Why is the sky blue?
It's something we all take for granted.
But there's some amazing science at work
in the skies up above us
that we can actually repeat at home.
Ask any child to draw a picture
of the sun and sky,
and they'll draw a beautiful yellow sun
surrounded by a wonderful blue sky.
But viewed from space,
the sun is actually white,
and it's surrounded by black.
The same should be true here on Earth.
So what's going on?
Well, it's all to do with how the light
coming from the sun
interacts with the gases in our atmosphere.
As light passes through our atmosphere,
it will bounce off the gas particles,
and it will be scattered
all in different directions.
We call this Rayleigh scattering.
What's interesting is the higher frequencies of light,
the blue light,
gets scattered more than the lower
frequencies of light, the red light.
And it's the scattered blue light
that lights up our sky
and hence we get a blue sky.
Now, with this blue light missing,
the sun appears yellow.
As the sun gets lower on the horizon,
all of the blue light and the green light
gets scattered away,
leaving only the red part.
This is why the sun appears red at sunset.
What's interesting
is that you can recreate this at home.
If we fill a container with water
and shine a lamp from the opposite side,
you should be able to see the lamp clearly
all the way through.
Now, if we add some milk,
the fat particles
act just like the gases in our atmosphere,
scattering away the blue frequencies of light.
The more milk we add,
the more scattering will occur
until we can see that the lamp has turned red
just like a sunset.
