NOT ALL GREAT RESEARCH PROFESSORS ARE GREAT LECTURERS. Rabi and Teller were both world-class research scientists, but by general consensus they were both dismal in the classroom.
In contrast, Fermi was an outstanding lecturer. His teaching in Rome was legendary, and students flocked to summer sessions in the United States to hear him lecture. At Los Alamos, physicists clamored to attend his lectures, particularly after the end of the war. Now, back in Chicago, he threw himself into teaching with renewed vigor. The results were spectacular.
ONE OF THE VERY FEW FERMI LECTURES THAT WE CAN LISTEN TO today is the speech he gave before the American Physical Society in January 1954, when he told the story of his fission work at Columbia. He did not speak from a fully prepared text. After the war he would routinely accept lecture invitations and inform his hosts that he would not be preparing a text of the talk. Instead, he worked from fragmentary notes that gave him topics on which he would elaborate to create an overarching structure to the talk. The Columbia talk exists in print only as a transcription of the recorded version.
He spoke slowly. His voice was deep and heavily accented even in 1954, some fifteen years after he moved to the United States. He could read his audience and when he felt a digression was appropriate—as was the case when he started to describe his work with Szilard—he would take the opportunity to enjoy a good laugh along with the audience.
In contrast to other lecturers who, like Fermi, deliver from fragmentary notes, Fermi knew exactly what he was going to say and delivered each thought in full, complete, grammatically correct sentences. In the frequent long pauses during the talk, one can almost hear him think through each sentence before speaking it. The transcription needs little editing, because he delivered it perfectly.
This speech provides just a hint of why his students, as well as his colleagues, found his lectures so illuminating. No matter how complicated the subject matter, he moved through it slowly, at a pace allowing less gifted students to keep up as well as giving those more gifted students a chance to appreciate Fermi’s specific approach to problem solving: eliminate the extraneous considerations, strip the problem down to its essential elements, and proceed step by step toward solution.
In his brilliant essay on Fermi’s Chicago years, colleague and collaborator Valentine Telegdi notes that Fermi was obsessive about his preparations for course lectures, writing out notes on large sheets of paper to which he would refer during the course of any given lecture. He never showed annoyance with students who did not understand a point the first time around. “On the contrary,” Telegdi writes, “if Fermi had to repeat an explanation he seemed to derive twice the pleasure.”
Fermi’s enthusiasm for teaching is evident in the course load he managed throughout his postwar Chicago career. A man of his stature could easily have found ways to do the bare minimum of teaching required, but he consistently taught two or three courses each term. His course load for the academic year 1946–1947 included introductory lectures on physics for undergraduates, the courses that his graduate student Jack Steinberger felt so lucky to work on as a teaching assistant. Fermi taught quantum mechanics, thermodynamics, and nuclear physics. He taught virtually every discipline required for an undergraduate physics major and also taught seminars on special topics and high-level research seminars for advanced undergraduates and graduate students. The only period in which he chose not to teach classes, for reasons that are not entirely clear, was from the fall of 1947 through 1948, picking up again in 1949.
One particular course he taught became something of a legend. In the period between 1952 and 1953, he lectured on nuclear physics. His teaching assistants, Jay Orear, Arthur Rosenfeld, and Robert Schluter, prepared mimeographed notes of the lectures for distribution to anyone interested. Word spread that these notes were available, first through the Chicago community and then, incredibly, to other campuses. Requests came in from far and wide until the overburdened secretaries at the physics department office could no longer keep up with the demand. Anticipating a major problem, the three graduate students approached the editors at the University of Chicago Press to see whether they would be willing to lend a hand. The editors were delighted to do so and the mimeographed sheets were compiled into the textbook Nuclear Physics, which sold well for the next three decades. Known among physicists as “Orear-Rosenfeld-Schluter,” its authors never claimed that Fermi wrote it and for his part Fermi never reviewed the manuscript. It was successful simply because the authors took notes that conveyed brilliantly Fermi’s methodical clarity. The book quickly became a classic.
The students who attended his lectures were fortunate and they knew it. Harold Agnew later recalled a moment in the spring of 1954 when he was passing the physics department building. Suddenly, he heard a huge commotion emanating from the building, loud enough to attract the attention of a nearby campus security officer. The two of them dashed into the building to see what was going on. Other faculty members were emerging from their offices, equally concerned. The din was coming from one of the large lecture halls. Upon opening the door to the room, they found some hundred undergraduates on their feet, applauding and cheering Fermi, who had just delivered his final classroom lecture of the term. There had never before been such a disturbance on the normally sedate campus, Agnew noted.
