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Time travel question

  1. Oct 25, 2009 #1
    From what I've seen, most speculations of time travel seem to say that when you go back in time, everything else around you returns to an earlier state that it used to be. For example, if you stand outside your house and go back in time, the house will "un-build" itself and there will be nothing there.

    However, what it seems like is that everything else AROUND you is going back in time, not you. If it were just you that went back in time, you would simply get younger.

    But here's what I don't get if this is true. Let's say you went back one year. You would supposedly get one year younger. However, during that year, you interacted with the outside universe in a number of ways; you breathed and modified air molecules, you ate food, and you manipulated objects (like driving a car, picking up things, etc.). In addition, in order for the universe and you to exist in two separate states of time, the matter that you are composed of would have to be put on "hold", because if everything else around you went back in time, a certain portion of matter would disappear. If it were just you that went back in time, all those ways in which you interacted with the outside world would have to be undone, but this would cause the entire universe and all it's contents to shift back in time in equal amounts, thus creating no net time travel effect at all.

    If this is true, then any attempt to go back in time will require an almost infinite amount of energy (since you are modifying the state of everything) and it will appear that absolutely nothing has happened.

    I don't see how time travel is even remotely possible.
  2. jcsd
  3. Oct 26, 2009 #2
    Hi sciencectn and welcome to the forum.

    Just like to say I think you raised some really pertinent questions. Have to say also that I think you've hit the nail on the head when you said that time travel is not even remotely possible.
  4. Oct 26, 2009 #3
    I am pretty sure that is the idea of entropy or at least the result of it. It has away of saying time goes one way. And with irreversible processes, you have to put in more energy to get them back to their original state. Pretty cool idea.
  5. Oct 26, 2009 #4
    What you're saying does make sense. Essentially, time's arrow is identified with entropy and vice-versa...its not so much that time travel is impossible...I think its more along the lines of having to modify our outlook on the behavior of energy (if time was flexible).
  6. Dec 17, 2009 #5
    if someone were to go 'back in time', then they would 'remember' their future in exactly the same way we remember our past.
    The person going back in time in this regard would be fascinated at the prospect of 'remembering' a past event, such as when he turned 16, drove a car for the first time; dated his GF for the first time. Such concepts of 'memory' that are common to us would fascinate the imagination of the guy who's going backwards in time.
  7. Dec 17, 2009 #6


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    I've been an SF fan for over 40 years, and I honestly think that the OP brings up aspects of time travel that I haven't seen explored before. (At least, not in that particular form.) Good job, Sciencectn.
  8. Dec 25, 2009 #7
    Hi, sciencectn, welcome to PF.

    I like your view. You raised points which I have not heard or thought about before.
  9. Dec 25, 2009 #8


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    sciencectn, if you haven't read the book "Time Travel in Einstein's Universe" by J. Richard Gott, you might consider looking at it - sounds like you might be interested. He brings up some similar points in the section on djinni (objects with closed cyclical worldlines), and there are a bunch of other more or less wacky ideas about time travel.
  10. Dec 26, 2009 #9

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    I'd like to encourage everyone to take a look at the PF rules on Overly Speculative Posts. Neither time travel nor souls are observed or can be studied scientifically.
  11. Dec 26, 2009 #10
    Doesn't QM say that atoms will have only one history .
  12. Dec 26, 2009 #11


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    But based on your previous concern, aren't we actually traveling through time right now, at the fixed rate of 1 second per second?
  13. Dec 26, 2009 #12
    As far as I know, the many worlds interpretation of QM actually states that particles have infinitely many histories and infinitely many futures.
  14. Dec 26, 2009 #13
    my comment has been removed because I violated the speculative rules. That is interesting because time travel is totally speculative. Anyway, I am not a physicist and I dont think I will be back here. Good luck with the moderator of this forum (ZapperZ) who confess being a dork in his profile. Remove me forever if you want and stop the incomming of new ideas "dork"
  15. Dec 26, 2009 #14


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    That statement is quite unnecessary and rude, Pyocote. Note that the rule applies to overly speculative posts. Every scientist speculates, but does so within the bounds of what is accepted as physically possible. I didn't see the post that you refer to, but it must have violated that aspect of the subject to be deleted.
  16. Dec 26, 2009 #15
    my mistake
  17. Apr 17, 2010 #16
    Incorrect. We are actually travelling forwards in time at a rate slightly smaller than that due to gravitational time dilation. See [A HREF=http://en.wikipedia.org/wiki/Geocentric_Coordinate_Time]Geocentric [Broken] Coordinate Time[/A]. Perhaps we should say that backwards time travel (with this method) is not remotely possible.
    Last edited by a moderator: May 4, 2017
  18. Apr 17, 2010 #17
    If somebody in future discovered the time machine, why didn't they come back in time [to the present] to visit us?
  19. Apr 17, 2010 #18


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    Because they haven't built the time machine yet. GR time machines can only take you back to a time after the time machine was built.
  20. Apr 17, 2010 #19
    how do you know they haven't :cool:
  21. Apr 17, 2010 #20
    If you say they haven't discover the time machine. Is that means time machine is not in existance? This is because far in future there should be an existance of time machine, this is what been predicted by the physicist [in the present time]. This only could be a myth in my point of view. I'm just giving my opinion, so take it easy.

    Thank you.
  22. Apr 18, 2010 #21
    I don't understand why time travel is impossible. Time travel is possible and some human beings already went in to the future.
    It is calculated that astronaut who spent a great deal of time orbiting the earth in the international space station would be traveling to the future by a very minuscule amount. I do not remember the exact amount but it was smaller than one hundredth of a millisecond or something. He or she would be that much younger as they arrive back on earth. Imagine them keep on going faster and faster around the earth. The faster you go, the slower the time passes for you. There is your time travel to the future.
    Time travel to the past is highly disregarded because of many physical and philosophical arguments.
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