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The first chain reaction

1942

Under the stands of a disused sports field in Chicago

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In depth

Chicago Pile-1 had no radiation shielding and no cooling system, in the middle of a city of three million. Its safety consisted of cadmium rods, a man with an axe beside a rope, and three people holding buckets of cadmium solution on top. The experiment showed that a chain reaction could be controlled — the precondition for both nuclear weapons and nuclear power. The message to Washington was coded: “The Italian navigator has landed in the new world.”

For children

In a squash court under the stands at the University of Chicago, Enrico Fermi and his team built a pile of graphite blocks and uranium. When the last control rod was withdrawn, the first self-sustaining nuclear chain reaction made by people began. It ran for 28 minutes.

Sources

  • Rhodes, The Making of the Atomic Bomb (1986)
  • Argonne National Laboratory: Chicago Pile-1

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Part of Terra Saga — the story of Earth on a timeline. terrasaga.org · Last changed 2026-08-16