We will deal with carbon dating first and then with the other dating methods.
Radiometric dating, or radioactive dating as it is sometimes called, is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes.Different methods of radiometric dating can be used to estimate the age of a variety of natural and even man-made materials.Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.However, rocks and other objects in nature do not give off such obvious clues about how long they have been around.
So, we rely on radiometric dating to calculate their ages.
These long time periods are computed by measuring the ratio of daughter to parent substance in a rock and inferring an age based on this ratio.
This age is computed under the assumption that the parent substance (say, uranium) gradually decays to the daughter substance (say, lead), so the higher the ratio of lead to uranium, the older the rock must be.
The process, called radioactive decay, is often accompanied by the emission of high energy electromagnetic radiation (gamma radiation), electrons (beta radiation) or helium-4 nuclei (alpha radiation).
These particles are easy to detect at extremely low levels using fairly simple equipment.
Because the number of atoms in a typical laboratory sample is extremely large, methods involving the use of radioactivity are among the most sensitive in all science.