The Space Problem of Time Travel
A science-fiction cornerstone is time travel. Thanks to some wonderful machinery invented in the future, human beings can go back in time, disappearing from their present to find themselves in the same place in any past era. But is such spatial precision physically possible?
One of the most prolific and compelling themes of science-fiction literature and cinema is undoubtedly time travel. An incalculable number of films — from Terminator to Back to the Future, from 12 Monkeys to X-Men: Days of Future Past — bases its plot on the return of the protagonists to previous eras, with the idea of doing something that, in one way or another, alters the course of history and creates a different future (or rather a different present, from the point of view of those who come from the future).
But time travel inevitably produces paradoxical situations, such as the possibility that the time traveler will encounter a younger copy of herself or that she kills her parents before they conceive her. However, there’s another enormous theoretical difficulty that makes the invention of a time machine that can do what is shown in movies highly unlikely. And it is a difficulty that is rarely thought…
