Related to radiocarbon dating: Potassium argon dating radiocarbon dating n. A form of radiometric dating used to determine the age of organic remains in ancient objects, such as archaeological specimens, on the basis of the half-life of carbon and a comparison between the ratio of carbon to carbon in a sample of the remains to the known ratio in living organisms. Also called carbon dating, carbon dating. The 14C decays to the nitrogen isotope 14N with a half-life of years. Measurement of the amount of radioactive carbon remaining in the material thus gives an estimate of its age.
The carbon 14 present in an organism at the time of its death decays at a steady rate, and so the age of the remains can be calculated from the amount of carbon 14 that is left. The cells of all living things contain carbon atoms that they take in from their environment. Back in the s, the American chemist Willard Libby used this fact to determine the ages of organisms long dead.
Most carbon atoms have six protons and six neutrons in their nuclei and are called carbon Carbon 12 is very stable. But a tiny percentage of carbon is made of carbon 14, or radiocarbon, which has six protons and eight neutrons and is not stable: Carbon 14 is continually being created in the Earth's atmosphere by the interaction of nitrogen and gamma rays from outer space.
Since atmospheric carbon 14 arises at about the same rate that the atom decays, the Earth's levels of carbon 14 have remained constant. In living organisms, which are always taking in carbon, the levels of carbon 14 likewise stay constant. But in a dead organism, no new carbon is coming in, and its carbon 14 gradually begins to decay. So by measuring carbon 14 levels in an organism that died long ago, researchers can figure out when it died.
The procedure of radiocarbon dating can be used for remains that are up to 50, years old. Radiometric dating based on the decay of the isotope carbon It is used to date organic materials less than 70, years old.