5 ms·

In my view, there is no 'going back' with time travel. Rather, you appear in realty A+B where A is a similar state of the world at that moment in time that now

by jadbox 5y ago

In my view, there is no 'going back' with time travel. Rather, you appear in realty A+B where A is a similar state of the world at that moment in time that now has B applied to it by having present self placed in it. This solves all paradoxes with time travel as you never change the past, but rather, you are creating/finding forks of reality that appear backwards/forwards in time. Each time you 'travel in time', you are mearly moving between possible states of the universe. In this lens, nothing you do in 'the past' when affect you in the present because you're never actually in the past, but rather a fork of that time/space with you in it. That's just how I've always imagined it.

jessriedel 5y ago
> In my view, there is no 'going back' with time travel. There are many distinct models of time travel, some self-consistent and some not. You are describing one you like, but this does not tell us much about how time travel works in the actual universe, if it occurs at all.
state_less 5y ago
What about the future affecting the past? Rather than A+B, there is A. In this scenario, you don’t go to the past, you were/are already there. In other words, there never was a past without you in it. You never could go back and kill your mother/father since it would break a causal loop. You may think you have the agency to do so, but try as you might, you won’t/don’t.
- justinpombrio 5y ago
  What this means is that the universe is solving a fixpoint equation: find a history that is self-consistent. The question this raises is, which one does it pick? There are infinitely many to choose from, and no clear criteria that I know of. You can have a fixpoint where someone is their own parent, but what chose this fixpoint over any other? I don't mean "woah man, who get's to decide?", I mean "this description of physics is incomplete; to complete it you need to specify the method of selecting which fixpoint gets chosen".
  - state_less 5y ago
    I’m not sure how self consistent histories might be chosen. It seems like some futures should be more common based on our physical understanding. Maybe they are all there (many worlds) and we happen to find ourselves in the compatible (most common?) ones.
r00fus 5y ago
This would seem the most logical to me as well - time being viewed not as a line, but a plane (or even a 3d space), where attempts to alter "the past" put you in a distinct branch of the timeline (a different spacetime). Of course, this isn't as romantic or digestible as time-travel as envisioned in most fiction (BttF).
webmaven 5y ago
> This solves all paradoxes with time travel as you never change the past, but rather, you are creating/finding forks of reality that appear backwards/forwards in time. You would be breaking conservation of mass/energy, though. Either you restate 'conservation' such that it applies across all universes instead of just within one (and you are moving energy/mass , in which case the number of timelines has to be fixed (which leaves open the possibility of paradoxes), or you're still violating conservation by creating entire universes every time you fork the timeline. There are ways to get it all to work out, but they are all pretty weird and unintuitive. The first is that paradoxes are simply not permitted (or more accurately, can't be observed) and that the universe hides attempts to create them the same way it hides information that would violate the uncertainty principle. The other main way you can resolve it is by asserting that while there are an infinity of parallel universes, and more are being spawned all the time, just as many are merging, keeping the number of universes at the same infinite number. Time travel is then permitted to spawn a new universe as long as the books remain balanced. Of course, the easiest way to balance things is for any changes to not matter enough to prevent timelines from merging again.

by jadbox 5y ago

jessriedel 5y ago

> In my view, there is no 'going back' with time travel. There are many distinct models of time travel, some self-consistent and some not. You are describing one you like, but this does not tell us much about how time travel works in the actual universe, if it occurs at all.

state_less 5y ago

What about the future affecting the past? Rather than A+B, there is A. In this scenario, you don’t go to the past, you were/are already there. In other words, there never was a past without you in it. You never could go back and kill your mother/father since it would break a causal loop. You may think you have the agency to do so, but try as you might, you won’t/don’t.

justinpombrio 5y ago
What this means is that the universe is solving a fixpoint equation: find a history that is self-consistent. The question this raises is, which one does it pick? There are infinitely many to choose from, and no clear criteria that I know of. You can have a fixpoint where someone is their own parent, but what chose this fixpoint over any other? I don't mean "woah man, who get's to decide?", I mean "this description of physics is incomplete; to complete it you need to specify the method of selecting which fixpoint gets chosen".
- state_less 5y ago
  I’m not sure how self consistent histories might be chosen. It seems like some futures should be more common based on our physical understanding. Maybe they are all there (many worlds) and we happen to find ourselves in the compatible (most common?) ones.

r00fus 5y ago

This would seem the most logical to me as well - time being viewed not as a line, but a plane (or even a 3d space), where attempts to alter "the past" put you in a distinct branch of the timeline (a different spacetime). Of course, this isn't as romantic or digestible as time-travel as envisioned in most fiction (BttF).

webmaven 5y ago

> This solves all paradoxes with time travel as you never change the past, but rather, you are creating/finding forks of reality that appear backwards/forwards in time. You would be breaking conservation of mass/energy, though. Either you restate 'conservation' such that it applies across all universes instead of just within one (and you are moving energy/mass , in which case the number of timelines has to be fixed (which leaves open the possibility of paradoxes), or you're still violating conservation by creating entire universes every time you fork the timeline. There are ways to get it all to work out, but they are all pretty weird and unintuitive. The first is that paradoxes are simply not permitted (or more accurately, can't be observed) and that the universe hides attempts to create them the same way it hides information that would violate the uncertainty principle. The other main way you can resolve it is by asserting that while there are an infinity of parallel universes, and more are being spawned all the time, just as many are merging, keeping the number of universes at the same infinite number. Time travel is then permitted to spawn a new universe as long as the books remain balanced. Of course, the easiest way to balance things is for any changes to not matter enough to prevent timelines from merging again.