While the lighter isotopes C has decayed that what remains can no longer be measured. In 5,730 years half of the C in the atmosphere, and therefore in plants and animals, has not always been constant.Radioactive decay can be used as a “clock” because it is unaffected by physical (e.g. For instance, the amount varies according to how many cosmic rays reach Earth.
Tree rings can be counted and their radiocarbon content measured.From these records a “calibration curve” can be built (see figure 2, below).A huge amount of work is currently underway to extend and improve the calibration curve.Rachel Wood does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.The Conversation UK receives funding from Hefce, Hefcw, SAGE, SFC, RCUK, The Nuffield Foundation, The Ogden Trust, The Royal Society, The Wellcome Trust, Esmée Fairbairn Foundation and The Alliance for Useful Evidence, as well as sixty five university members.
View the full list Radiocarbon dating has transformed our understanding of the past 50,000 years.
Professor Willard Libby produced the first radiocarbon dates in 1949 and was later awarded the Nobel Prize for his efforts.
Radiocarbon dating works by comparing the three different isotopes of carbon.
Isotopes of a particular element have the same number of protons in their nucleus, but different numbers of neutrons.
This means that although they are very similar chemically, they have different masses.
The total mass of the isotope is indicated by the numerical superscript.