The Pope of Physics

by Gino Segrè

  The Fermis lived on Via Gaeta for ten years, then moved to a nearby apartment in 1908. Slightly more spacious, but still far from luxurious, it had no central heating and its bathroom, as was not unusual at that time, was equipped with only a sink and a toilet. Baths were taken in two zinc tubs, a smaller one for children and a larger one on casters for the parents. By then Ida and Alberto had three children. Maria was born in 1899, Giulio in 1900, and Enrico on the twenty-ninth of September, 1901.

  The closeness in age of the children and Ida’s desire to continue teaching resulted in Enrico’s being placed in a farm family. The tradition of having wet nurses for infants was centuries old in Italy, usually only adopted by the upper classes. A young woman who had recently given birth would be brought in from the countryside to nurse and care for the baby, living with the family at least until the child was weaned.

  Toward the end of the nineteenth century, the reverse was becoming common for middle-class couples living in big cities: their children were sent to the countryside. With three children in less than three years, the Fermis made such arrangements for Enrico, the youngest. At the time farms still existed close to Rome; it was not too hard to find a suitable family willing—for a fee, of course—to take on a little boy for a few years.

  A child psychologist, ruminating on where such a beginning would lead, might conclude that in adulthood the person would be either very self-reliant and controlled or overly needy and dependent. Enrico was obviously an example of the former.

  One can speculate that the farm family provided a loving environment and a place where he could observe, explore, and enjoy nature. The security that Fermi exuded, as well as his love of the outdoors, might be related to those farm years. Yet the pain of separation from his family of birth must have affected his development, too, and is probably related to why Fermi kept emotions to himself and never complained. This is how he learned to cope.

  And those coping skills served him well in later life.

  2

  THE LITTLE MATCH

  (Il Piccolo Fiammifero)

  Enrico’s sister remembers him being “small, dark and frail-looking” when he rejoined the family at age two and a half. She also recalled how, probably worried by the sudden appearance of all the strangers, he immediately began crying, only to be told by his mother “to stop at once; in this home naughty boys are not tolerated.” Little Enrico did stop crying. But with bottled-up frustrations, he was known to occasionally break into flaming rages, earning him the family nickname of Piccolo Fiammifero (Little Match).

  Rages were not tolerated any more than an untidy appearance. Perhaps rules had been slacker in a farm environment. In a city setting, his mother apparently would insist that his face always be clean, stopping at fountains to wash up during their excursions. Despite Alberto and Ida’s strictness in child rearing, the Fermi family appears to have been close, with a special bond developing between the two brothers, Giulio and Enrico, only a year apart in age.

  Alberto and Ida had advanced in their careers despite not having university degrees; but, like many upwardly mobile parents, they wanted more for their children. All three of those children, through a combination of natural ability and the self-discipline learned from their parents, excelled in their studies, each of them consistently at the top of his or her class.

  At the beginning of the twentieth century the advanced school curriculum was still oriented toward a classical education, emphasizing Latin and Italian literature with Greek added in the final five years. Mathematics, history, and science were also taught, but regarded as secondary. In particular a student preparing for the culminating graduation exam, the so-called Maturità, was expected to know practically by heart Dante’s Divina Commedia, Italy’s national literary treasure. Fermi had little interest in music or visual arts, but a love of poetry, and not only Dante, remained with him. On long hikes he could occasionally be heard reciting under his breath verses he had learned in his youth.

  Maria, who eventually would become a high-school literature teacher, was drawn to the humanistic side of the studies. By contrast, Giulio and Enrico were more interested in science or at least in the technical skills they acquired by building models and little electrical motors.

  The first recognition that Enrico was exceptional occurred shortly after he turned thirteen. Alberto Fermi, nearing sixty, had continued to rise in his profession and had become a chief inspector in the Ministry of Maritime and Railroads. Its offices were located in a building a little less than a mile from the Fermi apartment, and Enrico had started meeting his father at the building’s door after work and walking home with him. Adolfo Amidei, a thirty-seven-year-old engineer employed in the same office as Enrico’s father, often joined them for part of the way since his apartment was in the same direction as theirs.

