Determining how the environment might have affected a rock also falls under historical science. Since radioisotope dating uses both types of science, we can’t directly measure the age of something.We can use scientific techniques in the present, combined with assumptions about historical events, to estimate the age.Types of igneous rocks include granite and basalt (lava).Sedimentary rocks, which contain most of the world’s fossils, are not commonly used in radioisotope dating.
This is because we failed to take into account some critical assumptions.If scientists fail to consider each of these three critical assumptions, then radioisotope dating can give incorrect ages.We know that radioisotope dating does not always work because we can test it on rocks of known age.Once the rock cools it is assumed that no more atoms can escape and any daughter element found in a rock will be the result of radioactive decay.The dating process then requires measuring how much daughter element is in a rock sample and knowing the decay rate (i.e., how long it takes the parent element to decay into the daughter element—uranium into lead or potassium into argon). Half-life is defined as the length of time it takes half of the remaining atoms of a radioactive parent element to decay.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).