Stone to Silicon

Energy · 1942

Nuclear reactor

Chicago Pile-1 achieves the first self-sustaining chain reaction.

Enrico Fermi's team brought a graphite-and-uranium pile under Stagg Field to criticality on 2 December 1942. Controlled chain reactions made plutonium production, naval propulsion and nuclear electricity possible.

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Arcs above join it to what it stood on, arcs below to what it led to. The bar places this stretch on the tree's whole timeline.

What it built on 2

What it led to 7

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Related measurements

The dashed line marks when it first worked.

Nuclear electricity generation Latest: 2.81k TWh (2025) Source: Our World in Data

Share of electricity from low-carbon sources Latest: 42.6 % (2025) Source: Our World in Data

World energy per person by source since 1800 Latest: 20.1k kWh per person (2025) Source: Our World in Data