Light's Pinball Game

Sunlight appears white but contains every visible wavelength — red, orange, yellow, green, blue, violet. When this light enters Earth's atmosphere, it collides with nitrogen and oxygen molecules. These collisions scatter the light in different directions.

Rayleigh scattering — named after Lord Rayleigh, who explained it in the 1870s — describes how small particles scatter short wavelengths far more than long ones. Blue light scatters several times more than red, painting the sky blue in every direction you look.