Cindy Sversa, age 9, o,f Plainfield, N.J., for her question:

WHY DO STARS TWINKLE?

You've all said the old rhyme that goes: Twinkle, twinkle, little star, how I wonder what you are. And you've all seen what appears to be twinkling stars in the sky. But the stars do not twinkle. If you could get above the earth's atmosphere, you'd see they all shine with clear and steady light. Twinkling is caused by the light passing through the earth's atmosphere where there are differences in air temperature. Some layers of air are hotter than others, and one layer is usually swirling and moving through another. These various layers bend the starlight in different ways and at different angles, making it unsteady. And the light appears to twinkle.