The colors of the sunset result from a phenomenon called scattering, says Steven Ackerman, professor of meteorology at UW-Madison. Molecules and small particles in the atmosphere change the direction of light rays, causing them to scatter.Scattering affects the color of light coming from the sky, but the details are determined bythe wavelength of the light and the size of the particle. The short-wavelength blue and violet are scattered by molecules in the air muchmore than other colors ofthe spectrum. This is whyblue and violet light reaches our eyes from all directions on a clear day. But because we can't see violet very well, the sky appears blue.Scattering also explains the colors of the sunrise and sunset, Ackerman says.“Because the sun is low on the horizon, sunlight passes through more air at sunset and sunrise than during the day, whenthe sun is higher in the sky. More atmosphere means more molecules to scatter the violet and blue light away from your eyes. If the path is long enough, all of the blue and violet light scatters out of your line of sight. The other colors continueon their way to your eyes. This is why sunsets are often yellow, orange, and red.”And because red has the longest wavelength of any visible light, the sun is red when it’s on the horizon, where its extremely long path through the atmosphere blocks all other colors.