"Everything which has come down to us from heathendom is wrapped in a thick fog; it belongs to a space of time we cannot measure.
We know that it is older than Christendom, but whether by a couple of years or a couple of centuries, or even by more than a millenium, we can do no more than guess." [Rasmus Nyerup, (Danish antiquarian), 1802 (in Trigger, 19)].
Archaeologists can then measure the amount of carbon-14 compared to the stable isotope carbon-12 and determine how old an item is.
For the most part, radiocarbon dating has made a huge difference for archaeologists everywhere, but the process does have a few flaws.
The aim here is to provide clear, understandable information relating to radiocarbon dating for the benefit of K12 students, as well as lay people who are not requiring detailed information about the method of radiocarbon dating itself.
Once an organism is decoupled from these cycles (i.e., death), then the carbon-14 decays until essentially gone.
For example, if an object touches some organic material (like, say, your hand), it can test younger than it really is.
Also, the larger the sample the better, although new techniques mean smaller samples can sometimes be tested more effectively.
Unless something was obviously attributable to a specific year -- say a dated coin or known piece of artwork -- then whoever discovered it had to do quite a bit of guesstimating to get a proper age for the item.
The excavator might employ relative dating, using objects located stratigraphically (read: buried at the same depth) close to each other, or he or she might compare historical styles to see if there were similarities to a previous find.