Colors of a sunset
What causes the sunrise and sunset to have so many colors?
When the sun is directly overhead, the sunlight has to only
pass through a few miles worth of thick atmosphere. But when the
sun is close to the horizon (at sunrise or sunset) the light goes
a much longer distance through the atmosphere. This causes
attenuation of the shorter wavelengths (blue - this is why the
sky is blue at other times of the day) leaving only the longer
wavelengths like orange and red to reach us. Having clouds in
the sky and a variety of other atmospheric effects also contributes
to the play of colors.
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Update: June 2012