Scientists come in at least as many flavors as fruit. Some are inspired philosophers, others are get-your-hands-dirty mechanical craftsmen, yet others are like birds which can survey multiple parts of the scientific landscape from a very high altitude. But whatever other classification you may use, there are two distinctions which scientists have always exemplified. They can be either theoreticians or experimentalists, and especially these days, they are all specialists. In an age where it can take a lifetime to understand the complexities of even a narrow part of your science, excelling at every subfield of a scientific discipline, let alone both theory and experiment, would seem like an impossible feat.
Enter Enrico Fermi, the likes of whom we are unlikely to see for a very long time. Bucking almost every neat scientific distinction, Fermi was the only scientist of the twentieth century who was supremely accomplished in both theoretical and experimental physics. Almost any of his discoveries would have been enough to net a Nobel Prize, and yet he made at least half a dozen of them. In addition he was one of the three or four physicists of the century who were universalists, making contributions to and displaying a sound grasp of pretty much every branch of physics, from the microscopic to the cosmic. In my opinion, among his contemporaries only Hans Bethe, John von Neumann, Richard Feynman and Luis Alvarez came close to demonstrating the same breadth, and none of them excelled in both theory and experiment. You could ask Fermi any problem, and as long as he could calculate it he could give you an answer: no wonder that his colleagues called him the "Pope of Physics". It also helped that he lived through a century in which physics made momentous contributions to the human intellect and condition, and he was both fortunate and supremely qualified to be a major part of these contributions. As just one aspect of his extraordinary imprint on physics, no scientist has as many measurements, rules, laws, particles, statistics, units, and energy levels named after him as Fermi. He was also one of America's greatest immigrants.
This is a fine biography of Fermi written by Gino Segre and Bettina Hoerlin - a practicing physicist and a historian of science - who both had connections to Fermi through their families. Hoerlin's father worked on the Manhattan Project. Segre is the nephew of Emilio Segre, Nobel Prize-winning physicist and one of Fermi's closet friends and collaborators. The authors document Fermi's upbringing in Italy at the turn of the century. The Fermis came from a verdant, hilly region of Italy known for its industrious farming community, and throughout his life Fermi maintained his love for manual labor and the mountains, qualities endemic to many people from this region. His father was a railway inspector. Enrico was a child prodigy who combined great intellect with hard self-reliance and perseverance, qualities which were inculcated by his hardworking parents. A life-changing tragedy at age fifteen - the sudden death of his brother with whom he was best friends - turned him toward physics and mathematics. His performance as a seventeen year old in the entrance examination for a well-known university in Pisa displayed knowledge that would have been substantial for a graduate student. From then on his scientific development proceeded smoothly, and before he was 30 he was both Italy's leading physicist as well as one of the world's greatest scientists.
The book lays out many of Fermi's major discoveries. Two in particular bracket his unsurpassed talents as both a theoretician and an experimentalist. In 1933 Fermi came up with a mathematical theory of radioactive decay and the weak nuclear force. And in 1942 he and his team assembled the world's first nuclear reactor. It is almost impossible to imagine any other scientist accomplishing these two very different and very important feats; the famed historian C. P. Snow paid Fermi the ultimate tribute in this regard when he said that, had Fermi been born twenty years before, he could have discovered both Niels Bohr's quantum theory of the atom (theory) and Ernest Rutherford's atomic nucleus (experiment). In the 1930s Fermi and his team became the world expert on neutrons; life in the physics institute on Via Panisperna in Rome was bucolic in spite of being intense. He almost single-handedly discovered the power of slow neutrons which are used to harness nuclear energy in reactors. He and other leading physicists also narrowly missed discovering nuclear fission, mistaking fission products for elements beyond uranium. Rome under his scientific tutelage became a magnet for scientists like Hans Bethe and Edward Teller who learnt the art of problem-solving in physics from the master. Fermi's marriage to a very intelligent and resourceful woman, Laura, cemented his family life. But the pall of fascism was dropping on Italy through the person of Benito Mussolini. Laura was Jewish, and by 1938 Fermi realized that he had to emigrate to another country. Fortunately the receipt of the 1938 Nobel Prize gave him the perfect opportunity to flee to the United States. Along with other brilliant scientists like Bethe, Albert Einstein, Leo Szilard and John von Neumann, Fermi became one of fascism's greatest gifts to this country.
In the United States Fermi was already known as the leading nuclear physicist of his generation. When nuclear fission was discovered in Germany at the end of 1938, there were legitimate fears that the Nazis would harness it to build an atomic bomb. Efforts to investigate fission in the US kicked into high gear, especially after Pearl Harbor. It was not surprising that the scientific community turned toward Fermi to assemble the world's first nuclear reactor. The book's account of this tremendous feat involving black graphite bricks and faces, the squash stand at the university and the sometimes amusing consequences of secrecy is worth reading. First at Columbia and then memorably at Chicago, Fermi and his team achieved the first self-sustaining nuclear reaction on December 6, 1942: a coded telegram went out to the leaders of the Manhattan Project saying that the "Italian navigator had landed in the New World". Even if he had accomplished nothing else this would have been sufficient to enshrine Fermi's name in history. But he kept on making major contributions, first at Chicago and then at Los Alamos. At Los Alamos Fermi's universal expertise was so valued that Oppenheimer created an entire division named after him (the F division). He became a kind of all-round troubleshooter who could solve any problem in theoretical or applied physics, or in engineering for that matter. He had an uncanny feel for numbers, and became known for posing and solving 'Fermi problems' which benefited from quick, back of the envelope, order-of-magnitude estimates. The iconic realization of the Fermi method was during the world's first atomic test in New Mexico on July 16, 1945, when, as the shockwave reached him, Fermi threw pieces of paper into the air and calculated the yield of the test based on the distance at which they fell. This calculation compared favorably with more sophisticated measurements that took several days to acquire.
