The classic big bang theory is great at describing what happened after the bang. Yet until recently, particle physicists and cosmologists were stuck on many questions that the big bang theory couldn't answer, including: What made the big bang BANG in the first place? If matter can be neither created nor destroyed, how could so much matter arise from nothing at all? Why can we only see a minute part of the mega-universe? In 1979, a young particle physicist named Alan Guth answered these questions and made front-page news with one of the greatest discoveries in modern cosmology: cosmic inflation. This is the compelling, first-hand account of Guth's paradigm-breaking discovery of the origins of the universe; and it is a fascinating chronicle of his dramatic struggle to justify it. Guth's startling theory states that in the billion-trillion-trillionth of a second before the big bang, there was a period of hyper-rapid "inflation" that got the big bang started. Inflation modifies our picture of only the first small fraction of a second in the history of the universe, and then it joins onto the standard big bang theory, preserving all of the successes of the older theory. But because inflation explains the bang itself, it is a much richer theory than the older versions of the big bang.