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I've read that if radiometric decay rates were different in the past, the observations that we make on the oklo reactor would be different. Things such as different isotope ratios, etc. if all radiometric decay was uniformly sped up, would it be possible to get the same nuclear byproducts/observations that we see today on oklo? (By uniformly increased, I mean for each respective type of radiometric decay they would be increased by the same percentage respective to their own half-life)

rob
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Hurdlegreen2
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    Not 100% sure, but my gut instinct is that the "reactor" aspect of the Oklo formation led to a greatly enhanced rate of fission, rather than the standard alpha decay that U-235 usually undergoes. IIRC one of main points of evidence for the natural reactor was the presence of a large number of fission products in the same ore formation (zirconium, neodymium, etc.) compared to the usual daughters in the U-235 decay chain. – Michael Seifert Dec 04 '23 at 12:39
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    And I'm more confident in my half-remembered details above than I am that ChatGPT knows what it's talking about. – Michael Seifert Dec 04 '23 at 12:39
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    Please don't use computer-generated text in questions or answers. – rob Dec 04 '23 at 14:20
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    It's not clear what you mean by "uniformly speed up." Are you imagining that clocks ran faster in the past? Or, only clocks that given nuclear processes, but not clocks that given atomic processes? Or has your reading left you unclear about the difference between the decay processes of low-density uranium versus the processes which occur in a reacting uranium pile? – rob Dec 04 '23 at 14:25
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    I'm meaning that all types of radioactive decay being sped up by the same amount. For example if one element has a half-life of one year, and they are all sped up by 20%, the new half life would be 0.8 years, ultimately I'm just wondering if the observations that we make of Oklo today would be the same if the same amount of decay happened just in the shorter time frame. My guess is no but I don't know the logistics. – Hurdlegreen2 Dec 04 '23 at 15:10

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You can't uniformly speed up all the clocks, except by magic, and that is off-topic here. What has been hypothesized is that the fundamental constants could slowly change with time, but there is no way to change these constants to cause all nuclear decay rates uniformly. The Oklo natural reactor actually provides little new information about any changes in nuclear decay rates.

What you have likely read about is that stable isotope ratios in the Oklo natural fission reactor constrain how much the fine structure constant could have differed at the time the reactor was active two billion years ago. This limit is actually based on the cross-sections for certain nuclear processes when the reactor was active, not the rates of nuclear decays over the past two billion years. Since the limit is based on stable fission product isotope ratios (such as $^{150}$Sm/$^{149}$Sm or $^{139}$La/$^{138}$La), decay rates are irrelevant.

It is true, as discussed in the answers to "How do we know that radioactive decay rates are constant over billions of years?", that changes in fundamental constants could change decay rates. These changes would not be uniform, however, since different decays depend in different ways on the fundamental constants, so changing the constants changes different decays rates by different amounts.

For example, you could try changing the Fermi Constant to uniformly change the rate of weak beta decays, but this would not affect the rate of strong alpha decays. To change the alpha decay rates by the same amount, you might think you could change the strength of the strong interaction, but that would cause wild variations in different weak decay rates because those are proportional to $Q^5$, where $Q$ is the energy released in the decay. That energy mostly depends on the strength of the strong interaction and the up and down quark masses. There are simply not enough adjustable parameters (fundamental constants) to change all decay rates uniformly.

David Bailey
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