With radiocarbon dating scientists compare an object carbon 14 levels with the fossil or rock for which the age measurement is required
Radiocarbon, or carbon 14, is an isotope of the element carbon that is unstable and weakly radioactive. The carbon-14 method was developed by the American physicist Willard F. Libby about 1946. It can be used to determine the age of a rock or a fossil by comparing the specimen of the required or fossil and compared it with the carbon 14 sample. Carbon 14 decays at constant rate therefore an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon and comparing it with Carbon 14.