Measuring 14C To obtain the radiocarbon age of a sample it is necessary to determine the proportion of 14C it contains.
Originally this was done by what is known as “conventional” methods, either proportional gas counters or liquid scintillation counters.
Hereafter these isotopes will be referred to as 12C, 13C, and 14C.
Carbon-12 accounts for ~99.8 % of all carbon atoms, carbon-13 accounts for ~1% of carbon atoms while ~1 in every 1 billion carbon atoms is carbon-14.
14C enters the dissolved inorganic carbon pool in the oceans, lakes and rivers.
From there it is incorporated into shell, corals and other marine organisms.
When a plant or animal dies it no longer exchanges CO with the atmosphere (ceases to take 14C into its being). 14C decays by emitting an electron, which converts a neutron to a proton, converting it back to its original 14N form.
The History of Radiocarbon Dating Willard Libby invented radiocarbon dating in the late 1940s.
This brings us to two reasons why a radiocarbon date is not a true calendar age.