Why is time travel so difficult to think about? Changing the temporal order of events changes the causal order and confuses the logical order. Poul Anderson avoided the kind of blatant absurdities that make some time travel fiction unreadable.
Someone asked me, "If I time travel and prevent my parents from meeting, will I cease to exist?" No, why should you? You have originated in a timeline where your parents met and you were born and grew to adulthood and you have initiated a second timeline where your parents did not meet and you were not born and did not grow to adulthood but there cannot possibly be a third timeline where your parents did not meet and you were not born, yet you grew to adulthood and then ceased to exist.
Does a bachelor return home to encounter a young woman who then ceases to exist because she is the daughter that he would have had if he had not been prevented from marrying twenty years previously? Absurd. Poul Anderson circles around this kind of question in the Time Patrol series but avoids absurdities like time travelers ceasing to exist.
5 comments:
Kaor, Paul!
I think there are some ambiguities here. The older idea in some of the Time Patrol stories about "deleted" universes ceasing to exist at all when the change causing them to exist in the first place comes close to that "absurdity."
Ad astra! Sean
Dang! I meant to write "..when the change causing them to exist in the first place WAS CORRECTED comes close to that "absurdity."
Sean
The "kill your grandparents" (or prevent them from meeting) comes up when Everard gets to the Patrol Academy. You wouldn't cease to exist in that event, because you'd be present before the point of divergence -- but the future that produced you would be gone (or no longer available).
"Infinite discontinuities in the world-line" was the way the Patrol instructor put it.
Kaor, Mr. Stirling!
And I think those "Infinite discontinuities in the world lines" means ending up with tinelines/universes inaccessible to each other. The Carthaginian universe of "Delenda Est" was not snuffed out, it became inaccessible to time travelers from the Danellian universe.
Ad astra! Sean
I just presume that the physicists of the far future know more than I...
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