Also called absolute dating, scientists use the decay of radioactive elements within the fossils or the rocks around the fossils to determine the age of the organism that was preserved.This technique relies on the property of half-life.The amount of the isotope in the object is compared to the amount of the isotope's decay products.
It is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration.
Measurements should be taken on samples from different parts of the rock body.
Anything which changes the relative amounts of the two isotopes (original and daughter) must be noted, and avoided if possible.
Contamination from outside, or the loss of isotopes at any time from the rock's original formation, would change the result.
Half-life is defined as the time it takes for one half of a radioactive element to decay into a daughter isotope.