Natural Nuclear Fission Reactor

The Oklo reactor(s) in Gabon are such a wonder. I have to be careful to say &quot;The world&#x27;s first <i>man-made</i> chain nuclear reaction was achieved in a squash court at the University of Chicago in 1942.&quot;<p>While Oklo georeactors are relatively well-known now, have you all heard of the crazier hypothesized georeactors? Like that the Moon may have formed in a nuclear excursion? [1]<p>[1] <a href="https:&#x2F;&#x2F;phys.org&#x2F;news&#x2F;2010-01-moon-nuclear-explosion.html" rel="nofollow">https:&#x2F;&#x2F;phys.org&#x2F;news&#x2F;2010-01-moon-nuclear-explosion.html</a><p>Or the case for a terracentric georeactor (uranium is dense and would go down...) [2]<p>[2] <a href="https:&#x2F;&#x2F;www.pnas.org&#x2F;content&#x2F;100&#x2F;6&#x2F;3047" rel="nofollow">https:&#x2F;&#x2F;www.pnas.org&#x2F;content&#x2F;100&#x2F;6&#x2F;3047</a><p>Uranium-235 decays faster than U-238. The current natural enrichment is 0.711%. 4 billion years ago it was 25%, well above levels necessary to make a chain reaction even in far less than ideal conditions.<p>Somewhat related, it also continues to blow my mind that about half of the internal heat budget of Earth comes from radioactive decay of primordial nuclides (while the other have is just what&#x27;s left over from residual cooling) [3]. So geothermal energy is really just a gigantic Radioisotope Thermal Generator.<p>[3] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Earth%27s_internal_heat_budget#Radiogenic_heat" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Earth%27s_internal_heat_budget...</a>

I wonder how much such natural nuclear reactor played a role in biological evolution. If I remember correctly the oldest ediacarian fossils were found at the same place, such nuclear reaction and thus accelerated mutations could have been a starter for multicellar life

Nice explainer (I love his videos): <a href="https:&#x2F;&#x2F;youtu.be&#x2F;pMjXAAxgR-M" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;pMjXAAxgR-M</a>

Has been posted here many times. For some reason it never gets any discussion, maybe because enough people are familiar with it now.

The physics interest in this which tends to get quoted is related to possible variation of the fine structure constant. I was trying to remember what I think was the original paper in that vein, placing limits on strong, electromagnetic, and weak coupling constants, which I think should be referenced, by Max Irvine: <a href="https:&#x2F;&#x2F;royalsocietypublishing.org&#x2F;doi&#x2F;10.1098&#x2F;rsta.1983.0084#pane-pcw-figures" rel="nofollow">https:&#x2F;&#x2F;royalsocietypublishing.org&#x2F;doi&#x2F;10.1098&#x2F;rsta.1983.008...</a> (article paywalled)