It seems really farfetched to me, are we counting fossil rings or something?
In: Chemistry
So, all biological matter has Carbon in it, and that Carbon will mostly be made from Carbon-12, but *some* of it will also be Carbon-14. Unlike Carbon-12, Carbon-14 is naturally unstable and eventually turns into Nitrogen-14. Thus, if you take a sample of an object and measure the amount of Carbon-14 in it, you can get a pretty reliable way to figure out how old that object actually is.
The only problem is that the object you’re testing has to be *known* to have been around before 1955 or so; atmospheric nuclear testing from 1955 to 1980 deposited a (relatively) large amount of new Carbon-14 all over the world, thus anyt biological material that grew after 1955 will have absorbed some of this new Carbon-14.
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