Radioactive dating is a technique which allows for accurate determination of the age of materials. The most common type of radioactive dating is called radiocarbon dating, which can be used to find the age of organic materials. A long-lived isotope of carbon, 14 C, is similar chemically to the stable isotope of carbon, 12 C. Living organisms exchange carbon with their environments constantly, so they accumulate 14 C. The amount contained in an organism quickly reaches the same abundance that is found on the earth, about one atom of 14 C for every 7 x 1011 atoms of 12 C. When the organisms die, they stop accumulating 14 C, and the abundance of 14 C decreases due to radioactive decay. By measuring the radioactivity of the sample, the abundance of 14 C relative to the amount of 12 C can be found, thus determining how long the organism has been dead.

14 C is produced in the upper...