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Light from the sun has to travel through much more atmosphere compared
to when the sun is overhead from us.
Blue light and all the other colors are scattered around (and diluted)
so much by all this atmosphere that only red, orange and yellow light remains visible.
Light is not scattered just by the atmosphere itself (oxygen and nitrogen). It is more correct to say that light is scattered by the particles in the atmosphere.
The particles in the atmosphere are mainly:
- oxygen,
- nitrogen,
- clouds containing:
- liquid water,
- water vapor (water in gas from),
- ice (frozen water)
- snow (water in gas form that is frozen).
- pollution.
(Red, orange and yellow light has the longest wavelengths and is least affected by
'bumping' into oxygen atoms in the atmosphere.)
The red, orange and yellow you see at sunsets reached your eyes more or less in a straight line
directly from the sun.
By comparison, the blue sky is from billions of scattered (bounced around)
reflections of blue light coming from all directions.
Take these short online quizzes to test your understanding of this explanation
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