All these questions are essentially imponderables. Still, the very fact that they are imponderable leads to the conclusion that, in common with all scientists of great stature, the specific circumstances of Fermi’s life had an enormous impact on his scientific career. So though one doesn’t need to know much about Fermi’s personal life to study his specific scientific achievements—it is possible, for example, to read the beta decay paper without having any insight whatsoever into the circumstances of its creation—it is incorrect to conclude that an understanding of Fermi’s life is irrelevant to our understanding of his life as a scientist. It is, indeed, essential to grasp the relationship of circumstance to scientific creativity and achievement, to comprehend how history, personality, and circumstance combine to shape the development of any particular scientific achievement. In another context, the British historian of science Charles Percy (C. P.) Snow put it succinctly when he wrote, “If Fermi had been born a few years earlier, one could well imagine him discovering Rutherford’s atomic nucleus, and then developing Bohr’s theory of the hydrogen atom. If this sounds like hyperbole, anything about Fermi is likely to sound like hyperbole.” Snow was alluding to Fermi’s brilliance, but this assessment underscores the importance of circumstance in the development of a scientific career. Yes, Fermi may have discovered the atomic nucleus, he may have thought of the Bohr model of the atom, but he never had the opportunity to do so because he was born two decades too late. We are all are prisoners of the era into which we are born, scientists being no exception.
THE RECEIVED NARRATIVE OF HIS LIFE RINGS TRUE, BUT IT OBSCURES as well as illuminates. Why is there such a difference between the memories of his Italian students and those of his American students, particularly in regard to Fermi’s willingness to encourage them and to promote their careers? Why did he remain so long in Italy, working under a thuggish, essentially evil regime? Was there a part of him that grudgingly supported the fascist dictatorship? Did he really decide to come to the United States only when Mussolini promulgated the anti-Semitic laws that would have targeted his wife? Was he an enthusiastic participant in the Manhattan Project, as so many of the histories of the period suggest? Or was he perhaps somewhat reluctantly pulled along by events out of his control? In October 1949, he was an outspoken opponent of the development of the hydrogen bomb, but by the summer of 1950 he was working intensively on the project. Why? Any biographer must grapple with these questions, even if there are, in the end, no clear-cut answers.
HIS FAME DIMINISHES, EVEN AS HIS LEGACY GROWS.
Perhaps the most enduring of his discoveries as far as the general public is concerned are those relating to his work on the atomic bomb, for which he earned the sobriquet “father of the nuclear age.” Even this, though, raises some important questions. The history of the Manhattan Project is the history of many thousands of scientists, engineers, soldiers, and others who had a hand in bringing about the development of nuclear weapons. Where the epithet most clearly fits is in his role in the development of the first nuclear reactors, devices that demonstrated the possibility of nuclear fission chain reactions that form the basis for nuclear explosions and that served as the production engines for plutonium, the element that formed the core of one of the two atomic bombs that ended World War II. These reactors were built in great haste, under enormous pressure, largely without well-formed engineering plans. Indeed, the first one, at the University of Chicago, emerged more or less fully formed directly from Fermi’s brain. In retrospect, the amazing fact is that they worked as anticipated and that the effort was scalable to a degree that astonishes engineers even today.
His role in the development of the atomic bomb itself is more difficult to assess, being that of a highly valued adviser rather than an architect or designer. In the traditional narratives he is overshadowed by the scientific director of the project, J. Robert Oppenheimer, a physicist as different from Fermi as it is possible to be. But when in the summer of 1944 the work at Los Alamos came to a grinding halt owing to unforeseen technical problems, it was to Fermi that Oppenheimer appealed, asking him to come to the secret city on a New Mexican mesa to help inspire and lead. Fermi did so effectively and without complaint.
For physicists, several of his other achievements rank far higher than those of the Manhattan Project, if not existentially then certainly scientifically. His success in integrating quantum rules into statistical mechanics, in what we now call Fermi-Dirac statistics, is the basis for virtually all condensed matter physics and much else besides. Fermi-Dirac statistics are, if anything, even more useful today than they were when they were proposed in 1926. His 1933 theory of beta radiation, though not considered precisely accurate today, gave rise to an enormous amount of fascinating research in particle physics, resulting in more than a dozen Nobel Prizes to date. After World War II his experimental work in high-energy particle physics helped to lay the groundwork for the quark theory of matter and the Standard Model of particle physics, producing another string of Nobel Prizes. Alone among his true peers, his expertise extended across both theory and experiment, a significant anomaly among world-class physicists. And though he may have had a handful of peers in either theory (Paul Dirac, Werner Heisenberg, Wolfgang Pauli) or experiment (Arthur Compton, James Franck, I. I. Rabi), in the art of teaching, he had none. Some five of his graduate students went on to win Nobel Prizes and several other future Nobel Prize winners thought of him as their primary graduate or postgraduate mentor. In terms of influence as a teacher and mentor, he was truly unique.
