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The best theory ever

  1. Sep 22, 2007 #1
    i think realtivity is the most beautiful theory in the history of physics. what i doubt in this theory is the existence funny objects like wormhole.
     
  2. jcsd
  3. Sep 22, 2007 #2
    .. welcome to the mainstream
     
  4. Sep 22, 2007 #3

    JesseM

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    Most of the "funny" solutions in GR like traversable wormholes are of questionable reality since there isn't any obvious way to create them in a universe that doesn't have them to begin with, and also because the matter/energy distributions which are needed would violate various energy conditions...I think wormholes violate both the weak and null energy conditions, and although a lot of physicists do believe weak energy condition can probably be violated by quantum effects, I think violations of the null energy condition are a lot more questionable. That's what I've gotten from skimming a few papers on arxiv.org anyway, someone correct me if I'm wrong.
     
  5. Sep 23, 2007 #4
    best theory ever

    Thanks for your reply but man I am a intermediate student so i can not understand your reply totally. Please tell me detail about energy condition.
     
  6. Sep 23, 2007 #5

    JesseM

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    I don't really understand the details of the energy conditions myself, but they're basically just all restrictions on what types of distributions of energy are considered physically realistic. For example, I think the "weak energy condition" basically translates to the condition that there be no such thing as negative energy, so the energy density everywhere must either be positive or zero.
     
  7. Sep 24, 2007 #6
    best theory

    Then how does wormhole violate energy condition?
     
  8. Sep 24, 2007 #7

    JesseM

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    The only way to keep a traversable wormhole open is to have negative energy densities in the "throat", without them the wormhole collapses before anything can get through. I'm not sure how it violates the null energy condition though...I've read in a few papers that it does.
     
  9. Sep 24, 2007 #8
    space time curvature

    Man let's forget this. According to general relativity space and time is bend due to presence of matter in it. Then isn't it possible that the whole universe is completely curved into a spherical shape so that the universe is finite. But what may lie outside such universe. Do you some idea?
     
  10. Sep 24, 2007 #9

    JesseM

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    General relativity doesn't require there to be anything outside it. In this sort of universe the universe is curved into a 4-dimensional sphere whose "surface" is all of 3D space, there's no direction you can travel in space that will take you off this surface.
     
  11. Sep 24, 2007 #10
    multiple universe

    But according to quantum mechanics there may be infinite no. of universes that has own physical laws. Every universe is self contained and each universe is separated with another and no matter or energy can ever be exchanged between these univeses. How the idea is? Man i want to have some personal
    talk with you. send me your email adress in your reply please.
     
  12. Sep 24, 2007 #11

    Demystifier

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    I agree with that. However, a potential danger is that it could be too beautiful to be correct.
     
  13. Sep 24, 2007 #12
    No way man

    Man don't you think that relativity is absolutely correct theory? But I do. Relativity is as sure as sun goes round the earth. many predictions of relativity like bending of light, gravitational waves, existence of black hole etc. had already been proved by observations. So relativity will never be endangered man. i too dont understand clearly but i am continously try to undestand it. Anyway thank you for your wonderful reply.
     
  14. Sep 24, 2007 #13

    Demystifier

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    I am not saying that (general) relativity could be completely wrong, but that it could be an approximation of a more fundamental theory that does not look so beautiful.
     
  15. Sep 24, 2007 #14

    JesseM

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    Are you talking about the many-worlds-interpretation of quantum mechanics? The different "worlds" in this interpretation aren't thought to be separated in space, in fact they exist as a quantum superposition in the same space...check out where are the other worlds? from the Everett interpretation FAQ for more info.
    If you click my name you'll see an option to send me a private message...but if you want to talk physics, why not just do it on the thread so anyone can contribute?
     
  16. Sep 25, 2007 #15
    Parallel Universe

    Yes they all exist in same space. But they must be separated from each other by a horizon the barrior from which light can't escape. So there exists no connection between these worlds at all. Right now many of these universe may be dying in Big Crunch or something like that and many of them may be in Big Bang condition. I even read that to make one such universe you won't need to much energy only but such energy should be confined in very small regions of space like black hole which we can't.
     
  17. Sep 25, 2007 #16

    JesseM

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    No, in the many-worlds interpretation there is no such barrier--the fact that we don't see photons from alternate "worlds" is explained in terms of a quantum phenomenon called decoherence, see the FAQ for more details.
    You may have read about something different than the many-worlds interpretation, then. Perhaps you were reading about the idea of "chaotic" or "eternal" inflation discussed here and here, in which new "baby universes" inflate from tiny regions of previous universes.
     
  18. Sep 25, 2007 #17
    Great Mistake

    Yes man you reminded me I had read the chaotic inflation. Thank you very much. i was in a great mistake. Yes in this model universe the new universes are being constantly being created put of their parent universe. But i actullay do not believe this idea. Man thanks for your suggestion regarding fabric of cosmos but................. I will say more privately.
     
  19. Sep 28, 2007 #18
    This is statement is against the spirit of science.

    No model of the universe can ever be considered to perfectly describe the universe forever - there is always the possibility that experiments we have done to confirm the model don't agree exactly (once we get better accuracy on the experiments) and new phenomena that isn't described by the model.

    I agree that general relativity is the most beautiful theory I have come across. But that doesn't mean it's a perfect model. As I have outlined above, no model can claim to be perfect.
     
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