Around 2 billion years ago, Earth ran nuclear reactors.
Uranium deposits at Oklo, in what is now Gabon, sustained natural fission reactions—long before humans existed.
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Earth built nuclear reactors before humans
The geology supplied concentrated uranium. Groundwater slowed the neutrons, helping the chain reactions continue.
The right rock, water and ancient uranium composition came together naturally.
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Earth built nuclear reactors before humans
The evidence was discovered in 1972. Scientists noticed unusual uranium isotope proportions and found traces left by fission.
These surviving rock samples preserve the story of a natural nuclear reactor.