  When Enrico discovered that Amidei had an interest in mathematics, he asked him a few questions about geometry that his father had been unable to answer. To help his colleague’s son, Amidei lent Enrico a geometry book. The young boy quickly worked out the solutions to the problems it contained, some of which even Amidei had not been able to solve. Impressed, Amidei inquired of his senior colleague whether anybody else had commented on his son’s skill and precocity. Alberto told him that Enrico had always done well in school, but none of his teachers had noted anything out of the ordinary.

  At about the same time, early January 1915, tragedy struck the family. Giulio had developed a throat abscess that was interfering with his breathing, not an uncommon consequence of a severe tonsil infection. Today, treatment is by massive doses of antibiotics, thereby usually avoiding any surgical intervention. The standard procedure in 1915 was an incision and drainage of the abscess under a local anesthetic. This surgery was performed on Giulio in a clinic, his mother and sister waiting to take him home after the anesthetic wore off. But Giulio had a dramatic adverse reaction to its administration, went into anaphylactic shock, and died on the operating table.

  The family was devastated. Alberto became even more taciturn and Ida fell into a deep depression; Giulio, warmer and more outgoing than Enrico, had been her favorite. Ida’s fits of inconsolable crying lasted for hours and she was in no shape to help alleviate the pain of others. Enrico was left to grieve on his own. To prove to himself that he was not a total wreck, a week later he deliberately walked by the clinic where his brother died. It was a striking example of Fermi’s early need for emotional control.

  One way for thirteen-year-old Enrico to fill the traumatic and heartbreaking void was by hard work. Amidei, recognizing both the boy’s loneliness and his eagerness to learn, tried to do what he could by continuing to lend him books; the more he did, the more impressed he was by Enrico’s intelligence and thoroughness. When Amidei once asked his young protégé if he wanted to keep a calculus book he had lent him, he was told that it wasn’t necessary because he had thoroughly assimilated the material. As people would repeatedly say over the next forty years, “When Fermi knew something, he really knew it.”

  Another precious balm for Enrico was having a schoolmate of Giulio’s become his close friend. Enrico Persico shared his interests in science and in building mechanical objects. The two of them soon began taking long walks together, discussing their common dreams. Fifteen years later, the two Enricos would be Italy’s first two professors of theoretical physics. And almost forty years later, they would still take long walks together and share dreams.

  The young Fermi, insatiable in his quest to learn more about science, found his first real physics book in Rome’s Campo dei Fiori (literally Field of Flowers). This square, located between the Tiber and the ruins of Pompey’s Theatre, the site of Caesar’s assassination, remains to this day one of Rome’s liveliest areas. Now a popular outdoor food market, during Enrico’s childhood it was a horse market two days a week and once a week held stalls where one could purchase new and old books. Most of them were novels or, this being Rome, theological treatises. Occasionally one might find some
thing else.

  One day in late 1915, the two Enricos were looking through the collections in the Campo. Fermi picked up a nine-hundred-page two-volume set entitled Elementorum Physicae Mathematica. It was a text on mathematical physics written in the 1830s by a priest named Andrea Caraffa who had taught science and mathematics at the Collegio Romano, a Roman university founded in the sixteenth century by the Jesuit order. With more than four years of intense study of the language completed, Enrico had no problem with the Latin text. In any case, all the equations were in the universal language of mathematics.

  Purchasing the book with his allowance, Enrico studied it carefully in the weeks that followed, making notes when he had questions. Caraffa’s subject matter was early-nineteenth-century physics, chiefly the mechanics of celestial motion and wave theory. The mathematics Caraffa employed might have provided an insurmountable obstacle had Enrico not already studied the subject on his own with books lent by Amidei. Not only was Fermi the only twentieth-century physics genius to be entirely self-taught, he surely must be the only one whose first acquaintance with the subject was through a book in Latin.

