An Etymological Dictionary of Astronomy and Astrophysics

A radioactive dating technique, applied to organic materials, which
measures the content of the radioactive isotope of carbon ¹⁴C.
The radioactive carbon isotopes created by the impact of cosmic rays with the nitrogen atoms of the atmosphere find their way, via carbon dioxide and photosynthesis, into living material. When an organic material dies it ceases to acquire further ¹⁴C atoms, and its ¹⁴C fraction declines at a fixed exponential rate due to the radioactive decay of ¹⁴C. Comparing the remaining ¹⁴C fraction of a sample to that expected from atmospheric ¹⁴C allows the age of the sample to be estimated.

See also: → radiocarbon; → dating.