So, why is the sky blue?
The sun is a nice yellow-white.
But don't look directly into it, that is bad for your eyes.
As you may know, white is really all colours together.
You can see that with a rainbow, for example,
where the light gets split by raindrops.
Now, if light goes through air,
sometimes a ray of light gets send in a direction it wasn't going at first.
We call this scattering.
Blue light scatters a lot more than red.
The more to the inside of a rainbow a colour is, the more it scatters.
All colours scatter, but blue scatters more, so we see the sky as blue.
When the sun is really low in the morning or evening,
part of the sky can look red or yellow.
That's because light has to go through a lot of air.
Then all the blue scatters away before it gets to your eye, and you're left with red and yellow.
What happens if there is no air to scatter the light?
Well, then it looks black.
This is a photo taken on the moon.
On the moon, there is no air, so the sky is black, even when it's day.
So that, my dear viewers, is why the sky is blue.
Hope you enjoyed the video.
But wait a moment!
The colour of the inside of the rainbow isn't blue.
It is violet, which most people call purple.
So, why isn't the sky purple?
I first read this question in this comic by Randall Munroe, a few years ago.
And the answer I have is in two parts:
First, there just isn't that much violet in sunlight.
That's just how the sun is.
And second, our eyes are a lot better at seeing blue than they are at violet.
So if you put those together, well, that's why the sky is blue, and not purple.
Bye!
