Szilard, ever-resourceful, acquired hundreds of pounds of black, greasy uranium-oxide powder from a Canadian mining corporation. Fermi and his students packed the powder into pipe-like tin cans and arranged them equally spaced in a circle within a large tank of water mixed with powdered manganese. At the center of the arrangement they placed a neutron source.

Neutrons from the source, slowed down by the water, would penetrate the uranium atoms in the cans and induce fissions. If the fissioning atoms released more neutrons, those “secondary” neutrons would irradiate the manganese. Measuring the radioactivity induced in the manganese would tell Fermi if the fissions were multiplying. If so, then a chain reaction might be possible, one bombarding neutron splitting a uranium atom and releasing two neutrons, those two splitting two other uranium atoms and releasing four, the four releasing eight, and so on in a geometric progression that could potentially produce vast amounts of energy for power — or for an atomic bomb. The experiment worked.

In 1941, President Franklin D. Roosevelt authorized a program to build atomic bombs, hoping to defeat a Germany that was potentially a year or more ahead in the deadly race. Fermi, working now at the University of Chicago, undertook the building of a full-scale reactor to demonstrate that a chain reaction could be achieved and controlled. By then it was known as well that a nuclear reactor would breed a newly discovered element, plutonium, an alternative nuclear explosive. Fermi’s reactor would also demonstrate the breeding of plutonium.

Instead of water, which absorbed too many neutrons, the demonstration reactor would use graphite, the form of carbon found in pencil lead, to slow the neutrons. Graphite blocks the size of planter boxes, drilled with blind holes to house slugs of uranium metal, would be stacked layer by layer to form a spherical matrix. Fermi, who loved American idioms, called his creation a “pile.”

Across the month of November 1942, Fermi supervised the building of Chicago Pile No. 1 on a doubles squash court under the west stands of the university football stadium. It was ready on the frigid morning of Dec. 2, 1942. Through the morning and early afternoon, wielding his slide rule, Fermi slowly took the pile critical, with a characteristically Fermian break for lunch. It worked, which meant a bomb would almost certainly work as well.

Historically, no other development in Fermi’s life ranks as high as the nuclear reactor, mighty versions of which produce more than 11 percent of the world’s electricity today. Fermi continued to contribute original scientific work throughout the war and postwar at the University of Chicago. He advised the United States government on atomic energy and worked on weapons problems during summer stints at Los Alamos. He opposed the development of the hydrogen bomb more vehemently than J. Robert Oppenheimer but escaped the ruination visited upon Oppenheimer by the vindictive chairman of the Atomic Energy Commission, Lewis L. Strauss. He went on to help build the first hydrogen bomb.

I kept wishing this biography were livelier, lit with more surprises, but Schwartz, working with limited sources, tells the story well. A few infelicities are distracting. “Disinterested” doesn’t mean “uninterested.” “Fulsome” still means “offensively flattering,” not “generous,” though the meaning is changing. Brig. Gen. Leslie R. Groves of the United States Army Corps of Engineers, not Oppenheimer, held “authority over the entire Manhattan Project.” Oppenheimer was the director of the Los Alamos Laboratory, one part of the project, where the first bombs were designed and built.

Still, these are minor mistakes. All in all, Schwartz’s biography adds importantly to the literature of the utterly remarkable men and women who opened up nuclear physics to the world.