- Carbon Dating
- The isotope used to date organic materials is carbon 14- a radioactive isotope of carbon.
- The amount of carbon 14 in the air hasnt changed for 1000's of years- as it is continousally formed by the action of cosmic rays on nitrogen 14 in the air.
- This carbon 14 than reacts with oxygen to form carbon dioxide, that plants and other materials will take in to use for food. When scientists want to date a material, they then compare the amount of carbon 14 in an active, living material with the carbon left in a dead person or material- as once a material dies the carbon 14 in their bodies begins to change back into nitrogen.
- Finding out the ratio of the current activity of carbon in living matter compared to that activity in a dead sample- possibly including adjustments based on previous samples measured- leads to relatively accurate ages being concluded
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