Ever since early stargazers discovered that some heavenly bodies wandered among the others, people have been fascinated by the planets. Kepler calculated their orbits from naked-eye observations; Galileo's telescope made it possible to discern their markings; now observations from spacecraft provide electronically enhanced images that bring these distant worlds even closer.   In Worlds in the Sky, William Sheehan gives us a history of this long fascination, weaving together scientific history, anecdotes surrounding planetary discoveries, and the personal reflections of an incurable amateur astronomer. He describes how we arrived at our current understanding of the Moon and the planets and shows how certain individuals in history shaped the world's knowledge about the Solar System. The University of Arizona Press's Century Collection employs the latest in digital technology to make previously out-of-print books from our notable backlist available once again. Enriching historical and cultural experiences for readers, this collection offers these volumes unaltered from their original publication and in affordable digital or paperback formats.