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Arbon dating

Radiocarbon dating is one of the most widely used scientific dating methods in archaeology and environmental science.

As explained below, the radiocarbon date tells us when the organism was alive (not when the material was used).

This fact should always be remembered when using radiocarbon dates.

By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.

But that assumes that the amount of carbon-14 in the atmosphere was constant — any variation would speed up or slow down the clock.

The technique hinges on carbon-14, a radioactive isotope of the element that, unlike other more stable forms of carbon, decays away at a steady rate.

Organisms capture a certain amount of carbon-14 from the atmosphere when they are alive.

All animals in the food chain, including carnivores, get their carbon indirectly from plant material, even if it is by eating animals which themselves eat plants.

The net effect of this is that all living organisms have the same radiocarbon to stable carbon ratio as the atmosphere.

Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases.

Carbon-14 has a half-life of 5,730 ± 40 years—, half the amount of the radioisotope present at any given time will undergo spontaneous disintegration during the succeeding 5,730 years.

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