RadiationEnergy dispersion through matter or space. In atomic physics... emitted from the natural radioactive substancesRadioactive substances within the meaning of the Atomic Ener... in the ground. Terrestrial radiationEnergy dispersion through matter or space. In atomic physics... causes external radiationEnergy dispersion through matter or space. In atomic physics... exposure of human beings. (See Radiation exposure, terrestrialTerrestrial radiation comes from the natural radioactive sub...).