this post was submitted on 02 Jan 2025
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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
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[–] [email protected] 6 points 4 days ago

The first one makes the most sense to me, which is why I think time travel should be used to make significant changes. Go big or go home

[–] sumguyonline 1 points 3 days ago (1 children)

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 1 points 3 days ago (1 children)

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

[–] sumguyonline 1 points 3 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.

[–] [email protected] 8 points 4 days ago (2 children)

The one where you can only jump forward, not backward. It avoids the common paradoxes.

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[–] [email protected] 5 points 4 days ago

Something else entirely, I don't think we're capable of understanding time (yet?)

[–] [email protected] 5 points 4 days ago

Something else, namely: Time isn't real and uncaused events are not only possible but more common that most people think.

[–] irotsoma 3 points 4 days ago

I think time travel as a being who perceives one dimensional time linearly is not possible. And for any entity who doesn't perceive time linearly it would be no different from traveling in a spacial dimension. It's just travel. Anything that entity does in that point is a permanent fixture to the entities that perceive it linearly.

So yes, if someone could travel in time in the SciFi sense, they wouldn't be able to change anything in their past experience (direct experience or prior to their perception, but in their event line) because that's already part of that point in spacetime to anyone who experiences it linearly.

But also, it's likely that time is not one-dimensional just like we know space is not only three-dimensional. So it is possible that you could end up in a separate "branch" of time that your past self from your perspective will never experience (directly or as past events), because it's not the same point in spacetime as the event in your direct past timeline. But it's not like there is a specific set of "branches". They likely don't branch off from a single trunk into the other dimension(s) or if they did "branch", it was at the same time as all other "branches", the beginning of the universe, not as specific events occur like in SciFi. And the changes you make in those branches were always part of those branches to people who will perceive the future of that timeline.

[–] [email protected] 6 points 4 days ago

Whatever Primer did, cuz that movie scratches my brain real good.

[–] [email protected] 4 points 4 days ago (2 children)

Paradoxes slowly disintegrate the timeline you're in. Thousands of years, Deadpool 3 rules.

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[–] [email protected] 6 points 4 days ago

Probably something like attractor field theory from Steins;Gate. In my view it's basically timelines with a bit of topological though thrown on it to combine closely related timelines into bundles, similar to some algebraic topology concepts I guess.

[–] RBWells 3 points 4 days ago* (last edited 3 days ago)

Like in Black Science, I think time travel would fuck with the fabric of reality. Make it shreddy.

I do not believe in nexus events; there is a personal reason (experience ) I don't expect anyone else to believe based on something I experienced but I don't. ETA: Unfortunately, everything has happened already, and I was very angry about it.

Just watched Arrival again yesterday and that's my other guess. More like your choice of "you have already done it, you can't alter the timeline" but can't go outside your lifetime, time doesn't work the way we think and we can perceive other "times" because they aren't really linear, just some quirk of our perception makes it seem that way, you really exist concurrently all along your existence.

But if some machine was designed to take you before or after your lifetime, it would tear at the fabric of reality (lifetime not exactly the correct word but your existence that has a beginning and end of some sort).

[–] [email protected] 5 points 4 days ago* (last edited 4 days ago)

Are you asking which system I think is the most plausible, or which is the most desirable?

Plausibility:

Well, I'd guess that time travel probably isn't possible, and if it is, it's probably under extremely limited conditions that render it impractical for viable exploitation. But if you're operating under the assumption that it is, I'd say the "your actions do not affect this timeline" or similar type.

Why?

We have had no record of time travel or seen phenomena likely resulting from it. If at time T, time travel is discovered, it seems unlikely that someone after that time wouldn't have come back in time and done something that we'd have noticed.

And it's not just us. If self-timeline-affecting time travel is possible, then you consider all the possible civilizations out there in the universe who might discover it at some point in time and want to take advantage of it. Yet we've seen nothing from them. It's the Fermi Paradox on steroids. The Fermi Paradox asks why intelligent aliens, half of whom statistically probably evolved before us and should have colonized the universe if they're out there, aren't visible to us. The time to travel over even huge distances, though it is large, is small compared to the time required to evolve a spacefaring civilization. But in the presence of self-timeline-affecting time travel, then even the evolutionary time becomes a non-factor, since civilizations from the future could also show up, and roll back in time with their advanced technology and make use of it from then. The question is no longer just "where is everyone", but the even harder to explain "where is everyone from all time?"

Okay, that's the plausibility question. How about the desirability one, which system I'd like to exist?

Hmm. I guess I'd give the same answer, the "no affecting your own timeline" form. I think that if you could affect your own timeline, that probably some kind of incident in the future -- only takes one -- would be likely to have mucked up things sufficiently to wipe out civilization, and we probably wouldn't be around to even be pondering the matter.

