Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Time travel and Multiverse Theory

  1. Dec 7, 2003 #1
    I am curious as to others' beliefs/opinions on how time travel and/vs. multiverse theory correlate.

    Theory/Question 1. If you could go back in time and try to alter an event, could it turn out that you can't change it and are actually only helping history along it's course?

    Theory/Question 2. Or could you go back in time and actually change the event, effectively creating a parallel universe, an alternate reality where events will now play out differently?

    Scenario: Your family is killed. You go back in time and save them.

    What happens then if you succeed in your endeavor and travel forward in the timeline you just altered to when you last left only to find yourself trapped in a branch of the timeline where you are out of place? You could potentially find yourself living alongside yourself since the alternate version of you would then have no motivation to travel through time, thus leaving the time traveling version of you displaced. To return to your place of origin, you would then need to find new means to travel through alternate time dimensions. If traveling through your own timeline is like traveling in a straight line, then you would have to find a way to travel across parallel lines to return to the point where there isn't another you. Would this then not defeat the whole purpose of having traveled through time in the first place?

    I myself like to fall back on Occam's Razor for this one.
     
  2. jcsd
  3. Dec 7, 2003 #2

    selfAdjoint

    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    Yup. A very good point that has been made, as far as I know, only in fiction. Lord Dunsany had a short short story on it back in the 1920s, I believe it was, and there was a long series of paperback novels by a Viet Nam vet where the hero tried to help a future civilization using time travel/multiple universes, but became trapped (multiple copies of him) in a quagmire where the bad guys won as often, and in as many branches, as the good guys.

    Seems to me this argument could be rigorized, and used against Kaku's idea that many worlds gets us off the hook on causality violation.
     
  4. Dec 8, 2003 #3
    Thank you selfAdjoint, that is also what I was thinking about Kaku's theory after reading Hyperspace. I myself have not seen the theory I presented elsewhere, even in fiction. (I'll have to check this out Lord Dunsany to see how portrayed it). I have seen it posted elsewhere on the internet, but after I thought it up one night after arguing with some friends of mine.

    But on to another subject: What about travel forward through time? What happens? Will you meet an older version of yourself or will time play out as if you did not live out those years? Thoughts, opinions?
     
  5. Dec 8, 2003 #4
    I think your point is a very good illustration of how the “ branched timeline solution” is a logical fallacy. It shows that the argument is rhetorical.
     
  6. Dec 8, 2003 #5

    selfAdjoint

    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    I really have no thoughts, but I would point you to another piece of fiction: Harry Turtledove's Counting Up - Counting Down. It's about a man who meets his younger self through time travel and tries to fix some of the problems he remembers, with disastrous results. It's in the form of two novellas, each telling the story from one of the ages' point of view. Another cautionary tale, I seem to be drawn to them.
     
  7. Dec 9, 2003 #6
    sorry, i dont think that whole paralell worldline thing is possible...

    if you go back in time and kill yourself, you changed history, so you dont know how you would react do you? maybe you would be able to kill yourself and still exist, because you existed to kill yourself, either that or you would cease to be altogether.
     
  8. Dec 10, 2003 #7
    Well, I don't believe that history can be changed. I don't think time paradoxes are possible and that's why I thought up of the whole timeline thing, I was trying to rationalize IF you could change things, then how would it work?

    My belief was if you go back in time and kill yourself either you'ld fail, because here you are, or, you'ld create a parallel timeline that you'ld be stuck in.

    I think time paradoxes are overly complicated and superfluous. Especially ones like killing yourself in the past. Why not save the universe some trouble and kill yourself in your present?
     
  9. Dec 11, 2003 #8
    I agree with chronus, leaning more towards the "history cannot be changed" theory.

    Mad_Gouki didn't really explain his arguement well. You can't go back to
    the past to kill yourself because you are alive now. If you killed yourself, you wouldn't
    be able to live to the time when you would go back in time and
    kill yourself. (i guess i am just reiterating what chronus said earlier)

    Altering time is not possible. It is there,
    always has been, the future, present and past, ever progressing for us,
    yet in many ways static.
     
