Radioactivity

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Radioactivity has nothing to do with active radios! It is the breaking up of particles or nuclei into smaller ones. These go shooting off at high speed, hitting other nuclei and making them hot. All the smaller particles which are produced are called radiation, hence the name. Because of the energy released, radioactive decay releases heat. It is the source of heat in the Earth, keeping the core hot, and causing continental drift. It may also have caused the Earth to release the gases which made the first atmosphere.

There are several types of radioactivity.

Alpha Radioactivity
Beta Radioactivity
Gamma Radioactivity
Nuclear Fission

Everybody on Earth receives radioactive radiation (correctly called ionizing radiation) from various sources. Almost all of it comes from the Earth and other natural sources, as shown in this chart. Notice that most man-made radiation comes from medical X-rays and other treatments. Only a tiny amount comes from pollution such as discharges from nuclear power plants.