[–] Feathercrown 3 points 4 days ago (1 children)

The most interesting one to me, and the one that makes the most sense, is that changes propagate forward in time at the same speed as everything else, so 1 second per second. Why would causality suddenly decide to go any faster than that? This effectively means that all "alternate timelines" exist on the same timeline, and overwrite each other as they move forward.

You can visualize this by coloring the original timeline red. When you time travel backwards, you arrive at an earlier point on the timeline and it begin overwriting it orange, with the "head" of the orange section expanding into its future, which is previously red. If someone travels into the orange area again, it turns yellow, etc. If the instant where you time travelled backwards to make the orange region gets overwritten, the color of the timeline to the left of the orange region would begin expanding to overwrite it at the same speed as any other change.

This does lead to some interesting things, like two time travel loops that include the same point in time literally slowly corrupting the timeline. One loop, where you travel back, wait until when you left, then travel back again, would cause the future from your departure point to continually be overwritten by each new loop color, sending constant-width "bands" of colored time forward before they're overwritten by the band from the next loop. Two loops' bands would almost certainly not be commonly divisible, so you'd eventually end up with "bands" moving forward and within the loop that get smaller and smaller, fragmenting the timeline into colored noise. If you lived on the timeline, though, you wouldn't notice-- even if you're in a timeline band that's only 1 second wide, you move with it, so nothing seems out of the ordinary. But if you travelled back to the same point in time repeatedly to check on it, or could freeze yourself in time and watch the bands pass through your point in time, things would be changing incredibly quickly. This also means that waiting time in the future before travelling backwards in time would let the past have time to be overwritten by a different band, so the same point in time would be different depending on when you left the future. All timeline damage would be repaired (at band-expansion speed) if you could remove all instances of time travel backwards to the offending loops, though.

IRL, the speed of causality depends on your speed, too, and in theory, timeline changes would expand outward at the speed of light. My brain is not big enough to think through all the potential consequences of relativistic weirdness and time travel at once, though. I suspect it would allow for "bands"/fragmentation not only in time but in space as well.

[–] [email protected] 4 points 4 days ago (1 children)

The reason time depends on speed is because you are always moving at the speed of light, but the vast majority of that is going in the 4th dimension: time. If you speed up in a given direction you're losing speed through time to make up for it.

[–] Feathercrown 2 points 4 days ago

I always found that idea so cool for some reason

[–] gnomesaiyan 3 points 4 days ago (2 children)

Traveling to the past: You can't go into the past because doing so would change who you are and thus your reason for traveling in the first place. For example, killing Hitler when he was a baby would completely change the world as we know it, thus change you as you are. You might not have been born, or if you were, you wouldn't know who Hitler was, so there was no reason to go into the past, thus your time travel never happened in the first place. It's a paradox via butterfly effect. To underscore this further, you couldn't even change the history of another planet's species simply because it's still a part of your timeline. Same universe.

The only scenario where it might work is going into the past as an impartial observer and not having any impact at all (some kind of magical bubble where you are invisible and no effect on the past). That would be fun, because you get to learn about history firsthand.

An interesting time travel alternative is Trunks' timeline from Dragonball Z, where he went to the past, saved their future, but the androids in his timeline still persisted. This leads me to believe it was not just another time but another dimension (a la Rick and Morty).

Traveling to the future is a bit easier. Technically, with the proper spacecraft, you can go into the future (go sit around Sag A* for a bit), but it would be a future where you weren't around to have an influence in it. It would be like temporarily kidnapping yourself. This might be similar to how people came back five years later after being snapped by Thanos in the MCU.

IMO, the best use of time travel would be to go to the future tomorrow to scan ahead and see what happens (as long as you wouldn't have been needed in that future), then going back to the present time just seconds after you left. So little would have changed that your timeline would remain intact (only your biological clock would be off). So, you might be able to prevent incidents in the world by constantly jumping ahead to see what was going to happen. A future-scanning time traveler might have been able to prevent the recent New Orleans tragedy from happening. They could also be lazy and just learn the winning lottery numbers.

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[–] Tikiporch 3 points 4 days ago

The one that exists.

[–] [email protected] 2 points 4 days ago

I mean I would say causality would be followed. So you change things and essentially create a new timeline. The only thing with that is if your time travel system could handle it. If you go back will you go back to your old timeline or your new one? Maybe you could choose but not necessarily. and of course any time you return to a point before you left you are further creating a new timeline. You would have to return after you left to preserve whatever you return to. So basically causality follows the individual and timelines pretty much always get created when time travel happens. Another interesting possibility is if you can manage to not change anything at all maybe you could stay in the original timeline. Its hard to say if that could even happen though as it would need at some point an original timeline without time travel to work off of.

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