Traveling backward in time does not affect 'reality prime'. Any changes affected by a backward-time-traveler will create a 'beta reality' in which events unfold differently, but 'reality prime' will never have been affected by these changes. This is why we have never seen evidence of time travelers from the future, and never will. The problem, of course, is that moving mass backwards in time subtracts matter from Reality Prime, and adds it into the newly-created Beta Reality, thus causing imbalance and instability. This instability and imbalance increases exponentially with every new Beta Reality created, and is made even worse whenever someone within a Beta Reality also goes back in time, thus creating a Delta Reality, and so, much like a fractal branches and re-branches, seemingly into infinity. Eventually Reality Prime becomes so unstable that the entirety of all the Realities collapses into a singular 'Event', which would be, essentially, the Big Bang all over again, basically a Universal Reset Button. So, yeah, time travel is probably not a good idea anyway.
There isn't a past to look at, there is only an ever changing now. Even if you went faster than light in one vector, stuff is still moving away from you at the speed of light in every other vector, so it's all changing relative to you. You'd be looking at something different than what was your actual past.
Some great responses in here. Thanks all Explain this one to me. As I noted scientists are now looking at light from galaxies that is 13 billion years old and studying the early days of the universe. Are they looking at something different than what actually took place? Uh... Great contribution. Care to explain astrophysics to enlighten the rest of us, Mr. Hawking? Lol
