Why is the sky blue? PLEASE can anyone tell me? I know about sex, dammit. But when it comes to the sky all I can say, vaguely, is 'because there are blue bits in it'. There's more to it than that, isn't there? <shuffles off all embarrassed that am clearly bringing up daughters to be fluffy types rather than clear-eyed scientists saving the world in manner of Marie Curie or Sigourney Weaver or Captain Janeway or suchlike>