Looking at the Starry Sky

Picture, if you will, our solar system. In the middle is the Sun. Spinning around it are the planets and asteroids, whose orbits surround the Sun roughly the way the grooves on a record album encircle the label in the center.

That idea, drilled into us in childhood, would have astonished ancient stargazers. They never doubted that the Sun, Moon, and planets revolved around the Earth. And although we know better, thinking so didnít make them stupid. The Sun really does look as if it revolves around the Earth. It seems to rise in the east and set in the west. And it always stays within the confines of a ribbon of space that encircles the Earth like a giant hoop. That strip of sky is called the ecliptic.

Following are the three most important facts about the ecliptic:

• The ecliptic represents the apparent path of the Sun around the Earth - apparent because, in fact, the Sun doesnít spin around the Earth at all. It just looks that way.

• Like a circle, the ecliptic is divided into 360 degrees ó and each degree is, in turn, divided into 60 minutes. The first 30 degrees of the ecliptic are Aries, the next 30 degrees are Taurus, and so on.

• The stars that are scattered like dust along the entire length of the ecliptic form the constellations of the zodiac.

Here comes the confusing part: The signs of the zodiac and the constellations that share their names aren't the same. The signs are divisions of the ecliptic, each exactly one-twelfth of the total length ó 30 degrees. The constellations have nothing to do with the signs. I explain this sorry state of affairs in the sidebar "The signs, the constellations, and the precession of the equinoxes."