Radiocarbon dating is a technique to estimate the age of an organic object. The technique initially was developed by the american chemist Willard Libby in 1940. The idea behind radiocarbon dating is very simple. In nature, carbon exists as three different isotopes (forms) including carbon-12 and carbon-13 nonradioactive isotopes, and carbon-14 (radiocarbon) radioactive isotope. As you may know over the time the amount of any radioactive material decays (it will be converted to energy). Therefore a radioactive material has a limited life time which in chemistry is shown by a parameter called half-life. The half-life of carbon-14 is approximately 5370 years, i.e. after each 5370 years a specific amount of carbon-14 will be reduced to half of its initial value. Now considering an organic body which continuously exchange carbon with its surrounding environment until it dies. In an alive organic body the ratio of carbon-14 to carbon-12 stays constant however once it dies this ratio starts to decrease because the amount of carbon-14 decays (as it illustrated in the figure, carbon-14 will be converted to nitrogen-14). The rest of radiocarbon dating story is very straightforward. Once the ratio of carbon-14 to carbon-12 is calculated, one just need a calibration table which relates this ratio to the age of the organic sample under investigation.
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