Do You Know Why the Sky Is Blue?

Why is the sky blue? It’s the one question BL readers ask more than any other.

The short answer is that the sky is blue due to the Earth’s atmosphere and the way it reflects the sun’s light.

But that’s not good enough, so let’s dig a little deeper.

First, you should know that the Sun’s light is made up of all the seven colors of the rainbow: Red, Orange, Yellow, Green, Blue, Indigo and Violet (You know, Roy G. Biv). Those colors of lights travel in waves, each of different size and frequency.

Typically, all light travels in somewhat straight line, unless something gets in it’s way. Like a mirror or prism. Or in the case of the Earth’s atmosphere, molecules and gas.

Sunlight reaches Earth’s atmosphere and is scattered in all directions by all the gases and particles in the air. The blue light is scattered more than the other colors because it travels in shorter, smaller waves. So, we see more blue light in the sky than any other color, making the sky look blue.

But what about sunset, when the sky or orange or red or purple? Great question.

As the Sun gets lower in the sky, its light passes through more of our atmosphere to reach us. So, even more of the blue light is scattered, which allows the reds and yellows to pass straight through to our eyes.

Still confused? Take a look at this video explanation:

Have a better grasp on the the whole “Why is the sky Blue” question?

If not, never hesitate to ask us more. Send us a question about the sun, the sky or anything else you can think of in the “Ask Us Anything” box to the right.


  1. Huh. So purple comes through too, not just blue, but our eyes just can’t see it because we’re more sensitive to blue. Well, a purple sky would be wierd, wouldn’t it? But not a purple bird! 🙂 Peechtival!

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