Angela Smith, age 10, of Tucson, Arizona, for her question:

Exactly how many miles is it to the moon?

Around Apollo time, this is one of the questions that drive us all to distraction. The TV, the news reports and other authorities keep on telling us that the astronauts exploring the lunar landscape are 240,000 miles from the earth. This figure does not agree with other reliable authorities    who tell us that the distance of the moon is 238,840 miles. Perhaps the news reporters prefer a nice round figure of 240,000 and don't mind sacrificing 1,160 miles.

Actually this is not the whole story. Our own reliable authorities are careful to tell us that 238,840 miles is the average distance to the moon. This would be the correct mileage    if the orbiting moon stayed at the same distance from the earth. But the dizzy satellite does not do this. Its orbit is not a perfect circle. Sometimes it swings closer and sometimes farther away. Its closest distance is 221,593 miles; its greatest distance is 252,948 miles. Its middle distance may be a nice round 240,000 miles    but its true average distance is 238,840 miles.