  10. Feb 1, 2004 #9
    While I keep my mind open to ideas and theories on the subject I personally do not believe that it is possible to travel back in time. Having thought it over I don't really even believe that there is an actual 'temporal dimension' to travel through. The multiverse theory of which I have read seems to me really only to be a conceptual model for a dynamic universe that exists something like a probability wave. It would seem to me that if you were to have multiple time lines especially infinite time lines it wrecks the functionable logic. As an example if you have time travelers in the future that travel back in time then across the 'multiverse' there must be an infinite number of them or even an infinite number of any one of them. If you cross into parallel time lines when you time travel, ala John Titor, something of a bigger worry than running into a past self might be running into other time traveling yous.

    A good book involving time travel is 'Anubis Gates' by Tim Powers. I liked the way he dealt with the paradox of trying to change the past and the intricacy that he gives his plots does it justice.
     
  11. Feb 2, 2004 #10

    selfAdjoint

    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    Yes the Anubis Gates was a terrific novel. I wish Riobbins would write some more. Notice the "closed timelike loop" in the subplot of Ashbless' poetry.
     
  12. Feb 3, 2004 #11

    Why

    User Avatar

    Time Travel Is A Fallacy.

    Observable knowledge - why time travel is an illusion.
    ( I am in no way trying to be 'spiritual' or 'metaphysical' here. These observations are based on my experience of reality and I'll try to express them in as clear and simplistic terms as I can - thanks)

    What we call the 'moment' is existence.
    Everything happens 'here'.
    There is no existence outside of the moment.
    The moment has no beginning or ending, it is eternity.
    The whole, our collective essence/substance, cannot be outside of itself - it is all there is).

    Our primal essence or stuff is active...I call it energy.
    It is always moving and always changing.....parts of 'us' move in repetitive patterns and appear as form/matter.
    In totality, each movement or expression of energy(us) is different as all of us are always active and moving in slightly different ways. The more complex our movements get the more impossible it becomes for an 'exact' duplication.

    Their is no existence outside of our whole, collective field.
    What we call the past is no longer in existence or real it is just our memory or image of part of the movements of the whole(only our memory is in eternity...the 'now'). it is not 'stored' anywhere as there is no other place 'to be' besides existence.
    The future is not real either but is our image of part of the movement of everything to happen in the only place that is real - existence - the moment.

    In summation, all there is is our total expression right NOW.
    In fact we can simplify more by stating in reality the moment is our body and is always moving within itself.
    Our experience and focus as humans and a mind experiencing a subject-object experience fools us into believing there can be something outside of ourself.

    As far as multiple universes, dimensions, etc. I see no problem with that as it does not violate the reality of existence but is/can be another division of what is existing right now.
     
    Last edited: Feb 3, 2004
  13. Feb 3, 2004 #12

    selfAdjoint

    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    Just a suggestion. Find another word for what you call energy, at least on these boards. The word energy is a specific term of art for physicists, and we here follow their ideas. Call it chi or whatever, because if you don't somebody is likely to ask if it equals mc squared and how it transforms under Lorentz transformations.
     
  14. Feb 3, 2004 #13

    Why

    User Avatar

    'Stuff"

    Since scientists don't even know what the ultimate 'stuff' of reality is...no problem...I'm just a layman and I did say 'I' call it energy...the reason I do is because I believe the 'stuff' of reality is inherently active and indestructible and that is the given definition of energy.

    What do you call 'us'/'it'..'.string essence'?
    Factor 'x'?
    'Life'?
     
    Last edited: Feb 4, 2004
  15. Mar 8, 2004 #14
    Hello all,

    I am starting a portal to time travel forums and found your spot on the web. I like much of your content here. Compliments.

