Kevin Parker, age 9, of Utica, N.Y., for his question:

WHAT IS A MIRAGE?

When you're driving along the highway on a warm day, sometimes you can see ahead on the paved road something that looks like a distant pool of water. People on hot deserts often think they are seeing lakes where there is only flat sand. Both are mirages. The word mirage comes from a Latin word meaning to look at.

All mirages are caused by hot air near the surface of the earth that bends or refracts light rays from the sky toward our eyes. on the highway we are actually seeing part of the sky on the road ahead of us. Rays of light from the sky hit the hot air layers just above the pavement and are then refracted along our line of vision. Presto, we have a mirage. Because mirages are actual rays of light, they can be photographed.