The Manhattan Project through the eyes of Fermi
It’s hard to grasp the enormity of the development of the atomic bomb. The most absorbing scientific problem in the world, the problem of the makeup of the universe itself, turned out to hold the key to almost infinite energy and almost infinite destruction. This discovery coincided exactly with the largest war the world had ever known, in which the greatest political idea of the modern world, liberal democracy, faced its greatest threat, fascism. The realization of this on all sides set off an arms race, which the industrialized United States literally moved mountains to win. Then the United States became, as everyone expected, the undisputed heavyweight champion of the world, for a brief few shining years, before the Soviet Union entered the atomic fray and launched the world into existential uncertainty.
It’s a lot. And the personalities are just as big, even just on the scientific side: tortured poet Oppenheimer; shy, fatherly Bohr; his prodigal son-turned-Nazi Heisenberg; cerebral, impatient Szilard; retired, legendary Einstein; Martian genius von Neumann. All of them together, interacting, colliding and bouncing off each other like particles in a reactor.
To begin to grasp all facets of this monumental project requires a mammoth tome. Richard Rhodes’s The Making of the Atomic Bomb, which I’ve been reading recently, is a good attempt. It’s 700+ pages and choc-a-bloc full of technical and historical details. I think it’s incredible. However, it’s so large and complex that even relating its version of the development of the atomic bomb is intimidating for a blog such as mine.
So, I’m not going to do that. Instead, I’m going to take a crosscut of the development of the atomic bomb through one of the easier-to-digest personages of the atomic bomb sage: Enrico Fermi. Fermi, although brilliant, was an understandable sort of brilliant. He was a largely self-taught nerd who loved physics and pursued it throughout his life in theoretical and experimental form. He was not so political as Oppenheimer, alien as von Neumann, or prickly as Teller. He reminds me a lot of the nerds I know around Cambridge today, actually. Just, you know, a Nobel Prize winner.
Maybe an anecdote would help illustrate my point, before I start going through his life. Every great scientist has an anecdote that characterizes him (or her): Oppenheimer’s poisoned apple, Einstein’s days as a patent clerk, Feynman’s lockpicking. Fermi’s characteristic anecdote, for my reckoning, comes from Rhodes’s account of Fermi’s time at Los Alamos. Los Alamos was in the desert of New Mexico, and, as a lark, the scientists there adopted much of the dress and activities of cowboys, including swing dancing. Fermi, awkward nerd that he was, had no idea how to swing dance, and spent an entire night sitting on the edge of the dance and furiously trying to work out the pattern in his head. At some point, he got up, asked the instructor (one of the scientist’s wives) to dance with him, and, much to her surprise, carefully led her through all the steps with grim determination. This was Fermi in a nutshell: identify what’s interesting, work furiously to understand it, and then end up at the front of it.
Enrico Fermi was born and trained in Italy in the beginning of the 20th century. Italy was a relative backwater of physics, at least compared to Germany, Britain, or America. As such, Fermi, a prodigy from a young age, quickly surpassed his teachers, and was given free range of the physics laboratory from age 19 on. Fermi, brilliant and mathematically inclined, turned to the most interesting problems of his age: general relativity, quantum mechanics, and atomic physics.
His earliest works were both experimental and theoretical, signs of his flexibility to come. After leading his fellow classmates, Nello Carrara and Franco Rasetti, to create an X-ray photograph of a crystal, he published his first scientific works on trying to unite electromagnetism and gravity, following Einstein’s footsteps. Fermi, as an unknown 20 year old, was forced to publish in an Italian journal, but one of the papers was well-regarded enough that it was translated into German as well.
After graduation, Fermi spent about a year studying in Germany, the center of physics at that time. Here, he studied under Max Born, worked with Heisenberg, and met both Hendrik Lorentz (of Lorentz transformation fame) and Albert Einstein. If this seems like a lot to pack into a year for a kid fresh out of college, then you’re starting to get an idea of Fermi’s uncanny ability to be in the thick of things, as well as exactly how small the physics community was. By the way, ironically, Fermi considered this one of the few failures of his life, as it was one of the few times in his life he wasn’t recognized as the undisputed smartest person in the room. But that was Fermi.
