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They exist in equilibrium with the C14 concentration of the atmosphere, that is, the numbers of C14 atoms and non-radioactive carbon atoms stays approximately the same over time.As soon as a plant or animal dies, they cease the metabolic function of carbon uptake; there is no replenishment of radioactive carbon, only decay.The half-life () is the name given to this value which Libby measured at 556830 years. After 10 half-lives, there is a very small amount of radioactive carbon present in a sample.At about 50 - 60 000 years, then, the limit of the technique is reached (beyond this time, other radiometric techniques must be used for dating).As 14C decays it emits a weak beta particle (b ), or electron, which possesses an average energy of 160ke V.The decay can be shown: Thus, the 14C decays back to 14N.Desmond Clark (1979) wrote that were it not for radiocarbon dating, "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation" (Clark, 1979:7).Writing of the European Upper Palaeolithic, Movius (1960) concluded that "time alone is the lens that can throw it into focus".
Today, there are over 130 radiocarbon dating laboratories around the world producing radiocarbon assays for the scientific community.
Renfrew (1973) called it 'the radiocarbon revolution' in describing its impact upon the human sciences.
Oakley (1979) suggested its development meant an almost complete re-writing of the evolution and cultural emergence of the human species.
A sample of acacia wood from the tomb of the pharoah Zoser (or Djoser; 3rd Dynasty, ca. Libby reasoned that since the half-life of C years, they should obtain a C14 concentration of about 50% that which was found in living wood (see Libby, 1949 for further details).
The results they obtained indicated this was the case.
The 14C formed is rapidly oxidised to 14CO2 and enters the earth's plant and animal lifeways through photosynthesis and the food chain.