How exactly does carbon dating work?

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bandmanjoe | Middle School Teacher | (Level 2) Senior Educator

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Carbon dating is a technique used by scientists to determine the approximate age of once living materials.  It is based on the decay rate of the radioactive isotope of carbon, which is carbon-14.  Carbon-14 is a form of carbon taken in by all living things while they are alive.  Carbon-14 is produced in small quantities in Earth's atmosphere, as a result of interaction between the atmosphere and cosmic rays from space.  All living things absorb carbon-14 while they are alive; they cease to absorb the element when they die.  Carbon-14 has a "half-life" of 5730 years, meaning it takes that long for half the nuclei present to degrade to a more stable, less radioactive nitrogen-14.  Scientists compare the amount of radioactive nuclei present in the organic sample to the amount of carbon-14 available in the atmosphere.  Once that calculation is made, the number of half-lives that has passed may be calculated.  After that, the number of half-lives times 5730 years gives the approximate age of the organism.  Carbon-14 dating was developed by an American chemist, Willard Libby, 1908-1980.

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