Rayleigh Scattering

Ever wondered why clear skies are blue? It's because the sun's rays are scattered more effectively by the atmosphere's molecules when the wavelength of the rays are at the shorter (bluer) end of the spectrum. So when we look up on a clear day, it's the blue light which finds its way to our eyes more than the other colours in the spectrum. This phenomenon is named after Lord Rayleigh, a British physicist of the late 19th Century.