Over time, carbon-14 decays radioactively and turns into nitrogen.A living organism takes in both carbon-12 and carbon-14 from the environment in the same relative proportion that they existed naturally.Carbon-14 has a half life of 5730 years, meaning that 5730 years after an organism dies, half of its carbon-14 atoms have decayed to nitrogen atoms.Similarly, 11460 years after an organism dies, only one quarter of its original carbon-14 atoms are still around.When an organism dies it ceases to replenish carbon in its tissues and the decay of carbon 14 to nitrogen 14 changes the ratio of carbon 12 to carbon 14.Experts can compare the ratio of carbon 12 to carbon 14 in dead material to the ratio when the organism was alive to estimate the date of its death. The Radiocarbon Revolution Since its development by Willard Libby in the 1940s, radiocarbon (14C) dating has become one of the most essential tools in archaeology.Radiocarbon dating was the first chronometric technique widely available to archaeologists and was especially useful because it allowed researchers to directly date the panoply of organic remains often found in archaeological sites including artifacts made from bone, shell, wood, and other carbon based materials.
He was inspired by physicist Serge Korff (1906–1989) of New York University, who in 1939 discovered that neutrons were produced during the bombardment of the atmosphere by cosmic rays.
Once the organism dies, it stops replenishing its carbon supply, and the total carbon-14 content in the organism slowly disappears.
Scientists can determine how long ago an organism died by measuring how much carbon-14 is left relative to the carbon-12.
Geologists do not use carbon-based radiometric dating to determine the age of rocks.
Carbon dating only works for objects that are younger than about 50,000 years, and most rocks of interest are older than that.
Dedicated at the University of Chicago on October 10, 2016.