How does radioactive decay relate to radiometric dating?
The ease of using the formula for radioactive decay with common elements found in nature make it a powerful tool.
Radiometric dating is the technique of using isotopic ratios of common elements to determine the age (approximate) of materials associated with the element, such as trees, rock strata, fossils, human artifacts and the like.
Because radioactive decay follows a specific mathematical formula and is dependent upon unique decay rates (half-lives) of each element, formulas can be developed that compare the measured amounts of different elemental isotopes. The ratio of the difference is related mathematically to the time that is took for the original sample to decay into the ratios found.
That is the time duration that is used for radiometric dating.