This book tells the story of how physicists and astronomers have struggled for more than a century to understand the beginnings of our universe, from its origins in the Big Bang to the modern day. The book will introduce the science as a narrative, by telling the story of the scientists who made each major discovery. It will also address and explain aspects of our theories that some cosmologists are still hesitant to accept, as well as gaps in our knowledge and even apparent inconsistencies in our measurements. Clearly written by a master of scientific exposition, this book will fascinate the curious general reader as well as providing essential background reading for college-level courses on physics and astronomy.