Understanding carbon dating
But when gas exchange is stopped, be it in a particular part of the body like in deposits on bones and teeth, or when the entire organism dies, the ratio of carbon-14 to carbon-12 begins to decrease.The unstable carbon-14 gradually decays to carbon-12 at a steady rate. Scientists measure the ratio of carbon isotopes to be able to estimate how far back in time a biological sample was active or alive.
Anything that dies after the 1940s, when Nuclear bombs, nuclear reactors and open-air nuclear tests started changing things, will be harder to date precisely. As soon as a living organism dies, it stops taking in new carbon.The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced.How Carbon Dating works Carbon dating is one method scientists use to measure the ages of objects which were alive at some time in the past. In our atmosphere there are particles of carbon, when rays from the sun hit them it turns a few of them into carbon 14 (a radioactive carbon).
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Most radiocarbon dating today is done using an accelerator mass spectrometer, an instrument that directly counts the numbers of carbon 14 and carbon12 in a sample.