The Issue with Time Travel
There is one major issue that I see with almost any science fiction time traveler. They always end up in the same spot!
I mean, just think about it. The earth doesn't stay still, the sun is not stationary, neither is the galaxy. Somehow when people travel through time they also travel through space at an alarming speed. The earth has never been in the same exact spot in space as it has ever been before everything is in a constant state of motion. If I stood anywhere on earth and time traveled almost any amount in time I would suddenly find myself longing for some atmosphere very quickly!
Now of course if you were time traveling with a space ship, this would not be as big an issue. You would however have to predict where cosmic bodies would end up being in the time you are traveling to and make sure you pick a spot that is devoid of substance. Imagine the mess you might create if you time traveled and ended up at the center of a mountain. I am not even sure how solid matter would react to that sort of instant force I don't think it would be very pleasant though!
Just a few things to keep in mind as my fellow mad scientists out there work laboriously on bending the fourth dimension to their will!