Radiocarbon dating example
He reasoned that a state of equilibrium must exist wherein the rate of carbon-14 production was equal to its rate of decay, dating back millennia.
(Fortunately for him, this was later proven to be generally true.) For the second factor, it would be necessary to estimate the overall amount carbon-14 and compare this against all other isotopes of carbon.
Known as radiocarbon dating, this method provides objective age estimates for carbon-based objects that originated from living organisms.
The “radiocarbon revolution” made possible by Libby’s discovery greatly benefitted the fields of archaeology and geology by allowing practitioners to develop more precise historical chronologies across geography and cultures.
Korff predicted that the reaction between these neutrons and nitrogen-14, which predominates in the atmosphere, would produce carbon-14, also called radiocarbon.
We learned rather abruptly that these numbers, these ancient ages, are not known accurately; in fact, it is at about the time of the First Dynasty in Egypt that the first historical date of any real certainty has been established.” —Willard Libby, Nobel Lecture, 12 December 1960 The concept of radiocarbon dating focused on measuring the carbon content of discreet organic objects, but in order to prove the idea Libby would have to understand the earth’s carbon system.Using this sample and an ordinary Geiger counter, Libby and Anderson established the existence of naturally occurring carbon-14, matching the concentration predicted by Korff. Fortunately, Libby’s group developed an alternative. They surrounded the sample chamber with a system of Geiger counters that were calibrated to detect and eliminate the background radiation that exists throughout the environment.The assembly was called an “anti-coincidence counter.” When it was combined with a thick shield that further reduced background radiation and a novel method for reducing samples to pure carbon for testing, the system proved to be suitably sensitive.In a system where carbon-14 is readily exchanged throughout the cycle, the ratio of carbon-14 to other carbon isotopes should be the same in a living organism as in the atmosphere.However, the rates of movement of carbon throughout the cycle were not then known.