Tony Fava, age 8, of Santa Maria, Calif., for his question:

What is a light year in space?

Our lovely little world is in a great ocean of space that goes on and on forever. It is populated with other worlds, countless stars and vast clusters of stars. Naturally our scientists wanted to measure how far it is to the next star, the next and the next. But the distances in outer space are enormous. A million earth miles is just a tiny, tiny step in the vast ocean of space. So they invented the light year. And one light year is about as long as six trillion ordinary miles.

The fastest traveler in the universe is a beam of light. It whips along at about 186,282 miles a second    which is about seven million miles per hour. In a year it travels about six million million miles. And this is the length of one light year. Out there in space, the nearest stars are more than four light years from the earth. This means that their light beams take more than four years to reach us.