Carbon dating is possible because
- A. carbon 14 is stable
- B. living things take in carbon 14 while alive, and it then decays with a known half life after death
- C. all carbon is radioactive
- D. carbon 14 is produced in the body
Explanation
While an organism lives it exchanges carbon with its surroundings and holds the atmospheric ratio of carbon 14 to carbon 12, but after death intake stops and the carbon 14 decays with a half life of about 5730 years. Measuring the remaining ratio therefore gives the time since death. The method is useful up to roughly 50,000 years, after which too little carbon 14 remains.
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