    Chronus,

    You mention a multiverse model, but you wave it away by using logic often found in papers describing the possibilities or inpossibilities of linear time travel. If you think linear then maybe even Hawking's Chronology Protection would apply. The multiverse model is not linear, is very handy for time travel, no Chronology Protection is needed because history is automatically protected and it would remove all paradoxes.

    In the following I assume that a time machine exists which is able to travel to parallel universes to any given moment. In these parallel worlds nearly identical copies with a history close to yours or exactly like yours may or may not exist. BTW: How to built such a machine is another question, but you didn't ask that.

    It's easy to explain if you consider yourself to be part of a worldline. A worldline resembles history as one expercienced it. Decisions split worldlines. For an example, in one branch you may continue to read this response and in another you may not.

    Travelling back in time would cause a split in the worldline at the moment of arrival. In one branch of the worldline you did not arrive. That is the one you came from. In the other branch you did arrive. Anything you change in the worldline (you now occupy) would have effect only on the worldline you now observe. It means you cannot change your history, because it already happened, is happening or will happen in the other worldline (you came from). You will remember the history before your journey just like any history from a normal past. Because of the split of the worldline that history is safe as well.

    To go back to your scenario... If you would kill your father before your birth than you would see him die, but the other worldline (in which you did not arrive and which resembles your past before the journey) would still continue and thus ensures your birth. The "father" you killed is a near identical copy of your true father. Therefore it does not threaten your existence.

    Another scenario... If you would travel to a past after your birth then you would simply meet a nearly identical copy of yourself. You would be able to shake hands. If you kill him then you'll survive. Afterall, you are not killing yourself but a nearly identical copy.

    The main problem is when you want to go back to your own worldline. Because of your "unexpected" arrival, changes are that the future of the worldline you now occupy will be different, because the Butterfly Effect will kick in. So travelling from that point forward does not really work. The answer to that problem is a technique which I call backtracking.

    To backtrack you travel to a moment before your arrival in the past and then travel forward to a moment just after you left in the future. There is still a slight problem here, because your second journey to the past causes your presence there. That will cause a split again and it is important to travel ASAP to the future on your moment of arrival in that auxiliary moment. However, it will cause you to never arrive in the worldline of origin, but it will look nearly identical. No matter how well planned you do that, it cannot be the same.

    Remember that in each universe a nearly identical copy of you may exist who also travels to a momemnt in his past. Again, that's not your past. It may be nearly identical. Some of these copies may not jump afterall for some reason or another. They too would be backtracking to return to a time which resembles their origin.

    When returning you may end up in a worldline in which a nearly identical copy of you travelled as well so you may succeed in returning to a future which is nearly identical to your origin.
     
  16. Mar 10, 2004 #15
    Although many of these arguments have a very good point none are as helpful as the 2nd law of thermodynamics. If you went back in time, your matter would be exiting this universe, violating the 2nd law of thermodynamics.
     
  17. Mar 10, 2004 #16
    Well, actually there is no such thing as the butterfly effect (except for the movie), and it is called Chaos theory, or that is any slight deviation can have a tremendous effect in a (large) amount of time in the future. Though this is very radical, yet true, it does not have much to do with travel.
    Let us suppose that when indeed you do leave your universe and go to another time in the past (yes it has to be an alternate universe, since different time is different space), but it will be the same (unless you believe in there not being soul) unless you traveled to the future.
    To get to another universe they would have to go through the 4th spatial dimension and it might as well be that that parallel universe had its time behind ours, which would make it as if you didn't travel in time at all, but it is the same thing.

