Time travel occupies the strange middle ground between established physics and speculation, and this episode of Through the Wormhole, narrated by Morgan Freeman, sits right on that line. Einstein's relativity already permits travel forward in time, the film notes, since clocks run slower the faster you move, but going backward would mean outrunning light itself, a barrier no known physics allows. Researchers describe quantum nonlocality, the phenomenon where entangled particles seem to affect each other instantly across distance, as a possible loophole worth investigating rather than a proven mechanism. The episode uses that gap between what relativity forbids and what quantum weirdness might permit to frame its central question: could either idea ever be engineered into an actual machine. It also follows the thought experiment to its darker edges, asking what happens to cause and effect if paradoxes and branching universes turn out to be real rather than hypothetical.