What is radiometric dating?

Any technique which dates a material based on the known decay rate of a radioactive component of the material is a form of radiometric dating. There are many radioactive elements and thus many applications of the basic principle.

Examples:

Archeologists may employ the well known method of carbon 14 dating. The technique measures the radioactivity of carbon 14 in a biological sample that may have been preserved for hundreds of years or tens of thousands of years. Knowing that the carbon 14 has a half life of 5,730 years allows the estimation of the age of the object based on the fraction of carbon 14 remaining.

Uranium-lead dating is an established radiometric dating technique. Very old rocks have been dated by measuring the amount of lead in the mineral zircon (ZrSiO4) which forms with radioactive uranium that takes more than 4 billion years to decay. By this method, the age of the Earth has been estimated to be about 4.6 billion years. This figure is in good agreement with the age of meteorites and the age of the Moon as determined independently.

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