Carbon-14 is also passed onto the animals that eat those plants.
Once an organism is dead, however, no new carbon is actively absorbed by its tissues, and its carbon 14 gradually decays.
Libby thus reasoned that by measuring carbon 14 levels in the remains of an organism that died long ago, one could estimate the time of its death.
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.
This time varies from few-millionths of a second to millions of years for different radioactive isotopes.
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. 1979, 1986 © Harper Collins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Cite This Source radiocarbon dating A technique for measuring the age of organic remains based on the rate of decay of carbon 14.
Most carbon consists of the isotopes carbon 12 and carbon 13, which are very stable.
A very small percentage of carbon, however, consists of the isotope carbon 14, or radiocarbon, which is unstable.
Love-hungry teenagers and archaeologists agree: dating is hard.
But while the difficulties of single life may be intractable, the challenge of determining the age of prehistoric artifacts and fossils is greatly aided by measuring certain radioactive isotopes.
Carbon 14 has a half-life of 5,780 years, and is continuously created in Earth's atmosphere through the interaction of nitrogen and gamma rays from outer space.