h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

If time travel exists than it disproves the belief of humans free will and ability to decide their own future. If the "future civilizations" have traveled back in time, than that would imply that they already exist and it is already decided how they will turn out. I, being a strong believer in free will, do not think that time travel will ever exist. True it has made for some interesting books, Crichton's "Timeline" or Heinlen's "To Sail Beyond the Sunset, and of course DA's theory about insurance salesmen, but I don't think it will ever happen because that would lead back to our futures being predetermined. I did enjoy your mayonaise arguement though; that is an interesting spin on it.
~Psycho

The fact that some event occurs at time t2 as a consequence of an event occurring at t1 does not, I think, necessarily preclude the t2 event's being a consequence of a choice made at t1, since the t2 event could still be determined by the t1 choice, without the t1 choice's and the t2 event's having been determined at t0. It isn't the case that the t2 event has 'already' happened because, temporally, t2 follows t1. If the choice at t1 is between event x at t2 and event y at t2, then if x occurs at t2, x was chosen at t1, and if y occurs at t2, y was chosen at t1; but it doesn't follow that x was chosen at t1 because x occurred at t2, or that y was chosen at t1 because y occurred at t2, or that x was chosen at t1 and occurred at t2, or y was chosen at t1 and occurred at t2, because this state of affairs was pre-ordained at t0. We can choose what happens; then it happens, because we chose it.

I apologise for the rather less than crystal-clear exposition.

The fact that some event occurs at time t2 as a consequence of an event occurring at t1 does not, I think, necessarily preclude the t2 event's being a consequence of a choice made at t1, since the t2 event could still be determined by the t1 choice, without the t1 choice's and the t2 event's having been determined at t0. It isn't the case that the t2 event has 'already' happened because, temporally, t2 follows t1. If the choice at t1 is between event x at t2 and event y at t2, then if x occurs at t2, x was chosen at t1, and if y occurs at t2, y was chosen at t1; but it doesn't follow that x was chosen at t1 because x occurred at t2, or that y was chosen at t1 because y occurred at t2; neither does it follow that x was chosen at t1 and occurred at t2, or y was chosen at t1 and occurred at t2, because this state of affairs was pre-ordained at t0. We can choose what happens; then it happens, because we chose it.

I apologise for the rather less than crystal-clear exposition.

RFJS is correct about the free will argument being irrelevent to time travel.

If someone goes back in time, they are within the flow of time at that specific point, and whatever happens there happens in the context of the time they are in. Put it another way - just because I know my mother married my father does not mean that she didn´t have to think about it. If I - or another time traveller - went back in time to whenever he popped the question it would not affect whether or not she was thinking about it.

Ach, quantum physics and this sort of thing is so counter-intuitive anyway, that discussing it unless you have four separate degrees in physics is pretty pointless.

Maybe it is both a wave and a particle, both free will and predestination, both possible and impossible to travel in time?

Who cares, we've got mayo, and that's all I'm bothered about. Glad you liked the entry.

Ben

Thanks for the agreement and the clarification.