Radiometric dating or
radioactive dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they formed. The method compares the abundance of a naturally occurring radioactive
isotope within the material and the abundance of its
decay products, which form at a known constant rate of decay. The use of radiometric dating was first published in 1907 by
Bertram Boltwood and is now the principal source of information about the
absolute age of rocks and other geological features, including the
age of the Earth itself, and can be used to date a wide range of natural and man-made materials.