why is the sky blue?

Question

askNib · Accepted Answer

Sunlight looks white, but it's actually every color mixed together, each traveling as a wave of a different length. Red light has long, lazy waves. Blue light has short, tight waves. That difference is the whole secret. That sunlight has to punch through our whole atmosphere, full of tiny nitrogen and oxygen molecules — far smaller than any light wave. Those tiny molecules scatter short blue waves far more than long red ones — about ten times more strongly. This is Rayleigh scattering. So blue light gets bounced all over the sky in every direction, reaching your eyes from every patch of sky you look at — that's why it looks blue. Blue light gets scattered every which way across the sky, so wherever you look, blue is what reaches your eyes.