Carbon 14

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Want to know how do the clever people (not shamans) know what happened thousands of years ago without any clear files? The answer is the 14 carbon test! Explanation, carbon 14 is a radioactive isotope that has 6 protons of 8 neutrons, more than 2 neutrons than the usual carbon2 which weighs 12 atomic weights. Carbon 14 bsa is found anywhere. This isotope begins to decay when a plant or animal dies and half-time in which half the initial amount of carbon14 to be non-radioactive is 5,730 years. Carbon 14 becomes radioactive because of the supernovae exploding cosmic rays from outer space piercing the nucleus! So! So do not have any questions "loh, koq can know the age thousands of years ago?"