This article claims to refute the butterfly effect with no support. I get that strange things happen in Physics. I would have liked more support.
Paradox-free time travel is theoretically possible
131–140 of 215 posts
Re: Paradox-free time travel is theoretically possible
#132Earlier quoted context omitted.
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.
The thing about this "self-correction" is that nobody, but nobody has a mechanism to explain this force. Not how it works or worse yet, how it will know how to self-correct. What particular force decides that the friction on some surface will briefly rise and cause the gun to jam? How does it know to do that? In all of the paradox-forbidding time travel scenarios, nobody has ever mentioned anything deeper than "Well,…
Of course there's a mechanism to explain it: determinism.
It's got nothing to do with 'knowing' anything, it's just that we experience life as a vivid playthrough of causes and effects that could never have started or ended any differently.
Now, you might not agree with that explanation, but it can't be precluded, and it solves all of your concerns above.
Re: Paradox-free time travel is theoretically possible
#133Earlier quoted context omitted.
> pump energy at your destination What does that even mean? This is the kind of hand-waving the OP was pointing out. He probably meant the first law.
> What does that even mean Any variation on this: “sending this item in the past, will grab the same amount of mass from the past, taken at random in a way that preserve the energy on both ends”
So like the gate of truth from Fullmetal Alchemist?
Re: Paradox-free time travel is theoretically possible
#134Earlier quoted context omitted.
I think the flaw here is assuming "knowing" rather than a mechanism that makes it impossible to express the paradox, or alternatively, impossible for you to find yourself in a world where an action that created a paradox happened. One option: We tend to see time as mutable, but it's not clear that time needs to be mutable. Imagine time as a window into an immutable graph of deterministic state transitions, for exampl…
That option implies time travel is not possible, since your mere existence at a past moment is already mutating it. Which is the opposite of what the article claims.
My description explicitly hypothesised a universe that is entirely immutable, and where the passage of time is purely "read only". Your presence at any given point in time then would never mutate anything ever, any more than watching a movie mutates the movie.
EDIT: You can certainly imagine more "relaxed" models that would also work, where mutability is possible, but where constraints increasingly restrain which mutations are possible when looping back on itself, but an immutable model is the simplest to describe in order to illustrate that models that allows loops can be made self-consistent.
Re: Paradox-free time travel is theoretically possible
#135Earlier quoted context omitted.
That option implies time travel is not possible, since your mere existence at a past moment is already mutating it. Which is the opposite of what the article claims.
Why? If time is immutable (essentially a Block Universe where everything is predetermined) then you traveling in time doesn't mutate anything, just as you experiencing the current time isn't mutating anything. Of course it (seems to) follow that you don't have any free will. But there's nothing in science or philosophy contradicting that (if anything we seem to find more and more evidence to support that idea).
I think free will is orthogonal to mutability/immutability of time.
Re: Paradox-free time travel is theoretically possible
#136Earlier quoted context omitted.
The thing about this "self-correction" is that nobody, but nobody has a mechanism to explain this force. Not how it works or worse yet, how it will know how to self-correct. What particular force decides that the friction on some surface will briefly rise and cause the gun to jam? How does it know to do that? In all of the paradox-forbidding time travel scenarios, nobody has ever mentioned anything deeper than "Well,…
> The thing about this "self-correction" is that nobody, but nobody has a mechanism to explain this force. I have a hypothesis: it's about stability. First, let us discard the notion of time "happening" from a perspective of the universe as a whole. Now, let us posit that only universes with stable structures can exist the same way that quantum superpositions can only collapse into certain states based on conditions…
I like this explanation, but it essentially doesn't solve the paradox. It just shifts it to knot-stability.
The question is: can I create a situation which can not lead to stability? And if so, what happens? Will it simply not work? Or will every situation lead to the possibility of stability?
Say, I travel back in time at the moment the universe "ends", and from that point onward in the past I destroy all time machines with a certain technology. Then, no one can fix what I did, and no stable loop could exist.
Now it is the same paradox all over again.
I mean, my guess is that such a situation simply can not exist, therefore I can not experience it - I can not live in this universe where this is possible. So, I can only live in the universe where my technology somehow fails exactly when someone travels back in time to correct my loop.
Re: Paradox-free time travel is theoretically possible
#137It’s impossible to create a paradox, because the events that led to you being able to go back in time were created by whatever you did in the past in an attempt to change the future. If you did successfully change the past so that you never ended up going back, you would not live the life where you go back in time to make that change. But if you did find yourself even going back in time it means your efforts already…
This is the "there's no such thing as free will" argument, which is even more implausible than time travel.
If cause comes before effect, then there is free will but there is a limited possibility of effects. If cause comes after effect, there isn’t free will but there is an unlimited possibility of effects.
Re: Paradox-free time travel is theoretically possible
#138Earlier quoted context omitted.
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.
The thing about this "self-correction" is that nobody, but nobody has a mechanism to explain this force. Not how it works or worse yet, how it will know how to self-correct. What particular force decides that the friction on some surface will briefly rise and cause the gun to jam? How does it know to do that? In all of the paradox-forbidding time travel scenarios, nobody has ever mentioned anything deeper than "Well,…
> The thing about this "self-correction" is that nobody, but nobody has a mechanism to explain this force. Not how it works or worse yet, how it will know how to self-correct.
You could think of it that the universe where we exist must have a stable/consistent state.
If we go back in time and change the state, then that universe can't (didn't) exist, so it can't be the universe that we are in. From our point of view in the present (before time-travelling), the state change was in the past, it will have already happened before we start time-travelling.
This doesn't technically preclude us from going back in time. It's more that the present state (at least as we observe it) is pre-determined, since we already exist in the present.
Re: Paradox-free time travel is theoretically possible
#139Earlier quoted context omitted.
Why? If time is immutable (essentially a Block Universe where everything is predetermined) then you traveling in time doesn't mutate anything, just as you experiencing the current time isn't mutating anything. Of course it (seems to) follow that you don't have any free will. But there's nothing in science or philosophy contradicting that (if anything we seem to find more and more evidence to support that idea).
I think free will is orthogonal to mutability/immutability of time.
Free will is a nonphysical illogical concept. It's impossible to define free will inside physics in a way that feels "free".
Re: Paradox-free time travel is theoretically possible
#140Earlier 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.
So this is essentially magic.
Any self correcting mechanism implies magic.
How does 'universe' know what needs to be done to fix timeline?