone that Enrico was not well. There is a photo of Enrico on a tennis court at the villa with the Amaldis and Persico; Enrico worked hard to look well for the photo, but in fact they were only able to play a few minutes before he called it quits.

Enrico may not have been at his best, but he still had the energy and enthusiasm to jump at the chance for informal teaching. Edoardo asked him about his current work and Enrico told him of the important research that was being done with some of the world’s first digital computers. Eduardo apparently showed interest, because over several evenings Enrico conducted an intimate seminar—for Edoardo, Giulio, and Ugo—on how to program these new computers in machine language. At the end of each evening, he would give everyone a problem to solve by the next session the following evening. Ugo, who fancied himself quite a strong mathematician, was frustrated to discover that his father took to programming much faster than did he. Ugo does not recall how Giulio fared, but by this point Giulio was a strong mathematician himself, so he probably did well. This informal seminar would be the last class Enrico Fermi would ever teach.

Ugo recalls a dinner during that short vacation when everyone realized just how ill Fermi was. Sometime during the meal, Fermi started to gag. Rising abruptly, he scrambled to the bathroom, where he was sick. To Ugo and everyone else at the table, this was a clear sign that something was seriously wrong with Fermi.

THE FERMIS RETURNED TO THE UNITED STATES THROUGH NEW YORK and dropped Giulio back at school for his sophomore year at Oberlin. While there, they met Giulio’s good friend Robert Fuller. Giulio had made light of his father’s importance and rarely if ever spoke about what it was like to be the son of such a great physicist. In fact, he avoided any discussions of his life prior to Oberlin. Fuller knew exactly who Enrico Fermi was, though, and although they met for only a few minutes, that meeting has stayed with him for more than sixty years. It was not apparent to Fuller that Fermi was ill, though Fuller had never met Fermi when the man was full of the energy and vigor that characterized him throughout most of his life. What Fuller noticed, though, were Fermi’s eyes—bright, piercing, darting this way and that, taking in everyone and everything. Fuller had the feeling that Fermi was looking right through him. Even in his increasingly serious condition, Fermi was engaging and engaged, intensely curious about this young man who was to become Giulio’s lifelong friend.