Radiocarbon dating Organic matter contains a certain amount of carbon-14, a radioactive isotope of carbon (under normal conditions carbon has an atomic weight of 12).
Carbon-14 (14C ) is unstable, and degrades exponentially over time.
All organisms have a certain amount of 14C present in their bodies – it is absorbed out of the atmosphere by plants during the process of photosynthesis, and transferred to animals when the plants are eaten.
Calibration Curve Image Source: “Radiocarbon Dating”. Carbon Dating is a controversial dating practice which involves going on dates with lumps of carbon.Carbon daters each have their own preferences for the size and shape of the pieces of carbon they go on dates with.When an organism dies, the intake of 14C ceases, and what was left in the organism begins a measurable disintegration.Carbon-14 has a half-life of 5730 years (±40 years), meaning that (in accordance with the law of radioactive decay) it will take that length of time for half of the carbon present in an organism to decay into stable carbon isotopes.
The levels of 14C present in a specimen can be measured in a variety of ways; however the invention of accelerator-based mass spectrometric techniques have drastically increased measurement accuracy, as it provides a count of the number of 14C atoms present in a sample.It has been used to date specimens up to 60,000 years in age.This analysis provides a radiocarbon age of the sample, which must then be calibrated in accordance with a radiocarbon dating calibration curve such as the one pictured below.A variety of factors have caused the amount of 14C present in the atmosphere to vary over time, resulting in deviations between the age predicted by radiocarbon dating and the absolute date of a specimen. Sample contamination must be carefully avoided to ensure measurement accuracy. Cornell University Press, Itha “Dating In Exposed and Surface Contexts”, ed.: Beck, Charlotte. Seminar Press, New York: NY, 1973 “Radiocarbon Dating”. Carbon dating produces the most reliable results when multiple samples can be tested to ensure accuracy and limit potential interferences. University of New Mexico Press: Albuquerque, NM, 1994. Alternative dating techniques such as dendrochronology may be employed to confirm the results of radiocarbon dating.