IT IS THIS COMBINATION OF LASTING SCIENTIFIC ACHIEVEMENT AND profound influence on several generations of physicists, in the United States and in Italy, that make his story directly relevant to us today. Underlying these achievements was a foundation built on enormous talent, but equally important, on a disciplined, almost terrifyingly comprehensive effort as a young man to teach himself all of known physics. During the period in which he laid down this awe-inspiring foundation, he also developed a unique way of thinking about problems that allowed him to achieve what he did and to inspire those around him. He learned at an early age how to strip a problem to its essentials and structure the solution in a straightforward manner, invariably starting at the right place and avoiding complications that might bedevil others. He used this technique in a wide variety of settings, notably in solving problems that now bear his name. “Fermi problems” can be simplified into a finite set of variables whose values can be estimated to within an order of magnitude. Linking those variables together not only provides a quick, rough-and-ready solution but also forces one to think about the elements of the problem that are essential and those that can be safely discarded. Fermi problems often have at their core estimates of the probability of one event or another occurring. This was the type of problem that Fermi excelled in solving, in part because during that formative period of his intellectual development he mastered probability and statistics as a central part of his scientific repertoire. Calculations of probabilities run like a bright thread throughout his work and at several crucial points in his career provided a focus for his most important breakthroughs—the Fermi-Dirac statistics, for example, or his later fascination with Monte Carlo simulations. This way of thinking, which he passed along to colleagues and students, is one of his greatest legacies. Recruiters at firms like McKinsey and Goldman Sachs pepper potential hires with Fermi problems to see how they think and probably never realize the debt they owe to this giant of modern physics.
Fermi’s ability to grind out solutions to difficult problems using a well-developed toolkit of techniques was paired with an extraordinary sense of what problems were important and an affinity for the quick-and-dirty solution when appropriate to his needs. The former set him apart from most of his contemporaries and ensured that he would be at the forefront of his field throughout his career. The latter was sometimes misinterpreted as laziness or, worse yet, a fear of complex mathematics. He was neither lazy nor afraid—he had enormous reserves of energy t
hat drove him to work longer and harder than many younger colleagues, and he was a fine mathematician, able to hold his own with geniuses like John von Neumann—but he valued his time and chose to work only hard enough to get a practical solution. He once quipped to his daughter, Nella, “Never make something more accurate than necessary.” Offered in the context of some unattractive but functional carpentry for the living room of the family home, it was a philosophy that also guided him in physics.
HE MAY HAVE BEEN A WORLD-CLASS PHYSICIST, BUT HE WAS NOT A world-class family man.
As a husband he could be a frustrating and sometimes infuriating person to live with, as his wife Laura makes clear in her largely affectionate but sometimes arch account of their marriage, Atoms in the Family, published in 1954, just prior to his death. The incessant teasing, the long periods—sometimes months—spent away from her, his unwillingness to take her into his confidence during his work on the Manhattan Project all took their toll. Physics was the most important thing in his life and everything else took second place. Laura knew this when she married him, of course, and if she had any illusions to the contrary, they were shattered the afternoon during their honeymoon when he insisted on teaching her Maxwell’s equations. There is no doubt, however, that they loved each other and eventually accommodated themselves to each other’s idiosyncrasies, as most successful couples do.
He was also not the best of fathers. He helped Laura little in domestic matters relating to raising their children, and Laura seems not to have expected anything different. His daughter, Nella, had great affection for him, although even she admits he could be distant. His son, Giulio, chafed at living in his father’s shadow and ultimately put as much distance as possible between himself and his family legacy. Whether Fermi was any worse a father than other successful, driven men of the time is an open question. Parenting in the 1940s and 1950s was not the art it is today, and the profile we have of Fermi as a father is not substantially different from the profile of many others at that time. In his final years he took his parenting role a bit more seriously, but by then much of the damage had already been done. It was, to say the least, difficult being a child of Enrico Fermi.
THAT HE IS NOT BETTER KNOWN, THAT PHYSICISTS LIKE RICHARD Feynman and Stephen Hawking are more well known to the general public, may simply reflect the circumstances of his death in 1954 at an early age and before the widespread advent of television. Few films of his lectures survive, and his television appearances were rare. In later years he may have resented the adulation of Einstein, but in response he did little in the way of self-promotion. Not that he had any sense of false modesty. One of Fermi’s University of Chicago colleagues reported being told of the following conversation between Fermi and his brilliant but troubled graduate student Majorana:
MAJORANA: There are scientists who “happen” only once in every five hundred years, like Archimedes or Newton. And there are scientists who happen only once or twice in a century, like Einstein or Bohr.
FERMI: But where do I come in, Majorana?
MAJORANA: Be reasonable, Enrico! I am not talking about you or me. I am talking about Einstein and Bohr.
