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Temporal thermodynamics

  1. Dec 1, 2003 #1
    Not sure where to post this. You can move it if you like.

    There is no right answer to this but I hope it makes you think as
    much as it made me think.

    A long time in the future, man-kind can travel backwards in time by
    breaking the light barrier. The research team calculate that according
    to Einstien's equations, they will trace a smooth path through
    space-time as they are travelling backwards through time. The same
    set of events can be viewed form inside and outside the ship. They are
    however, curious as to what happens if they drop one of the glasses
    of champaign aboad.

    According to the 2nd law of thermodynamics, the glass drops then
    smashes as time goes forward. This gives rise to a simple paradox.
    Which way is forwards?

    If the second law is obeyed in the reference frame of the space ship,
    the on-board team experience nothing unusual, but the rest of the team
    on the ground will see the same events, but to them, the glass is
    smashing, then rising from the floor! Events aboard seem to go
    backwards from the reference frame of the GROUND team.

    To correct the paradox, the ground team argue that the second law must
    be obeyed in the reference frame of the ground team, now they would
    see it the right way round. BUT the on-board team complain
    that they would experience the glass smashing, then rising from the
    floor as they travel backwards through time! Events aboard seem to go
    backwards from the reference frame of the ON-BOARD team.

    Only one can be correct. The two teams place a bet. Who wins and why?
     
    Last edited: Dec 1, 2003
  2. jcsd
  3. Dec 1, 2003 #2

    chroot

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    Simple. Nothing can go faster than light, and thus time-travel to the past is impossible.

    - Warren
     
  4. Dec 1, 2003 #3
    Yes

    I quite agree, but did you think it through?
     
  5. Dec 1, 2003 #4

    chroot

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    Re: Yes

    Yes. And I answered:
    - Warren
     
  6. Dec 1, 2003 #5
    Imagine...
     
  7. Dec 1, 2003 #6

    chroot

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    Imagine what? Shall I also imagine that 1 = 2? And left = right?

    - Warren
     
  8. Dec 1, 2003 #7
    Yes! Anything to expand the mind! Please!
     
  9. Dec 1, 2003 #8

    chroot

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    The real world is much more fascinating than any imagined.

    - Warren
     
  10. Dec 2, 2003 #9
    Well, jackle, if it's not enough for you that we can never end up in a situation where this problem would become relevant, then perhaps the fact that reality is different depending on your inertial reference frame will help. Basically, the people on the ship are only going backward in time in some reference frames, and not in others.

    Also, if I were to drop a glass before having begun traveling backward, then I could logically expect to see the cup "pick itself up" so to speak. However, if I drop it while traveling backward in time, then it will indeed fall, and shatter. Traveling "forward" or "backward" is only relevant when you have to change it.
     
  11. Dec 2, 2003 #10

    Ivan Seeking

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    Igor Novikov: an essay printed [p57] in The Future of Spacetime; Cal Tech, 2002


    Stephen Hawking: p87 The future of Spacetime
     
  12. Dec 3, 2003 #11
    But either way, will not the same chain of events be viewed in reverse from the ground team? Wouldn't this mean that the second law has to be violated from at least one observer's perspective?
     
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