Why is the sky blue short answer

Why is the sky blue?

There is a physical explanation and a psychological explanation for this.

The physicist is concerned with the scattering of light: sunlight has to pass through the atmosphere to reach Earth. In turn, the atmosphere is filled with all kinds of gas molecules.

When sunlight hits these tiny particles, it gets scattered, that is, deflected. At the same time, white light breaks down into its components like a prism.

So it is divided into the colors of the rainbow: blue, green, yellow, orange, red. Different colors are spread apart. The shorter the wavelength, the stronger the propagation, or in other words, the more energetic the rays.

Now blue rays are more energetic than red rays. Hence the components of blue light are more strongly deflected during diffusion. Let us now imagine a cloudless sky.

Somewhere in this sky is the sun; It ranges from white to yellow, in any case quite bright, but it shines in all directions, not only in our eyes, but also in the rest of the environment.

Some of these rays are then scattered so intensely in the atmosphere that they are directed back in our direction, that is, they hit our eyes.

But these are only highly scattered light rays, that is, the bluest part. On the other hand, red light rays are not deflected as much, meaning they no longer reach us.

So the sky is blue because only the blue light rays are scattered and deflected so strongly 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 don’t differentiate between green and blue, but they only have one word for it.

It can be assumed that these people do not see green and blue as two different colors, but as different shades of the same color.

And there are also languages that have only three color words, namely black, white and red, so black and white are roughly synonymous with dark or light.

And if you ask the people of this linguistic region what color the sky is, for them the sky is mostly dark, sometimes light and maybe red in the evening.

But they don’t know about the “blue” sky, because they don’t have a word for blue and apparently they don’t even understand blue as an independent color. In this sense, language actually shapes perception.

short answer:

The sky appears blue during the day because sunlight is scattered primarily by nitrogen and oxygen molecules in the Earth’s atmosphere into short wave blue light.


The Sun gives off light that travels through the atmosphere in waves. If you look at the rays of light in their entirety, that is, if you look directly at the Sun, they appear yellowish-white.

On the other hand, the color of the sky is formed by the diffused light that is deflected towards us by the gas molecules in the Earth’s atmosphere. Mainly from nitrogen and oxygen.

The distance traveled by light changes depending on the position of the Sun. During the day, when the sun is high, the road is relatively short for us.

This means that shortwave blue light is mainly scattered by the color light spectrum.

  • Light is scattered by gas molecules in the atmosphere.
  • Light is scattered by gas molecules in the atmosphere. Photo: Lucas Bohl / Pictochart
  • During twilight, when the sun is low, the path is longer for us and the light appears red to orange.

The colors change at sunset.

The colors change at sunset.

The fact that we also know why the sky is blue is due to the Englishman John Strutt, 3rd Baron Rayleigh. He discovered the phenomenon of light scattering in the atmosphere, which is why he got its name: Rayleigh scattering.

What does this mean in detail?

When light passes through the atmosphere, it causes the electrically charged particles (protons and electrons) of the air molecules to vibrate.

The particles then generate electromagnetic radiation at the same frequency as light rays, which distributes the light in different directions: diffusion.

there is blue light

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