Physicists have puzzled for more than a century about the nature of time. Why does it go in one direction? Time could go backwards, and physics formulas would still work properly. Researchers from the University of Chicago think they might have an answer: we live in a universe of ever increasing entropy. Instead of one Big Bang going off, and then the Universe expands and cools forever, small fluctuations in nearly empty space could set off new Big Bangs - the Universe would never reach equilibrium.