# Radiometric dating wikipedia the encyclopedia

The mathematical expression that relates radioactive decay to geologic time is: This equation uses information on the parent and daughter isotopes at the time the material solidified. It shows the age of the sample, and the original composition.

The method works best if neither the parent nuclide nor the daughter product enters or leaves the material after its formation.

I think that I will start by answering the second part of your question, just because I think that will make the answer to the first question clearer.

I should mention that the decay constants basically a value that indicates how fast a certain radioactive isotope will decay for some of these isotope systems were calculated by assuming that the age of the earth is 4.

The decay constants for most of these systems have been confirmed in other ways, adding strength to our argument for the age of the earth.

A mass spectrometer is an instrument that separates atoms based on their mass.

Because geochronologists want to measure isotopes with different masses, a mass spectrometer works really well for dating things.