It's a long shot, but some of the world's top physicists don't think time travel is impossible. Einstein's special theory of relativity combines space and time into a single entity, space-time, which does not prohibit the notion. Stephen Hawking has proposed using wormholes to connect our universe with an infinite number of parallel universes, while others have advanced black holes or cosmic strings as possible time-travel portals. Of course, just because the laws of physics don't prohibit time travel doesn't mean it's going to happen. But a journey in time would be the ultimate adventure, an utterly transformative experience for the universe.