Carbon dating illustration
For example, uranium will radioactively decay through a series of steps until it becomes the stable element lead. The original element is referred to as the parent element (in these cases uranium and potassium), and the end result is called the daughter element (lead and argon).
We can use scientific techniques in the present, combined with assumptions about historical events, to estimate the age.
Scientists use observational science to measure the amount of a daughter element within a rock sample and to determine the present observable decay rate of the parent element.