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Phoenix666 writes:

(*Spoiler alert: This post refers to key elements of the movie.)

If we can walk backwards and forwards in space, why not in time?

Scientists, especially theoretical physicists, like to play such games — controlling time with pencil and paper. Going forward in time, traveling to the future, is actually OK, according to the Theory of Relativity. All we need is a super-fast spaceship, traveling close to the speed of light. A technological, and not a conceptual obstacle.

Going back in time is more complicated. Much more. Remarkably, closed-time loops are not just the stuff of sci-fi stories. (Why a closed-time loop? Most people don't want to go back in time and be stuck there. A short visit to the past should suffice.) In 1949, the brilliant Austrian mathematician Kurt Gödel found a solution of Albert Einstein's equations of general relativity where it is possible, at least theoretically, to travel in a circle in time as we can in space, returning back to the starting point. The movie brilliantly plays with this notion, not least since 13.7's own Adam Frank worked as a scientific consultant.

In practice, Gödel's solution and any of its modern versions are a very, very long shot. There are issues with how to keep such spacetimes from collapsing upon themselves, not to mention weird time paradoxes like the Grandfather Paradox: If you travel back in time and kill your grandfather before he marries, would you exist? However, in a Marvel universe it is possible. When Dr. Strange discovers that he has this power, we see a disturbingly beautiful image of an apple being eaten and reassembled again and again, a small patch of space where a closed-time loop is possible.

Original Submission