## Why Is the Sky Blue? | Physics for Kids

Do you ever lie on your back outside on a sunny day?

There’s so much to see!

There are birds, and airplanes, and maybe even clouds, all way up in a pretty blue sky.

But why is the sky blue?

Why not green, or red, or any other color?

It all starts with light from our big, bright sun.

Now, it may not /look/ like it, but the light from the sun is made of all of the colors

of the rainbow.

And you might already know that it takes /many/ colors to make up a rainbow — red, orange,

yellow, green, blue, and violet!

All of the colors of the rainbow are in sunlight, /all/ of the time.

It’s just that they’re all mixed together, so we don’t see them /most/ of the time!

It’s kind of like when you’re painting and you mix together all the colors.

With paint, mixing all the colors makes brown, but when you mix together all the colors of

light, you get white light.

You can actually see the different colors in light sometimes!

One way to do it is by using a special tool called a prism, which is usually just a specially-shaped

piece of glass or plastic.

But you can even make a prism out of a glass of water!

Prisms bend light in a special way, so that we can see all of the colors that make up

light.

Say that I shine a bright flashlight into a prism.

The rays of light move in a straight line away from the flashlight.

When the light hits the prism, it separates into lots of different colors, and we have

a rainbow.

So, the light is white when it moves in a straight line until it hits the prism.

Then, it bends, and we can see colors.

That’s a little like what happens to the light from the sun.

Rays of light leave the sun in a straight line, too, as they move through outer space.

They stay in a straight line until they reach the layer of air that surrounds the Earth.

Now, the air around the Earth is made of tiny little particles, or pieces, that we can’t

see.

But they’re there!

If you try moving your hand back and forth really quickly through the air, you’ll feel

the air moving past your hand.

What you’re really feeling is all those little particles!

When the rays of light hit these tiny particles of air, they don’t just bend, like they

did when they hit the prism.

The light rays scatter, meaning that they go off in lots of directions, and bounce around.

And here’s the cool thing — some of the colors scatter more than others.

What color do you think scatters more?

[Squeaks guesses]

Right you are, Squeaks!

Blue!

Blue is one of the colors of light that scatters the most!

So, as light from the sun moves into the air that’s way high up, the blue-colored light

bounces all over the place in the sky.

So when we look up, our eyes see a lovely blue sky.

But a lot has to happen to turn it blue!

So the next time you’re outside, don’t forget to look up.

You never know what you might see!

Thanks for joining us for this episode of SciShow Kids!

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