A handful of proposals exist for time travel. The most developed of these approaches involves a wormhole—a hypothetical tunnel connecting two regions of space-time.

Astrophysicist Charles Liu discusses the possibilities of navigating the Fourth Dimension with quantum physicist Michio Kaku in this Space.com/TechMediaNetwork video.

[youtube]http://www.youtube.com/watch?v=X5pS9KtYNfQ[/youtube]