Carbon-14, the radioactive version of carbon, is rare — it only makes up one trillionth of all the carbon in the world.Chemically, carbon-14 is no different from non-radioactive carbon atoms, so it ends up in all the usual carbon places — one trillionth of the carbon atoms in air, plants, animals and us are radioactive.But don't panic — of the 800,000,000,000,000,000,000,000,000 carbon atoms in every one of us, about 800,000,000,000,000 are carbon-14, so we've got a few to spare.Not only that, we top up our carbon-14 levels every time we eat.-14 is continually formed in nature by the interaction of neutrons with nitrogen-14 in the Earth’s atmosphere; the neutrons required for this reaction are produced by cosmic rays interacting with the atmosphere.Radiocarbon present in molecules of atmospheric : it is absorbed from the air by green plants and then passed on to animals through the food chain.All radioactive atoms eventually decay into something more stable, and carbon-14 decays into nitrogen.
It's not that the radioactive carbon in air or food doesn't decay, it does.
But something else is going on that keeps producing new carbon-14 — otherwise it would have all turned to nitrogen millions of years ago.
Radiocarbon decays slowly in a living organism, and the amount lost is continually replenished as ...
Radiocarbon dating is used to work out the age of things that died up to 50,000 years ago. As far as working out the age of long-dead things goes, carbon has got a few things going for it. The proteins, carbohydrates and fats that make up much of our tissues are all based on carbon.
Everything from the fibres in the Shroud of Turin to Otzi the Iceman has had their birthday determined the carbon-14 way. There's plenty of hydrogen, oxygen and nitrogen in living things too, but carbon's got something none of them do — a radioactive isotope that can take thousands of years to decay.
(You can read up on radioactivity and isotopes here).