CRIM 356 Lecture Notes - Lecture 10: Radiocarbon Dating, Willard Libby, Shroud Of Turin
29 Nov 2017
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Discovered by willard libby and ernest anderson in 1946. Atmospheric co2 contains about 99% 12c, small amounts of 13c (0. 99%) and even smaller amounts of 14c (0. 0000000001%) Only 14c is radioactive and has a half life of 5730 +/- 40 years. 14c usually produced by interaction between thermal neutrons and 14n in the upper atmosphere: Anything that does photosynthesis will obtain carbon 14. The co2 (and hence the radioactive 14c) in the atmosphere is taken up by plants through photosynthesis. Since plants are at the base of much of the food chain, the net result is that every living organism has the same radiocarbon to stable carbon ratio as the atmosphere. This ratio has and continues to change through time. Once an organism dies, 14c no longer updated. The radioactive 14c present in the organism decays at a given rate according to the half life. The stable carbon also decays, but the ratio of 1c/12c stays the same.
