Earth's Ancient Natural Nuclear Reactor Discovered from 2 Billion Years Ago
Over 2 billion years ago, a natural nuclear reactor formed in Oklo, Gabon, long before human-made reactors existed. Discovered in 1972, the site showed unusual uranium isotope ratios, indicating a sustained natural fission reaction had occurred. This ancient reactor operated under conditions that are unlikely today, requiring higher uranium-235 concentrations and groundwater to sustain the reaction, similar to modern reactors. The process eventually ceased after thousands of years.