The amount of carbon-14 gradually decreases through radioactive beta decay with a half-life of 5,730 years.So, scientists can estimate the age of the fossil by looking at the level of decay in its radioactive carbon.However, once the organism dies, the amount of carbon-14 steadily decreases.By measuring the amount of carbon-14 left in the organism, it's possible to work out how old it is.Some chemical elements have more than one type of atom. Carbon has two stable, nonradioactive isotopes: carbon-12 (12C), and carbon-13 (13C).
By about ten half-lives, or 58,000 years, the amount of carbon-14 left in the fossil is very little- about 1/1000 of the original number of carbon-14 atoms in the fossil.
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Libby was awarded the Nobel Prize in chemistry for his work in 1960.
Carbon dioxide in the atmosphere contains a constant amount of carbon-14, and as long as an organism is living, the amount of carbon-14 inside it is the same as the atmosphere.
However, it is also used to determine ages of rocks, plants, trees, etc. When the sun’s rays reach them, a few of these particles turn into carbon 14 (a radioactive carbon).