It seems really farfetched to me, are we counting fossil rings or something?
In: Chemistry
There are various methods. Some things are discovered in geological strata that were formed a known time (or, really, range of times) ago. Other times, the date is derived from some form of radioisotope dating, often referred to as “carbon dating”. There is a known proportion of radioactive carbon and stable carbon in the world. Living things constantly exchange carbon with their environments, so they’re at that same proportion. When they die, they stop exchanging carbon with their environment, and the radioactive carbon in them decays at a known rate. By measuring what portion of the carbon within their remains is radioactive, we can calculate how long ago that thing died. It’s also possible to do things like analyze trapped pockets of gas, particularly in ice formations, to try to match them up with an atmospheric composition known to exist a certain time ago.
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