JS-Guy said Only caveat - there's no changing your own past then - so assuming you go back and hang out with your grandfather and NOT kill, he would go on to have a son and that son would go on to have a second copy of you. So there would be 2 of you. In that case it would mean there's no changing your own past. Like if you wanted to not have that scar you can't go back and warn yourself to be careful cutting that salami. Because when you "returned" to your time, the younger "you" from your own world would not have been the one you talked to.  So, in a way it would mean your own universe is knowable but unchangeable (immutable). If time is immutable than what's the point of time travel other than just trying to figure out who killed John F Kennedy or time-touristy shit like watching the fall of Rome IRL?```