Why is the sky blue?
I don’t suppose you happen to know Why the sky is blue? It’s because
the snow Takes out the white. That leaves it clean For the trees and
grass to take out the green. Then pears and bananas start to mellow And
bit by bit they take out the yellow. The sunsets, of course, take out
the red And pour it into the ocean bed Or behind the mountains in the
west.
You take all that out and the rest Couldn’t be anything else but blue.
—Look for yourself. You can see it’s true.
[Why the Sky Is Blue]{.smallcaps} John Ciardi
This is a fun way to explain why the sky is blue, but it isn’t true, of
course. The sky really gets its color from the sunlight passing through
the air.
Sunlight contains all the colors of the rainbow. These colors are
scattered as the sunlight passes through the molecules of gas that form
the air. On a clear day, when the sun is high in the sky, blue is
scattered most of all. It is reflected into your eyes from all parts of
the sky. So, the sky looks blue.
But at sunrise and sunset, the sun appears low in the sky. Its light
passes through particles of smoke and dust close to the ground. These
particles scatter all the colors except red and orange. So, the sun
looks like a big orange-red ball. The red and orange reflect off the
bottoms of low clouds and make the sky look red or pink.
