Charles Lewis jr., age 12, of Atlanta, Ga., for his question:

How can we tell stars from planets?

The ancient stargazers of Babylon charted the paths of the heavenly bodies over the skies. They noted that most members of the heavenly parade keep to seasonal schedules. There are starry constellations that appear in spring and others that march through the summer. There are fall and winter constellations and patterns that circle the polar region of the sky throughout the year. These heavenly bodies with seasonal paths are the stars    and they are spattered all over the sky.

The stargazers of old noted that a few heavenly bodies wander in paths of their own against the background of fixed stars. They were called planets, meaning wanderers. They ignore the seasonal schedules of the stars. And unlike the stars the planets keep more or less to one part of the sky. They follow, to and fro, along the broad belt of the heavens traversed by the sun and the moon. And there is one more clue to spot them. A star twinkles with shifting darts of light. A planet shines down upon us with a steady stare  it never sparkles or twinkles.