Professor Willard Libby, a chemist at the University of Chicago, first proposed the idea of radiocarbon dating in 1946. Three years later, Libby proved his hypothesis correct when he accurately dated a series of objects with already-known ages.

Where does carbon 13 come from?

C and 13C are stable, occurring in a natural proportion of approximately 93:1. C is produced by thermal neutrons from cosmic radiation in the upper atmosphere, and is transported down to earth to be absorbed by living biological material.