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.
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.
For example, the remaining radioactive parent material will decrease by 1/2 during the passage of each half-life (1→1/2→1/4→1/8→1/16, etc.).
Half-lives as measured today are very accurate, even the extremely slow half-lives.
Since we did not observe the initial conditions when the hourglass time started, we must make assumptions.
All three of these assumptions can affect our time calculations.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.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.Dating methods must also rely on another kind of science called historical science. Determining the conditions present when a rock first formed can only be studied through historical science.Many accept radiometric dating methods as proof that the earth is millions of years old, in contrast to the biblical timeline.