14c dating method
Radiocarbon, or carbon 14, is an isotope of the element carbon that is unstable and weakly radioactive. Carbon 14 is continually being formed in the upper atmosphere by the effect of cosmic ray neutrons on nitrogen 14 atoms.The ratio of radiocarbon to stable carbon atoms in the atmosphere has varied in the past.This is because the amount and strength of cosmic radiation entering the earth's atmosphere has varied over time.From then on, the ratio of radiocarbon to stable carbon will decrease, because the unstable radiocarbon atoms will slowly decay. From this measurement the age in radiocarbon years is calculated. Modern radiocarbon dates are calibrated using long tree-ring chronologies.
After about 50,000 years, the radiocarbon concentration remaining is too small to be measured for the purpose of radiocarbon dating. This is necessary to remove errors in raw radiocarbon dates caused by fluctuations in the amount of radiocarbon in the atmosphere in the past.
An age could be estimated by measuring the amount of carbon-14 present in the sample and comparing this against an internationally used reference standard.
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