Lucky indeed were the undergraduates who studied with Fermi, but luckier still were those who received their PhDs from him.
ONE OF THE MOST INTERESTING GRADUATE STUDENT STORIES relates to two young Chinese nationals who, in November 1945, escaped war-torn China and made their way to the United States determined to study either with Fermi or Wigner. One was Chien Ning Yang. (He later adopted the American name “Frank.”) The other was Tsung-Dao (T. D.) Lee. They arrived at Pupin Hall at Columbia looking for Fermi but were met with blank stares. They then traveled to Princeton, where they were told that Wigner was not taking on students until the following year. They heard, however, that Fermi was about to start up a new institute in Chicago. They traveled there and before long were accepted into the program. Lee was admitted as a graduate student despite never having received an undergraduate degree.
The two worked closely with Fermi over the next several years.
Lee went on to do a thesis directly under Fermi, studying the inner processes of white dwarf stars. He still recalls his days with Fermi with fondness. Early on during his thesis research, he and Fermi were discussing white dwarfs and Fermi asked Lee if he knew what the temperature was inside the sun. Lee gave him the answer and Fermi asked how he derived it. Lee admitted that he had looked it up, offering as an excuse that the calculations were quite tedious and in any case could not be done on a slide rule because the units involved extended from well below the range to well above the range on available slide rules. In a burst of creative enthusiasm, Fermi suggested that together they build a slide rule large enough to be capable of doing the calculations. It turned out to be six feet in length, and unwieldy, but it did the job.
In the end, Yang’s thesis supervisor was Edward Teller, but given Yang’s talent it was inevitable that he would spend time with Fermi. Yang collaborated with Fermi on an important paper analyzing whether the pion was a fundamental particle in the same sense as the muon or whether it was composed of other, smaller particles. The paper suggested that it might be a combination of a nucleon and an antinucleon—for example, a neutron and an antiproton. It was a fruitful collaboration and pointed the way to further research. We now understand the pion to be a combination of a quark and an antiquark. Yang has written widely of his experiences during this formative period in his life and summarizes Fermi this way: “He had both feet on the ground all the time. He had great strength, but never threw his weight around. He did not play to the gallery. He did not practice one-upmanship. He exemplified, I always believe, the perfect Confucian gentleman.”
None of Fermi’s other Chicago graduate students had quite the struggle these two had in getting to Chicago, but each had particular stories of life as a graduate student under Fermi.
Geoffrey Chew, Fermi’s young colleague at Los Alamos, enrolled at Chicago after the war and began his PhD work with Teller. Given Fermi’s ongoing research at Argonne, Chew assumed that Fermi would only take on experimental students. However, when in mid-1947 Teller informed Chew that Fermi had decided to take on two theory students while waiting for the cyclotron to be built, Chew jumped at the chance and shifted from Teller to Fermi. That same day Chew ran into Marvin “Murph” Goldberger, a fellow theory student, and Chew informed Goldberger that Fermi was looking for one more theory student. The words had barely left Chew’s mouth when Goldberger turned and dashed off to find Fermi. He, too, was accepted. Chew and Goldberger worked together on a theoretical study of how neutrons behave inside the deuterium nucleus.
Fermi decided for both Chew and Goldberger when their work was ready for publication, a requirement for the PhD at Chicago, and arbitrarily split the joint work into two separate pieces, effectively separating the conjoined twins without harming either one. Chew later recalled this generosity with great affection. Chew is particularly vivid in his recollection of Fermi’s enjoyment in explaining things, especially to people who did not “get it” at first. He also has described Fermi as “the last man who knew everything,” not simply because of his ease with both theory and experiment but also because of his mastery of every aspect of the physics of his day, from astrophysics to geophysics, from particle physics to condensed matter physics.
Jack Steinberger, whose PhD thesis resulted in an important new understanding of beta decay, gives Fermi enormous credit for taking him under his wing and helping him develop into a strong experimentalist. “I am completely indebted to Fermi,” he said in 2014, “for my understanding of what a physicist should be like as a model. Even more impressive was his kindness to me.” According to Steinberger, Fermi emphasized that “in order to understand something one needs to study it thoroughly; that one should not require reassurance but rather have confidence in one’s own ability; and that one should be open to all students, that it should not matter whether a student is bright or average or below average, they should all be treated with respect.”
