a radiometric method of dating organic material that is based on the rate that unstable radioactive carbon-14 atoms, which are present in all living things (humans, trees, etc.), decay into carbon-12 and carbon-13 atoms

By comparing tree-ring dates with radiocarbon dates, scientists realized that the radiocarbon dates drift, or need to be calibrated, to reflect actual dates.

Posted online on Monday, January 1st, 2001