Carbon-14 is radioactive, and has a half life of about 5700 years.Plants get their share of carbon atoms from the atmosphere. It is seen that at any given point of time, the ratio of stable carbon and radiocarbon in the atmosphere, is almost same as the ratio of stable carbon and radiocarbon in living organisms like plants, animals, and humans.Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon.
The atmosphere contains many stable carbon atoms and relatively few radiocarbon atoms.
An unstable form of carbon isotope, carbon-14, also known as radiocarbon, is formed when cosmic rays hit atoms in the upper atmosphere of the earth.
When cosmic rays collide with the atoms, it creates an energetic neutron, which, upon hitting a nitrogen atom (7 neutrons and 7 protons), creates a carbon-14 atom (6 protons and 8 neutrons) and a hydrogen atom (1 neutron, 0 proton).
Carbon-14 dating is a scientific technique to determine the age of archaeological objects of a biological origin.
This technique works for objects that are up to 50,000 years old.