Name: Beautiful Science - The sky IS NOT BLUE.
Uploaded: 2025-06-18T17:59:41.000Z
Duration: 2 min 45 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Have you ever wondered why the sky above us is blue, and not red or green or even polka dot pink and brown?

Well, it has to do with the combination of light and how we perceive color.

Visible light is a small part of the electromagnetic spectrum, a form of energy waves that range in frequencies from longer radio waves to shorter gamma rays.

These waves are all around us, but our eyes can only see a certain section of this we call the visible light spectrum.

The waves in the visible light spectrum define how humans perceive color.

There are actually seven colors in the form of waves that combine to make this white light.

These are the same as the colors of the rainbow, red, orange, yellow, green, blue, indigo, and violet.

You can test this yourself by shining light through a prism.

These colors all have different wavelengths, red being the longest through to violet, which is the shortest.

All the color wavelengths travel in a straight line at the speed of light from the sun towards us on the earth.

When the light gets to earth, a small percentage of the waves hit the gases and particles in the atmosphere, mainly oxygen and nitrogen.

The shorter the wavelengths, the more likely they are to hit a particle and scatter.

This scattering is called Rayleigh scattering.

Red is more likely to pass by the particles, whereas blue is more likely to scatter.

Blue wavelengths are in fact 16 times more likely to scatter in the atmosphere than red wavelengths.

So when you are looking up at the sky, it is millions of these scattered blue waves reaching your eyes that you are seeing.

But doesn't indigo scatter more than blue?

And violet scatter even more than indigo, meaning the sky should appear violet?

Yes, violet does in fact scatter the most, but our eyes are adapted to see the colors in the middle of the light spectrum more clearly than the outer colors, meaning that we see blue a lot easier than indigo and violet.

If you were to use a prism or see a rainbow, you will notice the central colors are a lot more visible and vibrant.

This means our eyes pick up the blue scattering more than indigo and violet, and the reason the sky appears blue.

So there you go, that is why the sky is blue.

You might now be interested in knowing why then sunsets are not blue, but hues of red, orange and yellow.

Watch on our video here on it to find out.

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