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Radiocarbon Dating

RADIOCARBON DATING

RADIOCARBON DATING is the measurement of the age of dead matter by comparing the radiocarbon content with that in living matter. The method was discovered at the University of Chicago in the 1940s, but


further research had to wait until the end of World War II. Radiocarbon, or radioactive carbon (C-14), is produced by the cosmic rays in the atmosphere and is assimilated only by living beings. At death, the assimilation process stops. Living matter, wherever found on earth, always has the same ratio of radioactive carbon to ordinary carbon. This ratio is enough to be measured by sensitive instruments to about 1 percent accuracy.

The bold assumption that the concentration of radiocarbon in living matter remains constant over all of time appears to be nearly correct, although deviations of a few percentage points do occur. It has been possible to determine the accuracy of the basic assumption back some 8,000 years, and a correction curve has been produced that allows absolute dating by radiocarbon back 8,000 years. The deviation is about 8 percent, at maximum.

The discovery of the radiocarbon dating method has given a much firmer base to archaeology and anthropology. For example, human settlers, such as the big-game hunting Clovis peoples of the American High Plains and the Southwest, first came to the Americas in substantial numbers at least 12,000 years ago. On the other hand, the magnificent color paintings of the Lascaux Cave in France are 16,000 years old, made 4,000 years before the first substantial number of human beings came to the Americas. By the end of the twentieth century, firm radiocarbon dates for human occupation of North America had never exceeded 12,000 years—the famous Kennewick Man, discovered in Oregon in 1996, was determined to be 9,300 years old—whereas in Europe and Asia Minor these dates reached back to the limits of the radiocarbon method and well beyond, according to other dating methods.

BIBLIOGRAPHY

Libby, Willard F. Radiocarbon Dating. Chicago: University of Chicago Press, 1965.

Renfrew, Colin. Before Civilization: The Radiocarbon Revolution and Prehistoric Europe. Cambridge, U.K.: Cambridge University Press, 1979.

Willard F.Libby/a. r.

See alsoArchaeology ; Chemistry ; Indian Mounds .

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"Radiocarbon Dating." Dictionary of American History. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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"Radiocarbon Dating." Dictionary of American History. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/history/dictionaries-thesauruses-pictures-and-press-releases/radiocarbon-dating

radiocarbon dating

radiocarbon dating(14C dating) A dating method for organic material that is applicable to about the last 70 000 years. It relies on the assumed constancy over time of atmospheric 14C:12C ratios (now known not to be valid), and the known rate of decay of radioactive carbon, of which half is lost in a period (the ‘half-life’) of every 5730 years ± 30 years. The earlier ‘Libby standard’, 5568 years, is still widely used. In principle, since plants and animals exchange carbon dioxide with the atmosphere constantly, the 14C content of their bodies when alive is a function of the radiocarbon content of the atmosphere. When an organism dies, this exchange ceases and the radiocarbon fixed in the organism decays at the known half-life rate. Comparison of residual 14C activity in fossil organic material with modern standards enables the calculation of the age of the samples. Since the method was first devised it has been realized that the atmospheric 14C content varies, as the cosmic-ray bombardment of the outer atmosphere that generates the 14C varies. Correction for these fluctuations is possible for about the last 8000 years by reference to the 14C contents of long tree-ring series (e.g. those for Pinus longaeva, bristlecone pine).

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"radiocarbon dating." A Dictionary of Ecology. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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"radiocarbon dating." A Dictionary of Ecology. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiocarbon-dating-0

radiocarbon dating

radiocarbon dating (4C dating) A dating method for organic material that is applicable to about the last 70 000 years. It relies on the assumed constancy over time of atmospheric 14C: 12C ratios (now known not to be valid), and the known rate of decay of radioactive carbon, of which half is lost in a period (the ‘half-life’) of every 5730 ± 30 years. (The earlier ‘Libby standard’, 5568 years, is still widely used.) In principle, since plants and animals exchange carbon dioxide with the atmosphere constantly, the 14C content of their bodies when alive is a function of the radiocarbon content of the atmosphere. When an organism dies, this exchange ceases and the radiocarbon fixed in the organism decays at the known half-life rate. Comparison of residual 14C activity in fossil organic material with modern standards enables the age of the samples to be calculated. Since the method was first devised it has been realized that the atmospheric 14C content varies, as the cosmic-ray bombardment of the outer atmosphere that generates the 14C varies. Correction for these fluctuations is possible for about the last 8000 years by reference to the 14C contents of long tree-ring series, e.g. those for bristlecone pine (Pinus longaeva).

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"radiocarbon dating." A Dictionary of Earth Sciences. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

"radiocarbon dating." A Dictionary of Earth Sciences. . Encyclopedia.com. (December 11, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiocarbon-dating

"radiocarbon dating." A Dictionary of Earth Sciences. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiocarbon-dating

radiocarbon dating

radiocarbon dating (14C dating) A dating method for organic material that is applicable to about the last 70 000 years. It relies on the assumed constancy over time of atmospheric 14C: 12C ratios (now known not to be valid), and the known rate of decay of radioactive carbon, of which half is lost in a period (the ‘half-life’) of every 5730 years ± 30 years. The earlier ‘Libby standard’, 5568 years, is still widely used. In principle, since plants and animals exchange carbon dioxide with the atmosphere constantly, the 14C content of their bodies when alive is a function of the radiocarbon content of the atmosphere. When an organism dies, this exchange ceases and the radiocarbon fixed in the organism decays at the known half-life rate. Comparison of residual 14C activity in fossil organic material with modern standards enables the calculation of the age of the samples. Since the method was first devised, it has been realized that the atmospheric 14C content varies as the cosmic-ray bombardment of the outer atmosphere that generates the 14C varies. Correction for these fluctuations is possible for about the last 8000 years by reference to the 14C contents of long tree-ring series, e.g. those for bristlecone pine.

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"radiocarbon dating." A Dictionary of Plant Sciences. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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"radiocarbon dating." A Dictionary of Plant Sciences. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiocarbon-dating-1

radiocarbon dating

ra·di·o·car·bon dat·ing • n. another term for carbon dating.

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"radiocarbon dating." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

"radiocarbon dating." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (December 11, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/radiocarbon-dating

"radiocarbon dating." The Oxford Pocket Dictionary of Current English. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/radiocarbon-dating

radiocarbon dating

radiocarbon dating See carbon dating.

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"radiocarbon dating." A Dictionary of Biology. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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"radiocarbon dating." A Dictionary of Biology. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiocarbon-dating-2