The impact of Einstein's relativity is perhaps most dramatic in astronomy, radically altering our interpretation of the observations of the stars and galaxies. Astronomers now encounter challenging phenomena that Einstein never lived to see, in which the bizarre effects of relativity played out on a cosmic scale. This accessible overview explains to general readers the many applications of relativity that have not been shown in earlier popular-level books. Using no mathematics beyond e=mc2, it explains how deeply relativistic ways of viewing the Universe have informed our interpretations of it, and how many of the amazing discoveries of these decades have made sense only as part of Einstein's universe. Some principal observers provide fresh commentary on their discoveries, accompanied by illustrations, newly produced from data in the archives of such observatories as Hubble and Chandra.