Transcript: The constellations of the night sky are among the oldest human artifacts.  For thousands of years humans have been noticing patterns and using them to navigate, or to keep track of the sky, or to tell myths and legends.  There are 104 constellations in the modern sky.  Some of them are extremely old. There is evidence that Ursa Major, the great bear, which includes the asterism of the Big Dipper, dates back to at least 10,000 years.  Asian tribes named this constellation, and knowledge of this constellation traveled from Asia through to Europe and to North America. The thirteen original, and then twelve, constellations where the sun, moon, and planets travel, were divided into the Zodiac, the circle of animals.  Those are the familiar twelve constellations of the star signs.  But in general, the constellations are a rich source of human history as myths and legends have been posited in the constellations for many, many years.  The constellations don't look like the things they are supposed to represent; you have to use your imagination.  Remember, the constellations were used as shorthand by people who depended on the night sky for their very existence.