There is probably no writer today who is so successful in translating scientific facts and terms into language the average reader, with even a dim interest in the subject, can read. Here he traces for early teens the story of how the secrets of our own planet in relation to the Moon were probed. He goes back to the Greeks, bringing their inquiries down to the great contribution made by Ptolemy; goes on to the Arabs- and then the Western Europeans, with Marco Polo, Christopher Columbus and Magellan. Try to go back to the assumptions that the earth was fixed and forward to the contributions made by today's space science, and you'll realize what a span of intellectual development Mr. Asimov has achieved. He has high pointed his story with names of men who contributed largely to this growth: Galileo, Newton, Cavendish; and with significant advances and turning points relating to what is under the earth, what is outside the earth's crust, what outer space signifies to better comprehension of our role in the system. With the Soviet achievement in photographing the other side of the Moon, this sort of information is vital to every inquiring mind.