In our experience, events occur in a temporal and causal sequence. Thus, I drink a lot,
then I am very drunk. Time travel as a fictional premise is the idea that the temporal order of events might differ. Thus, I am very drunk today because I will drink a lot tomorrow, then time travel to today. Sometimes people imagine that a process describable as "time travel" might occur but that nevertheless the familiar temporal sequence would continue. Thus, it is sometimes imagined that, if a time traveller departs from 2022 intending to prevent the birth of Hitler, then, immediately after his departure and not before, the world will change into whatever state it would have been in now if Hitler had not been born back then. Clearly, any consequences of a successful prevention of the birth of Hitler would have come into effect immediately after that successful prevention, not all these years and decades later after the departure of a time traveller from the 2022 of a history in which Hitler
was born and in which World War II
did occur to be followed by the Cold war etc. Poul Anderson's Time Patrol series avoids this blatant logical error but nevertheless raises subtler logical conundra which, however, we have discussed before perhaps
ad nauseam. But I think that it might be helpful at least to clarify such basic issues as this one.
5 comments:
To think about time travel, you need to shed the notion of an "absolute" time shared by everyone and concentrate on your own time -line-, that is, duration as you experience it.
Even time travel doesn't alter this. If I go back to 1953, I don't become a newborn infant.
Some people think, e.g.:
when I left school, I made a bad career decision;
if I had a time machine, then I would travel back to that time and make a better decision.
No, they wouldn't. The older time traveller, having arrived in the past, would coexist with his younger self making the bad decision.
Well, you could advise your younger self -- as happens in THERE WILL BE TIME. In that book, the hero remembers his older self doing just that, or in other cases recalls what happened and realizes that his older self caused it.
But in the Time Patrol universe, with a single mutable timeline rather than the immutable one of the other book, that means that there will now be a different -future you-.
That is, this version of you remembers a past in which he -wasn't- advised by his older, wiser self.
He goes back and advises his younger self.
But now if he returns to the future, it won't be the one he departed from; and there will now be a different "him" there, the result of that decision being made differently.
He can't change his own past life by time travel, the one he remembers and which produced him.
He can only create a new future in which he doesn't share.
That is correct.
OTOH, say you (in the Time Patrol universe) sent a "message capsule" back with a note to your earlier self -- we're shown the Patrol using them.
Then the 'original you' would -not- be present before the divergence.
So there would be a new "you" with no memory of the previous course of events, but a memory of receiving the message and making a different decision.
Yet there would be no point at which the new "you" actually sent the message back.
The message capsule would exist back then, but it would also exist in the future. If it was kept around long enough, you'd have two versions of the same machine with different pasts.
In fact, if you tried to duplicate the previous event -- the message, the time it was sent, etc. -- TWO messages would arrive!
And potentially, any number of such messages.
No wonder the Patrol tries to discourage that sort of thing! 8-).
Post a Comment