How can scientists determine the age of artifacts?
(Lansing State Journal, August 3, 1994)
All living things contain carbon. Therefore, anything made out of something that was once alive, such as wood, cotton, paper, etc., contains carbon. Normally, carbon has 12 electrons, 12 neutrons and 12 protons. There is a form of carbon present, in very small amounts, in living systems. However, that has 14 neutrons instead of 12. This is called a carbon 14 isotope. Over time, carbon 14 decays with a half life of 5,730 years. This means that in any given sample containing carbon, half of the carbon 14 will have decayed after 5,730 years. By determining the amount of carbon 14 left in a sample, scientists can come up with a good estimate of the age of an artifact. This technique can be used for carbon containing artifacts that are 1,000 to 50,000 years old. After 50,000 years, there isn't enough carbon 14 present in a given sample to get a good estimate of age, and before 1,000 years, there is too much carbon 14 present in a given sample to get a good estimate of age.