17. From Earth why does the Moon look sometimes white, sometimes yellow, sometimes orange . . .? (A K2S Question)
From The Space Library
The different colors of the Moon appear to be determined by the wavelengths the Earth's atmosphere filters out. All energy travels in waves, much like ocean waves. Light is a form of energy and also travels in waves. The different wavelengths of light produce different colors. The longer the wavelength (distance between the top of the waves) of light, the redder it appears. The shorter the wavelength of light, the bluer it appears. Because the atmosphere of the Earth stops shorter wavelengths, objects closer to the horizon look red or orange, because the light has to travel through more of the atmosphere and, as a result, only the longer wavelengths (toward the red end of the spectrum) get through the atmosphere. By contrast, light from objects that are higher up in the sky does not have to travel through as much atmosphere to reach our eyes and so the shorter (blue) wavelengths are able to get through the atmosphere with the long (red) wavelengths. Since all the colors are now getting through the atmosphere, to our eyes the Moon appears white. The colors of the Moon as seen from the Earth's surface are also determined by the dust or moisture found in the atmosphere. Dust also absorbs the shorter (blue) wavelengths of light making the Moon redder in color. For example, the orange color often associated with the harvest, or fall moon in European culture, is the result of dust in the atmosphere from farmers burning their harvested fields to prepare them for winter. This dust stops the shorter (blue) waves from getting through making the Moon appear redder in color. http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/971021d.html (See CDROM)
Answer provided by Thomas Matula, Ph.D. & Kenneth J. Murphy
Question and Answer extracted from the book Kids to Space - by Lonnie Schorer
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