How do scientists determine the age of ancient artifacts?
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They use a variety of methods because it’s only with redundancy that they can gain confidence.
One of the most important methods is “context.” Were was it found? In what state was it found? What was around it when it was found? If the context says “this belongs to *this* already dated ruin/find” then there ya go.
Another fantastic method, though one that is not always applicable, is radiometric dating, usually carbon dating. When cosmic rays hit the atmosphere it converts some of the nitrogen into an unstable form of carbon called Carbon-14. Over a predictable period of time it decays into the much more stable Carbon-12 or Carbon-13 isotopes. Because it’s constantly being created and constantly decaying, the atmosphere has a relatively consistent amount of carbon-14 in it. As plants grow they take carbon from the atmosphere and incorporate it into their structure, meaning that living plants have a fairly consistent amount of carbon-14 in them. But when they die they stop incorporating new carbon-14 into their structure and the clock starts (this is also true for the animals that eat those plants and the animals that eat those animals). As more and more time passes the amount of carbon-14 gets lower and lower. By measuring the percent of carbon-14 they can determine, to a reasonable degree of accuracy, when the organism died. There are limitations, of course, which is why they use a multitude of methods, but it does mean that if they find a tool that incorporates organic elements (such as a wooden handle) then they can radiocarbon date the handle and narrow down the range for when that handle was made – or at least when the wood used to make it died.
There’s also certain key indicators that can be used. For example, if the thing is buried in a soil layer that includes markers from certain events of a known date — such as a flood, a volcanic eruption, things like that — and the context of the find suggests that it wasn’t buried there later, then we have a pretty good idea of when that thing was buried because we already know when that particular flood happened.
There’s lots and lots of different methods used that have varying degrees of accuracy. By using many methods they can increase the confidence of the age.
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