Astronomers have been scratching their heads for years trying to figure out why exploding stars at the very edge of the universe seem to be moving faster than ones in the middle. Some theories say the acceleration is due to mysterious "dark energy,"but a new one posits that the stars aren't speeding up at all—but that time itself is slowing down. If time was moving faster billions of years ago, it would explain the apparent acceleration of images of stars reaching our sight now. It also suggests that time itself could one day stop completely, leaving the universe frozen in time forever. "We believe that time emerged during the Big Bang, and if time can emerge, it can also disappear—that's just the reverse effect," a cosmologist said.