Since , scientists have reckoned the ages of many old objects by measuring the amounts of radioactive carbon they contain. New research shows, however, that some estimates based on carbon may have erred by thousands of years. It is too soon to know whether the discovery will seriously upset the estimated dates of events like the arrival of human beings in the Western Hemisphere, scientists said. But it is already clear that the carbon method of dating will have to be recalibrated and corrected in some cases. They arrived at this conclusion by comparing age estimates obtained using two different methods - analysis of radioactive carbon in a sample and determination of the ratio of uranium to thorium in the sample.
Martin D. Kamen, 89; Scientist Who Discovered the Element Carbon - Los Angeles Times
This included cloth fibers, bone, bits of wood and charcoal. Libby had realized that since all living things had a relatively constant carbon 14 to carbon 12 ratio as found in the atmosphere. Carbon 14 is a radioactive isotope type of atom and carbon 12 was a stable isotope. The reason was that plants took on carbon dioxide CO2 through photosynthesis and animals did so through breathing, eating plants and eating other animals.
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When news is announced on the discovery of an archaeological find, we often hear about how the age of the sample was determined using radiocarbon dating, otherwise simply known as carbon dating. Deemed the gold standard of archaeology, the method was developed in the late s and is based on the idea that radiocarbon carbon 14 is being constantly created in the atmosphere by cosmic rays which then combine with atmospheric oxygen to form CO2, which is then incorporated into plants during photosynthesis. When the plant or animal that consumed the foliage dies, it stops exchanging carbon with the environment and from there on in it is simply a case of measuring how much carbon 14 has been emitted, giving its age. But new research conducted by Cornell University could be about to throw the field of archaeology on its head with the claim that there could be a number of inaccuracies in commonly accepted carbon dating standards. If this is true, then many of our established historical timelines are thrown into question, potentially needing a re-write of the history books.
This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature. C is by far the most common isotope, while only about one in a trillion carbon atoms is C C is produced in the upper atmosphere when nitrogen N is altered through the effects of cosmic radiation bombardment a proton is displaced by a neutron effectively changing the nitrogen atom into a carbon isotope. The new isotope is called "radiocarbon" because it is radioactive, though it is not dangerous. It is naturally unstable and so it will spontaneously decay back into N after a period of time.