This is now the most widely used method of age estimation in the field of archaeology. How it works Certain chemical elements have more than one type of atom. Different atoms of the same element are called isotopes. Carbon has three main isotopes. Carbon-14 is radioactive and it is this radioactivity which is used to measure age.
Radioactive atoms decay into stable atoms by a simple mathematical process.
Half of the available atoms will change in a given period of time, known as the half-life. For instance, if 1000 atoms in the year 2000 had a half-life of ten years, then in 2010 there would be 500 left. In 2020, there would be 250 left, and in 2030 there would be 125 left. However knowing how many carbon-14 atoms something had before it died can only be guessed at. The assumption is that the proportion of carbon-14 in any living organism is constant.