C.S. Lewis, in the Chronicles of Narnia, says a few times that, "We are never told what would have happened, but only what happened." (my paraphrase). Very interesting. Aslan will not tell what would have happened if someone had acted differently.
Last week, on my way home from Friday SIAW (at 11:30 PM after 15 hours of work), I was tired and watching the cars drive past us on the way home. I thought, "If there is a large enough gap between two cars on the road, someone could run between the two cars without getting hit." Then, I began to consider what would happen if the person was traveling forward at the same speed as the cars and then tried to cut between them. I realized that it would be like the cars weren't moving. (Amazing, I know. Keep in mind that I was really tired at this point.) Then I was thinking some more and realized that if the person went faster than the cars, it would appear to him as if the cars were going backwards.
The I began to think about light. We are traveling at a speed less than that of light, so it appears to us that time occurs as it does. If we were to go faster than the speed of light, we wouldn't actually be able to go back in time, we would just perceive events before they happened. But this was only our perception of events, not really going backwards in time.
So how does this relate to C.S. Lewis? Even if we could travel faster than the speed of light, we could never know what would have happened. We can only know what will happen.
My apologies if the above post was too metaphysical for you all.