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Time Travel

  1. Feb 20, 2009 #1
    I don't know much about physics, but I was wondering the other day whether what I was thinking was a popular theory.

    If time is like a one dimensional line and it starts at the orgin and it grows like a vector along the line as time progresses, then wouldn't it only be possible to travel back in time since that portion of the vector has already been created. And if you went back in time, the all of the vector after the time you went back to erases. So once you go back in time you can't go back to he original time.

    Does that make sense?
     
  2. jcsd
  3. Feb 20, 2009 #2

    Ivan Seeking

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    In order to return to the point of origin you would only need to travel at speeds near the speed of light. Do this for a few minutes, turn around and come back at similar speeds, and you could arrive at a time decades later [or whatever length of time is required]. This is the effect of time dilation from Special Relativity. Going backwards in time is the tough one. The short answer is that we don't know if travel to the past is possible. Also, even if it is theoretically possible, it may never be practical. We just don't know. Of course it is no small challenge to travel at speeds near the speed of light either - about 186,000 miles per second. The fastest manmade object ever to carry humans was the Apollo 10 capsule, which reached a maximum speed of just under 25,000 miles per hour upon reentry.

    Here is some good information.
    http://math.ucr.edu/home/baez/physics/Relativity/GR/time_travel.html
    http://plato.stanford.edu/entries/time-travel-phys/#10
     
    Last edited: Feb 21, 2009
  4. Feb 20, 2009 #3
    do you think we will know?
     
  5. Feb 20, 2009 #4

    Ivan Seeking

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    Should I look into my crystal ball? :biggrin:
     
  6. Feb 21, 2009 #5
    I think it was Stephen Hawking who showed (in a theory of entropy) that the universe could not reverse itself. What I understand from this is that relatively lightlike configurations can not repeat their past.
     
  7. Feb 21, 2009 #6

    Ivan Seeking

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    Could you be a little more specific?

    Are you referring to the chronology protection conjecture?
     
  8. Feb 21, 2009 #7
    That sounds about right: http://en.wikipedia.org/wiki/Chronology_protection_conjecture" [Broken]. My informed guess was pretty close, but with more accurate physical description this link explains better what Hawking probably had in mind.
     
    Last edited by a moderator: May 4, 2017
  9. Feb 21, 2009 #8

    Ivan Seeking

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    http://plato.stanford.edu/entries/time-machine/#Conc
     
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