Shows about time travel

Discussion in 'Physics & Math' started by arfa brane, Apr 9, 2018.

  1. Write4U Valued Senior Member

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    But the destination is a spacetime coordinate. When "travelling back", at best you would be super-imposed and that is problematic to your physical existence.

    Can you travel back in time without travelling back in your own time-line of existence other than as a loop? A loop means observation only, just like a movie it is reality passing you from a distant past. You are not part of it.
     
    Last edited: Aug 8, 2018
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  3. DaveC426913 Valued Senior Member

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    No destination. If I look at a crater on the Moon but cannot interact with it, have I really travelled to the Moon?
     
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  5. Write4U Valued Senior Member

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    A telescope is a instrument that allows you to look back in time as an observer only. But mentally it allows us to travel back in time, depending on your ability to zoom in on the center of the crater and not get singed by the heat. But all you can do is observe.

    Your presence is explicated as a hologram.
     
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  7. DaveC426913 Valued Senior Member

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    When you put travel in bold like that, you are using it as an analogy. One does not travel when one thinks of the Moon.

    Here's why: if I were to use the term travel to the Moon literally, then I would be close enough to experience things I'd never seen before like this football-shaped rock, or that degree of fineness of the sand. Those would be real things, not simply stuff from my imagination. We could learn facts.

    When we mentally "travel to the Moon", we cannot learn anything new from it. We can only go by what we've seen, and what we can make up, using our imagination, but we can't discover extant things.

    Thus thinking of the Moon is kind of like travelling to the Moon. It is an analogy. It falls apart at a certain degree of scrutiny.
     
    Last edited: Aug 8, 2018
  8. Write4U Valued Senior Member

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    I guess I am arguing that it is impossible to split you own time-line into two interacting but independent time-paths. The past you cannot kill the present you, because you would not be able to be there then. The present you cannot kill the past you, because you would not be alive to visit the past you. It is logically impossible. There is no freedom of choice.
    https://en.wikipedia.org/wiki/Time_travel#Ontological_paradox

    I am not excluding the possibility of time travel such as wormholes, but I am convinced we would not be able to physically interact with the world in the past.
     
    Last edited: Aug 8, 2018
  9. DaveC426913 Valued Senior Member

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    Indeed. Which is why time travel is fraught with pardoxen.


    See, that's the problem. As soon as you grant time travel, there's no reason to think you can't create a paradox.
     
  10. DaveC426913 Valued Senior Member

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    There is a scenario wherein time travel does not create paradoxen.

    Essentially, your arrival in the past creates an alternate universe that carries on its merry way, its future independent of the original. You can kill your grandmother (or your younger self), but this does not create any paradox, since your origin is not that younger self; it is the original universe.
     
  11. Dr_Toad It's green! Valued Senior Member

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    I saw that movie already. Crazy that I saw a movie in 1763 about 2018 from 1973, and I can still talk about it. Of course if I go into detail the fabric of the universe will unravel like a Chinese sweater, so you'll have to take my word for it.

    I can tell you this, though. Dukakis went back to murder Kennedy, tried to pin it on Castro, but Curtis LeMay wasn't having any of that. He wanted Idi Amin to take the fall, but Idi was eating diseased human livers instead of good Sevruga, drinking applejack instead of good Tennessee moonshine. Poor pawn Oswald, the unlucky rabbit.

    Who knew?
     
  12. Write4U Valued Senior Member

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    I disagree with that scenario. As soon as you make any alterations to the (your) past, your future is compromised. A loop has been created.
    The only way no paradox is created is when you are unable to affect the past in any physical way.
     
  13. Write4U Valued Senior Member

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    When we look through a microscope at an atom are we travelling through space and time? Or are we just looking?
    When we look through a telescope at a galaxy are we travelling through space and time? Or are we just looking?
    Does it make a difference if the observer is near or far away as long as we can get sufficient magnification?
     
  14. Yazata Valued Senior Member

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    Only if one imagines time as if it was a one-dimensional line.

    If one imagines time as an ever-multiplying tree, then traveling into the past and changing it might just result in directing the time traveler into a different alternative future than the one in which he originated.

    Must a causal loop be identical to a logical paradox?

    What about the modal realist metaphysical models of modal semantics? Or the many-worlds interpretations of quantum mechanics? (Those two aren't the same thing, but they look similar and may be mutually supporting.)

    https://en.wikipedia.org/wiki/Modal_realism

    https://www.iep.utm.edu/mod-meta/

    https://en.wikipedia.org/wiki/Many-worlds_interpretation
     
    Last edited: Aug 8, 2018
  15. Throbber Registered Senior Member

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    Time-travel is without paradoxens. Should you reverse time to "alter" the past, that past event already happened. The only new information discovered is that it was YOU who stepped on that bug.
     
  16. Write4U Valued Senior Member

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    But then how would he end up back in the first time-line when that would result in a new time-line which may not allow him to travel back into the past? Seems to me one would get lost in multiple realities and non-compatible time-lines

    The paradox results only when the traveler is able to interact with the past and change it into a new time-line. As pure observer there would never be a problem.

    Only "no change" results in the ability to visit the past repeatedly and remember your present!
     
  17. DaveC426913 Valued Senior Member

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    You don't understand. You don't have any effect on your own past. No paradox, no loop.

    This is Universe U.
    I get in my time machine, and travel to 1968.
    The moment I arrive, a new universe is created: U'. It shares its past with U but it immediately begins to diverge - because of my presence.
    Everything I do from that moment on - including killing my gramma or myself - affects U', but has no effect on U.
    I can never return to U.
     
  18. DaveC426913 Valued Senior Member

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    Mentally travelling is what we were discussing:

    Post 183: . "...But mentally it allows us to travel back in time..."
    No, it doesn't.
     
  19. DaveC426913 Valued Senior Member

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    Paradoxen is already plural.

    1 ox, many oxen.

    That is not necessarily the way time travel works.

    The grandfather paradox highlights the problem. If I altered the past to one where I killed my grandfather - or worse - myself, then it is impossible for me to exist to go back in time and kill myself. Which means I lived. Which means I can kill my younger self. Which means I can't.
     
  20. Write4U Valued Senior Member

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    Isn't that what I said? You can never return to U (your deterministic past) is the paradox.
    As soon as you physically return to it you change it. Unless you just observe it....

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  21. DaveC426913 Valued Senior Member

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    It's not a paradox.
    You travel to the past of U (it really is U), but your arrival spawns a new universe, U'.
     
  22. Dr_Toad It's green! Valued Senior Member

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    I'm not going to search thread, but have any of you seen "Timeline"?

    I've enjoyed it a couple of times now.

    Edit: The title is a link to the Imdb synopsis. I tried to color the link to make it apparent, but no dice. Sorry.
     
  23. DaveC426913 Valued Senior Member

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    9,219
    You should be able to. You may have put the color outside the link tag. It needs to be inside.
    I also bold and underline it, for good measure.
     

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