Uses of radiation dating

Radioactive isotopes are often used to date samples of material.

Organic substances can be dated by measuring the amount of carbon-14 they contain, while the age of a sample of rock can be determined by comparing the amounts of various radioactive isotopes present.

To be stable, a nucleus cannot be too heavy, and needs to have the right balance of protons and neutrons.A heavy nucleus — one that has a large number of protons and neutrons — will sooner or later lose some weight, or mass, by emitting an alpha particle, which consists of two protons and two neutrons bound together.Gamma rays have no weight, and travel at the speed of light.Some heavy nuclei can, instead of emitting alpha particles, actually split apart, releasing a lot of energy, a process known as nuclear fission.Radioactive decay is a random process, meaning that it is physically impossible to predict whether or not a given atomic nucleus will decay and emit radiation at any given moment.

Instead, it is quantified by half-life, which is the period of time it takes for half of a given sample of nuclei to decay.Although these transformations release energy in the form of mass, they can also leave the remaining nucleus in an “excited” state, where it has more than its minimum amount of energy.It will therefore lose this extra energy by emitting a gamma ray — a very high frequency form of electromagnetic radiation.This is sometimes called positive beta decay, and results in the atom turning into an element with fewer protons.Both types of beta decay produce electrically charged particles that are very lightweight and fast.In medicine, radioactivity can be used in a targeted way to destroy cancerous growths.