Wayne Guard, age i7, of Peterborough, Ont., Canada, for his question:

Who first measured the distance of the moon from the earth?

Astronomers have known the accurate distance of the moan from us for more than i800 years. Pythagoras gave the ancient world a Bystem of mathematics, and in the third century B.C. Ar3.starchus Of greece used pythagorean methods t0 compare the distances of the sun and the moon. However, his figures were not accurate.

In the next century, Hipparchus of Alexandria worked on the same problem and figured the distance of the moon from the earth to within an accuracy of l%. His error was corrected in 140 A.D. by the great astronomer Ptolomy, who also did his work in the famous school founded by Euclid at Alexandria. The eccentric orbit of the moon, and therefore its distance, is highly complex. The ancient scholars used only the simplest instruments and relied mostly on logical brainwork to solve their problems.