That's almost the same thing I said, actually, apart from the reference to free will. Add that in, and we are of one mind. You mean, the person making the decision will think and feel it is free, but actually, it is predetermined, and there is no other choice that he is allowed to make? Because that is pretty much what you seem to be saying, to me. No they don't. That's like saying a ball knows it is about to rebound off a wall once thrown. It just obeys the laws of physics. If there's a wall, it will rebound (unless it's made of putty, then it will stick ). That's actually a very nice idea. Mathematically, you can already show it is very much like this for several situations. Whether this would work to explain time travel is, however, perhaps a little difficult to say. Yes! Not just two pasts, a nearly infinite number of pasts. According to the multiple universe theory, a new "universe" branches off at every quantum decision, and there's probably on the order of 10^80 of them per second or more, so it's nearly an infinite number of "pasts". I'm sorry, I think I don't understand this question. Can you use A and A' like I did? In the example I constructed, you are already in the past of your own world (A @ T-t), but it immediately creates a new world (A' @ T-t) just by your being there. If you jump back into your old world (A), without shifting time (@ T-t[+dt] for the sake of the argument), you create a new world again (A'' @ T-t+dt) immediately. If you jump back to where you started, your old world (A @ T) you are not in the past. I guess it would help our discussion immensely, if we were to separate between the different time travel regimes and theories, namely (as taken from the Wikipedia article, but I like their classification system): 1. There is a single fixed history, which is self-consistent and unchangeable. (This is the system which Novikov was talking about) 2. History is flexible and is subject to change. 3. Alternate timelines. (Which is supported by the multiple universe theory, and of which I am a major fan). By the way, I can only say again I really recommend the "Ideas from fiction" part of the Wikipedia article on time travel, since it is really relevant to this discussion, no matter what the stance is one has on the issue. That is a very interesting thought. I had forgotten about Einstein for a moment. I will go and meditate about that for a while.
