Carbon dating radioactive
When they die no new carbon-14 is taken in by the dead organism.The carbon-14 it contained at the time of death decays over a long period of time.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.Later called Ötzi the Iceman, small samples from his body were carbon dated by scientists.The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. Uranium has a very long half-life and so by measuring how much uranium is left in a rock its approximate age can be worked out. The most common of the radioactive dating techniques currently in use involves the isotope 14 of carbon, the radiocarbon.This radioactive isotope of carbon is present in the atmosphere in trace amounts, and in chemical processes is indistinguishable from normal carbon 12.The cosmic rays originating from the Sun collide with nuclei in the upper atmosphere and are capable of breaking off individual neutrons.
These neutrons, once freed, can interact with atoms of nitrogen 14 in air, causing the expulsion of a proton and the formation of carbon 14.
So by measuring carbon 14 levels in an organism that died long ago, researchers can figure out when it died.
The procedure of radiocarbon dating can be used for remains that are up to 50,000 years old.
One naturally assumes that the cosmic bombardment responsible for this transmutation remains constant over the millennia.
The rate of cosmic rays which hit the Earth depends on two very slowly changing factors: the solar activity and the Earth's magnetic field.
We will deal with carbon dating first and then with the other dating methods.