Paradox-free time travel is theoretically possible
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Re: Paradox-free time travel is theoretically possible
#2When you take this theory to it's logical conclusion, you end up with some strange outcomes. The strangest is the idea of going back and killing baby Hitler. When you attempt to do that, the universe, in it's self righting ways makes the assassination attempt not work. Since Hitler is a pretty big enemy for a lot of people, many people over time try to go back and kill Hitler.
Hitler, on the other hand is just living his life as an Austrian child and young adult suffering from constant attempts on his life from people who he has no way of knowing. He gets the idea that people are always out to get him (because they are) and becomes evil, and uses the assassination attempts to justify creating the Holocaust.
Re: Paradox-free time travel is theoretically possible
#3> Researchers ran the numbers and determined that even if you made a change in the past, the timeline would essentially self-correct, ensuring that whatever happened to send you back in time would still happen.
I'm sure these researchers are pretty smart, but nothing in this article goes beyond the level of a grade-school debate. Maybe there's something enlightening in the paper. But if there was, you'd think it would make its way into the article.
Re: Paradox-free time travel is theoretically possible
#4Just give it to me in popular movies: Back to the future style time travel can’t happen but Terminator style time travel can.
It doesn’t say what constitutes a “major” change and what is a minor one though. The only guidance we are given is that the original motivation for going back must be preserved but otherwise very large changes can happen (planet of the apes marky wahlberg version)
Re: Paradox-free time travel is theoretically possible
#5Pasting the abstract from the paper:
The theory of general relativity predicts the existence of closed time-like curves (CTCs), which theoretically would allow an observer to travel back in time and interact with their past self. This raises the question of whether this could create a grandfather paradox, in which the observer interacts in such a way to prevent their own time travel. Previous research has proposed a framework for deterministic, reversible, dynamics compatible with non-trivial time travel, where observers in distinct regions of spacetime can perform arbitrary local operations with no contradiction arising. However, only scenarios with up to three regions have been fully characterised, revealing only one type of process where the observers can verify to both be in the past and future of each other. Here we extend this characterisation to an arbitrary number of regions and find that there exist several inequivalent processes that can only arise due to non-trivial time travel. This supports the view that complex dynamics is possible in the presence of CTCs, compatible with free choice of local operations and free of inconsistencies.
FWIW, the last sentence of the paper itself (prior to the conclusion) reads: It is an open question how generic is this situation and what are the spacetimes and physical systems for which nontrivial, self-consistent time travel is possible.
As usual, non-scientific reporting overplays the ramifications.
Link to paper: https://iopscience.iop.org/article/10.1088/1361-6382/aba4bc
Re: Paradox-free time travel is theoretically possible
#6When you take this theory to it's logical conclusion, you end up with some strange outcomes. The strangest is the idea of going back and killing baby Hitler. When you attempt to do that, the universe, in it's self righting ways makes the assassination attempt not work. Since Hitler is a pretty big enemy for a lot of people, many people over time try to go back and kill Hitler. Hitler, on the other hand is just living…
Self-fulfilling prophecy, yes.
But the article reads like some sci-fi bs tbh. What's considered the 'same outcome'. If I kill baby Hitler, would the universe create another just like him? Or someone else will do same things? If someone else does them, surely it won't (for example) kill as much people. So someone dead would now be alive in the future (or vice versa). And now the outcome isn't the same yeah?
Sorry but this is bs.
Re: Paradox-free time travel is theoretically possible
#7This suggests concepts like fate and the universe having a will and intent. It seems absurd. Wouldn’t a branching creating a new universe with its own timeline make more sense? Each unit of influence you exert as a time traveler branches a new universe in which you continue to exist and which has a completely new and separate timeline without paradoxes.
Re: Paradox-free time travel is theoretically possible
#8When you take this theory to it's logical conclusion, you end up with some strange outcomes. The strangest is the idea of going back and killing baby Hitler. When you attempt to do that, the universe, in it's self righting ways makes the assassination attempt not work. Since Hitler is a pretty big enemy for a lot of people, many people over time try to go back and kill Hitler. Hitler, on the other hand is just living…
Self-fulfilling prophecy, yes. But the article reads like some sci-fi bs tbh. What's considered the 'same outcome'. If I kill baby Hitler, would the universe create another just like him? Or someone else will do same things? If someone else does them, surely it won't (for example) kill as much people. So someone dead would now be alive in the future (or vice versa). And now the outcome isn't the same yeah? Sorry but…
I find the concept absurd as well. If you do something like go back in time and murder Hitler, you're going to be impacting the actions of every single human being alive. Within a few generations there's going to be an entirely different set of people alive than the set of people alive in the universe in which Hitler was not murdered. This idea that you would still have to go back in time because the universe corrects itself makes no sense because there's just no way you would still exist. I'd be willing to entertain the idea that someone else would go back in time for the same reason, but it's all just wild speculation.
Re: Paradox-free time travel is theoretically possible
#9Sounds like they're describing the Novikov self-consistency principle [1] in a roundabout way.
[1] https://en.wikipedia.org/wiki/Novikov_self-consistency_princ...
Re: Paradox-free time travel is theoretically possible
#10In Isaac Asimov's "End of Eternity" he posed a similar concept where contrary to the butterfly effect where minor changes ripple through time, time has a mechanism of self-preservation which is resistant to change. Asimov never ceases to amaze me with how prescient he was for his time.