Radiocarbon dating

Radiocarbon dating is a method for estimating the age of material by measuring the amount of radiocarbon in it. This technique is based on assumptions about the concentration of carbon-14 in the atmosphere, and measured half-life of carbon-14 as approximately 5568 ± 30 years.

When the age of the material is a few thousand years old, the assumptions become more important and the estimates are less reliable. Sometimes due to atmospheric disturbances the level of carbon-14 varies. For example, testing of nuclear weapons in the atmosphere nearly doubled the concentration of carbon-14 in the Northern Hemisphere. For this reason, other isotopes with longer half-lives are used to date objects beyond the accuracy levels of carbon-14. For instance, the decay of potassium-40 is often used to accurately date dinosaur fossils.