Two other isotopes of carbon are and , and these are respectively 99% and 1% of the earth carbon atoms.
Carbon-14, on the other hand, represents only a very small amount; one in one billion, .
All organic molecules contain carbon atoms, all organic matter also consists of a small amount of these carbon-14 atoms.
Even though it is very small, it is still possible to measure the carbon-14 atoms content in an organic material.
They use absolute dating methods, sometimes called numerical dating, to give rocks an actual date, or date range, in number of years.
This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.
Therefore, the carbon-14 atoms also represent 1 in 1 billion of all the carbon atoms of all living organisms.