The sky is blue because of the scattering of blue wavelengths of incoming solar radiation by nitrogen in the atmosphere.

Question

Quizplus · Accepted Answer

This is a well-established scientific fact known as Rayleigh scattering. Nitrogen and oxygen molecules in the Earth's atmosphere scatter short-wavelength light, such as blue and violet, to a far greater degree than than long-wavelength light, such as red and yellow. This causes the sky to appear blue to an observer on the ground.

The Sky Is Blue Because of the Scattering of Blue