RaffB said:
3.You can't change history in any way
4.You exist in that time, but people will not pay too much attention to you.
But see, right there, you are contradicting yourself.
If you exist in a previous space and time at any X,Y,Z coordinates in the world, you are changing time. Someone has to walk around you because you are in his path - YOU JUST CHANGED TIME. Perhaps even history! What if got hit by a car thinking about how strange you were just standing there? See what I mean? "People won't pay TOO much attention" That means they will, to some extent, notice you and their thoughts will be different. See? Time is already altering.
Also, if you attended a concert that had an empty seat, that means that you altered history by making that seat no longer empty. A little more money was made that evening than before. If you attend a concert that was, originally, full, that means that someone who SHOULD have been at that concert no longer was. What happened to him/her? Did they get into a car wreck because they were somewhere else?
The only way to view the past without interfering would be to view it from another time. Basically, a non-physical viewing of the past while you were still in the present.
Sorry, but I had to say it ...
Now, OT, if I could remotely view another time, I would choose to go to the one of the Zodiac Killer murders when it happened and follow him until he took off the mask. Just to see if it was REALLY Arthur Leigh Allen or not. *EDIT* I knew a girl who thought that it was Arthur L Allen and was, instead, a Virgo police officer(?). (The name of her suspect escapes me, but we were both astrology fanatics and Virgos, so that's the part that sticks in my mind.) I guess I would want to see if she was right.