Skip to main content
Why is the sky blue?

Why is the sky blue?

Did you ever ask yourself why the sky is blue? Here is what you need to know:

The color of the sky is a result of a phenomenon called Rayleigh scattering.

  • Sunlight is composed of different colors of light, each with its own wavelength - just think of Pink Floyds album cover for The Dark Side of the Moon or the Rainbow flag. These colors include red, orange, yellow, green, blue, indigo, and violet, with red having the longest wavelength and violet having the shortest.
  • When sunlight enters Earth’s atmosphere, it interacts with tiny particles and molecules, such as nitrogen and oxygen — just the stuff you find in the atmosphere. These particles are much smaller than the wavelength of visible light, making them in-visible.
  • Rayleigh scattering occurs when these small particles scatter sunlight in all directions. However, shorter wavelengths of light, such as blue and violet, are scattered more effectively than longer wavelengths like red and yellow.
  • This leads to blue and violet light being scattered in all directions, resulting into the blue light that we see when we look at the sky from down here.
  • The human eye is more sensitive to blue light, which is why we perceive the sky as blue during the day.
  • When the sun then goes down, the light travels in a larger angle through the atmosphere, making us see more colors.

To keep it short: the sky appears blue because of the scattering of sunlight by atmospheric particles, with shorter blue wavelengths being scattered more than longer wavelengths. And we humans are just not evolved enough to see more than just blue in that case.

By the way, I am now on BlueSky, too. The link to my profile there replaced the link to another former social network I am not frequenting anymore, now. Because they still have no logo (it seems) I am doing what they are doing themself and use a filled square as logo :) see you “in the sky”!

Back to top
Back Forward