Here is more info. as we continue to have beautiful sunups and sundowns..
- Todd

Q: Why are some sunset skies bright orange and red, while others are
not?

A: Sunsets appear orange and red because of the way sunlight is
scattered as it passes through the Earth's atmosphere. Sunlight, like
all forms of radiation, travels as waves. The wavelengths at which
visible light travels range from about 0.4 micrometers (or microns; 1
micrometer = 1 millionth of a meter) to about 0.7 micrometers.

At the short end of this range are the blue and violet colors, while the
oranges and reds have longer wavelengths. During the day, air molecules
in the atmosphere scatter incoming sunlight in different directions -- a
process known as Rayleigh scattering (named for Lord Rayleigh, an
English physicist and mathematician who first described the effect.)

Since Rayleigh scattering occurs more at the lower wavelengths at which
visible light occurs, the blue portion of sunlight is more effectively
scattered and the sky appears blue on a cloudless day. During sunrise
and sunset, however, sunlight must pass through more of the Earth's
atmosphere, allowing more scattering to take place. By the time it
reaches us, most of the shorter wavelengths of the sunlight have been
completely scattered, leaving the longer wavelength portion --the
oranges and reds.

The most brilliant orange and red sunsets are often due to the presence
of particles larger than air molecules -- such as smoke, dust, or ash --
in the atmosphere. These particles help scatter out even more sunlight
at shorter wavelengths, resulting in sunsets that appear redder than
they would otherwise. Events such as wildfires and volcanic eruptions
can create spectacular sunsets, even very far away and long after the
created the brilliant red and orange sunsets that were the inspiration\u003cbr /\>for Edvard Munch\'s painting, "The Scream."\u003cbr /\>\u003cbr /\>For more, see our graphic on what gives the sky its color and our page\u003cbr /\>on understanding sky color.\u003cbr /\>\u003cbr /\>(Answered by Sean Potter, a certified consulting meteorologist and\u003cbr /\>science writer in Washington, D.C., June 12, 2005)\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>\u003cbr /\>---------------------------\u003cbr /\>\u003cbr /\>\u003ca onclick\u003d\"return top.js.OpenExtLink(window,event,this)\" href\u003d\"http://www.usatoday.com/weather/resources/askjack/wasksky.htm\" target\u003d_blank\>http://www.usatoday.com\u003cwbr /\>/weather/resources/askjack\u003cwbr /\>/wasksky.htm\u003c/a\>\u003cbr /\>\u003cbr /\>Q: What does a red moon signify? Perhaps a change in the weather?\u003cbr /\>\u003cbr /\>A: A red moon means there is a high concentration of particles in the\u003cbr /\>air, such as dust and smoke. These particles “scatter” away the short\u003cbr /\>and intermediate wavelengths of light (violet, blue and yellow), leaving\u003cbr /\>only the longer wavelengths (orange and red) to reach our eyes. A red\u003cbr /\>moon does not mean there is a change coming in the weather.\u003cbr /\>\u003cbr /\>See our page on optical phenomena for more information.\u003cbr /\>\u003cbr /\>(Answered by meteorologist Dennis Feltgen, National Weather Service,\u003cbr /\>Silver Spring, Md., April 26, 2006)\u003cbr /\>\u003cbr /\>\u003cbr /\>Q: What causes a red moon?\u003cbr /\>\u003cbr /\>A: The same process that brings colorful sunsets – when the Earth’s\u003cbr /\>atmosphere filters out the blue end of the sun’s visible light – causes\u003cbr /\>the moon to appear red or orange when near the horizon. The most\u003cbr /\>breathtaking red moons occur during a total lunar eclipse, when the moon\u003cbr /\>passes through the Earth’s shadow. Again, the scattering of the blue end\u003cbr /\>of the visible light spectrum allows the red end of the spectrum to\u003cbr /\>illuminate the eclipsing moon.\u003cbr /\>\u003cbr /\>Without the Earth’s atmosphere, the moon would look much different to us\u003cbr /\>during a lunar eclipse. While some sunlight would still reach the moon,\u003cbr /\>it would be much dimmer and it wouldn’t appear red or orange.\u003cbr /\>\u003cbr /\>(Answered by Bob Swanson, USA Today\'s assistant weather editor, July 4,\u003cbr /\>2005)\u003cbr /\>\u003c/div\>",0] ); //-->event. The 1883 eruption of Krakatoa in Indonesia, for example, may have
created the brilliant red and orange sunsets that were the inspiration
for Edvard Munch's painting, "The Scream."

For more, see our graphic on what gives the sky its color and our page
on understanding sky color.

(Answered by Sean Potter, a certified consulting meteorologist and
science writer in Washington, D.C., June 12, 2005)