actually, that is not true. if you travel back in time and change something it would have no effect on the present because, technically, it already happened.
EVERYTHING THAT HAS EVER HAPPENED SINCE THE UNIVERSE CAME IN TO BEING HAS LED UP TO YOU BEING HERE TODAY. THE SLIGHTEST VARIATION ANYWHERE ALONG THAT TIMELINE COULD HAVE EASILY NEGATED YOUR EXISTENCE.
Caption this Meme
