George Townsend, age 12, of Beechhurst, New York, for his question:

What did the earliest astronomers discover?

Some of the best early astronomers were the magi of ancient Mesopotamia. They had no telescopes to spy beyond the range of the human eye, but they were skilled mathematicians. And most of all they were patient, accurate star gazers. They observed and charted the positions and paths of the heavenly bodies. They charted the daily positions of the sun and discovered the relationship between this and the changing seasons. They discovered celestial ways to clock the passing of time. Their patient records of the stars covered thousands of years. Later astronomers needed these long term observations to back up their new theories.     

Early astronomers made many sound discoveries. The most astounding one was a reliable way for predicting eclipses far into the future. They recorded eclipses for thousands of years and observed a patternthat repeats and repeats on schedule. They called it the Saros period and astronomers can still use this ancient discovery to predict eclipses of the sun. Modern instruments have refined early measurements, but we still refer back to details discovered and charted by the magi and other early astronomers.