Friends, have you ever looked at the sky and wondered why the sky always looks blue? And the same sky appears red-brown at dusk. What is the true color of the sky? Why does this happen? Find out in this blog.

Why is the sky blue?

When sunlight reaches Earth’s atmosphere, it is scattered or refracted by small molecules of gases (mostly nitrogen and oxygen) in the air. Because these molecules are much shorter than the wavelength of visible light, the amount of scattering depends on the wavelength.

Shorter wavelengths (violet and blue) are scattered most strongly, so blue light is reflected more toward our eyes than other colors. You might wonder why the sky doesn’t appear purple because violet light is scattered even more strongly than blue. This is because sunlight is not purple to begin with and our eyes are more sensitive to blue.

The blue light that gives the sky its color is bright enough that all the stars we see at night disappear because the light they emit is so dim.

Is the sky blue on other planets too?

It all depends on what’s in the environment! For example, Mars has a very thin atmosphere composed of carbon dioxide and filled with fine dust particles. These microscopic particles scatter light differently than gases and particles in Earth’s atmosphere.

Photos from NASA’s rovers and landers on Mars have shown us that sunsets are the exact opposite of what you experience on Earth. During the day, the Martian sky takes on an orange or reddish hue. But as the sun sets, the sky around the sun begins to take on a blue-grey tone.

What causes a red sunset?

As the sun falls lower in the sky, its light passes through more of the atmosphere to reach you. More blue light is scattered, allowing red and yellow to pass directly through your eyes.