|CALIFORNIA RED—Photographed by Pillar to Post contributor Phyllis Shess taken on the highway between Blythe, CA and 29 Palms, CA, September, 2015. Images on this posting were from sources other than National Geographic magazine.|
What makes the sky so red or orange or both at sunset? For an answer we read a terrific explanation by meteorologist Stephen Corfidi, who was interviewed by National Geographic magazine’s Amanda Fiegl, in her article “Red sky at night: The Science of Sunsets.”
Q: Do dust and air pollution make sunsets more dramatic?
A: No, you often hear that, but—assuming you mean typical pollution in the lower atmosphere—it's a myth. It's actually the opposite: Large particles in the lower atmosphere tend to mute and muddy the colors because they absorb more light and scatter all the wavelengths more or less equally, so you don't get that dramatic filtering effect. In areas with a lot of haze, you don't typically see the types of sunsets that are likely to appear on a wall calendar—or in, say, National Geographic.
Q: Okay, so let's talk about the typical Earthling's perspective. Why do we see more orange and red colors in the sky during sunrise and sunset than we do at other times of day?
A: When a beam of sunlight strikes a molecule in the atmosphere, what's called "scattering" occurs, sending some of the light's wavelengths off in different directions. This happens millions of times before that beam gets to your eyeball at sunset.
The two main molecules in air, oxygen and nitrogen, are very small compared to the wavelengths of the incoming sunlight—about a thousand times smaller. That means that they preferentially scatter the shortest wavelengths, which are the blues and purples. Basically, that's why the daytime sky is blue. The daytime sky would actually look purple to humans were it not for the fact that the sensitivity of our eyes peaks in the middle [green] part of the spectrum—that is, closer to blue than to purple.
But at sunset, the light takes a much longer path through the atmosphere to your eye than it did at noon, when the sun was right overhead. And that is enough to make a big difference as far as our human eyes are concerned. It means that much of the blue has scattered out long before the light reaches us. The blues could be somewhere over the West Coast, leaving a disproportionate amount of oranges and reds as that beam of light hits the East Coast.
For the rest of Amanda’s interviews go to the following address and learn why butterflies and reindeer see sunsets different than humans:
MORE ORANGE SKIES:
MORE ORANGE SKIES:
DAILY ABSTRACTS—Sunsets combined with clouds give skywatchers daily abstract paintings to admire. In this scene Mother Nature has painted a version of North and South America.
|Thank you and Amen.|
|PHONE IN--Just when Phyllis Shess decided to buy a camera to replace the one she lost in Madrid, then her android phone captures an image like the one above off of Punta Razza, Florida. November 2015.|
DAWN’S A YAWN compared with the sheer brilliance of sunsets as noted in this image of day break in Cienfuegos, Cuba, April 2015. Image by Pillar to Post contributor Mike Shess.