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Years ago, I would occasionally visit the Haydn Planetarium in New York City. The show projected onto the giant dome would vary, but it invariably started with the announcer pointing out the major constellations. I listened intently to his explanations and tried to remember the shapes floating over my head. The first constellation was easy; it was called the Big Dipper or the Great Bear. Unfortunately, by the time the announcer pointed out the fifth or sixth constellation, I had already forgotten the earlier ones. Later on, I would walk upstairs to see an exhibit that clearly showed that the stars of the Orion constellation were not even close to each other and that they just happened to appear as a pattern when viewed from the Earth. I then decided that if the ancient Greeks wished to see bears, lions, and horses gallivanting around the sky that was fine with me, but that I had better things to do with my time than to try to remember names of groups of stars, especially when the stars did not really have anything to do with one another. Twenty years passed before I went back and started to learn the sky.
A constellation is not merely the figment of someone’s overactive imagination while looking at the sky thousands of years ago. The purpose of the ancient Greeks and Babylonians in assigning names to different groups of stars was not to draw pretty pictures, but to create some sort of order in the heavens. Ancient peoples used the constellations to impose a structure on the sky. You might protest that this structure is a very arbitrary one and you would be right. But even an arbitrary structure is sometimes better than none at all.
Without constellations, the sky will always appear as a jumble of random stars. Learning the constellations gives us intimacy with the sky, and you can no more learn the sky by memorizing the locations of individual stars than you can learn your neighborhood by memorizing the latitude and longitude of each building. Your familiarize yourself with an area by first learning any major topographical features, such as a river, then you subdivide the main sections into streets and the streets into houses and other buildings. Since the sky has almost no natural “topographical” features except the ecliptic and the Milky Way, we have to almost arbitrarily create “streets” in the sky. The streets of the sky are its constellations.
The constellations that we now use are generally based on Greek mythology, but there is nothing sacrosanct about them. Other cultures have invented other constellations, which are just as satisfactory as those that we have received from the Greeks. You can even invent your own. If you prefer to imagine the sky filled with telephones, video recorders and food processors instead of gods, hunters and animals that will be fine. Of course, if you make up your own constellations, you will have a bit of trouble talking about the sky with anybody else beside yourself. Learn a few of the constellations and you will feel that you are looking at something familiar whenever you gaze upwards.