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Time travel?

  1. Aug 15, 2004 #1
    Time travel??

    I was wondering if its actually theoretically possible to travel back in time. I know its possible to "travel to the future" because of time dilation, but I just dont understand what the deal is with traveling back in time. I've heard many times since I was a little boy, that going faster than the speed of light would make time run backwards. Can anyone tell me why this would happen? :smile:
  2. jcsd
  3. Aug 15, 2004 #2


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  4. Aug 15, 2004 #3
    Von Stokum's Cylinder

    If you can get yourself there, and where this is located, what potential lies in its function?

    Does such a place exist? Look up Ronalds Mallets experiment. A true patriot of Time Travel. :smile:
  5. Aug 15, 2004 #4
    of you want to travel back intime, you do have to travel with speed exceeding c. This in itseld if an impossibility because no object with and mass can reach the speed of light, let alone surpass it. Also traveling back in time causes a bumch of paradoxes. Lets say you travel back in time and kill yourself when you were younger, what happens to you. Do you die imidiatelly or do you stil live on, time travelling around like Mr. Peabody.
  6. Aug 15, 2004 #5
    My favourite paradox is brought up in the short story, "All You Zombies" by Robert Heinlein. If time travel back in time was possible, then even if it turns out you can't change to past, only fulfill it, the story points out how someone could end up having no history...they're their own mother, father, daughter, and son!
  7. Aug 15, 2004 #6
    Why a Cylinder?


    Weak gravitational field of the electromagnetic radiation

    Ronald L. Mallett Department of Physics, 2152 Hillside Road and UniÍersity of Connecticut, Storrs, CT 06269, USA Received 19 January 2000; accepted 3 April 2000 Communicated by P.R. Holland

  8. Aug 16, 2004 #7
    Kip Thorne and Hawkings have a bet on travelling back in time.

    What's that conjecture......... um........ the Time Protection Conjecture or something. Basically any time machine would destroy itself the instant you tried to use it to travel back in time. Something like that.
  9. Aug 16, 2004 #8
    Thanks for the links. It was interesting, but unfortunatly talked about time travel assosiated with GR, which was a little over my head. :confused:

    Very true, this is better known as the Grandfather paradox. But quantum mechanics has a theoritical solution to it...if you went back in time and killed your grandfather before he fathered your father, then you would create a parallel universe to the one you traveled from. In one universe your grandfather was murdered by you, in the other, he's alive.

    Very interesting, to say the least.

    Oh, I had no idea. Last I remember, Hawking said you can time travel, but not farther than the time your time machine was built. Or in other cases, where you use blackholes, you couldnt go back farther than when the blackhole was formed.
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