Dear Eckard,
The above post has a slight misquote. I said "the future has not yet been written", and you quoted me as "the past has not yet been written". The difference between the present and the future is defined by Entropy. Without a clock tick (the obvious Relativity approach), or the occurance of an event (a change in Entropy), I wouldn't know if it was now or a femtosecond later.
I fully understand the idea of an infinitesimal transformation, and integrating over a series of those infinitesimal transformations to obtain a finite transformation. It seems that such a transformation in the direction of the future could easily be confused with a "normal" passing of time (if there is anything "normal" about the nature of time), whereas such a transformation in the direction of the past would violate the Second Law of Thermodynamics.
In another essay, Hans-Thomas Elze proposes that spacetime is discrete in nature. If this is true, then our "infinitesinal" transformations become discrete quantum ones. I realize that this is where many physicists-turned-philosophers go off "the deep end" with the Many Worlds Interpretation. I have my own "crazy" ideas about multiple dimensions and String Theory. But my opinion is that Quantum Gravity is the only tenuously possible way to break strings so that we can travel in a direction contrary to what Entropy demands. Because we don't understand Quantum Gravity, we can't understand time travel, and Mr. Smith's analysis of the situation is reasonable.
I realize that FQXi had an essay contest about time last year, and many people have special interests and opinions. In another essay, Ettore Minguzzi disturbed me by proposing closed timelike curves (CTC's) and then comparing them to God. Once again, without a Theory of Quantum Gravity, we can only speculate about the possibility of CTC's.
I see you have an essay in the contest. Mine is topic #520.
Have Fun!
Ray Munroe
