Why is the sky blue?

Why is the sky blue?
Why is the sky blue?

Scattering of sunlight is more effective in the short wavelength (blue/violet) part of the spectrum, so the sky appears blue (but not today, because clouds and rain tend to mask that!). See: hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html for a more thorough explanation.