Radio active carbon dating
The solution came using dendrochronology (tree ring dating).
Since tree rings provide an annual calendar, and some trees live for thousands of years, by C-14 dating the rings themselves one could correct the radiocarbon dates and calibrate the differences. should refer to the year the method was recognized, 1950.
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Radioactive elements "decay" (that is, change into other elements) by "half lives." If a half life is equal to one year, then one half of the radioactive element will have decayed in the first year after the mineral was formed; one half of the remainder will decay in the next year (leaving one-fourth remaining), and so forth.
The formula for the fraction remaining is one-half raised to the power given by the number of years divided by the half-life (in other words raised to a power equal to the number of half-lives).
The ratio of normal carbon (carbon-12) to carbon-14 in the air and in all living things at any given time is nearly constant.
Maybe one in a trillion carbon atoms are carbon-14.
C is created in the atmosphere by cosmic radiation and is taken up by plants and animals as long as they live.The Bristlecone pine trees in the Sierra Nevada mountains made this possible and today there are international tree ring databases and agreed-upon calibration curves. Another problem derives from the “reservoir effect” in which old material, limestone or graphite, has contaminated the samples. Cosmic rays enter the earth's atmosphere in large numbers every day.For example, every person is hit by about half a million cosmic rays every hour.
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