Thomas Vera, age 10, of Long Island City, New York, for his question:

How can space be black when the sun is so bright?

An astronaut sees the sky as velvety black, with an even more dazzling sun and spattered with even more brilliant stars. That is, if he happens to be viewing the heavens from above the earth's atmosphere. From the ground, we can see the sky only through the air that reaches many hundreds of miles above our heads. We get only a veiled view of the sky as it really is.

Air, of course, is made from free floating molecules. They are widely separated but each is a tiny particle of matter. And the airy shell of atmosphere is very, very deep.

Altogether, they spread a hazy film over the true sky. What's more, the tiny particles play tricks on the sunbeams on their way down to the ground. They chip off their blue rays and scatter them in every direction. This is why the sky is blue when we look up from the ground.

Above the atmosphere, there are no airy molecules to screen or play tricks on the light of the sun. Out in space, the sky takes on its true color of velvety black.