radiation

The emission, propagation, and transfer of energy in any medium, through electromagnetic waves (electromagnetic radiation) or subatomic particles (particulate radiation). Most of the radiation reaching the Earth comes from the sun, followed by cosmic radiation, which, although highly energetic, comes from very distant celestial objects. Both flows of radiant energy cross the atmosphere from top to bottom, while the radiation emitted by the Earth's surface does so in the opposite direction, from bottom to top.