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Dimensions/parallel universe questions

  1. Sep 5, 2005 #1
    i'm quite vague on today's modern theories of the universe so wondered if anyone could clear up some questions ive always had

    i heard somewhere that math can prove there are as many has 11 dimensions is that right? and what would these dimensions be like in layman terms.
    if i understand right, time is the 5th dimension? how and what is that exactly

    does a copy of us exist in a parrallel world? if we time traveled wouldnt it be like in the tv show sliders, like you couldnt kill your own grandfather in your world but rather go to a parallel and do it?

    if you make a decision, does it spawn another parralel to a world where you made the other decision in an infinite tree like fashion for every living thing since the beginning or does that have no validity?
  2. jcsd
  3. Sep 5, 2005 #2


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    The theory called M-theory requires 11 dimensions, and within the assumptions of that theory the need for 11 dimensions is proved. But we don't have to accept thoise assumptions, because M-theory, like all of string theory, has never made a testible prediction.

    To the first question, we have no reason to think that; no real physics theory predicts it. As to time travel, in order to preserve cause and effect, you would have to be prevented from killing your grandfather as a baby, but the problem is, how would the universe arrange to do that. For this and related reasons, physicists prefer not to believe in time travel. If it's ever discovered for real, the questions will be answered by experiment.

    The Many Worlds interpretation of quantum mechanics posits that every time a quantum wave function is reduced several new worlds sprout off like branches on a tree. Assuming your decision was the result of s sequence of quantum events, you would get the result you describe. In the MWI, we only ever experience one path through the tree.
  4. Sep 6, 2005 #3
    so does any theory show the possibility to go into another branch of this tree. i dont follow the "wave function is reduced" thing.

    now about dimensions, can a physical body exist in any other than ours, and what would any one of them be like or look like to us? i assume we wouldnt see things like how we do in this dimension right?

    do any theories describe anything about the possibilities of an afterlife, what about other living things like insects?
    and what dimension would a soul exist in if its possible.

    i plan on getting one of mkaku's books but wonder if i'll actually read it, which does anyone recommend, hyperspace or visions?

    thanx in advance for the insight
  5. Sep 6, 2005 #4

    I think Visions is more a look into the future. It's about future technologies and what we can look forward to in medicine, gadgets, etc. I think Hyperspace is more of a classical book in that it won't "age" as quickly as Visions will.
    Maybe we don't have glasses with the internet built in them yet but once we do, that book will be old news.
    Hyperspace may get outdated eventually but it's a good instructional book in my opinion and at the rate String Theory's going, it might be a while before it's considered old school.

    If you're just starting out, I'd read Brian Greene's Elegant Universe. He lays it all out pretty simply and goes into a fair amount of detail. Dr. Kaku's stuff is a little harder if you're not familiar with it (although I personally consider his stuff to be simpler to understand than Stephen Hawking's.....God help us laymen if Mr. Whitten ever puts out a theoretical physics book)
  6. Sep 6, 2005 #5


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    No, we are stuck in one path through the tree, according to MWI.

    I don't know what you mean by dimension here. It seems like you are talking about another world. Supersymmetry and String theory, two branches of physics study, need more dimensions than four. But the things they talk about are elementary particles and even tinier elementary strings. what these add up to is ... (drum roll) ... us!

    No physics very emphatically does not discuss an afterlife. Some physicists are religious, in various religions, but that is as "private citizens".

  7. Sep 7, 2005 #6
    well i'm trying to seperate in my mind the difference of parallel world vs alternate dimensions..i've always had in mind that other dimensions is the backbone of things that make up the 3rd dimension, or if god existed it would exist in another dimension..etc

    i heard steven hawkings talk about afterlife in one of his theories but dont recall the details, perhaps he was just talkn bout his beliefs. i figured maybe one of the physics theories of dimensions explained how it could be possible

    also if were stuck on 1 path in the tree, does the other paths still move on, so there would be countless copies of ourselves going about through life on that path? seems there would have to be a connection somewhere, couldnt even something like a wormhole take us to another branch, to me it just seems it has to be possible if another branch exists.
    Last edited: Sep 7, 2005
  8. Sep 8, 2005 #7


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    Well if you take the MWI literally, it seems the other branches have to exist. I know some of the physicists who favor the MWI dance around this issue, but I don't see how they can escape it, except by extreme subjectivism, i.e. "It only exists if we experience it", but that takes you back to the problems with interpreting quantum mechanics that the MWI was trying to avoid.
  9. Sep 20, 2005 #8
    I've been 'psychic' all of my life. I'm getting near my halfway point in my life and all my impressions, and experiences in that realm are very real to me. I've also been really big on physics all my life and see them as one.. In those experiences I see the idea of time travel and other dimensions very possible.. or else I'm just crazy.
  10. Sep 24, 2005 #9
    Possible bridge from relativity to string?

    Everyone is always going on about marrying Einstein's theory to quantum string theory, and I for one don't really go for the whole parallel universe bit. That said, I wonder what you all think of this idea? http://www.mqins.com/theory.htm I would lover to hear feedback on it.
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