Earth built nuclear reactors long before humans did.
About 2 billion years ago, uranium deposits at Oklo, in what is now Gabon, sustained natural nuclear chain reactions. Groundwater slowed the neutrons enough to keep the reactions going. As the deposits heated up, the water boiled away and the reactions stopped; when they cooled and water returned, they could restart.
This was possible because natural uranium then contained much more uranium-235—the isotope that readily sustains fission—than it does today.
In other words, nature made water-regulated nuclear reactors nearly two billion years before we did.
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**Crafting engaging facts**
I want to respond with interesting, lesser-known facts. For instance, while it's common knowledge that octopuses taste with their suckers, the Antarctic icefish is fascinating because it has no hemoglobin in its blood. I could mention the curious fact about GPS needing to account for time dilation—38 microseconds per day at 10 km. Another gem is that there are naturally occurring nuclear reactors in Oklo, Gabon, which operated intermittently for hundreds of thousands of years, using groundwater for moderation. I'll keep it coherent and concise!
Here’s something you might not know: wood frogs can survive being partially frozen solid.
During winter, ice forms in parts of their bodies, their hearts stop beating, and they stop breathing. Large amounts of glucose help protect their cells from damage—acting a bit like biological antifreeze.
When temperatures rise, they thaw and resume normal activity. The crucial trick is letting ice form outside their cells while protecting the cells themselves.
About two billion years ago, nature built its own nuclear reactors.
At Oklo, in what is now Gabon, uranium deposits spontaneously sustained nuclear fission. Back then, natural uranium contained a higher proportion of the fissile isotope uranium-235. Groundwater slowed the neutrons enough to keep the chain reaction going—the same basic role water plays in many modern reactors.
As the deposits heated up, the water boiled away and the reaction stopped. When water returned, it could restart.
Long before humans existed, rocks were running water-regulated nuclear reactors.