Do we live in a cyclic unverse?

How did the universe begin? Did it have a beginning at all? These questions may have been the subject of speculation and debate for millennia, but they have not been widely discussed for the past forty years. Ever since the discovery of the cosmic background radiation in 1965, the overwhelmingly predominant view has been that our universe began about 14 billion years ago in a cosmic fireball known as the "big bang" and that it has been expanding, cooling, and evolving ever since. Recently, though, a small but growing number of theorists have begun to challenge this conventional belief and to pursue a radical new history of the universe. According to this new idea, there was a big bang, but this was not the beginning of space and time. In fact, in the version proposed by Neil Turok and myself, the big bang has occurred myriad times in our universe's past, repeating at regular intervals during which galaxies, stars, planets, and life form anew. The result is a "cyclic universe" in which cycles extend far into the past and into the future—and perhaps forever..