Some physicists think that wormholes are the key to time travel, but is wormhole travel possible? It's a tough question that brings debate in from both sides, but there isn't much evidence one way or the other.
The Einstein-Rosen bridge theory suggests that wormholes may form when two black holes bridge together, but it would still take immense amounts of energy to overcome the extreme gravitational forces that black holes impose.
Another problem is the instability of black holes. As the Hawking radiation theory suggests, a black hole can continuously emit energy until it disappears from existence. If this happens during a bridging event, then a wormhole would inevitably become disturbed.
Given just how little humankind actually knows about black holes and wormholes, it's apparent that further research is needed to understand how these forces of nature work.