is a technique used by scientists to learn the ages of biological specimens – for example, wooden archaeological artifacts or ancient human remains – from the distant past.
Later called Ötzi the Iceman, small samples from his body were carbon dated by scientists.
The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. It is found in the air in carbon dioxide molecules.
The amount of carbon-14 in the air has stayed the same for thousands of years.
There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain.
Once an organism dies, it stops taking in carbon-14.
The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.
Atoms of the same element that have different numbers of neutrons are called isotopes. Most carbon on Earth exists as the very stable isotope carbon-12, with a very small amount as carbon-13.
Here’s an example using the simplest atom, hydrogen. Carbon-14 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-12.
Before we get into the details of how radiometric dating methods are used, we need to review some preliminary concepts from chemistry.
Recall that atoms are the basic building blocks of matter.
By measuring the amount of carbon-14 left in dead organic material the approximate time since it died can be worked out.