Enrico Fermi: Unleashing The Atom

The Italian physicist made the key theoretical leap that led to the atom bomb and nuclear power

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On a frigid December morning in 1942, a group of physicists gathered outside a squash court under the unheated stands of the University of Chicago's football stadium. Almost filling the court was a huge round pile of graphite bricks laced with uranium. When all was ready, team leader Enrico Fermi gave an order that would create the world's first self-sustaining nuclear reaction and usher in the Atomic Age.

A short, muscular Italian with striking gray-blue eyes, Fermi was already a towering figure. He had won the Nobel Prize in physics for experiments with radioactivity -- yet he was also a pure thinker, developing a new theory of atomic interactions that still holds up today. The historic squash court test would showcase both facets of his genius.

Fermi had made the key theoretical leap on the road to the atom bomb and nuclear power. His insight: If you split an atom of, say, uranium by hitting it with neutrons, the fission produces more neutrons. Those, in turn, could split more atoms, which spew out more neutrons. Presto. The whole thing could keep going, releasing vast amounts of energy.

To test the idea, Fermi designed and built piles of uranium and graphite, which slows neutrons down and makes them better "splitters." By Dec. 2, 1942, his biggest pile was ready. Fermi told colleague George Weil to begin pulling out, inch by inch, the pile's cadmium control rods, which absorb neutrons. As the hours crept by, the radioactivity slowly increased, precisely as Fermi had predicted. Ever the creature of habit, he even ordered a break for lunch. Then, in mid-afternoon, the instruments showed that the momentous goal had been achieved. Fermi raised his hand. "The pile has gone critical," he announced. He shut the reaction down after four minutes. Just 15 years later, the same basic reaction fired up in the first full-scale nuclear power plant in Shippingport, Penn.

Born to an Italian railroad administrator and a teacher in 1901, Fermi showed his brilliance early. He took up the study of physics at 14 in the emptiness following the death of his older brother. The university entrance paper he wrote was so sophisticated that the examiner deemed it worthy of a doctoral thesis. By his mid 20s, Fermi was the leader of an exceptional group of young Italian physicists. His friends nicknamed him the Pope, because he seemed all but infallible on the subject of quantum mechanics.

Fermi, his Jewish wife, and their two children fled Mussolini's Italy in 1938, using his freshly awarded Nobel prize money to emigrate to the U.S. via Stockholm. A gadget lover, Fermi gave his wife and biographer, Laura Fermi, what she describes as a "never-forgiven" step-on garbage can as her first Christmas present in the U.S. But though Fermi may have lacked spousal sensitivity, his mind was exceptional for its sharpness and clarity of thought. "He was able to analyze in its essentials every problem, however complicated it seemed to be," wrote physicist Hans A. Bethe.

Fermi became a key member of the Manhattan Project. And he went on measuring the world, even while dying of cancer at age 53 -- calculating his intake of artificial nutrients by timing the drops with his stopwatch. Wrote Nobel laureate, Emilio Segrè: "With Fermi disappeared the last individual of our times to reach the highest summits in both theory and experiments and to dominate all of physics."

By John Carey

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