Some ideas are:

  • You branch off into another timeline and your actions make no difference to the previous timeline
  • You’ve already taken said actions but just didn’t know about it so nothing changes
  • Actions taken can have an effect (so you could suddenly erase yourself if you killed your parents)
  • Only “nexus” or fixed events really matter, the timeline will sort itself out for minor changes
  • something else entirely
  • Dizzy Devil Ducky@lemm.ee
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    1 day ago

    Probably the branch off one.

    Though, speaking of time travel, I really don’t understand/like the whole Harry Potter dementor (however it’s spelt) lake scene in the movie where future Harry saves past Harry. How does that work? Wouldn’t in an initial timeline Harry have to somehow save himself before he could travel back in time to save his past self? The way I see it, it just looks like an infinite cycle of Harry saving his past self with no origin point.

  • dual_sport_dork 🐧🗡️@lemmy.world
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    2 days ago

    From a narrative sense the “nexus” theory is certainly the most amusing, which is probably why Terry Pratchett posited it works exactly that way on numerous occasions. It turns out that history really is kings and battles and speeches and dates, and in order for history to have actually happened someone has to observe those critical events. The things in between really don’t matter. History as a whole further finds a way of happening whether people are involved in it or not, and regardless of – or possibly despite – anyone attempting to hinder, help, or change it. The key events will always happen eventually. All anyone can do is slightly influence how long it takes for them to do so, which is why there are so many boring spans in history where it seemed like nothing really happened; That’s because it didn’t. Possibly until some history monk noticed, and came along to pull out whatever spanner was holding up the works.

  • jaxxed@lemmy.ml
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    3 days ago

    Time travel does exist, but you can only go forward. You just need to approach the speed of light relative to a frame of reference, and you will travel a shorter time span compared to it.

  • Appoxo@lemmy.dbzer0.com
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    2 days ago

    I like the idea that the timeline you exist in is that and can still be determined but everything that happened in the pasr is set in stone. Future time travel is not possible.

  • pixeltree@lemmy.blahaj.zone
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    3 days ago

    I really like the nothing is changeable and travel is possible and anything you do while traveling has already happened / was already going to happen concept

    • lukewarm_ozone@lemmy.today
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      3 days ago

      I wouldn’t say I “like” the idea, since it’s one of the most doomed ways for a universe to be, but Greg Egan’s Arrows of Time is a good exploration of this idea.

    • modality@lemmy.myserv.one
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      3 days ago

      This is my biggest issue with multiverse time travel in popular culture. Somehow they always travel back and forth between 2 of Infinite timelines

    • SwingingTheLamp@midwest.social
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      3 days ago

      Holy existential horror, Batman! By time traveling, you’ve just caused an entire universe full of new alternate-timeline versions of people to pop into existence. What happened to the timeline you left? It must still exist. You couldn’t have been the only consciousness that was experiencing it. To think otherwise is some extreme solipsism. Gosh, did some other time traveler create the timeline you left by entering it? For that matter, are you actually a duplicate, having just popped into existence with the memory of having time-traveled, but the timeline was created by another time traveler?

      Alternatively, perhaps it’s another timeline out of an infinite number of possibilities that all co-exist? Yikes! That means there’s an infinity of each person across the multiverse. Therefore, you could just murder everybody within reach, and time travel back before your started the rampage. The lives in a particular timeline don’t matter, there are an infinity more. I think Rick & Morty did an episode with that premise.

      • dukeofdummies@lemmy.world
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        3 days ago

        What happened to the timeline you left? It must still exist. You couldn’t have been the only consciousness that was experiencing it. To think otherwise is some extreme solipsism.

        Why does it need to remain? It seems like solipsism to assume it must remain because it’s your point of origin. If something or someone has the power to drop something into the past why wouldnt it overwrite everything? I don’t see why consciousness even gets applied. The universe keeps on whether I am alive, asleep, or dead.

        I see the path of time like a laser beam in a house of mirrors. If someone has the power to add a mirror somewhere. Yep, the whole beam after the fact is a vastly different pattern. Any multiverse would be entirely virtual and theoretical.

        • SwingingTheLamp@midwest.social
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          3 days ago

          Why does it need to remain? Because that timeline was populated by 8 billion human, and who knows how many non-human minds. I think it would be solipsism to think that only your own mind was the “real” one keeping the timeline in existence, and it collapsed because you leave it.

          If the time travel power does overwrite everything, all of those minds and all of their subjective experiences are just, nothing? That’s where the existential horror comes in for me.

          • dukeofdummies@lemmy.world
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            2 days ago

            Oh I agree, it’s horrifying. And I have noooo guarantee that it’s me doing the jump. Don’t misunderstand I am NOT the only real mind in this example. I’m curently just hitching a ride on said laser beam. No guarantees that I will be the same or even exist if somebody so much as moves a pebble into the past from the future.

