Ask anyone on the street to name a telescope, and odds are good he or she will reply, “the Hubble Space Telescope.” Hubble has gained worldwide fame for its spectacular pictures, which grace T-shirts, posters, and postage stamps. But Hubble is much more than just an instrument for taking pretty pictures. Since its launch in 1990, this great space observatory has been one of the most powerful science machines ever built. Hubble has contributed major discoveries to almost every field of astronomy, from planetary science to cosmology. Join former Sky & Telescope Editor in Chief Robert Naeye as he describes Hubble’s most profound contributions to human understanding of our wondrous universe.