Radioactive dating uses the decay rates of radioactive substances to measure absolute ages of rocks, minerals and carbon-based substances, according to How Stuff Works.Scientists know how quickly radioactive isotopes decay into other elements over thousands, millions and even billions of years.
By dating rocks, scientists can approximate ages of very old fossils, bones and teeth.
Radiometric dating (often called radioactive dating) is a way to find out how old something is.
The method compares the amount of a naturally occurring radioactive isotope and its decay products, in samples. It is the main way to learn the age of rocks and other geological features, including the age of the Earth itself.
For instance, if an object has 50 percent of its decay product, it has been through one half-life.
A popular way to determine the ages of biological substances no more than 50,000 years old is to measure the decay of carbon-14 into nitrogen-14.