This book is written primarily for young teens (ages 13 to 16). It can, however, be enjoyed by anyone from 13 to 113 who has an interest in science - especially if they have never given astronomy or cosmology much thought. Informally presented in an entertaining and chatty style, the book teaches some of the basic science and associated math (dead simple algebra) that astronomers work with - but more importantly - it shows how these geeky scientists actually use this stuff to figure out what's going on in the universe. For example, you will learn: (1) Not just what chemical elements reside in the sun (some 150 million kilometers from the nearest chemistry lab), but how astronomers figure it out. (2) Not just how far away a remote galaxy is, but how astronomers determine that distance. (3) Not just how fast a galaxy is moving toward or away from us, but how astronomers calculate that velocity. (4) Not just how old the universe is, but how astronomers arrive at that figure. And guess what! None of this learning is nearly as scary as it sounds. It's a lot easier than rocket science and a lot more fun than what goes on in most classrooms. You will also learn just how much astronomers and cosmologists still do NOT know about the universe. They figure that a whopping 96 percent of it is made up of dark matter and dark energy, but they don't have a clue what this dark stuff really is. How cool is that? This situation is downright embarrassing, so it's always a neat topic to bring up at any party where cosmologists are present. (You do go to such parties, right?) Talk about future job opportunities in science for young minds!