By his mid 20s, which were also the mid-1920s (funny how that worked), Fermi had moved back to Italy and began to seriously examine quantum mechanics, paralleling the field’s heating up. Through a combination of theoretical and experimental work on gases, he discovered the existence of fermions, particles that obey the exclusion principle that two particles can’t occupy the same quantum state. Around the same time, he applied to become one of the first professors of theoretical physics in Italy.
Fermi’s star kept rising. By 29, he was appointed a member of the Royal Academy of Italy by Mussolini himself. Fermi, largely apolitical, joined the Fascist party soon after, likely out of convenience. He published a popular Italian textbook on atomic physics, hired boatloads of research assistants and graduate students, and even began attracting foreigners to study physics with him in Italy, like the German Hans Bethe.
As the focus of science turned to the forces of the atom, so too did Fermi’s. He postulated the existence of the neutrino, then turned to see if he could determine the makeup of the atom. With his research group, the Via Panisperna boys, he set up a clever experiment to induce radioactivity in different elements. He and his group assumed that, by inducing radioactivity, they had transmuted old elements into new, heavier elements (the transuranics), but they had actually discovered radioactive decay by forcing heavier elements to decay into a mixture of lighter elements, arguably a more important discovery. Unfortunately, in those heady times, by the time they figured that out in 1938, 4 years later, Fermi was already receiving the Nobel Prize for his “discovery of the transuranics”, and he had to add a footnote to his Nobel Prize speech that he hadn’t, in fact, done that.
Still, as Fermi’s rapid 4 year journey from publication to Prize indicated, this was an exciting time for physics. Around the same time, Fermi discovered slow capture of neutrons, a key part of the development of the atomic bomb, along with his experimental confirmation of nuclear fission. Unfortunately, this was an exciting time for Fermi’s personal life, too, as Mussolini decided to impress Hitler by suddenly instituting racial laws in 1938 banning Jews from government work and education. Although Fermi wasn’t Jewish, his wife and many of his physics colleagues were, and even Fermi saw the writing on the wall that things were only going to get worse.
So, Fermi and his family escaped to America. As befitting Fermi, this was actually pretty easy. He didn’t have the dramatic rowboat escape of Niels Bohr and his son, Aage, or, for that matter, Bohr’s beneficial humanitarian impact on the situation of Jews in his homeland. Fermi just sailed directly from the Nobel Prize ceremony to America and set up work at Columbia in 1939, just in time to help make the atomic bomb for his new country.
You see, it wasn’t just Fermi who had figured out that radioactive decay was occurring with induced radioactivity, and that might lead to a chain reaction that would ultimately result in an atomic bomb. By this point, every physicist had realized that. In fact, Szilard, the Hungarian physicist and boy genius (who famously did his best thinking in the bath), had realized it all the way back in 1933, secretly patented the idea of a chain reaction in 1934, and had convinced Albert Einstein to convey a letter to FDR by August 1939 warning him of the same.
Fermi arrived in America in the middle of all of this excitement, along with a bunch of other mostly Jewish European physicists who had wisely escaped their increasingly antisemitic homelands. Fermi, like everyone else who wasn’t a Nazi (e.g. not Heisenberg), had come to the conclusion that, if anyone should have the atomic bomb, it definitely shouldn’t be Hitler. This probably provided some impetus for Fermi to shift his work towards engineering the atomic bomb. But, I think the bigger impetus for Fermi was that making the atomic bomb was by far the most exciting thing happening in physics.
This is how Fermi ended up causing atomic fission to happen in Columbia University, right in the middle of New York City: first in 1939 with a cyclotron, and then, and more dramatically, in 1941, with six tons of uranium oxide and thirty tons of graphite carefully arranged into a “pile”. This proved not big enough to achieve criticality (i.e. become a self-sustaining nuclear reaction), although it was still a giant pile of radioactive material in one of the most populated places in New York City and the world, long after it was understood exactly how dangerous that was. Following this, Arthur Compton at the “Advisory Committee on Uranium”, which at that point was fully governmentally commissioned and funded, realized how big a mistake that was, asked Fermi to build his next, presumably critical pile somewhere else. Compton suggested/told Fermi to move it close to Chicago, which was where the plutonium part of the atomic bomb work had become concentrated. He suggested a nature preserve 20 miles outside of the city. Fermi, reluctantly, agreed.