In the later crop of students, Arthur Rosenfeld was notable for being at the top of the cohort in the basic exam. In fact, Fermi later told him that Rosenfeld had, unbeknown to him, discovered an error in the solution set to the exam. Rosenfeld “screwed up his courage” and asked Fermi if Fermi would be his thesis adviser. The memory of Fermi smiling at him and saying, “So, I’ve been expecting you,” remained a high point for Rosenfeld, even more than sixty years later. When Fermi decided to lecture on nuclear physics, Rosenfeld was one of his teaching assistants. Rosenfeld recalls that solving the problem sets Fermi gave to his students so that Rosenfeld and his fellow teaching assistants could grade them was “an education in itself.” It was Rosenfeld who alerted Fermi to the Shepley-Blair book and helped draft the press release issued in Fermi’s name defending Los Alamos against charges of foot-dragging on the Super. Eventually, when Luis Alvarez called Fermi from Berkeley looking for talent to bring to Berkeley as a post-doc, Fermi offered up Rosenfeld as “the second best student I have ever had.”* Alvarez pressed Fermi to tell him who the top student was, but that was a secret Fermi was unwilling to share. Rosenfeld went on to a notable career in experimental physics at Berkeley, but during the energy crisis of 1973 he shifted his focus to energy efficiency technology and policy, becoming over time one of the most influential experts in that field. In 2006, Rosenfeld received the Enrico Fermi Award from President George W. Bush, and in 2011 President Barack Obama awarded him the National Medal of Technology and Innovation.
Rosenfeld’s fellow student, Jay Orear, was intensely affected by his years with Fermi. He spent a good deal of time talking to Fermi about experimental technique and particularly about the use of probability and statistics in experimental design and evaluation. He took extensive notes of these conversations and published them in 1958, not long after Fermi passed away. He has written with unusual affection about his time with Fermi and the impact Fermi had on his career. Perhaps most significantly, Orear organized a series of Fermi alumni reunions at Cornell, which a large group of former students and colleagues attended at regular intervals. Unfortunately, Orear passed away in 2014 and the reunions no longer take place.
Another graduate student was Owen Chamberlain, who came to Chicago in 1946 and agreed to pursue an experimental thesis at Fermi’s urging. He later recalled that his first meeting with Fermi was at Los Alamos. Segrè, with whom Chamberlain would later share a Nobel Prize for the discovery of the antiproton, introduced the two. To Chamberlain’s surprise, Fermi was quietly puttering away in a corner.
I knew exactly what a Nobel Prize winner looked like and Ernest Lawrence fit the bill exactly: big, with a voice that echoed down the hall. Here was this little man sitting motionless in the corner of the very small room.
Chamberlain’s subsequent work with Fermi had a huge impact on the young student. In early 1954, at the end of a short cover letter accompanying some experimental measurement taken by Segrè and Chamberlain, Chamberlain adds, completely unprompted, a lovely tribute to his former professor: “I am very grateful for the time and effort you have invested in me in the past. If I am to be regarded as a decent physicist, it is mostly because of your training.”
Jerome Friedman was Fermi’s last graduate student. A future Nobel laureate, Friedman’s experimental thesis with Fermi was within weeks of being finished when Fermi passed away. This could have spelled catastrophe, because finding a faculty member to sign off on a thesis he or she had not supervised is no small feat. Fortunately, as the impact of Fermi’s death became apparent, John Marshall realized that Friedman was in this difficult position and agreed to sign off once the work was completed. Friedman tells of his last interaction with Fermi, the day Fermi returned from the summer school in Italy in September 1954. They saw each other from a distance and Fermi waved hello to Friedman from down the hall; however, Friedman barely recognized Fermi, who was quite thin and haggard. Friedman was unaware of the health difficulties Fermi began to experience during the Varenna summer session and was surprised by Fermi’s condition. The small, tightly knit particle physics community, usually fueled by gossip, was reluctant to spread the news of the rapid, catastrophic decline of one of its greatest members.
