Billions for sure - we know because the natural reactor at Oklo 1.7 billion year...

		sgt101 on Jan 1, 2019 \| parent \| context \| favorite \| on: A fifth of Earth’s geologic history might have van... Billions for sure - we know because the natural reactor at Oklo 1.7 billion years ago is still very much detected. https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...

Very cool. Glad to learn about that!