    Let us suppose for argument's sake that when you exit this universe, in the near distance, the exact amount of particles have come with you (so as not to violate the 2nd law of thermodynamics).
    Now we go to the above questions. If you did kill yourself, then how would you ever live to do it? I suppose that the previous post was right that you would live to do it and live beyond that, since your previous self was in that other universe parallel to this parallel one. It just so happens that in the universe you are now, your own self (following exactly what the world did, had you not interfered and had that been an exact copy of the previous universe, the original,) would just continue to exist, and I suppose the you that was to jump to the another parallel universe from the one you are already in, would not do it, and so not really achieve anything but see the world from the time you went back and on,(and you might give some grief to relatives, esp parents).
    The other options that u would have no free will, since it will all add up to u coming back to that moment again, and not killing urself (as the episode in the Twilight Zone where the woman was supposed to kill Hitler). These options would not be available, since if it is in a different time, different space. Further logic, if it were an event, if you were to prevent it, then in the future, you would have no way of knowing about it to go back in the past and prevent it. For all we know, people would have to time travel for every second of the universe for every inch, and have a supercalculator to calculate what disaster they have prevented, so that they could prevent it from being prevented and not knowing that they should prevent it.
    This just isn't possible, but fortunately, neither is time changing, or at least none of us would miss what didn't happen, if somebody came from another universe.
    I guess this only brings us to whether different dimensions can interact, and as to whether a 3D object could move in the 4th dimension. In my opinion it cannot, since it would have 0 hypervolume.
    Hey, this kind of makes me feel safer that I would exist right now!
     
  18. Mar 12, 2004 #17
    Laws have been made in time and broken in time. This time runs a straight pass through our lives we think but what if time could be stopped??? Would we have any sideaffects of having or "mass" frozen in time??? Laws have also been broken in the past and today are all the laws we have come but the "truth" or correct??? Not trying to insult you in any way but thermodynamics is not my specialty because i have only very briefly read over the laws it states and maybe they will be broken just like the theory that the world dropped off beyond the horizon.

    I dont mean to dismiss people but my one question is... Why do the laws we think everything follows have such assurance that nobody seems to be looking at the possibility that in the future these laws COULD be bent or even broken???
     
  19. Mar 13, 2004 #18

    selfAdjoint

    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    Why do the laws we think everything follows have such assurance that nobody seems to be looking at the possibility that in the future these laws COULD be bent or even broken???

    Because we have no evidence NOW that they will have been broken. Science works on minimal assumptions, and finds no need to assume the breaking of laws that as far as anyone can see today, work just fine.
     
  20. Mar 15, 2004 #19
    The way I see it, all you would have to do is travel back to a point before you came and saved your family, and then move forward again. After all, would you not be going back to a point before the universe branched off in two? I don't think you would run into yourself going forward in time to save your family, as your mere appearance before your appearance would spawn another universe that would be very similar to the original.
     
  21. Mar 16, 2004 #20
    renassault,

    Why? In Max Tegmark's theory everything is accounted for. I am not sure if he ever mentioned TT, but there would be nothing disappearing or appearing as far as I can see. His Level III multiverse is the quantum version of our obeservable Level I multiverse (in which we - because of its size - observe part of our own universe). See Parallel Universes.
    You may exit the universe, but you'll stay in the multiverse. Nothing gets lost and nothing appears. You are changing location instead.[/QUOTE]If you want to change something in the past then return to that time and change whatver you want and stay in that worldline. I.e. stop travelling and stay in that worldline. But remember that the parallel universe you are now in is just one which closely resembled the past of your own and contains all the changes you made since you got there. You should avoid terms like "yourself" because it's not "you". It's a being that closely resembles you. It's not copied either. It was already there. If you mix these things up then it will get you nowhere.

    And about the free will... Yes. That's the price you may have to pay. You don't like that thought, right? Well, neither do I. It's probably like most laws in maths and physics: They don't give you a choise. It either works that way or it doesn't. ;)
    Erm... We already are doing it. The famous plane experiment with the two atomic clocks (one in the plane and one on the ground) or the one with 2 clocks on different heights on earth, etc.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Time travel and Multiverse Theory
  1. Multiverse theory (Replies: 8)

  2. Multiverse theory (Replies: 4)

Loading...