Natural Nuclear Reactors, Then (2 Billion Years Ago) and Now

NASA Astronomy Picture of the Day: Remnants of ancient, natural nuclear reactors

NASA's page says "No natural reactors exist today, as the relative density of fissile uranium has now decayed below that needed for a sustainable reaction." A geophysicist named J. Marvin Herndon would disagree: he believes the earth's core is a natural nuclear reactor. See:

Discover Magazine: Nuclear Planet "Is there a five-mile-wide ball of hellaciously hot uranium seething at the center of the Earth?"

OK, so let's say the core's a nuclear reactor. On to the sci-fi premise...

What if the core nuclear reactor is not 'natural', but rather was intentionally created as a power-rich habitat for someone? Hell, let's say for a race of super-intelligent computational nanomachines who took up residence billions of years ago. We live -- indeed all surface life has evolved -- on their waste heat and the elemental byproducts of their reactor, as those byproducts have slowly risen to the surface.

But why did these in-dwellers choose a shielded power source at a planet's core, instead of the more plentiful energy from outward-facing stars -- a "Dyson sphere" approach? Well maybe the in-dwellers are prisoners. Or better yet fugitives -- yes, fugitives hiding from a terrible power. They were safe inside, hidden from a vengeful universe, our Earth utterly undeserving of attention from Those Who Would Do Them Harm. But they didn't count on humanity popping up, sending up rockets and radio signals that will be noticed and investigated. Now they've got a problem. And we've got a problem, too... because if the in-dwellers don't decide to snuff us out to maintain their cover, the Vengeful Powers might arrive... and they would judge us as harshly as the in-dwellers...

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