Picture this: it’s the fall of 1942. Germany was full bore into its simultaneous wars in Africa and Russia and bearing the strain. The Pearl Harbor sneak attack had happened one year earlier, and America was fully aware that it was going to have to enter its full might into the war. Fermi, his wife, and other refugees huddled in America, feeling grateful that they had avoided the horrors wreaked upon those who hadn’t managed to get out, but still unsure in their new country, burying gold in the backyard of their home in case they needed to leave in a hurry.
And then Arthur Compton, a genteel, Mennonite, Nobel Prize winning American physicist who Fermi barely knows, tells Fermi that he needs to move his giant uranium pile across the country. Money and manpower is no object. The only concern is speed and scientific accuracy. Fermi recognizes the need for speed and accuracy. It fits in with Fermi’s natural scientific drive. And when the blueblood Boston engineering firm contracted to develop the nature preserve into a nuclear testing site gets caught up in a labor dispute, Fermi proposes to move the uranium pile to the University of Chicago squash court instead. Compton agrees.
So now Fermi, 3 years into being an American, is in charge of building the first self-sustaining nuclear reactor in the world in a city and university he’s been in for just a few months. And, based on his calculations, 30 high school dropout laborers under the direction of 6 scientists machine 45,000 graphite blocks enclosing 19,000 pieces of uranium and uranium oxide, held together in a giant somewhat spherical pile by wooden timbers and a 25 foot cubic balloon filled with carbon dioxide. This pile is meant to become a self-sustaining nuclear reactor, so it has some small chance of blowing up and making Chicago an uninhabitable wasteland.
Fermi is aware of this risk, of course, as is Compton and the rest of the scientists (the laborers and the rest of Chicago probably weren’t, though). But they feel confident in their calculations and their safety precautions, even though both are based on science not even half a decade old. And so, on December 2, 1941, the cadmium control rods are slowly withdrawn from this large, radioactive pile, inch by inch, as a small audience of scientists stands around the squash court and listens to the tick of the Geiger counter. One scientist stands with an axe, ready to cut the emergency control rod, the “zip”, if the reaction goes critical beyond control. Another scientist stands ready on a ladder with a bucket of cadmium nitrate, a last ditch safety measure that would have ruined tons of uranium and graphite if it had to be used.
The control rods start to be removed at 9:54 in the morning. As each control rod is slowly withdrawn, and as the detector’s frequency slowly ticks up, Fermi furiously calculates how close the pile is to criticality with his slide rule. After a brief false alarm from the zip and a break for lunch, Fermi calmly announces at 3:54 in the afternoon that the reaction has gone critical. From there on, the electric current from the boron trifluoride detector rapidly increases, until 28 minutes later when the current passes the predetermined threshold of half a watt, enough to power a dim lightbulb. The scientist in charge of the zip releases it, and it slides down into its slot in the pile, ending the chain reaction. Fermi finishes his calculations, confirming that they had just released the power of the atom in a University of Chicago squash court. Humanity would never be the same.
And that was Fermi’s November/December 1942. By September 1944, Fermi had become the scientific architect of the Hanford site, which was designed to be an actual plutonium production site, this time on the banks of the Columbia River in Washington. It had been built at breakneck speed by DuPont at a profit of $1 (DuPont was afraid of being once again seen as a “merchant of death” after their disastrous WWI publicity), from government acquisition of the 400,000+ acres in early 1943, to the hiring and housing of 45,000 construction workers by June 1944, to the completion of the plutonium reactor itself by September 1944.
