4 ms·
The fossil reactor at Oklo https://apod.nasa.gov/apod/ap100912.html https://apod.nasa.gov/apod/ap100912.html and https://en.wikipedia.org/wiki/Natural_nuclear_f
by shagie 2y ago
The fossil reactor at Oklo https://apod.nasa.gov/apod/ap100912.html https://apod.nasa.gov/apod/ap100912.html and https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto... can be used for that question.
From Wikipedia:
The natural reactor of Oklo has been used to check if the atomic fine-structure constant α might have changed over the past 2 billion years. That is because α influences the rate of various nuclear reactions. For example, ¹⁴⁹Sm captures a neutron to become ¹⁵⁰Sm, and since the rate of neutron capture depends on the value of α, the ratio of the two samarium isotopes in samples from Oklo can be used to calculate the value of α from 2 billion years ago.
Several studies have analysed the relative concentrations of radioactive isotopes left behind at Oklo, and most have concluded that nuclear reactions then were much the same as they are today, which implies that α was the same too.
- User23 2y agoIs there a good explanation of how that isn’t just measuring the expansion and contraction of a ruler with itself? Don’t we know the reactor is 2 billion years old because of radio dating?
- Vecr 2y agoIt would be somewhat hard to tell if there's circularity somewhere, but you should be able to date it somewhat with the quantity of oxygen in the atmosphere at various times and general geological processes.
- AstralStorm 2y agoWell, it's dated against pulsars and stars. But those sources of information have a bit of an error bar on time-space distance. Which is why a synthetic clock is needed here. That will have a known inception date and the changes if any can be compared. The problem with both is they're not exactly fully closed systems anyway so there will be some margin of error ever with the length of the operation. And during the test, we might just find out something completely unaccounted for in current physics... That isn't a universal constant related at all.
- thowawatp302 2y agoNo, because you’re comparing the various proportions, it’s like comparing the contraction of various rulers made from different woods.
- adastra22 2y agoNo, those are separate processes. The isotopes produced during the natural nuclear reactor 2 billion years ago were produced in certain ratios because of the relative sizes of their nuclear cross sections, which depend on the fine structure constant. The isotopes used in radio dating are produced by spontaneous transmutation over time, which is governed by entirely different processes.