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Carbon dating

Carbon-14 is radioactive and is found in all living organisms.

Plants absorb carbon dioxide from the atmosphere and animals eat plants.

This means all living things have radioactive carbon-14 in them.

When an organism, eg a tree, dies it stops taking in carbon dioxide.

The amount of carbon-14 in the wood decreases with time as it decays into nitrogen with a half-life of about 5730 years.

By comparing how much carbon-14 there is in the dead organism with the amount in a living one, the age of the dead organism can be determined.

Sample being removed from bone for carbon dating using accelerator mass spectrometry.
Image caption,
Sample being removed from bone for carbon dating using accelerator mass spectrometry
Y axis shows amount the percentage of carbon 14 remaining (0-100).  X axis shows time in years beginning at 0 and ending at 28500.  The curve goes from 100 on the y axis down to 28500 on the x axis.
Figure caption,
Half life graph showing carbon dating