Nuclear fission is the process responsible for the controlled creation of massive amounts of energy using nuclear reactors or the uncontrolled release of massive amounts of energy using nuclear weapons. Nuclear fission was discovered in 1938, and the first fission reaction inside a nuclear reactor took place in 1942. Fast forward three years and the first nuclear detonation occurred on July 16, 1945 at the Trinity Site in New Mexico.
According to two developing scientific discoveries, these man-made reactions weren’t the first to take place here on Earth.
In 2011, the light from GRB 090423–13 billion light years away–reached our planet. The exploding star responsible for this energy was probably about 30 to 100 times larger than the sun. The burst of energy lasted only a single second, yet released enough to place it an order of magnitude greater than that which our sun will release in its 10 billion year lifespan.
Should such a blast be directed anywhere near our little nook of the galaxy, all life on our planet would be fried once it reached us. It’s that powerful.
We all know that mother nature is capable of unleashing pure devastation. What might come as more of a surprise is her ability to create something stable and long-lasting–but that’s exactly what she did in Gabon, Africa a long, long time ago.
The first stable nuclear fission reaction occurred over 2 billion years ago!
Nuclear excavators discovered the natural wonder in the 1970s, and it took the rest of us this long to really appreciate the marvel.
The natural Oklo reactors, as they’re called, resulted in a stable nuclear fission reaction that lasted for about 300,000 years, beginning nearly 2 billion years ago. Explaining how this is possible isn’t easy, and scientists today are still struggling to answer questions regarding the phenomenon.
Counter-intuitive though it may seem, an old hypothesis explored the idea that the physical constants restricting nuclear fission today may have somehow been different 2 billion years ago. A fresh analysis suggests that this isn’t the case. The ancient reaction would still have required the same proportions of today’s man-made nuclear fission.
So how did it happen?
Well, 2 billion years ago Earth was still relatively young. Unstable nuclear isotopes degrade at a set rate called a half-life, and so the nuclear materials found naturally were more prevalent at that time. Today’s uranium-235 accounts for about 0.7202% of forms found in nature, down from about 17% when the solar system was born. It’s been degrading ever since, and will continue to do so.
2 billion years ago, the uranium-235 would have been nearing the enrichment threshold for a nuclear fission reaction. Oklo’s reaction likely stabilized due to a large volume of water that would slow the neutron transfer and allow a chain reaction to begin–resulting in the natural reactor.
Scientists believe it most likely started for about a half hour, then shut down for 2.5 hours before starting the recurring process over. The nuclear waste that resulted from Oklo sat underground, untouched for almost 2 billion years. How amazing is that?
If you have a more scientific mind, you can read a more detailed version of the story published at ExtremeTech.