At sunrise and sunset, the Sun is very low in the sky, which means that the sunlight we see has travelled through a much thicker amount of atmosphere. Because blue light is scattered more strongly by the atmosphere, it tends to be scattered several times and deflected away in other directions before it gets to us. This means that there is relatively more yellow and red light left for us to see.
The diagram below shows that at midday, light has less atmosphere to travel through. Reaching Earth's atmosphere, it is scattered in all directions, therefore we see blue sunlight. Blue is scattered more than other colours because it travels as shorter, smaller waves. Sunlight encounters more air molecules when the sun is low in the sky than when the sun is overhead.
Even more blue light is scattered away, leaving mostly the reddish component of white sunlight to travel the straighter path to your eyes. So the setting sun looks red. Your Info Source. English Deutsch. Why is the sun red at sunset? Rage, rage against the dying of the light.
The scarlet skies inspired many viewers to grab their cameras , and prompted a question: Why are some sunsets so spectacular, and others a mere muddle? I guess it depends on how you define "good," but I'm going to assume you mean a strikingly colorful one, where the colors are spectrally pure—say, vivid orange or red—as opposed to a more muted palette. Keep in mind that what we see with our human eyes is just a tiny part of the electromagnetic radiation that's given off by the sun.
That radiation contains a wide spectrum of wavelengths, but your eyes are only sensitive to certain parts of it: the so-called visible wavelengths. Different colors are associated with different wavelengths. And depending on what happened to the light before it got to you, some of those visible wavelengths don't even reach your eye. Portions of it are absorbed and filtered out in the atmosphere. So really, there's a good sunset every night; we just can't always see it from the ground.
You may have noticed this if you've ever taken off in an airplane at sunset. It might not look like anything special from the ground, just a whitish-pink sky, because you're still within the atmosphere's "boundary layer.
But as the plane gets above the boundary layer, into cleaner air, suddenly the sunset looks very vivid. It's all a matter of perspective. 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? 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. So the same ray of sunlight is hitting people in both the Rockies and the Appalachians? Basically, the East gets the West's leftovers at sunset? Yes, I think a lot of people don't realize that. Everything is connected. And as humans, we like to think color is concrete: "Oh, that's a blue sky," or "That's a brown table.
Absolutes don't really exist in color perception. It's rather disquieting when really you start thinking about it!
0コメント