Evening Dunes

Gordon Louis Mortensen

This vivid evening scene captures the brilliant colors created by the atmosphere and the setting sun. The clouds are afire and the mesembryantheum plants appear as flames licking the mauve sand dunes. We are all wowed by sunsets such as this but there is science behind the beauty. According to Steven Ackerman, the colors of the sunset result from a phenomenon called scattering. Molecules and small particles in the atmosphere change the direction of light rays, causing them to scatter. The short-wavelength blue and violet are scattered by molecules in the air much more than other colors of the spectrum. But because we can’t see violet very well, the sky appears blue. Because the sun is low on the horizon, sunlight passes through more air at sunset and sunrise than during the day. 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 continue on their way to your eyes. This is why sunsets are often yellow, orange, and red. Romantic, right?