Sky Colors: Why Is the Sky Blue?

If you look at a glass of water, it’s clear. If you look at the air around you, it’s also clear. So why, when we look up at a big stack of air, does it look bright blue? For thousands of years, people thought the sky was blue because it reflected the ocean, but the truth is much more 'electrifying.'

To solve this riddle, we have to remember that sunlight is actually a mixture of all the colors of the rainbow. Each color travels as a wave. Red light travels in long, lazy waves, while blue and violet light travel in short, choppy, energetic waves.

As sunlight enters our atmosphere, it hits the gas molecules (like nitrogen and oxygen) that make up our air. These molecules are the perfect size to get in the way of the short, choppy blue waves. When the blue light hits a molecule, it 'scatters'—it bounces off in every single direction like a pinball.