ELi5 How can you find out how old an artifact is?
One way is too look where you find.
If you find it among a lot of other stuff that you know the age of that gives you an idea.
Of course if your home got buried in a land slide tomorrow and dug up again in a few centuries, they would find some antique you inherited from you grandmother alongside your latest generation iPhone.
Similarly people might just drop newer stuff among piles of old stuff too.
You might also look at how deep down something was buried to give you an idea of how old something is.
The problem with that is that people tend to bury their trash and other stuff quite often.
It can all be very unreliable.
One way that works well is radiocarbon dating.
It is a way to look at something and tell how long it has been dead. it works well for things made out of bone or wood or leather or other stuff that used to alive at some point.
It doesn’t really on things that were never alive like stone or metal. Thankfully people tend to pretty many of their things up with color and those are often made out of organic material.
Of course it only works to tell you how long something has been dead not how long ago it was made. If you make something from aged wood, the method will say when the tree died not when you carved your artifact out of it.
There are some other patterns like tree rings. if you find something that was made out of wood and can still see the tree rings you can match that pattern to known pattern of years.
Since none of the methods we have work 100% you need combinations of them to come up with a good reliable estimate.
There are many different methods, and typically more than one method is used.
Style and site history is probably the easiest one. If you know that a certain site was inhabited in a certain date range (for example from historical records) you can be reasonably certain that objects found there date to around that period. Different cultures use different styles of ornamentation and form, so it’s a reasonably good guess that artifacts with a certain style and form come from that culture and you might know when that culture is thought to have inhabited the area the site is in. You can be reasonably sure, for example, that artifacts with a Norse ornamentation found in England date to the viking age.
Stratigraphy can also be used to relatively date objects. Older stuff is found below newer stuff, so objects found in layers underground deeper than stuff from a certain era must be older than that. Probably.
Organic materials can also be dated using a technique called radio-carbon dating. Radioactive carbon-14 in the atmosphere gets absorbed by all living things via the food chain, but begins to break down radioactively over a very long time. Dead plants and animals no longer replenish with new carbon. So, if you know the typical carbon-14 concentration of living things, you measure the difference in carbon-14 in really old dead stuff to get an estimate on how long ago that thing died. This can be used to estimate the age of anything made of plants or animal parts, but not ceramics or stone tools.