The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay.
The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of the Earth itself, and can also be used to date a wide range of natural and man-made materials.
With uranium-lead dating, for example, the process assumes the original proportion of uranium in the sample.
One assumption that can be made is that all the lead in the sample was once uranium, but if there was lead there to start with, this assumption is not valid, and any date based on that assumption will be incorrect (too old).
Radioisotope dating (also referred to as radiometric dating) is the process of estimating the age of rocks from the decay of their radioactive elements.
There are certain kinds of atoms in nature that are unstable and spontaneously change (decay) into other kinds of atoms.
In the case of carbon dating, it is not the initial quantity that is important, but the initial ratio of C, but the same principle otherwise applies.
Recognizing this problem, scientists try to focus on rocks that do not contain the decay product originally.Additionally, elements may exist in different isotopes, with each isotope of an element differing only in the number of neutrons in the nucleus.A particular isotope of a particular element is called a nuclide. That is, at some random point in time, an atom of such a nuclide will be transformed into a different nuclide by the process known as radioactive decay. Radiometric dating is a method of determining the age of an artifact by assuming that on average decay rates have been constant (see below for the flaws in that assumption) and measuring the amount of radioactive decay that has occurred.Radiometric dating is mostly used to determine the age of rocks, though a particular form of radiometric dating—called Radiocarbon dating—can date wood, cloth, skeletons, and other organic material.Because radiometric dating fails to satisfy standards of testability and falsifiability, claims based on radiometric dating may fail to qualify under the Daubert standard for court-admissible scientific evidence.