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I What time structure supports info moving backward in time?

  1. May 28, 2018 #1
    This of course is speculative, but IF faster-than-light travel (or wormhole tunneling or some other exotic means) was found to be able to communicate information from the future to the present, what would that indicate about the structure of time? Some might argue that indicates a block-type of time structure, since from the perspective of the present the future doesn’t exist yet. But if the information literally “goes backward” ONLY at a moment in the future when the information is available, is the necessity for a block universe just an illusion, and another view of time could accommodate such communication?
     
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  3. May 28, 2018 #2

    berkeman

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    Thread is in Moderation temporarily...
     
  4. May 28, 2018 #3

    fresh_42

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    :welcome:

    I hope you will have fun.

    ... which might be a problem, as we only discuss scientific papers and textbook contents
    (see our rules here: https://www.physicsforums.com/threads/physics-forums-global-guidelines.414380/).
    Maybe you want to consider it as a thought experiment. I think there are serious considerations about e.g. more than one dimension of time, but I'm not aware of sources. You could search for it yourself on e.g. http://www.arxiv.org/

    There are always two essential arguments one has to deal with:
    • causality
    • the laws of thermodynamics
    So whatever one thinks about it, these two are strong observations which would make something you like to discuss pretty difficult.

    To transport information, you will need something to travel in spacetime and there is a natural speed limit. So we would have to either extend spacetime by dimensions we don't know yet, and this would imply pure speculation, or some mysterious stuff, that doesn't obey the speed limit which is also speculation. Neither of them have been found so far. This means, your thought experiment will have to make some very unusual assumptions before it could be discussed in which way such an information transfer could be even thinkable.

    It's not that scientists wouldn't have fantasy or denied everything they don't know, but at least some experimental evidence should be found to base such a theory on. And it's not as if we wouldn't try to find exceptions to our current models. We have built the largest machine mankind ever constructed to find them. And string theorists looked for new models since about half a century now and still can't claim any evidence.
     
  5. May 29, 2018 #4
    Thanks for the response. Is it fair to say that scientists are seriously researching and debating if quantum entanglement could be exhibiting faster-than-light behavior, even if there is no current means to utilize that mechanism for information exchange (by us, I mean, of course)? Basically what I'm looking for is if anything in any circumstance could ever go backward in time, how would that information plug into current established physics, the view of time, etc.? So I'm only interested in what the consensus would likely say it means, so I'm not trying to throw the baby (mainstream science) out with the bathwater.
     
  6. May 29, 2018 #5

    jbriggs444

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    Have you Googled for "closed timelike curve"
     
  7. May 29, 2018 #6
    I have. As you are probably thinking based on your suggestion, that is one of the possibilities that lurks in the equations (general relativity) viewed more favorably by mainstream science (as least for consideration). Of course their potential allowance by the math is different than confirmation of their existence, but they represent at least one door left slightly ajar for exchange between future and present. And I know there is debate about whether closed timelike curves would maintain consistency of events, and arguments regarding their quantum vs. classical natures, etc. You end up running into the issues about resolving relativity vs. quantum theory.

    I guess my core question could be rephrased as whether quantum theory/interpretations could shed any light on the implications of the "backwards in time" information transfer. So yes, I'm asking a question about something not yet proven, but it's still on the table as a possibility, and I'm only asking for the idea to be filtered through existing mainstream models (if possible). Only knowledgeable people could entertain the question seriously, so that's why I posted. Thanks!
     
  8. May 30, 2018 #7
    I agree with all of your assertions. Of course I should! First, thanks for the response, despite the speculative wrapping I gave the question. My conundrum is I'm looking to utilize mainstream views to inform what's currently not a very mainstream topic, so that fits this into an awkward box, and those educated views are only possessed by people in these types of forums. But back to your points...I completely agree that causality and thermodynamics would have to be fully accounted for by any sharing of information from the future (assuming there is one) and the present. So those constraints would be very difficult to overcome. But nature is full of surprises, and if there is a way, it will find it. But here's something interesting...the very constraints you would expect of information adhering to non-negotiable rules regarding maintaining causality and consistency could be what gives its presence away, or more specifically helps confirm where it's coming from.
     
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