# Radiometric dating made easy

(Note that this does not mean that the ratios are the same everywhere on earth.It merely means that the ratios are the same in the particular magma from which the test sample was later taken.) As strontium-87 forms, its ratio to strontium-86 will increase.The creationist "argon escape" theory does not support their young earth model.) The argon age determination of the mineral can be confirmed by measuring the loss of potassium.In old rocks, there will be less potassium present than was required to form the mineral, because some of it has been transmuted to argon.The amount of strontium-86 in a given mineral sample will not change.Therefore the relative amounts of rubidium-87 and strontium-87 can be determined by expressing their ratios to strontium-86: Rb-87/Sr-86 and Sr87/Sr-86 We measure the amounts of rubidium-87 and strontium-87 as ratios to an unchanging content of strontium-86.If we knew the fraction of a radioactive element still remaining in a mineral, it would be a simple matter to calculate its age by the formula To determine the fraction still remaining, we must know both the amount now present and also the amount present when the mineral was formed.Contrary to creationist claims, it is possible to make that determination, as the following will explain: By way of background, all atoms of a given element have the same number of protons in the nucleus; however, the number of neutrons in the nucleus can vary.    The formula for the fraction remaining is one-half raised to the power given by the number of years divided by the half-life (in other words raised to a power equal to the number of half-lives).The sum of protons plus neutrons is the mass number.We designate a specific group of atoms by using the term "nuclide." A nuclide refers to a group of atoms with specified atomic number and mass number.(Creationists claim that argon escape renders age determinations invalid.However, any escaping argon gas would lead to a determined age younger, not older, than actual.