Black body radiation is sort of a reverse of what happens when you are sunbathing and you absorb heat energy from the rays of the sun. The hotter an object is, the more it will emit heat radiation of its own. You have probably noticed that black clothes absorb heat radiation better. Similarly, black objects emit more heat radiation, which is probably the origin of the term 'black body radiation'. Planck's explanation of the energy distribution of blackbody radiation was one of the first steps toward quantum mechanics .