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The technique used is called carbon dating, and in this lesson we will learn what this is and how it is used. Carbon dating, or radiocarbon dating, is a method used to date materials that once exchanged carbon dioxide with the atmosphere. In the late 1940s, an American physical chemist named Willard Libby first developed a method to measure radioactivity of carbon-14, a radioactive isotope.
Libby was awarded the Nobel Prize in chemistry for his work in 1960.
Notice that the nitrogen-14 atom is recreated and goes back into the cycle.
Atmospheric carbon-14 rapidly reacts with oxygen in air to form carbon dioxide and enters the carbon cycle.
You will notice that after around 40,000 years (or 8 half-lives), the amount left is starting to become very small, less than 1%.
Once the organism dies, the amount of carbon-14 reduces by the fixed half-life - or the time required for half of the original sample of radioactive nuclei to decay - of 5,730 years, and can be measured by scientists for up to 10 half-lives.Once they die, they stop taking in carbon-14, and the amount present starts to decrease at a constant half-life rate.Then the radiocarbon dating measures remaining radioactivity.By knowing how much carbon-14 is left in a sample, the age of the organism and when it died can be worked out.Radiocarbon dating has been used extensively since its discovery.