In general dating techniques are methods of estimating the
true age of rocks, paleontologists specimens,
archaeological sites, and so on.
Relative dating techniques
date specimens in relation to each other; for example,
stratigraphy is used to establish the succession of fossils.
Absolute (or chronometric) techniques give an absolute estimate
of the age and fall into two main groups.
The first depends on the existence of something that develops at a seasonally varying rate, as in dendrochronology and varve dating. The other uses some measurable change that occurs at a known rate as in chemical dating, and radiometric (or radioactive) dating. The types of radiometric dating currently available are
N = N_{0}exp(-yt), where y is called the decay constant (also called the disintegration constant). The reciprocal of the decay constant is the mean life. The time required for half the original nuclides to decay (i.e. N = 0.5N_{0}) is called the half-life of the nuclide. All radiometric dating, is based upon the premise that the radioactive decay rates of given isotopes are constant. There is a great deal of experimental evidence to suggest that decay rates are constant, and no evidence to suggest that they aren't, indeed if the decay rates of elements such as uranium or plutonium had exhibited varying decay rates both the nuclear power industry and nuclear weapons production would be in serious trouble from a production point of view. |