Fermi himself was the one who inserted the first uranium fuel slug into the B reactor, and he and fellow physicist John Wheeler were likewise the ones tasked with discovering why the reactor shut down just a few days later and the solution to this shutdown. The problem turned out to be neutron poisoning from xenon, a fission product of plutonium, and the solution turned out to be just more uranium, roughly speaking. But still, imagine: Fermi, just about 7 years gone from Mussolini’s Italy, 6 years from his Nobel Prize awarded for the wrong discovery, 4 years from burying his gold in his backyard in New Jersey, a small, middle-aged Italian man standing in front of an entire factory of thousands of American workers waiting anxiously for him to finish his calculations with his ever present slide rule and figure out what exactly was killing their plutonium production and preventing America’s creation and use of the greatest weapon the world had ever seen. What must he have thought?
As far as I can tell, not much beyond physics. We get some small hint of some political thought from Fermi’s suggestion to Robert Oppenheimer in April 1943 that they could use radioactive byproducts to contaminate the German food supply, if the Germans developed the atomic bomb before the Americans did. That suggests some worry on his part, some acknowledgement that lives depended on his calculations in more ways than one. But, beyond that, did Fermi ever stop to think about how weird this was? How exceptional his life had become? What hinge of history his life swung at, how he was probably one of the most important people in the world at that time?
But his reliability was part of who he was. He just did the things that were important, and interesting, and that was that. And so, as one would expect, he ended his wartime experience at the Manhattan Project, the most important scientific project in the world, as the director of arguably the most interesting division, F Division, short for, what else, “Fermi Division”. It was in charge of the fusion bomb, the research reactor, and general fission/fusion research. Fermi had a diverse set of experiences there: supervising critical research, learning to swing dance, and calculating the yield of the atomic bomb by dropping strips of paper into the blast wave and seeing how far they were blown.
Fermi’s brief postwar career was unremarkable by his standards. He consulted on the fusion bomb, although he opposed its development on moral and technical grounds; advised several future Nobel Prize winners; carried out important research into particle physics and cosmic radiation; and wrote on the Fermi paradox of extraterrestrial life. And then he died, relatively young at age 53, from the cancer that he always assumed would come as a result of his atomic work. His wife outlived him by 20 some years.
And that was it for Fermi. He was born, had an insanely huge impact on physics, science, and the geopolitical balance of the world, and then he died. He wasn’t a statesman, like Einstein; a philosopher, like Oppenheimer; or a figurehead, like Bohr. He was just a guy who really loved physics, science, and his Jewish wife, and that decided his life.
I can’t really say why I find Fermi so fascinating, except that I’ve been thinking a lot about the Manhattan Project recently and what it means. Nuclear power plants are, at last, coming back in vogue after their nadir. Russia is threatening, once again, to launch nuclear missiles at Europe. Trump is claiming that Elon Musk’s DOGE is his Manhattan Project, while a US government agency is explicitly calling for an AI Manhattan Project. I’m not sure if they understand the way in which the first Manhattan Project resulted from an arms race with Germany and ran the risk of us accidentally blowing up Chicago, with only a small team of physicists (including, crucially, a recent immigrant from a country we were literally at war with) to prevent it from happening. But they probably don’t care.
Maybe it’s because the world once again feels on the cusp of a change. I slowly have come around to the idea that this new artificial intelligence revolution does matter, fighting against my natural inclination to believe that nothing ever happens. Biology, chemistry, knowledge work, drone warfare: AI is upending all of it. And it’s tempting to turn to “crybaby” Oppenheimer, as Truman called him, to make sense of this, who simultaneously hated and loved the bomb he worked on.
But I know people working on AI, serious people, and I don’t think most of them are like this. I don’t think most of them think about the larger implications at all, not in a deep way. In fact, I think many of them that claim to do so cynically, or at least without deep moral conviction (i.e. Musk, Altman). They’re not stupid or unaware. I think most of them are just like Fermi, though, and find themselves irresistibly drawn to the most fascinating work going on.
And so through Fermi I see our present age. Stateless geniuses who relentlessly pursue what's important, forever useful, dragging the rest of humanity into a new age. Heroes? Villains? It depends on your perspective. Regardless, you know their work’s going to be interesting.
Brilliantly written.