Radioactive dating of fossils depends on the decay of
This normally involves isotope-ratio mass spectrometry. The precision of a dating method depends in part on the half-life of the radioactive isotope involved.
For instance, carbon-14 has a half-life of 5,730 years.
It is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration.
Precision is enhanced if measurements are taken on multiple samples from different locations of the rock body.
By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change.
Radiometric dating is also used to date archaeological materials, including ancient artifacts.
This predictability allows the relative abundances of related nuclides to be used as a clock to measure the time from the incorporation of the original nuclides into a material to the present.
Additionally, elements may exist in different isotopes, with each isotope of an element differing in the number of neutrons in the nucleus.
A particular isotope of a particular element is called a nuclide. That is, at some point in time, an atom of such a nuclide will undergo radioactive decay and spontaneously transform into a different nuclide.
While the moment in time at which a particular nucleus decays is unpredictable, a collection of atoms of a radioactive nuclide decays exponentially at a rate described by a parameter known as the half-life, usually given in units of years when discussing dating techniques.
After one half-life has elapsed, one half of the atoms of the nuclide in question will have decayed into a "daughter" nuclide or decay product.