Ok present day earth, you and your buddy goes to the future say 10 years from now. The world is throw into chaos.. maybe its a virus or a war or somthing.. You suddenly go back in time but you leave your buddy in future. You change a event in the past that prevents the chaos from happening. Or worse, you make it even worse. Or could be different maybe the future was pleasant but you still went back in time to change something. What happens to your buddy in the future if you changed the future? How can it they be changed with the future when they came from the past? Do they cease to exist replaced with a new copy of the future? Does time just sort of change around them? If so do they remember the events that were and what they are now? Hmmm....
