Black body

A black body in Physics is an object which absorbs all light that falls onto it (and thus reflects none). Although the name would make one think differently, black bodies actually radiate light. The division of light of various wavelengths is very characteristic, and depending (only) on the temperature of the black body.

In the laboratory, the closest thing to a black body is a small hole to a cavity with a non-smooth, black surface. In Astronomy, such objects as Stars are frequently regarded as black bodies, though this may be a bad approximation. An almost perfect black body spectrum is exhibited by the Cosmic Background Radiation.