Atmospheric Science Why is the sky blue

Why is the sky blue?

There is a physical explanation and a psychological explanation for this. The physical has to do with the scattering of light: The sunlight has to pass through the atmosphere on its way to the earth. The atmosphere, in turn, is full of all sorts of gas molecules. When sunlight hits these small particles, it is scattered, i.e. deflected. At the same time, the white light is broken down into its components, like a prism. So it is split up into the rainbow colors: blue, green, yellow, orange, red. The different colors are scattered differently. The smaller the wavelength, the stronger the scattering, or in other words, the more energetic the rays are.

Now blue rays are more energetic than red ones. The blue light components are therefore deflected much more strongly during the scattering. Now let's imagine a cloudless sky. The sun is somewhere in this sky; it is white to yellow, in any case quite bright. But it shines in all directions, not only into our eyes, but also into the rest of the atmosphere. Some of these rays are then scattered so strongly in the atmosphere that they are directed back in our direction, i.e. hit our eyes. But these are only the heavily scattered light rays, i.e. the more blue parts. The red light rays, on the other hand, are not deflected as much, that is, they no longer reach us. So the sky is blue because only the blue rays of light are so strongly scattered and deflected that they hit our eyes.

And the psychological explanation?

The sky also appears blue to us because we have our own word for the color blue. Linguistics tells us: There are languages ​​in the world that do not differentiate between green and blue, but only have one word for it. It can be assumed that these people also do not perceive green and blue as two different colors, but rather as different shades of one hue.

And there are even languages ​​that only have three color words, namely black, white and red - whereby black and white are more or less synonymous with dark or light. And if you ask people in this language area what color the sky is, then For them the sky is mostly dark, occasionally light and in the evening maybe red. But they don't know a “blue” sky because they don't have a word for blue and apparently don't perceive blue as an independent color either. In this sense, language actually shapes perception.

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