When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.
Radiocarbon dating is essentially a method designed to measure residual radioactivity.
Liquid scintillation counting is another radiocarbon dating technique that was popular in the 1960s.
In this method, the sample is in liquid form and a scintillator is added.
American physical chemist Willard Libby led a team of scientists in the post World War II era to develop a method that measures radiocarbon activity.
He is credited to be the first scientist to suggest that the unstable carbon isotope called radiocarbon or carbon 14 might exist in living matter. Libby and his team of scientists were able to publish a paper summarizing the first detection of radiocarbon in an organic sample. Libby who first measured radiocarbon’s rate of decay and established 5568 years ± 30 years as the half-life. Libby was awarded the Nobel Prize in Chemistry in recognition of his efforts to develop radiocarbon dating.1.
Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes.
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.
The impact of the radiocarbon dating technique on modern man has made it one of the most significant discoveries of the 20th century.
Over the years, other secondary radiocarbon standards have been made.
Radiocarbon activity of materials in the background is also determined to remove its contribution from results obtained during a sample analysis.
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Standard errors are also reported in a radiocarbon dating result, hence the “±” values.