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We will deal with carbon dating first and then with the other dating methods.
C has a half-life of just under 6000 years, and so would have long ago vanished from the earth, were it not for its constant formation by cosmic ray impacts on nitrogen in the earth's atmosphere.
When cosmic rays enter the atmosphere they undergo various transformations, including the production of neutrons.
Carbon dioxide also permeates the oceans, dissolving in the water.
Since it is assumed that the cosmic ray flux is constant over long periods of time, carbon-14 is assumed to be continuously produced at a constant rate and therefore that the proportion of radioactive to non-radioactive carbon throughout the Earth's atmosphere and oceans is constant: ca. Plants take up atmospheric carbon dioxide by photosynthesis, and are eaten by animals, so every living thing is constantly exchanging C gradually decreases through radioactive decay.
So, we have a “clock” which starts ticking the moment something dies.
Obviously, this works only for things which were once living.
in the late 1940s and soon became a standard tool for archaeologists.
Libby received the Nobel Prize for his work in 1960.
Another standard, Oxalic Acid II was prepared when stocks of HOx 1 began to dwindle. The ratio of the activity of Oxalic acid II to 1 is 1.29330.001 (the weighted mean) (Mann, 1983). There are other secondary radiocarbon standards, the most common is ANU (Australian National University) sucrose.
The ratio of the activity of sucrose with 0.95 Ox was first measured by Polach at 1.50070.0052 (Polach, 1976b:122).
The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age.Tags: Adult Dating, affair dating, sex dating