![]() The sciences of archaeology and palaeontology were about to be revolutionised.Ī major problem had to be overcome, however. ![]() So, by measuring the radioactivity of a sample taken from the organism, its carbon-14 content could be estimated and the date of its time of death could be measured. ![]() A chemist who had worked on the Manhattan Project to build the first atom bomb, Libby realised that when an organism dies, it will stop absorbing carbon, including carbon-14, and its existing store of the latter will slowly decay. “Every living thing on Earth thus becomes radioactive, albeit slightly,” says Marra.Īnd it dawned on Willard Libby of Chicago University that the radioactivity generated by carbon-14 could be exploited to tremendous advantage. In turn, these atoms combine with oxygen to create radioactive carbon dioxide that is absorbed by plants, which are then eaten by animals. These neutrons strike atoms of nitrogen, the main component of Earth’s atmosphere, and transform some into atoms of carbon-14. Cosmic rays batter the upper atmosphere and send cascades of neutrons through the air, they calculated. And since the discovery of a long-lived radioisotope of carbon, we have an amazing tool to delve into almost every aspect of existence on Earth – and perhaps the universe.”Īs Marra reveals in this remarkable history of carbon-14, scientists quickly realised the isotope must affect living beings today. It is fundamental also to how we live, how the Earth is habitable – pretty much everything. “Carbon is what we are made of,” says Marra, who is professor of earth and environmental sciences at Brooklyn College, New York.
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