The carbon-14 it contained at the time of death decays over a long period of time.
By measuring the amount of carbon-14 left in dead organic material the approximate time since it died can be worked out.
Carbon, uranium and potassium are just a few examples of elements used in radioactive dating.
Each element is made up of atoms, and within each atom is a central particle called a nucleus.
Radiometric dating is sometimes referred to as radioactive dating.
In fact, you might like this term better, because the dating method relies on the known decay rate of radioactive isotopes.
Because these rates do not change and because the radiation that rocks give off can be measured, it became possible to calculate the time the rock was formed or, in other words, the rock's birth date - give or take a few thousand years or so.Types of Fossils There are two main types of fossils: body fossils and trace fossils.A body fossil is the physical remains of an animal. Some very small organisms, called microbacteria, leave behind microscopic particles called filaments.There's a small amount of radioactive carbon-14 in all living organisms.When they die no new carbon-14 is taken in by the dead organism.Though there is no one age, a good rule is anything over 10,000 years old can be considered a fossil.