Photo Credit: Erik Herman
White light from the Sun is a mixture of all of the colors in the rainbow. Each color represents a different wavelength of the light. These waves are said to be scattered by air molecules and dust particles in the atmosphere. The light scatters because molecules and particles reflect the waves of shorter wavelength. These shorter light waves which happen to be blue are scattered throughout the sky. In other words, when you look up into the air, you see the scattered blue light that creates the sky.
This phenomenon in which small particles reflect certain wavelengths of light is called Rayleigh Scattering named after the physicist Lord Rayleigh (1842-1919).
Now at sunset, the light passes through more atmosphere and dust particles on the horizon. This dust scatters the larger wavelength red and orange light and hence creates the brilliant sunset. In Sedona AZ, the scattered light is so elaborate and beautiful that people cheer and applaud the sunset every night.