The Grandfather Paradox

Discussion in 'Physics & Math' started by Nogard, Oct 24, 2009.

  1. Nogard Registered Senior Member

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    17
    This is more of a philosophical point of view. I have no significant knowledge of physics, or science.

    Problem: Can you travel back in time with the intentions of killing yourself at a younger age?

    Obviously no since your alive in the future, but...

    I'm going to give you two solutions.

    Solutions

    Line
    1. We assume time is a line. This line extends in two directions ad infinitum with no beginning. Now we assume every event in our lives has, and will occur ad infinitum. Now if the man in question were to travel back in time he wouldn't be able to kill himself. It wouldn't be possible because he's alive in the future. So a man that plans to kill himself in the past cannot exist in this universe, but there is a possibility that a man was born and he succeeded and that's why he doesn't exist in our time ad infinitum. It does seem pointless in the line universe for someone to exist and then not exist, but it's still a possibility. This man wouldn't change the past or the future since he never existed, but he did exist because he didn't exist. But a man that already exists cannot kill themselves in the past.

    Solution to 1. He did exist because he didn't exist.

    Ray
    2. We assume time is a ray. Time had a beginning, and we exist in the future with no further point in time. In essence we have freewill. Imagine the man traveling along this ray at the furthest point in time. The man decides to travel to the past. This man has the option to kill himself, but in reality if he did kill himself he wouldn't exist anymore, so he never killed himself. If he did kill himself, he succeeded in changing the future and the past.

    Solution to 2. We exist in the future with no further point in time so we can travel back and kill ourselves.
     
    Last edited: Oct 24, 2009
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  3. John Connellan Valued Senior Member

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    Or you could devise a "many-worlds" hypothesis
     
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  5. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    I would have thought that a slightly more obvious answer is: we don't have any time machines.

    If we ever get one then your first answer would not necessarily be the correct answer.
    As per John Connellan's post, above.
     
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  7. Nogard Registered Senior Member

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    I also assumed we built a time machine. I didn't find it necessary to post assume we built a time machine since it's the grandfather paradox.

    Explain
    "If we ever get one then your first answer would not necessarily be the correct answer."
     
  8. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Once a time machine is built (taking it as a given) then it impossible to say "Obviously no since your alive in the future" because it's entirely possible that there would be a number of people who would be popping into and out of existence as they kill their grandfathers, thus making sure they weren't born, therefore they didn't kill them, thus making sure they were born.
    Plus there's the "many worlds" hypothesis as per John's post.

    In other words your answer is predicated on data we have not yet got. It's an assumption.
    IF we ever get a working time machine THEN we can see what is possible and what isn't - until then it's speculation and assumption.
     
  9. Nogard Registered Senior Member

    Messages:
    17
    Well you can't exist in the future if you were killed in the past. On a line universe the events would have already occurred so you wouldn't exist to begin with.

    I obviously don't have a time machine, so anything I say is an assumption. The whole point of this thread is to see if my solutions have any flaws.

    EDIT: Although on the ray universe people would be popping in and out of existence
     
    Last edited: Oct 24, 2009
  10. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    18,643
    Or, as in my example, it could start a cycle of existing/ not existing/ existing...

    And the flaws have already been pointed out.
    Since we have no time machine anything said about what could/ would happen is an assumption based on no data whatsoever.
    There's no "obvious" about it.
     
  11. Nogard Registered Senior Member

    Messages:
    17
    I think I already made it clear I don't have a time machine.

    Flaws?
    Please point them out. << I'm not saying there isn't any flaws. I'm just curious.
     
  12. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    No, he's on;y alive until he leaves the "present".
    He could go back, kill his grandfather and cause his own non-existence.
    And since he doesn't exist then he didn't go back and kill his grandfather, so he would be born, so he could go back and cause his own non-existence.
    Cycles...

    No, that's an assumption predicated on nothing.

    Functionally no different from (A).

    And as John has said there's the many worlds variant.
    You go back and kill your grandfather but it's only possible to kill "alternate universe" grandfathers, not ones from "our universe". All you'd do is prevent "other universe" versions of you being born.
     
  13. Nogard Registered Senior Member

    Messages:
    17
    Cycles...
    Yes, on a "Ray", but on a "Line", no.

    It's logical.

    I guess that's possible if time wasn't a line or a ray. But what would it be if it isn't a line or a ray.
     
  14. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    18,643
    "Ray" and "line" are purely your inventions, therefore I haven't seen any reason to take them as valid. Since, for the lifetimes of the men in question, there's no way of differentiating them.
    Ah, logic.
    Wonderful thing but can seriously fail when it comes to science.
     
  15. Nogard Registered Senior Member

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    17
    That's the whole point, lol.

    Here's what I posted earlier.

    Yes it would all be theoretical, but do they have any flaws?
     
  16. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    18,643
    One flaw is that "ray" and "line" are merely your inventions.
    So why in Earth do you think they have any application?

    And, as stated, there's no way of telling one from the other in the real world so either "solution" is possible for either "scenario".

    The main flaw is that you're assuming that your logic is valid: in circumstances we know nothing about.
     
  17. Nogard Registered Senior Member

    Messages:
    17
    Like I said,
    No the line and ray are not wrong unless you have evidence to disprove them. << No I do not have evidence for my solutions, but I already admitted that there possible solutions, I never claimed to know there true. I'm not saying there true. You're saying they aren't, so evidence please.
     
  18. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    It doesn't work like that.
    Unless there's evidence for them you can't claim they're true.
     
  19. Nogard Registered Senior Member

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    17
    I already said there possible there not true. You seriously have a hard time reading my posts.

    Here's my earlier post.

     
  20. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Yup and here's the one I replied to:
    So who has the hard time reading?

    If they're "not wrong" there should be some evidence to base the claim on.
    Otherwise they are merely speculation.
    And only as valid as any other speculation.
     
  21. Nogard Registered Senior Member

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    17
    So basically you cut out the part where I say I do not claim to know they are true. Yes, you would be right if I did type that, but you cut out an important part and you took it out of context.

    I know that, lol.

    What you did is equivalent to someone saying "God is real, but there's a 99 percent chance he doesn't exist" - Jerry Schnizel. Then posting on the forums "God is real" - Jerry Schnizel.
     
    Last edited: Oct 24, 2009
  22. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    So where you claim they're "not wrong", which means they must be right you actually meant...?
    Help me out here I'm lost.
    You don't know they're true, but you also claim they're not wrong?

    Apart from the other flaws pointed out -
    Big bang?
     
  23. Nogard Registered Senior Member

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    17
    You're so dense, I'm sorry man.

    What I said is like saying.

    I believe in a god, but I do not know or claim he exists. << Agnostic theism

    Maybe that will help you?

    I never said they are true, I said there possibilities, and you can't say they are wrong without evidence. I never claimed my solutions to be right.

    Took me while but I think I figured out the problem. We both think that we are claiming things when in fact everything is neither true nor wrong. I retract my statement calling you dense, It was actually a misunderstanding. But I was almost positive you claimed to know mine were wrong?
     
    Last edited: Oct 24, 2009

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