Carbon dating carbon 14 carbon 12
There is a quantitative relationship between the decay of 14C and the production of a beta particle. That is, the probability of decay for an atom of 14C in a discrete sample is constant, thereby requiring the application of statistical methods for the analysis of counting data.It follows from this that any material which is composed of carbon may be dated.
As soon as a plant or animal dies, they cease the metabolic function of carbon uptake; there is no replenishment of radioactive carbon, only decay.
14C also enters the Earth's oceans in an atmospheric exchange and as dissolved carbonate (the entire 14C inventory is termed the carbon exchange reservoir (Aitken, 1990)).
Plants and animals which utilise carbon in biological foodchains take up 14C during their lifetimes.
Libby and his team intially tested the radiocarbon method on samples from prehistoric Egypt.
They chose samples whose age could be independently determined.
There is a useful diagrammatic representation of this process given here Libby, Anderson and Arnold (1949) were the first to measure the rate of this decay.