Radiometric **dating**, often called radioactive **dating**, is a technique used to determine the age of materials such as rocks.It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.Follow the links below to learn more about radiocarbon **dating**. Radiocarbon **dating** uses carbon **isotopes** A special kind of radiocarbon **dating**: Bomb radiocarbon **dating** What is an isotope?

Among the significant events that caused a temporary but significant spike in the atmospheric carbon-14 to carbon-12 ratio were above-ground nuclear test detonations in the two decades following World War II.

is a term for radiocarbon **dating** based on timestamps left by above-ground nuclear explosions, and it is especially useful for putting an absolute age on organisms that lived through those events.

Radiocarbon **dating** uses **isotopes** of the element carbon. Cosmic rays – high energy particles from beyond the solar system – bombard Earth’s upper atmosphere continually, in the process creating the unstable carbon-14. Because it’s unstable, carbon-14 will eventually decay back to carbon-12 **isotopes**.

Because the cosmic ray bombardment is fairly constant, there’s a near-constant level of carbon-14 to carbon-12 ratio in Earth’s atmosphere.

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.