Why Is the Sky Blue? A Simple Explanation

(Last Updated On: July 9, 2018)

Why Is the Sky Blue?
Have you ever looked up and wondered how the sky earned its azure shade? Why that color? Why is the sky blue? The next time you’re lying on the grass and staring up at the sky, here are some things to consider:

Why Is the Sky Blue? Let’s Talk About Light

Simply put, the sky is blue because of the way the Earth’s atmosphere interacts with sunlight.

Though sunlight appears white to the human eye, it’s actually a blend of every color of the rainbow. Each of these colors has its own respective wavelength. Violet has the shortest wavelength, while red has the longest. Blue light waves are slightly longer than violet waves.

All light travels on a straight path until it hits something, where it then proceeds to reflect it, bend it, or scatter it. When we see an object of a certain color, we’re actually seeing the light of that color’s wavelength being reflected off of it. Knowing this, you may start seeing things through a whole new perspective!

When sunlight filters through the atmosphere, it bounces off the oxygen and nitrogen molecules and is scattered in all directions. Since blue travels as shorter, smaller waves with higher frequencies, it is scattered more than any other color.

It’s that scattering that leads to why we see the sky as blue – most of the time.

What About the Sky’s Other Colors?

As we travel closer to the horizon, the sky continues to fade until it’s nearly white. At this point, the atmosphere’s air molecules have scattered the blue light multiple times, and in many directions.

It also explains why the sky is predominately red and yellow during a sunset. As the sun gets lower in the sky, it scatters even more of this blue light. This allows other wavelengths to pass easily through the atmosphere with minimal scattering, making it easier for reds and yellows to filter through.

Fun fact: Since violet light has the shortest waves, it is actually scattered more widely than blue. However, since human eyes are more sensitive to blue light than violet, the sky appears blue to us. Now, the next time someone says that you see the world through rose-colored glasses, you’ll be prepared to school them on the science of color and the true answer to the mysterious question, “why is the sky blue?”

Speaking of color, do you know the color of the universe? Yes, the universe has its own color. Click here to find out what that color is.

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