Carbon Dating

Name:
Carbon Dating
Detailed information:
Radiocarbon dating is a method of determining quite accurately the age of a carbon-bearing material derived from living plants or animals within the last 70,000 years. It is based on determining the ratio of carbon-14 in the material to that in a modern reference sample by measuring the radioactivity of the carbon-14 in the material. Since the half-life of carbon-14 is 5730 ñ30 years and the living precursor utilized carbon dioxide from the atmosphere or some other part of the earth's dynamic carbon reservoir, a process that ceased when the original plant or animal died, the amount of carbon-14 now present gives directly the age of the material. The carbon-14 in the reservoir is constantly being replaced by the sequence ¹⁴N→ ¹⁴C + O → ¹⁴CO₂. This has maintained the constant ratio of carbon isomers during the ages, however, burning of fossil fuels since the Industrial Revolution has lowered somewhat the fraction of carbon-14 in the atmosphere during the last few centuries, which does not affect measurements on older objects. The sample to be tested must be carefully prepared to prevent contamination by younger carbon. The radiocarbon technique was discovered by Willard F. Libby (1908–1980), who won a Nobel Prize (1960), and has been applied with great success in the fields of archaeology, geology, geochemistry, and geophysics. Its accuracy has been checked and verified by use of tree-ring counts (dendrochronology) and with the known ages of objects from ancient cultures, such as Egyptian and Chinese. The former shows that for the 2400–6000-year age of bristlecone-pine tree rings, 5200 ¹⁴C years equal 6000 calendar years.