Radiometric dating of the earth
In this case, U238 is the “parent” and Pb206 is the “daughter.” Scientists begin by measuring how long it takes for a parent isotope to decay into a daughter isotope.In this particular case, it takes 4,460,000,000 years for half of a sample of U238 to decay into Pb206.As an example of how they are used, radiometric dates from geologically simple, fossiliferous Cretaceous rocks in western North America are compared to the geological time scale.
Though his figures were too high by about 20 percent, their order of magnitude was enough to dispose of the short scale of geologic time proposed by Lord Kelvin. This device separates the different isotopes of the same element and can measure the variations in these isotopic abundances to within one part in 10,000.
A common element used for radiometric dating, or the dating of fossils to their time period of life, is Carbon-14.
It begins as a Carbon isotope, but at the end of its life it becomes Nitrogen-14.
Radiometric dating is a method which scientists use to determine the age of various specimens, mainly inorganic matter (rocks, etc.), though there is one radiometric dating technique, radiocarbon dating, which is used to date organic specimens. Basically, scientists take advantage of a natural process by which unstable radioactive “parent” isotopes decay into stable “daughter” isotopes spontaneously over time.
Uranium-238 (U238), for example, is an unstable radioactive isotope which decays into Lead-206 (Pb206) naturally over time (it goes through 13 unstable intermediate stages before it finally stabilizes into Pb206).