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Question about Time

  1. Aug 8, 2018 #1
    So, I asked a similar question in the fantasy media forum but I wanted to get answers based on physics from people in this forum. I'm writing a story and I sort of want it to be a reverse Groundhog Day (where time snaps back 24 hours, with only him retaining memories). I thought it would be a cool gimmick to make a story where time 'snaps' forward 20 years, so, if you're currently in your living room, aged 20, you'd suddenly be on a beach in Florida with your family, aged 40. But, nobody notices this snap, except the protagonist, so he must adapt to this future. I was wondering if there's any way to make this storyline work with throwing physics out the window? Or can you at least bend the laws of physics to make it sci-fi?
     
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  3. Aug 8, 2018 #2

    fresh_42

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    You could send the protagonist to a journey at almost light speed for some time and return him to earth twenty years later. Unfortunately, you imply that he has lived this twenty years for otherwise he wouldn't be married and had children. So you require him to do both, which would make a twin necessary, but then they wouldn't share the same memories. I suppose that the human factor is the basic difficulty here, not so much the physical.
     
  4. Aug 8, 2018 #3

    Dale

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    Sure, just hit him on the head.
     
  5. Aug 9, 2018 #4

    Drakkith

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    The problem is that all the 'plausible' ways to time travel into the past don't work for time travel into the future like you're suggesting because they physically remove the person from their current time period. So time traveling forward 20 years would lead to a world in which the person suddenly disappeared for 20 years. They wouldn't have been present to have a family in that timeframe.

    Of course, there's no reason you can't simply invent a way unless you're just dead set on trying to not break physics.
     
  6. Aug 9, 2018 #5
    You could have it be a form of amnesia where the protagonist permanently forgets the past 20 years without any sort of time travel. Of course that probably isn't plausible from a psychological perspective given that most people aren't going to have any recollection of what they were doing exactly 20 years ago and memories aren't chronological, but it could still be explained within the bounds of physics.
     
    Last edited: Aug 9, 2018
  7. Aug 9, 2018 #6

    Ryan_m_b

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    The premise reminds me of Rainbows End by Vernor Vinge:

    Robert Gu is a recovering Alzheimer's patient. The world that he remembers was much as we know it today. Now, as he regains his faculties through a cure developed during the years of his near-fatal decline, he discovers that the world has changed and so has his place in it. He was a world-renowned poet. Now he is seventy-five years old, though by a medical miracle he looks much younger, and he’s starting over, for the first time unsure of his poetic gifts. Living with his son’s family, he has no choice but to learn how to cope with a new information age in which the virtual and the real are a seamless continuum, layers of reality built on digital views seen by a single person or millions, depending on your choice. But the consensus reality of the digital world is available only if, like his thirteen-year-old granddaughter Miri, you know how to wear your wireless access—through nodes designed into smart clothes—and to see the digital context—through smart contact lenses...

    https://www.goodreads.com/book/show/102439.Rainbows_End

    Despite the protagonist having lived into the future his Alzheimers meant that he forgot most of it. As that was cured it was like waking up and finding large patches of his memories missing, as though he'd travelled into the future of his own life.
     
  8. Aug 9, 2018 #7
    Well, what I was going for was: Time itself skips forward 20 years, like you can skip forward 20 seconds on a YouTube video. So if now you're in your living room, but in 20 years time your on a beach on Florida, bam, your there. Is this possible? Also, on a side note, if that happened, would you notice the skip?
     
  9. Aug 9, 2018 #8

    Ryan_m_b

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    Emphasis mine: with this qualification the question makes no sense. The passage of time is measured by the rate in which things happen. There is no reference frame somehow separate from time. Asking "would you notice if time sped up for everything" makes about as much sense as saying "how big is a meter if everything in the universe is doubled in size".

    If you're asking about suddenly finding your present mind in your future body no that is not possible through any known mechanism. Hence why people have suggested amnesia as the closest you can get. Tbh though if you have a good idea for the story just write it. The interesting part is unlikely to be the mechanism by which said timeskip happens and virtually no reader will have a problem accepting a fantastical conceit for the sake of a story. The interesting part is how you write the consequence of such an event; how the character deals with it, what the ramifications are etc.
     
  10. Aug 9, 2018 #9
    Yeah, I understand. I just want to get the plot device not to be too crazy. But, surely if the universe itself skipped 20 years (in some reference frames that may be only 10 or 5 or 50 years), you would notice the missing time, wouldn't you? That's what I want my plot to be about, the protagonist notices the skip but everybody else doesn't, for some reason.
     
