Time Travel

Much as I’ve always enjoyed time-travel tales, its practical application has often tended to confound me rather. At least, as it is usually presented in movies, TV and books. There need to be some internally consistent rules, surely? So Marty returning to parents who took a different, more successful course at the end of Back to the Future, one of which he has no recollection, doesn’t really (mc)fly. Unless you account for it with multiple/ infinite potential timelines, each variation on a c...