If you believe the creations of science fiction, black holes serve as gateways to other worlds, either distant parts of this universe or other universes entirely. But the reality might be more complicated than that. And outside of the sci-fi realm, dropping into a black hole is a bad idea.
Science fiction literature is full of stories in which tunnels in space-time — known as wormholes — are used for time travel. How much fact lies within the fiction? The answer is, more than you might think. Scientists are looking at ways to use traversable wormholes (if they exist) to travel faster than the speed of light — and even to travel through time itself.