See our article on Rayleigh scattering for an explanation of why the sky usually appears blue, but why thicker slabs of air ( as seen at sunset, for example ) can appear other colours . ( See also green flash for a really neat atmospheric phenomenon . ) Lastly, check out Mie theory for an examination of how suspended particulate matter ( volcanic dust, industrial pollution ) can " also " colour the sky . ( Oops & mdash; I shouldn't forget diffuse sky radiation, too . ) The apparent blue colour of the sky isn't due solely to intrinsic'colour'of the air, but a combination of scattering effects, the nature of the source of illumination ( the Sun ), and the sensitivity of the photoreceptors in our eyes . talk ) 03 : 51, 1 November 2005 ( UTC)
