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| What is it? Carbon dating is a child of the atomic bomb. Willard F. Libby, anAmerican chemist at the University of Chicago, discovered its basicprinciples while working on the Manhattan Project during World WarII. After the war, Libby began research on cosmic rays. Cosmic rays are atomic particles, mostly electrons and protons,that travel through the universe. Some are emitted from the Sun; others come from exploding stars known as supernovas. It is possible that some may be materials left over from the beginnings of the universe. Libby found that when cosmic rays strike the Earth, they often smash intothe oxygen and nitrogen atoms that make up a large part of our atmosphere.When cosmic rays collide with nitrogen atoms, they create a radioactiveisotope known as carbon-14. Carbon-14 is created when a cosmic ray strikes a nitrogen atom, adding an extra neutron to its atomic structure. This impact creates a new radioactive isotope with an atomic weight of 14. Most of the carbon on Earth is not radioactive and has an atomic weight of 12. Carbon-14 represents about one percent of all the carbon in the Earth's atmosphere. This process quickly becomes biological. In the atmosphere, carbon-14 naturally combines with oxygen, creating carbon dioxide gas. This gas is absorbed by plants, which take carbon dioxide from the air during photosynthesis. The plants, in turn, pass the carbon-14 along to the animals that feed upon them. In this way, radioactive traces are passed along the food chain. This process of accumulating radioactive carbon only stops when an organism dies.
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