7. Parallel Dimensions
Parallel dimensions have been a staple of science-fiction movie since... well,
Back to the Future, Part II, we guess (and we'll argue the plausibility of that movie's time travel aspects from dusk 'til dawn). But filmmakers have oft-been wondering about the inherent dangers associated with time travel. Questions like: "What would happen if I met myself?" or "What would happen if I went back in time and shot my father?" (if you're, like, insane) have been explored a whole bunch of times in movies already. And it turns out that scientists like thinking about these prospects too. Kip Thorne doesn't think time travel is possible under the laws of physics, though some scientists do believe that - should somebody mess with the time line in such obvious ways - there wouldn't be any repercussions on the "regular time line," and that other "parallel time lines" (dimensions, if you will) would be created instead, generating the idea that a potentially infinite number of these things could exist at once with no noticeable effect on the others.