Q Why is the Sky Blue?

A. The sky is blue because air scatters light - and scatters different colors different amounts. In fact, the amount of light scattered by any small (by small we mean smaller than the wavelengths we’re interested in) particle is inversly proportional to the fourth power of the wavelength. The wavelength of blue light is roughly half the wavelength of red light, so blue light is scattered almost ten times as strongly as red light. For more details, you can try ou a simple experiment.