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how is carbon dating done?
There are two basic forms of carbon: one that occurs naturally, called carbon-12 (12C), and one that forms from processes acting on nitrogen in the atmosphere, called carbon-14 (14C). Both of these combine with oxygen to form carbon dioxide (CO2), which we breathe out and plants take in. When a cow eats grass, its body absorbs the carbon (both 12C and 14C) in the plant.
Bones

When the cow dies, it stops taking in carbon (for obvious reasons). The amount of 12C in the cow’s body stays the same after death, but the amount of 14C changes because it returns to nitrogen.

As time goes on, the amount of 14C continues to decrease until nothing is left, which is supposedly about 50,000 years later.

When a paleontologist finds a bone (or a piece of wood), she can measure the amount of 14C and 12C it contains. Based on how much 14C is left, she can supposedly calculate when the animal (or plant) died.


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