Cynthia Sutton, age 11, of Tucson, Ariz., for her question:

How did the signs of the zodiac originate?

The zodiac is a wide highway across the sky, populated by a parade of heavenly bodies. It is the pathway of the sun and the major planets. Because the earth spins on its axis and orbits the sun, the zodiac parade changes every hour. The starry constellations in this belt of sky change with the seasons.

Early stargazers noted the heavenly parade and this well traveled highway in the sky. They used it as a calendar to mark the 12 passing months of the year and named a starry constellation in each of its 12 sections. Most of these constellations were named for real or imaginary creatures, and the starry highway was named the zodiac, which means the circle of animals.