Because of the extremely small size of visible light waves less than one millionth of a meter , these light waves also interact the tiny gas molecules that make up the air itself. The light waves bounce off these particles just like you might bounce and get jostled in a busy hallway. As the light waves bounce in lots of different directions, we say they have been scattered.
How light waves get scattered depends strongly on the size of the particle compared with the wavelength of the light. Particles that are small compared with the light wavelength scatter blue light more strongly than red light. Within the visible range of light, red light waves are scattered the least by atmospheric gas molecules. So at sunrise and sunset, when the sunlight travels a long path through the atmosphere to reach our eyes, the blue light has been mostly removed, leaving mostly red and yellow light remaining.
The result is that the sunlight takes on an orange or red cast, which we can see reflected from clouds or other objects as a colorful sunset or sunrise. Large particles of pollution or dust scatter light in a way that changes much less for different colors. The result is that a dusty or polluted sky is usually more grayish white than blue.
I guess it's a question of who cares—maybe filmmakers or photographers would find that information useful, but most people just want to know if it's going to rain or not. There's often a slanting band of clouds on the back side of the departing weather system, and that can act as a sort of projection screen for the low-sun colors, better than a horizontal band would.
The slant means it captures more of the orange and red light, and if the cloud is thin enough, it will reflect those colors down to you. Also, storms wash a lot of the big particles out of the air. Yes, true sunset occurs a minute or so before you see the sun disappear. What you see is a kind of mirage; the light is getting bent around the horizon by the effect of refraction. Our eyes are sensitive to a very tiny part of the spectrum of the sun's wavelengths, and that's responsible for the way we see our environment.
Other creatures seem able to see the ultraviolet area of the spectrum. We can only see a tiny part of what's going on. So a butterfly or a reindeer , which can perceive ultraviolet light, might be seeing a different, perhaps more colorful sunset than we do? The more you look at things, the more you realize how unique your own experience is as a human on this planet, at this particular place and time.
All rights reserved. In simple terms, what makes a good sunset happen? Do dust and air pollution make sunsets more dramatic? Do the seasons affect sunsets? So conversely, could local weather forecasters predict a pretty sunset? Why are sunsets sometimes more dramatic after a major storm? Is it true that by the time we see a sunset, the sun is actually already gone?
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Materials provided by University of Wisconsin - Madison. Note: Content may be edited for style and length. Science News. Scattering also explains the colors of the sunrise and sunset, Ackerman says. ScienceDaily, 15 November University of Wisconsin - Madison. Retrieved November 10, from www.
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