Natural Isotopes
There are 3 naturally occurring isotopes of carbon: 12, 13, and 14. 12C and 13C are stable, occurring in a natural proportion of approximately 99:1. 14C is produced by thermal neutrons from cosmic radiation in the upper atmosphere, and is transported down to earth to be absorbed by living biological material. Isotopically the 14C constitutes a negligible part, but since it is radioactive with a half-life of 5700 years, it is radiometrically detectable. Since dead tissue doesn't absorb 14C, the amount of 14C is used for radiometric dating of biological material, among others within the field of archeology.
Read more about this topic: Carbon-16
Famous quotes containing the word natural:
“What is most interesting and valuable in it, however, is not the materials for the history of Pontiac, or Braddock, or the Northwest, which it furnishes; not the annals of the country, but the natural facts, or perennials, which are ever without date. When out of history the truth shall be extracted, it will have shed its dates like withered leaves.”
—Henry David Thoreau (1817–1862)