Continue Reading Carbon-14 is only a small percentage of the total carbon in the environment and originates in the atmosphere when cosmic rays and high-speed particles from space hit nitrogen atoms.
Carbon-14 dating uses the ratio of radioactive carbon-14 to non-radioactive carbon-12 to determine if the ratio is the same as in living organisms, or if it is lower, indicating that the carbon-14 has decayed during a period of thousands of years.
Carbon-14 has a half-life of 5,730 years, which is the amount of time that it takes for half of a given sample of carbon-14 to decay.
These organisms no longer take in new carbon-14 once they've died, so the carbon-14 isn't replenished as it decays back into nitrogen.
Carbon-14 dating currently uses a technique called accelerator mass spectrometry, and it's able to determine the ratio of carbon-14 to carbon-12 in a sample.
So the proportion of carbon-14 inside living things is the same as the proportion of carbon-14 in the atmosphere at that time.