            Existential dread all the way. If we get time travel I think it’s as horrifying a prospect as teleportation on a universal scale with only the traveller maintaining continuity.

  • Teknikal@eviltoast.org
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    3 days ago

    My belief is if you went to the past your actions would fully effect the future, no branches or anything else of course this will create paradoxes but if your a time traveller you will still exist even if you prevent your birth, if then you go back to the future there will be no record of your existence.

    Hope that makes sense.

  • LouNeko@lemmy.world
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    2 days ago

    In either scenario, I’m more interested in where the matter you’re made of will come from:

    • Either you go to the past and suddenly add additional atoms to the universe.
    • All the atoms you’re made of will suddenly be taken from their origin to form you.
    • You’ll be made from entirely new atoms created from pure energy meaning your arrival will cost ~6.75 Quintillion as in 10^18 Joules (I eyeballed the speed of light here so don’t @ me).
  • tht
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    2 days ago

    Branch off probably

  • Buddahriffic@lemmy.world
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    2 days ago

    Whatever it is, I don’t believe paradoxes are possible (other than language ones that basically just confuse any attempts to resolve a statement or set of statements to true or false without breaking any physical laws or causality).

    That said, I don’t think an unstable time loop would necessarily be impossible. Eg, you go back in time and kill your grandfather before your father is conceived, which results in you never existing in the timeline, which then means no one is there to go back in time and kill your grandfather, which means the loop disappears and the timeline snaps back to the version where you do go back, and it continually alternates from there.

    Not sure if any future outside of the unstable loop would exist, I think that would depend on if there’s a higher dimension of time that these loops could play out over.

    Or, if everything experiences the same present at the same time, it’s also possible that after the first loop, it wouldn’t go back to resolve the whole “killer pops out of literally nowhere” because it was in the past and no time traveler is bringing the timeline back to there, so it’s all in the past. Though I think in that case, you wouldn’t disappear after killing your grandfather. You’d just be an enigma that would require going outside of time to understand the origin of.

    Tbh though I’m 99% sure time travel just isn’t possible (paradoxes or not), just a fun thing to think about. And no, I don’t consider quantum effects being symmetrical in time to be time travel, they are just cases where you can reverse cause and effect and still have a valid cause and effect sequence.

  • sumguyonline@lemmy.world
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    2 days ago

    Wormholes. Travel some place faster than light and see light from the past from your source of travel when you arrive, travel again back to your original spot and theoretically you travel backwards in time to before the light from the past that you just saw was even produced yet. Might work the same for just seeing the future if you glimpse through a wormhole that leads to someplace in the future by doing an Allie oop to further into the future someplace far away, then back to someplace in your future but your destinations past. Speed and gravity both impact time. A wormhole fits that description to a T.

    • sumguyonline@lemmy.world
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      2 days ago

      Only 1 timeline matters. You’re own. Everything else becomes fluid around your timeline when you time travel.

      • sumguyonline@lemmy.world
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        2 days ago

        The timeline IS fragile, but the whole of existence is not in regards to time travel. If you go into the past and change it, the timeline changes, but only because the original timeline had you going back and changing it. You can see yourself. You can interact with yourself, but if everything is exactly as it should be you really don’t want to go mucking around and find yourself in a world where the south lost the civil war but things are thousands of times worse and you killed the ancesotor of the inventor of time travel after breaking your machine and can no longer access the timeline to fix any issues you may have caused.

  • steeznson@lemmy.world
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    3 days ago

    The current scientific theory is that time exists across space in cones that would require one to move faster than the speed of light to alter. Going to go with that one for now since I have no idea personally.

    • SpacetimeMachine@lemmy.world
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      3 days ago

      Light cones aren’t exactly literal cones of time, they are an abstraction to help us understand the mathematics of time and space. (Assuming you are talking about Penrose diagrams.)

      • steeznson@lemmy.world
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        3 days ago

        Yes, it was light cones. I was half remembering the uni module I did on the philosophy of time a decade ago. We spent more time on the grandfather paradox than the actual science!

  • 2ugly2live@lemmy.world
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    4 days ago
    • You branch off into another timeline and your actions make no difference to the previous timeline

    New actions, new consequences.

    • soupguy@lemmy.world
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      4 days ago

      This. Time traveling is a purely selfish endeavour.

      Go back and kill Hitler? Congratulations! Only you understand what changed. Doesn’t help the 7 billion people you left in your original timeline.

      • Birch@sh.itjust.works
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        3 days ago

        But you now get to live in a cool alternate reality where the soviet union clashed directly with the allied forces as the axis never existed.

        . . .

        Kirov reporting.