On holiday the sky may look a deeper shade of blue than even the clearest summer day at home. Some places, including Cape Town in South Africa and Briançon in France, pride themselves on the blueness of their skies. But is there really any difference?
The blue of the sky is the product of Rayleigh scattering, which affects light more at the blue end of the spectrum. The blue we see is just the blue component of scattered white sunlight.