After the war Fermi became a professor at Chicago where he again served as a magnet for the new generation of physicists exploring the frontiers of particle physics and cosmology. He was an incredibly clear and succinct teacher, and gave his students a true feel for the entire landscape of physics. Teaching was not just limited to classrooms but spilled over into the lunch cafeteria and on hikes. Physicists like Freeman Dyson and Richard Feynman made pilgrimages to see him from around the country, and six of his students received Nobel Prizes. Even after winning enough accolades for a lifetime, he worked harder and more diligently than anyone else. His colleagues joked that he was the man with an inside track to God, so all-encompassing were his scientific and computing abilities. His notes on thermodynamics, quantum mechanics and nuclear physics are still available and they attest to his clarity. At Chicago he not only made important contributions to experimental particle physics but he also made the first forays into computing. The so-called Monte-Carlo method which allows one to explore features of a system by making random jumps bears his imprint.
While not a very sentimental man, Fermi's friendliness, integrity, modesty and impartial, non-emotional attitude endeared him to almost everyone he came in contact with. He was friendly and had an impish sense of humor, but while not cold was also not a warm person who engaged intimately with those around him; this quality led to a family life which while not unhappy was also not particularly joyous, and his relative lack of affection was reflected in the brisk relationship that Fermi had with his daughter and son. He despised politics but still served on important government committees because of his feelings of duty toward his adopted country. Remarkably, his neutrality through some very politically fraught times was not detested, and he was one of the very few scientists who was admired by people who were each other's sworn enemies. While he opposed the hydrogen bomb on moral terms and testified on behalf of Oppenheimer during the latter's infamous hearing, he also served as a consultant to Los Alamos once he realized that the Russians might also get the bomb; characteristically enough, he correctly predicted how long it would take them to build their first thermonuclear weapon. People looked to him for impartial guidance in almost every matter which could benefit from rational introspection.
Art and music baffled Fermi, but his rational analysis of these things only endeared him more to his friends and colleagues. At an art exhibit on the immigrant experience for instance, he calculated the ratio of the lengths of legs and heights of the immigrants in the photos and concluded that his own dimensions fit the statistical distribution. At Los Alamos he quickly memorized the rules of square dancing and danced with unerring accuracy but almost zero passion. His modesty and tendency to shun the limelight was also a great draw. He could as easily chat with janitors as with other Nobel Laureates. No task was beneath him, and his great ability to perform routine work without complaints or fatigue was instrumental in his success: whatever it took to solve a problem, Fermi would do it. When flabbergasted scientists asked him how he did it, Fermi would often reply with a smile, "C.i.f, con intuito formidable" ("with formidable intuition"). Often his distinguishing quality was pure stamina; whether it was a tennis match or a physics problem, he would beat the problem (and his opponents) into submission by sheer perseverance and doggedness. His manner of playing sports mirrored his manner of doing science: shun the style and elegance, and go straight and relentlessly for the solution using every technique at your disposal. The method of approximate guesses which came to be named after him has been used to estimate a wide variety of disparate numbers, from the number of extraterrestrial civilizations in the galaxy to the number of piano tuners in Chicago (his favorite example).
This giant of science was struck down by cancer in 1954 when he was still in his prime. The book talks about visits made by various famous scientists and friends to the hospital where he was installed after exploratory surgery indicated no hope. They could not believe that the indefatigable Enrico would soon be no more. All came away shaken, not because they saw an emotionally fraught man in pain but because they saw a perfectly calm and rational man who had reconciled himself with reality. He knew exactly what was happening to him and was making plans for publishing his last set of notes. Characteristically, he was measuring the rate of saline intake and calculating how many calories he was getting from it. When he came home and his wife rented a hospital bed for him, he predicted that he would only need it until the end of the month. True to his amazing calculating prowess, he passed away two days before the predicted date, on November 28, 1954.
This book in general lays out a warm and engrossing picture of Enrico Fermi. As I see it, it is up against two challenges. Firstly, it's relatively sparse on the science and does not always provide adequate background. In this context it is a light read and comes across unfavorably compared to Richard Rhodes' seminal book "The Making of the Atomic Bomb" which goes into great depth regarding Fermi's work, especially on the Chicago nuclear reactor. Rhodes' volume is also better on giving us a detailed picture of Fermi's contemporaries. Secondly, it cannot resist comparison with two old Fermi biographies. His wife Laura's endearing biography of him named "Atoms in the Family", published only a few months before his death, provides as intimate a picture of the personally reticent Fermi as we can expect. This book's view understandably is not as intimate. The same goes for "Enrico Fermi: Physicist", a biography of Fermi written by his friend, fellow Nobel laureate and uncle of one of the present book's authors, Emilio Segre. Segre was a top-notch physicist who worked with Fermi from the beginning and who does much recreating the early days of Fermi's childhood and his experiments in Rome. That description provides another personal touch which is again not as vivid in this volume.
Notwithstanding these comparisons, I am glad that Segre and Hoerlin wrote this book to introduce one of history's greatest and most unique scientists to a new generation. No scientist has contributed more practically and in a more versatile manner to modern physics. And few scientists have combined extraordinary and universal scientific talents with the kind of personal humility and decency that Fermi exemplified. For all this his life story needs to be known anew.