He had an enormous confidence in his own abilities, confidence that was well placed. Perhaps he felt that self-promotion was a bit unseemly. Though he sometimes loved to show off to his colleagues, deriving complex theorems from scratch when he could just as easily have looked them up, he did not have the compulsion, notable in some less secure geniuses, to always make sure that everyone knew he was the smartest guy in the room. His lack of self-promotion, particularly after World War II, may also have resulted from a belief that his proper focus was on his research and teaching and not on his public profile. To the extent that he was a public figure, it was as a private adviser to public bodies such as the US Atomic Energy Commission. He was one of the first major scientists involved in public affairs, but his advice was highly classified and remained so for years after his death. His involvement in these matters was fraught, involving him in controversies that pitted friend against friend. When Oppenheimer asked Fermi to continue advising the Atomic Energy Commission in 1951, Fermi demurred, convinced that he was better suited to a world in which truth was clear and where opinion mattered little.
Another reason for his relative lack of profile may have been his resistance to pronouncements on broader political or philosophical matters. After World War II many physicists raised their voices in public on issues related to the development of nuclear weapons and the accelerating arms race between the United States and the Soviet Union. Fermi rarely spoke publicly about such matters, reserving most of his commentary, such as it was, for private councils of state. Nor was he deeply philosophical, never pondering the underlying reality behind quantum theory, never engaging in the kind of metaphysical debate that characterized the schools of quantum theory that arose in Copenhagen and Göttingen. He confined his intellect to matters of physical reality and to physical problems that could be solved using the physics he so loved. Perhaps for this reason quantum theorist Wolfgang Pauli once quipped, in his typical, acid-tongued way, that Fermi was a mere “quantum engineer.” The general public is fascinated by the philosophical conundrums of quantum theory, but Fermi chose to ignore these in favor of focusing on real physics problems with solutions that could be developed clearly through theory and experiment. He was at core an empiricist, driven by the empirical observations of the world around him. Yet Fermi’s antiphilosophical orientation was shared by some, like Feynman, whose fame has only grown over time. Feynman’s wit, colorful story-telling, and involvement in the Challenger shuttle investigation have contributed to the mystique that still surrounds him. Biographers continue to find him a fascinating subject, as they do Einstein and Oppenheimer. In the case of Fermi, some forty-six years have passed between English-language biographies.
Fermi’s reputation with the public has faded for all these reasons and perhaps others as well. As others have recently realized, a correction is long overdue.
NO ONE REALLY KNOWS HOW GENIUS WORKS, WHY IT MANIFESTS IN some instances and not in others. Even more perplexing, why do some scientists make great discoveries and others do not? Why do some, like Einstein, Wolfgang Pauli, Marie Curie, John Bardeen, or Fermi himself, make several great discoveries, while other scientists with apparently equal talent, like Oppenheimer, have no such discoveries to their name? Fermi used a well-defined set of techniques to attack problems in physics, and if a problem came up that did not seem to fit any of these techniques, he bent the problem to succumb to them. There were, of course, hundreds of physicists who knew these techniques, but almost none of them were able to apply them with Fermi’s effectiveness. At some point early in his career, working almost entirely on his own, Fermi learned how to look at a problem carefully, find the right starting point to address it, and cut through it steadily with an enormously powerful intellect, avoiding all the false starts and dead ends that might trap less talented thinkers, to get at its solution. How he did this, how Fermi became Fermi, is in some sense perhaps an irreducible mystery. Nevertheless, it is one worth trying to solve, because understanding how a young boy from Rome became, in the words of one of his former students, “the last man who knew everything” can help us to appreciate the full potential of the human mind and spirit.
PART ONE
BECOMING FERMI
CHAPTER ONE
PRODIGY
ON THE STREETS OF ROME, NOT FAR FROM THE CENTRAL TRAIN station, a middle-aged engineer meets an adolescent boy, the son of a colleague. The boy wants to talk about mathematics and science. The engineer quickly realizes that he is dealing with someone who has a profound gift for the subject matter, a sponge who absorbs complex ideas faster and more thoroughly than seems possible. The engineer decides to take the lad under his wing and give him a thorough education in mathematics and physics, one that goes far beyond what is available in the boy’s high school.
It is impossible to know what might have happened if thirt
een-year-old Enrico Fermi had not met his father’s friend and colleague Adolfo Amidei during the summer of 1914 and if Amidei had not taken a deep and sustained interest in the adolescent and his scientific education. How many promising intellects have withered on the vine because no one was nearby to cultivate them? What we do know is that Amidei decided to give young Enrico Fermi an undergraduate education in mathematics and physics, thus beginning the transformation of a teenage Roman boy into a master physicist.
ENRICO FERMI’S FATHER, ALBERTO, ARRIVED IN ROME IN THE 1880S in pursuit of his career at the Italian Ministry of Railroads. He was born in north-central Italy near the town of Piacenza, nestled in the fertile Po Valley some forty miles southeast of Milan and twenty-five miles due west of Cremona, the famous home to the great violin makers of the seventeenth century Antonio Stradivari and Andrea Guarneri. The Fermis had worked the land in the region of Piacenza for centuries, but Alberto’s father, Stefano, was ambitious and found himself an administrative job with a local nobleman, the Duke of Parma. Alberto, the second of Stefano’s children, did well in the local high school, but the family did not have the financial wherewithal to send him to university. He was, however, quite bright and, like his father, ambitious. The combination enabled him to land a job with the Italian railroads.
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