3: Cycles of the Moon

Did anyone ever warn you, “Don’t stare at the moon—you’ll go crazy”? For centuries, the superstitious have associated the moon with insanity. The word lunatic comes from a time when even doctors thought that the insane were “moonstruck.” A “mooncalf” is someone who has been crazy since birth, and the word is probably related to the belief that moonlight can harm unborn children. Everyone “knows” that people act less rationally when the moon is bright, but everyone is wrong. Careful studies of hospital, school, and police records show that there is no real correlation between the moon and erratic behavior.

The moon is so bright and its cycles through the sky are so dramatic we expect it to influence us, and many people are disappointed to learn the moon does not influence us. Some simply refuse to believe the evidence.

The cycles of the moon are indeed dramatic, and the moon is a rich source of myths and traditions. Many different cultures around the world explain eclipses of the sun as invisible monsters devouring the sun (Figure 3-1). A Chinese story tells of two astronomers, Hsi and Ho, who were too drunk to predict the solar eclipse of October 22, 2137 BC, or perhaps failed to conduct the proper ceremonies to scare away the dragon snacking on the sun. When the emperor recovered from the terror of the eclipse, he had the two astronomers beheaded. The cycles of the moon provide a wealth of beauty in the sky and an important part of the cultural beliefs of Earth’s peoples.
This chapter discusses the lunar cycles of phases and eclipses. Studying these events will help you understand what you see in the night sky. They will also introduce you to some of the most basic concepts in astronomy.

You will discover how light and shadow move through space, how the size and distance of an object affect what you see, and how cyclic events can be analyzed by searching for their patterns. Most of all, this chapter helps you to begin thinking of your home as a world in space.