The Flash vs Terminator Genisys

[Shadowknight]

Depends on how you're working the theoretical physics, Yeah we're getting into theoretical physics here, NERD GLASSES ON! Every decision creates an alternate world, and going back and altering the timeline doesn't change it, just causes it to branch, one world where the change happened and the world where everything went the way it had. It gets more messed up the more jumping back and forth you do and how the laws work in a specific story. Imagine trying to read one of those choose your own adventure books from cover to cover instead of jumping around, kinda becomes a mess like that. If you're interested Michio Kaku does a good piece on it.

http://mkaku.org/home/articles/the-physi...me-travel/