How to Use Carbon Dating
Carbon dating is a way to learn the age of an organism that may be thousands of years old. A chemist named Willard Libby worked out this method of dating in 1949. Since Libby's discovery, scientists have used carbon dating to determine the age of various environmental and archaeological artifacts. Learn what you need to do to find a good sample and date it within a narrow margin.
Instructions
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Gather some samples you can use for carbon dating. You can use carbon dating on bone, cloth, wood and plant fibers. A good way to start is by using a tree stump. Figure out the age of the tree by cutting off a piece of the stump and counting the rings. Once you determine the tree's age, you can find the amount of carbon in it.
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Take a scientific approach by using Libby's method to date carbon by measuring the amount of carbon radioactivity with accelerator mass spectrometry (AMS). Cut off a piece of the tree stump and measure it on a small scale to determine if the sample is two milligrams or more. Put the sample in the AMS to determine the carbon percentage. The level of carbon decreases by 50 percent if the sample is more than 5,568 years old in Libby's method, but that's rarely the case. Libby's standard percentage of carbon is 98.89 percent. You can use Libby's percentage in other tests.
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Determine the age of your sample by hand and with the help of a calculator. Take your sample's carbon percentage by dividing its age by the half-life of carbon, which varies depending on the source. Libby suggests is 5,568 years, while others argue that it's 5,730 years. Try both numbers to see what the differences are. For example, if the rings show the tree stump is 20 years old, you divide 20 by 5,730 and get a carbon percentage of 99.75 percent. Also use Libby's method and divide 20 by 5,568, which is .0036 percent. The answer is going to be lower, because Libby's method usually works better on older samples that are more 1,000 years old.
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Carbon date your sample by using the same method that gave you the percentage, but substitute the percentage for the age. For example, take the 99.75 carbon percentage and divide it by 5,730. The answer to the equation shows the age of your sample, which is around 20 years old. Or take Libby's standard percentage, which is 98.89 and divide that by 5,568. The answer will contradict the other method because Libby's method works better for older samples. The answer for the sample should be around 18 years.
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Try a carbon dating calculator and check your work by verifying your findings in another format. The 101 Science and the University of Pennsylvania websites both have effective calculators that give the carbon percentage and the age of the sample.
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Repeat your findings on other samples to accumulate a wide variety of data. Use what you've learned to finding out the age of just about anything you want. You can organize the data for your work or class assignment by creating a line graph that illustrates the varying ages of your samples.
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Tips & Warnings
Understand that various environmental factors affect the amount of carbon in an artifact. Various things can affect the carbon levels of artifacts, including nuclear testing and climate control. Expect your carbon dating results to vary depending on those environmental factors.
Use carbon dating only on biological organisms that get their carbon from the air and not from aquatic rocks. Carbon dating also doesn't work on artifacts over 50,000 years because the amount of carbon in them is too small to detect.
