Quote Originally Posted by Mouse View Post
Maybe light is more yellow at the equator, but blue at the poles because the red light is refracted and bounced back again out to space when the atmosphere is thicker - which is connected with the angle of incidence idea.
The path of sunlight at any latitude is longest at sunrise and sunset and shortest at mid-day. Sunrises and sunsets are more red than blue because atmospheric scattering is strongly wavelength dependent with shorter (bluer) wavelengths scattering more strongly than longer (redder) ones. It's why the sky is blue. See Index of Refraction, Rayleigh scattering and Mie scattering for more information.

The general color of light present is strongly influenced by secondary (scattered and reflected) light rather than direct illumination. At upper latitudes and during winter, most of the blue is coming in from all directions of the sky where it has been scattered and the ground is mostly white (snow or ice), which further reflects the blue back up (it's why glaciers are sky blue, after all). In warmer countries, there are a number of factors that contribute to pretty light, which include the color of the terrain (tan sand gives you a wonderful light), big poofy clouds that bounce the yellow light down from the sky, and a larger particulate load than very cold or hot places (the above-discussed wavelength-dependent extinction is strongly dependent on particle size and distribution).

Most photographers seek out the "golden hour" just before dawn and just after sunset where there isn't direct illumination to cause shadows and a lot of the blue has been scattered out, giving a beautiful golden light. I live a bit downwind from a large mountain range, which causes bands of clouds to form overhead a few times a year. Just after the sun goes behind the mountains, it lights up those clouds and gives a brilliant yellow light for twenty minutes or so that is beautiful but very hard to describe.