Novelists and screenwriters know that time travel can be accomplished in all sorts of ways: a supercharged DeLorean, Hermione’s small watch and, most recently, a spacetime-bending hot tub have allowed fictional heroes to jump between past and future.
Clockwise from top right: NATAQ/ISTOCKPHOTO; RADEKK/ISTOCKPHOTO;JNSOO1/FLICKR
Physicists have proposed several ways of getting around the grandfather paradox (shown).
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