A question for me!
Dear Ms. Readwell,
Why is the sky blue?
signed, Brown-eyed girl.
Dear brown-eyed girl,
I bet your parents hate this question.
Why is the sky blue.
You know, A BETTER QUESTION might be - why
is ANYTHING blue?
Why is anything the colour that it is?
Why is my hair brown?
Why is my shirt grey?
It’s because that’s the one colour that
is reflected back at you.
You know light looks white, right, like say,
a lightbulb looks like it’s giving off white
light, but really, that white light is made
of LOTS of different colours, like a rainbow.
You can see this for yourself by shining light
through a prism - that splits the white light
into all its separate colours.
The colours of light move like waves.
Some light waves move with a longer wavelength
- red is on the longer end, then the wavelengths
get shorter and shorter.
Orange, Yellow, Green, shorter and shorter.
Blue is one of the shortest.
Bzzzt.
Blue.
{hand motion to show short blue wavelength}
Okay, so imagine all those different colours
speeding through the air and bouncing against
my shirt.
The shape of the dye or pigment molecules
in my shirt are JUST the right shape to scatter
mainly this certain colour of light back directly
in the opposite direction.
In this case, GREY.
The same thing is going on in the sky.
There are lots of little particles in the
sky - we call the layer of stuff hugging the
earth the ATMOSPHERE.
It’s mostly made of molecules of oxygen
and nitrogen, which are really tiny particles.
When light hits the particles of the atmosphere,
the wavelength of light that’s small enough
to run into those tiny particles is blue,
for the most part.
So the colour of light that’s scattered
around in the sky is mostly blue.
So the colour that eventually bounces right
back at you, into your EYE, is BLUE.
Well, there’s one wavelength that’s even
smaller, so technically the sky is that colour
too.
The end of the rainbow is violet, right?
Why doesn’t the sky look violet?
Our eye doesn’t sense violet as well as
it senses blue.
Probably to some animals with better vision,
the sky looks blue and violet.
But to us, the sky only looks blue.
Now.
Who else has a question?
