Some of the isotopes used for this purpose are uranium-238, uranium-235 and potassium-40, each of which has a half-life of more than a million years.
Dinosaur bones, on the other hand, are millions of years old -- some fossils are billions of years old.
To determine the ages of these specimens, scientists need an isotope with a very long half-life.
Each of them typically exists in igneous rock, or rock made from cooled magma.
Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.
There are two techniques for dating in archaeological sites: relative and absolute dating.
Relative dating stems from the idea that something is younger or older relative to something else.
Meanwhile, Arthur Holmes (1890-1964) was finishing up a geology degree at the Imperial College of Science in London where he developed the technique of dating rocks using the uranium-lead method.
By applying the technique to his oldest rock, Holmes proposed that the Earth was at least 1.6 billion years old.
This week, Cherry Lewis of the University of Bristol presented a talk about the history of dating the Earth as part of the BA Festival of Science in York, England.