Dwayne Savage, age 12, of Warsaw, N.C., for his question:

WHY DOES THE MOON LOOK LARGER AS IT RISES?

When you see a full moon low in the sky, it appears to be much larger than when it is high in the heavens.

We all know that the moon is always the same size and always about the same distance from the earth. It appears to be larger at the horizon due to a simple trick of the mind. This trick of the mind on our sight is called an optical illusion.

When the moon is at the horizon, far off trees and buildings are outlined against it. To our minds, these familiar objects provide yardstick by which size can be judged. The moon seems huge because rit dwarfs whole buildings and tall trees.

Later, when the moon is high in the sky, we compare it with nearby objects. We see the moon overhead blotted out by the branches of a single tree. Our minds tell us then that the moon is small.