Thomas Wiendt, age 9, of Detroit, Michigan, for his question:

Why is the sky blue?

The filmy air is all around us and it reaches hundreds of miles above our hems. Up beyond the air is the vastness of empty space, when we look up towards the sky, we are looking out towards empty space:. But we are looking through the filmy blanket of air which surrounds the earth.

The air may seem like nothing at all. We cannot see it or smell it and we only feel it when it blows. But actually it is made of tiny particles ‑molecules of gases, smoke and dust. These tiny particles play tricks with the sunbeams. For sunlight must pass through the blanket of air on its way to the ground.

Sunlight, like air seems to be nothing at all with no color at all, it can fool you. For it is really a sort of skein of rays colored like the rainbow. The colored rays travel in waves, each traveling with waves of a certain size. The blue rays travel on shorter wave lengths and the red rays travel on the longest wave lengths.

The tiny particles of the air tend to bend off the rays with short wave lengths and scatter them from the skein of blended white sunlight. These are the blue rays, scattered all over the sky to make it look blue.