Physics
Scattering of Light
Quick fact
If the Earth had no atmosphere, the sky would appear black even during the day, because there would be no air molecules to scatter sunlight toward our eyes.
Why this is interesting
Have you ever wondered why the sky is blue during the day but turns brilliant red at sunset, or why clouds are white while the surrounding sky is blue? The same physical process—scattering of light—explains all of these common sights.