There were other graduate students as well, some fifteen altogether. The list reads like a who’s who of postwar particle physics. Perhaps the only comparable graduate program during this period was Rabi’s at Columbia. By general consensus, though, the brightest of all of Fermi’s graduate students was Richard Garwin, the young man from Cleveland who pitched up in Fermi’s office and helped build the analog computer that calculated solutions for Schrödinger equations. Everyone knew he was bright. Fermi is reputed to have said that Garwin was “the only true genius” he ever met. Apocryphal or not, the usually reticent Fermi sent a letter to the employment director at Los Alamos in the spring of 1949 recommending Garwin for summer work. Fermi was lavish in his praise of Garwin, describing him as “one of the most gifted students with whom I have ever come in contact,” which was high praise indeed coming from Fermi, who rarely if ever offered praise, even to his closest colleagues. Among the whole group of Fermi’s students, Garwin was the only one offered a position at the institute after graduation, another sign of the esteem in which Fermi held him. He did not stay in the field, instead pursuing an extraordinarily creative and productive career at IBM’s Watson Labs as well as a central role in advising presidents and government agencies on science and defense policy issues. This ensured that Garwin’s influence—and by association Fermi’s—would be felt in a much broader setting than that of his fellow students, with the possible exception of Arthur Rosenfeld. Garwin has won numerous highly prestigious awards, including the Enrico Fermi Award in 1996 and the Presidential Medal of Freedom in 2016.
Other graduate students were heavily influenced by Fermi, even though he was not their formal adviser. Yang was one of them; Guarang Yodh and future Nobel laureate James Cronin were two others.
Yodh, a native of India, was a student of Anderson but got to know Fermi during his graduate years. His own experimental work focused on pion scattering. One day, Fermi approached Yodh while the graduate student was adjusting a particle counter and said, impishly, “That is not the way it is done in the Mahabharata.” Fermi had just been reading an English translation of the classic Indian epic in his reading group and had fun teasing the young Indian student. Yodh recalls with warmth and affection the many parties he attended at the Fermis’ home, and the clarity and rigor of his teaching.
Cronin, a strapping native Chicagoan, would have liked to study directly with Fermi. Unfortunately, Orear, Rosenfeld, and Schluter had filled up the available slots, so Sam Allison became Cronin’s formal supervisor. Cronin nevertheless spent quite a lot of time with Fermi getting advice and guidance. There was also a social aspect to these relationships, an aspect that could sometimes lead to difficult situations. Cronin recalled with humor a moment when the institute staff were involved in a friendly game of baseball. No game, however informal, was friendly for Fermi, who played this game, as he did all games, with a determination to win. Cronin was on the mound, facing Fermi. It suddenly occurred to Cronin that if he threw a wild pitch and hit Fermi, he might go down in history as the man who killed the father of the nuclear age. He was torn, though, because Fermi demanded to be taken seriously in any athletic competition. Cronin found a way to pitch the ball just far enough away to walk Fermi without Fermi realizing what Cronin did. It was an unlikely dilemma for a graduate student.
Cronin was also one of those students invited by Fermi to lunches in Hutchinson Commons, where Fermi would playfully pose problems that kept students thinking on their feet.
Cronin considered Fermi the most influential person in his professional development. In fact, when it came time to organize a centennial celebration of Fermi’s birth at the University of Chicago, it was Cronin who took the lead in setting it up, inviting speakers, and editing a fine volume of papers to commemorate the occasion.
HARRIETT ZUCKERMAN, A SOCIOLOGIST WHO STUDIED THE INFLUENCE of Nobel Prize–winning scientists among future Nobel laureates, concludes that in this respect Fermi stands alone, at least in the United States. When one looks at a “family tree” of those who are linked, either directly or indirectly, to Fermi, that conclusion is only reinforced. Some five of his direct students went on to win Nobel Prizes: Chamberlain, Friedman, Lee, Segrè, and Steinberger. Two others, Cronin and Yang, also won Nobel Prizes and though not formally Fermi students, both credit him with providing career-enhancing inspiration and guidance. Many others went on to prominent and important careers in the field. It is an astonishing record, comparable perhaps only to that of Sommerfeld and Rutherford. Valentine Telegdi judges Fermi’s teaching to be his greatest contribution in the Chicago period. It is difficult to argue with him.
* Considering the quality of Fermi’s graduate students, being his second best student ever was quite an accomplishment.