Radiocarbon Dating Technique
Scientists have been dating fossils and rocks for more than 100 years. They use two similar methods with names that often confuse people. The process of radiocarbon dating was invented shortly after World War II and estimates the age of new fossils using a carbon isotope. Radiometric dating is usually used on much older material. The radiocarbon process is fairly simple, but its inventor needed ingenious techniques to prove the method works.
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History
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W.F. Libby unintentionally discovered radiocarbon dating in the mid-1950s through Serge Koff's work on cosmic radiation. Libby theorized from Koff's work that certain atmospheric reactions should indicate that carbon-14 exists in sizable quantities in nature. He then realized that carbon-14 could date organic objects because of its long half-life and necessity in the photosynthesis process (see Reference 1).
Formation of carbon-14
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Neutrons from cosmic radiation hit nitrogen (the main component of the atmosphere) to form carbon-14, although neutrons sometimes react with oxygen and carbon itself. A similar reaction occurs in nuclear weapons testing, which accounts for close to 5 percent of the amount of carbon-14 in our atmosphere. Most carbon-14, however, is stored in the oceans (see Reference 2).
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Dating
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Scientists easily date plant matter because it photosynthesizes carbon-14. Dating animals requires that they have consumed plant material before dying. Carbon-14 does not get replaced after death, and the expected half-life of carbon-14 is well-documented. Dating methods need to determine the amount of carbon-14 left to age the organism. A common Geiger counter can measure the electrons given off by a burnt piece of material. The final step is plugging information into the exponential decay formula (see Reference 3).
Limitations
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Radiocarbon dating does not work 100 percent of the time. Smaller sizes of organic matter create greater statistical variation on dates. The care taken when excavating a sample reduces chances of cross-contamination with atmospheric carbon-14 and contamination from nearby samples. The half-life of carbon-14 limits dating to no more than 50,000 years and no less than a few hundred years (see Resource 1).
Related Dating Techniques
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Scientists date very old fossils, geologic formations and ancient artifacts using a similar process to radiocarbon dating called radiometric dating. The principle of both methods are the same, using the presence of radioactive materials and their half-lives to approximate age. The main difference between the two methods lies in the fact that any radioactive material can be used as a radiometric dating process, and scientists mainly use radiometric dating for inorganic matter (see Resource 2).
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