Only when one takes additional physics classes does one learn that the
absorption and emission depend on the wavelength of the light. In the
visible spectrum, black objects absorb light well, but white objects do not
absorb light well. That is not true at other wavelengths.
The wavelength corresponding to hot (but not glowing) radiators is far into
the infrared, with a wavelength of perhaps 5 micrometers. At this
wavelength, all paint colors, including white, are "black" and emit and
absorb heat well.
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