  11. Aug 9, 2018 #10

    Ryan_m_b

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    "If the universe itself skipped 20 years" makes no sense as a sentence. Time is a measure of change within the universe so it can't "skip". Like I said above the question logically makes no sense, it's like asking what size a meter is if everything is doubled. Can you explain more precisely what it is you mean? You started by suggesting that the protagonist wakes up in a future life he has no memory of living (in between his last memory and the moment he woke up) but are now going off on tangents about the entire universe skipping.
     
  12. Aug 9, 2018 #11
    Well, my plot was that the universe itself skips forward 20 years (the cause yet to be decided), everyone is oblivious to this skip in time, maybe because they somehow have memories of the 20 years, except the protagonist. So he is now in the future, everyone he knows is older and everything is different, he has to adapt to this new world. So, that's why I asked about would we notice time skipping and is it possible to make it seem realistic etc.
     
  13. Aug 9, 2018 #12

    Drakkith

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    It's not too crazy. It's hard to make a plot device that's too crazy unless it breaks everyday laws that people actually know and does it in a way that doesn't make much sense or in a way that isn't properly explored by the author. When it comes to time travel, literally anything goes since there is no known way to travel through time except the mundane way that we all experience. You could write about a person who travels through time by being launched by an alien slingshot that uses the underwear of a giant as the sling and it could work.

    The real work of an author is to make ideas work. That is, they take an idea and they write a coherent, believable (not realistic) story using it. Realism is just a way to make a story believable and to give it a certain style or feeling.
     
  14. Aug 9, 2018 #13

    Ryan_m_b

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    The universe has not skipped forward 20 years in this scenario, your protagonist has somehow skipped forward in time into his body. This is a well established trope known as mental time travel:

    https://tvtropes.org/pmwiki/pmwiki.php/Main/MentalTimeTravel

    It has no realistic basis. The closest real life analogy is amnesia, or a long coma.
     
  15. Aug 9, 2018 #14

    Drakkith

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    Ah, there's a good philosophical question, "If everyone has memories of the past 20 years, is it the same as those 20 years actually happening?"

    I wouldn't word this as the universe itself skipping forward in time since it only affects the protagonist. I'd just say that the protagonist himself is jumping through time. Or something like that. Emphasis on the protagonist, not the universe.
     
  16. Aug 9, 2018 #15
    Ah yes, that's close to what I'm thinking of, it might work better, thanks. On a side not, could time skip anyways without violating the laws of physics or is it just impossible?
     
  17. Aug 10, 2018 #16

    Drakkith

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    The idea of a "time skip" is not well defined but it suggests a discontinuity in time. This would cause "world-lines" (the path an object takes through spacetime) to abruptly end. The only other places these abrupt discontinuities arise in physics are in the singularities of black holes. The problem with this is that singularities completely obliterate any predictive power our theories have beyond them. Normally you can always make at least some kind of approximation about what will happen if you don't know all of the details and these approximations will vary in their accuracy. But with a singularity there isn't anything. World-lines just end. Objects that pass into a singularity simply don't exist in the universe anymore in any sense. They are just gone.

    Of course, it is very widely believed that singularities are not real, but are in fact artifacts of our limited understanding of physics at the immense energy and density scales that give rise to singularities in our models. In other words we don't know the "actual" laws of physics and our current theories are merely good approximations until you get to these extreme scales.
     
  18. Aug 10, 2018 #17
    Yes, I understand, but if time skipped, wouldn't the worldline of objects just end and then start up again, with a big gap? And since there is a big gap, we would notice the missing time, wouldn't we? Basically my overall question is, can time itself skip forward in the real world (to make the novel realistic) or would that be fantasy?
     
  19. Aug 10, 2018 #18

    Drakkith

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    Not in real-world physics, no. World lines don't start or end except possibly during creation/annihilation events at the subatomic scale when particles are created or destroyed. I say 'possibly' because General Relativity and Quantum Physics are not united, so I'm not sure how wordlines (something from GR) are treated in QM, if they're dealt with at all. But in any case, the energy of these events is conserved and the events themselves follow known laws. With a 'skip' the wordlines, and thus the objects, simply end. There's no known event such as an annihilation event (which conserves energy and momentum and other conserved quantities) that follows. All of the major laws of physics, especially conservation laws, are broken.

    It would be pure fantasy. A time skip is simply not compatible with our current understanding of the laws of physics.
     
  20. Aug 11, 2018 #19
    Ok, thanks. If I do use the premise and avoid the laws of physics, realistically, if a skip in time occurred, would it be noticeable? I assume yes as at one moment you're 25 and in bed and the next you're 45 on holidays or whatever, with no memory, as the events never occurred. What do you think?
     
  21. Aug 11, 2018 #20

    Vanadium 50

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    If you're avoiding the laws of physics, it can be anything you want.
     
    Last edited: Aug 11, 2018
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