Amazing things are happening in the outermost reaches of space. Jetstars, black holes, and cosmic mirages, things scientists never imagined possible. This volume provides an up to date and authoritative account of the new ideas that are fundamentally changing our understanding of the universe. It explains what our cosmos is made of, how much matter it holds, and why matter is invisible to our telescopes and shows how our understanding of the universe has developed over the years, from Galileo to Albert Einstein, Edwin Hubble, Harlow Shapley and others.