Aboveground nuclear testing almost doubled the amount of carbon-14 in the atmosphere. The black arrow shows when the Partial Test Ban Treaty was enacted that banned aboveground nuclear tests. A special kind of radiocarbon dating: Bomb radiocarbon dating.

As we mentioned above, the carbon-14 to carbon-12 ratio in the atmosphere remains nearly constant.

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.

Radiocarbon dating uses isotopes of the element carbon. Cosmic rays – high energy particles from beyond the solar system – bombard Earth’s upper atmosphere continually, in the process creating the unstable carbon-14. Because it’s unstable, carbon-14 will eventually decay back to carbon-12 isotopes.

To understand radiocarbon dating, you first have to understand the word Although an element’s number of protons cannot change, the number of neutrons can vary slightly from each atom.

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.

Both Carbon-12 and Carbon-13 are stable, but Carbon-14 decays by very weak beta decay to nitrogen-14 with a half-life of approximately 5,730 years.

After the organism dies it stops taking in new carbon.

As you learned in the previous page, carbon dating uses the half-life of Carbon-14 to find the approximate age of certain objects that are 40,000 years old or younger.

In the following section we are going to go more in-depth about carbon dating in order to help you get a better understanding of how it works.

However, at the moment of death, the amount of carbon-14 begins to decrease because it is unstable, while the amount of carbon-12 remains constant in the sample.