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Tuesday 30th August 2016
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How do they date rocks using carbon dating?


Carbon dating – how do they do it? How do they tell that something is a hundred million years old?
Tony, Woodford


** Definitive **
Name: Professor Hal
Qualification: Mystery Hour’s rock
Answer: There are four isotopes of carbon - 11, 12, 13 and 14. Most matter is carbon 12, which is not radioactive. But there is a tiny bit which is carbon-14 which is radioactive and does decay. This isotope decays with a half-life of 5,730 years, which is the time that it takes for half of this to disappear. The way they measure it is to  measure the amount of carbon-14 in it to see how many half-lives have passed.

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