  At sixteen, Enrico skipped his final year of high school. It was time for him to begin thinking about what would come next. Obviously headed toward a university, Enrico was expected to stay at home, since Italian universities had no dormitories. But Amidei felt his young protégé would benefit greatly from being away from the oppressive atmosphere that dominated the Fermi household after Giulio’s death.

  Once again Amidei’s important role in Fermi’s development surfaced. He was familiar with an elite institution in Pisa, the Scuola Normale Superiore. Admission to its small entering class, some forty students in all, was by competition. Amidei was confident that Enrico would shine. Since the school provided room and board for its matriculating students, there would be no additional financial burden on the Fermi family. The classes were mostly big lectures held at the University of Pisa, but additional supervision and instruction would be available in the Scuola. Such an opportunity would enrich Enrico both intellectually and emotionally.

  Discreetly inquiring of Enrico whether he would like to attend, Amidei received an enthusiastic response. He next set out to speak to the boy’s parents. They were reluctant, particularly Ida, who felt she would be losing her other son. But Amidei was persuasive in convincing her and Alberto of the benefits to Enrico. He stressed that attending Italy’s premier institution of higher learning, a school from which many of the country’s most famous scholars, political figures, and writers had graduated, would open many doors for him. Ida and Alberto finally agreed to let him apply for admission.

  Amidei had also encouraged Enrico to study German. The boy learned French, part of the usual school curriculum, but an increasing body of the scientific literature was in German, and knowledge of that language would stand Enrico in good stead. It was an interesting although unpopular suggestion, since Italy was at war with Austria and Germany.

  When World War I began in August 1914, Italy initially opted to remain neutral. This probably would have been the wisest policy to continue and was generally favored by the population at large. However, in the spring of 1915, the Italian prime minister began secret negotiations with the French and British to enter the war on their side. He stoked popular opinion to this end, and in May 1915, Italy declared war on Austria. The Italian army suffered a series of defeats, climaxing in October 1917. During the closing weeks of the war, the Italian army managed to garner a significant victory against a demoralized Austrian army.

  Fortunately, Enrico Fermi had still been too young to be drafted into the army. Less than two weeks after the armistice was signed, he took the entrance examination for the Scuola Normale.

  3

  LEANING IN: PHYSICS AND PISA

  Though a superb mathematics student, Enrico Fermi selected physics as his field of study. One of the reasons was his affinity, since childhood, for performing experiments and his fascination with the apparatus they required. His interest in science had started with models and little motors built with his brother. After Giulio’s death he continued in the same vein with Persico, the other Enrico. They gradually embarked on more sophisticated ventures: accurate measurements of gravity’s acceleration, water’s density, and the level of atmospheric pressure.

  Part of their work was carried out at the Rome Meteorological Institute, a center Fermi had become familiar with because its director had been his high school science teacher, a man who helped him and Persico build barometers. At the center’s library Fermi found another influential book, denser and more up-to-date than the one he had purchased at Campo dei Fiori. This time French, not Latin, was the tome’s language.

  A four-volume five-thousand-page encyclopedic treatise on physics, it was then popular throughout Europe. It was written by a Russian physicist, Orest Khvolson, and had been translated into several languages, though not into Italian. Covering physical phenomena as well as state-of-the-art instruments, it is remarkably thorough even by today’s standards. Fermi studied Khvolson at a rapid clip in the summer of 1918, laying the foundation for his astonishing command of every aspect of classical physics. In letters to Persico, he described going through the book at more than a hundred pages a day, skipping large sections of material he was already familiar with.

