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Paradox-free time travel is theoretically possible

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51–60 of 215 posts

Re: Paradox-free time travel is theoretically possible

#51
post #18

Why time travelers in sci-fi also move to the position and rotation of the Earth at the given moment? They should end floating in space.

Oh actually, I've found the way to convenience myself about that: The "reality" is, when somebody travels through time, most of them (god knows how many) got killed in the process, but the story will just pick another "instance" who has survived the journey from the pool of "Multiverse" and continues.

Re: Paradox-free time travel is theoretically possible

#52
Why can’t the linear flow of time and a singular instance of reality just be the narrow lense through which we view the universe?

If reality is infinitely branching, then time travel is merely a way for the traveler to perceive and move between those infinite branches.

If you kill your grandfather in an alternate timeline your grandfather is still alive in the timeline you came from, hence no paradox. You (an alien in the new timeline) can then watch a world develop in that alternate reality where your grandfather died.

If time travel were in fact possible, this would be the only way my puny brain could conceive of it actually working.

If there’s only strictly one path that reality takes even from the perspective of an outside observer (God) then I can’t see how time travel could be possible in such a construct. If it is possible it seems you must implicitly admit that there is not in fact a singular thread of reality/time.

Just because we define some equations where t can flow in reverse and fit them into the standard model doesn’t seem to me to be persuasive evidence one way or another.

Re: Paradox-free time travel is theoretically possible

#53
Is there some sort of highly entropic and massive hash string being constantly printed, recorded, and widely distributed so that one could see if any changes happened in the past? Or rather, ensure, with a comparison, that the observer is still in the same timeline?

Is there any similar data that can be used? Perhaps global weather records?

Re: Paradox-free time travel is theoretically possible

#54

I'm so agnostic concerning the concept of time itself at the end of the day. I feel that we're so busy struggling to find a way to make time travel work, that we forget that time itself isn't a mechanism of the universe, and that it's just a word we use to describe some sort of effect or bi-product that we're observing. Here's a can of worms... Compare the concept of time travel to something like 'smell travel'. Is i…

So do you think that special relativity is misleading, or, if not, how do you reconcile this point with special relativity?

Re: Paradox-free time travel is theoretically possible

#55

I've never seen the past or future. Only physical things still or moving, combining with other things or not ... What we call 'the past' is a mental picture of where physical things used to be positioned and their condition. But everything in 'that now' has changed. Just as when we 'travel' in physical space, when we get 'back home' it has changed. If I were to 'time travel' I'd be gone from now. But everyone else wo…

How do you reconcile this idea with special relativity?

Re: Paradox-free time travel is theoretically possible

#56
post #7

This 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.

No, because time and universe is not discrete, there are no branching.

Re: Paradox-free time travel is theoretically possible

#57
post #27
post #16

Earlier quoted context omitted.

Exactly. The article mentions the grandfather paradox, but doesn't really address it at all. Can't "self correct" shooting your past self in the head.

Think what they're getting at is that it won't happen that way. Gun will jam, you die of a brain aneurysm. We don't exist in a universe where impossible things happen, so we can't bring them about. But yes, the article doesn't really sink its teeth into it.

I could see how a universe with such rules could exist. But is it our universe? In the universe you describe, wouldn't we already have seen time travellers from the future?

The only explanation I can think of for why we haven't seen any, if we live in such a universe, is that we need to build an "arrivals hall" first, and that as soon we manage to do that, people from all over start popping in for a visit.

Re: Paradox-free time travel is theoretically possible

#58
post #34

Are there ideas out there which "explain away" the problems arising from planetary/stellar movement? My naive understanding of time travelling back a single day would put me in a spot where earth will be a day later.

And why stop this line of reasoning with our local star system? There’s no absolute reference frame.

Re: Paradox-free time travel is theoretically possible

#60
In case anyone is interested, Sean Carroll did an amazing podcast episode on the mechanics of time travel in a scientifically accurate way [1]. He sometimes works as a scientific advisor on Hollywood movies and claims to be responsible (in part) for the line "You mean Back to the Future is bullshit?" in 'The Avengers: Endgame'. He also touches on the topic of killing Hitler as well as different tropes in time travel movies. He also points out one particular movie which he thinks did time travel logic best: Bill and Ted's excellent adventures.

[1] https://www.preposterousuniverse.com/podcast/2020/11/23/124-...

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