As the Hong Kong Observatory explains in an article on its website, during sunrise or sunset, “the sun shines from a low angle. Sun rays have to go through a thick atmosphere, resulting in scattering by water vapour, water droplets, dust particles etc. in the air. Light with shorter wavelength, e.g. cyan, blue or purple, is scattered away, leaving red, orange and yellow, turning the sky reddish.”
This explains why the sky looks red during dawn or dusk.
An article by the Library of Congress further explains that:
“The colors we see in the sky are due to the rays of sunlight being split into colors of the spectrum as they pass through the atmosphere and ricochet off the water vapor and particles in the atmosphere. The amounts of water vapor and dust particles in the atmosphere are good indicators of weather conditions. They also determine which colors we will see in the sky.
Last accessed date: 05 Jan 2012
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Call No.: English 551.631 FRE
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posted by: Norbishah