  At the end of August, when Fermi was seventeen years old, the announcement came for admission exams to the Scuola Normale, offered on four successive days starting October 28. Several hundred candidates were expected to apply for the few dozen openings available in all fields. No more than a handful of prospective future mathematicians and physicists would gain admission. Fermi’s acceptance by the Scuola, despite Amidei’s faith in him, was not a foregone conclusion.

  The exams were extensive. The first three days consisted of eight-hour written exams, and the fourth would be an oral one. Candidates for admission in physics and mathematics would be tested on their knowledge of algebra, geometry, and physics, each day’s exam positing one problem and one essay on a theme unknown to the candidates beforehand.

  The entrance examinations to the Scuola were postponed indefinitely on account of an influenza epidemic. The atmosphere in Rome that autumn, already grim because of the war, turned darker. However, by early November, the number of flu cases diminished, the war seemed to be drawing to a close, and the upcoming academic year was starting. The decision to delay was reversed and the examination rescheduled for November 12. Though the schedulers could not have known it at the time, the armistice would be signed one day earlier.

  Fermi performed brilliantly in the first two days of examinations, but his work on the third day is what led to his designation as a precocious genius. The topic for the physics essay was “Distinctive Characteristics of Sound and Their Causes.” A natural starting point was to consider how a vibrating string leads to sound waves propagating in air. Fermi displayed his bravura by going well beyond this scenario. He tackled the much harder problem of how the vibrations of a rod attached to a wall generate sound waves.

  Fermi derived the equation describing the motion of the rod and proceeded in masterly fashion to solve it. It was an essay that one could barely imagine a talented graduate student being able to write. It was unthinkable to see it from the pen of a self-taught high school student.

  The head of the three-man committee administering the examination in Rome was Giulio Pittarelli, a distinguished geometry professor at the University of Rome. Pittarelli, an unlikely person to break academic traditions, was well aware that communication with competing students was disapproved until exams were over and the Scuola Normale had decided whom to accept. Nonetheless, he could not restrain himself. He had been so impressed by Enrico’s essay that he called him in to his office.

  Quaking at the request of one of his examiners to see him privately, Fermi entered the dimly lit room. The boy, having just turned seventeen, stood before the sixty-six-year-old professor and was subjected to a round of questions
. After assuring himself that Fermi had understood everything he had written, Pittarelli informed him that he definitely would be admitted. It was unimaginable that any other candidate could do as well. Pittarelli also added that in forty years of teaching he had never encountered so gifted a student.

  This was a tremendous boost to Fermi’s self-confidence. Neither his parents nor his schoolteachers had thought there was anything truly exceptional about him. Amidei had, but he was a family friend and a modest man, not someone who was in a position to compare him to other would-be scientists. But Pittarelli had long been exposed to outstanding students, and was a university professor. He was going far out of his way to praise him, a fact for which Fermi would always be grateful.

  The examining committee awarded Fermi the highest possible grades in all his examinations. They unanimously recommended admission to the Scuola. Fermi was thrilled to begin a new phase of life—and to do so in the birthplace of Galileo. This city was the cradle of physics, where the great master was born, studied, and began his teaching career. Galileo had deduced the laws of motion by measuring the periods of a swinging pendulum in the Duomo and by observing objects falling from the Leaning Tower. The subject of physics had been created in his image: experiment, observe, and deduce.

  When Fermi arrived in Pisa in early December of 1918, it was a rather sleepy town of 65,000 inhabitants with signs of a glorious history but little else. The university had persevered over the centuries, as had the Scuola Normale affiliated with it. Fermi had taken the four-hour train ride from Rome to Pisa, descending at the station on a cold but sunny day with his two suitcases—one with clothes, the other with a few books and things for his room. A ten-minute walk brought him to the Arno River, smaller than he had imagined it would be. Crossing it on the Ponte di Mezzo, he entered the medieval part of the city with remnants of its circuit of old walls. A short walk along the Borgo Stretto soon led him to the glorious Piazza dei Cavalieri, the square that held the sixteenth-century Palazzo della Carovana where the school was housed.