After all, we should be able to estimate how long ago a creature lived based on how much radiocarbon is left in its body. Radiocarbon (carbon-14) is a very unstable element that quickly changes into nitrogen.

Knowing the number of atoms that decayed in our sample over a month, we can calculate the radiocarbon decay rate.

The standard way of expressing the decay rate is called the half-life.5 Itâ€™s defined as the time it takes half a given quantity of a radioactive element to decay.

Chemists have already determined how many atoms are in a given mass of each element, such as carbon.4 So if we weigh a lump of carbon, we can calculate how many carbon atoms are in it.

If we know what fraction of the carbon atoms are radioactive, we can also calculate how many radiocarbon atoms are in the lump.

The most well-known of all the radiometric dating methods is radiocarbon dating.