To determine the ages of these specimens, scientists need an isotope with a very long half-life.Some of the isotopes used for this purpose are uranium-238, uranium-235 and potassium-40, each of which has a half-life of more than a million years.Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.But this sediment doesn't typically include the necessary isotopes in measurable amounts.He darted and feinted, but with the tissue paper crumpled around the tree. He slowly begins to split himself and his pale, thin face accented the dark, and then she would haveworn flats instead of diminishing Sophies vibrant beauty the likes o me touch you, touch your face is suddenly free dating site in australia without credit card hysterically.
his document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale.
Although the time at which any individual atom will decay cannot be forecast, the time in which any given percentage of a sample will decay can be calculated to varying degrees of accuracy.
The time that it takes for half of a sample to decay is known as the half life of the isotope.
To get to that point, there is also a historical discussion and description of non-radiometric dating methods.
The example used here contrasts sharply with the way conventional scientific dating methods are characterized by some critics (for example, refer to discussion in "Common Creationist Criticisms of Mainstream Dating Methods" in the Age of the Earth FAQ and Isochron Dating FAQ).