Used in radiocarbon dating
Ninety-five percent of the activity of Oxalic Acid from the year 1950 is equal to the measured activity of the absolute radiocarbon standard which is 1890 wood. This is the International Radiocarbon Dating Standard.A very small percentage of carbon, however, consists of the isotope carbon 14, or radiocarbon, which is unstable.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.
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.