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How does M-theory explain genesis of the 11th dimension?

  1. Sep 24, 2010 #1
    I read Stephen Hawkings new book and did a little research on M-theory.

    Apparently in the 11th dimension there are different brains that crash into eachother. 2 of these brains crashing supposedly rendered our big bang, and explains why stuff came out in blobs (not homogeneous).

    But how does M-theory explain the genesis of the HIGHER dimensions, the ones that supposedly caused our universe to be seeded?

    They might be able to explain our universe, but if they can't explain the existance of the ones that supposedly made us then it doesn't seem like a very complete theory. Maybe I'm missing something, but I felt kind of cheated cause Hawking said M-theory had all the explanations needed for a universe without God.
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  3. Sep 24, 2010 #2


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    :rofl: :rofl: :rofl:

    Aren't you kidding a little bit? Did you really expect Stephen Hokum's new book to explain everything? Did you really feel "kind of cheated"? Or are you maybe secretly pleased that the book turns out to be something of a hyped-up potboiler?
  4. Sep 24, 2010 #3
    I'm not fully sure what your asking so I'll try to explain the two questions that you appear to be asking. In M-Theory an extra-dimension arises from the String Coupling constant going to infinity in Type IIA Superstring Theory. The other questions regarding the Bulk and colliding D-Branes isn't directly predicted by M-Theory, it was just an extension of some of the fundamental ideas. Some extensions are RS1 and RS2 (Randall-Sundrum) Models: http://en.wikipedia.org/wiki/5_dimensional_warped_geometry_theory

    By the way it is spelled "Brane".
  5. Sep 24, 2010 #4
    Sorry, I listened to the book out-loud, so I'm ignorant of spelling LOL.

    Thanks for your response.

    Can you give me a link which might explain the m-theory genesis better then (hopefully in layman's terms) if I'm misunderstanding it? I'm still really lost.

    Yes I do feel kid of cheated. I wasted 4 and a half hours of my life listening to something that doesn't give any of the answers it promised. In America, we call it false advertising or fraud.

    I don't feel bad about file-sharing the book either. Stephen claims that humans do not possess free will, so in that case, the Universe his book, not him, and he really has no claim on it. ;)
  6. Sep 24, 2010 #5
    I honestly think no one knows, the theory is still very young - M-Theory that is. It's funny, my brother said if you listen to the audiobook on a Kindle it sounds like Stephen Hawking is reading it to you.
  7. Sep 24, 2010 #6

    Oh LORD that's funny!!!!!!!!!!!!!!!

    You know M-theory almost makes me laugh. It is no more scientific than 'intelligent design", but taking occam's razor into account........
  8. Sep 24, 2010 #7
    It's considerably more scientific and well-motivated; unfortunately, though, it's a big mostly unopened box of mysteries that we can say very little about.
  9. Sep 24, 2010 #8
    Hmmm.. I rate the science the same in both parties.

    They are both at the stage of unprovable hypothesis.

    Science requires tests or it's not science yet. I'm not saying that they shouldn't focus on it...

    But when Einstein released his 3 page paper without a SINGLE reference, stating as a fact e=mc^2, it wasn't quite science yet either, even though it turned out to be true.

    In that sense both parties are equal in my opinion.
  10. Sep 24, 2010 #9


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    In a mathematical science like physics, theories only exist in an objective sense if their basic equations have been written down, typically grounded on basic principles (like e.g. relativity is grounded on principles like equivalence principle...) They can exist in that sense BEFORE they are tested, whether they are right or wrong. They just have to be clearly formulated in a testable way. Einstein's 1905 papers were science, as I understand the term. Excellent science.

    But in that sense M-theory does not exist. Hawking is not a string theorist, you'd do better to listen to David Gross (a real authority): We do not know what string theory is. What he means is M-theory. We do not know what M-theory is. Once it has some definite meaning and we know what it is, then it will be time to test and see if it agrees with nature.

    What we have now is fragment, rumor, interpretation of lucky coincidences, expert guesses, wishful thinking. Hopes for future theoretical work. There might eventually be something answering to current expectations about M. Or there might not.

    Credulous people talk as if M-theory is a real, known, well-defined theory----more than a hope.

    There are many books on the market which are pseudo-science---that claim they will give answers, but are hokum. Hawking is high-class hokum. There is no law against selling that kind of book. It's free-market capitalism and protected under the First Amendment. It is not covered by the laws against fraud or snake-oil advertising.

    Who knows, maybe it was good for you to spend those 4 and 1/2 hours.
    Many people have wasted upwards of 4 and 1/2 years on string theory and then gone looking for unrelated work in industry. Think of yourself as fortunate.
    Last edited: Sep 25, 2010
  11. Sep 25, 2010 #10
    I haven't read Hawking's book. But Hawking has his own idea on how to get something from nothing, which is independent of M-theory. I wrote about it http://comment.chinadaily.com.cn/articlecmt.shtml?id=11251378&page=3" [Broken].

    M-theory developed from string theory, which developed from particle physics. So it's really a theory of what the fundamental objects are. In particle physics you have electrons and protons and so forth; in string theory the particles are no longer points in space, they are very small vibrating loops; and in M-theory, the strings are found to be "membranes", sheets and tubes rather than lines. So according to M-theory, the world consists of these little branes interacting, and maybe our whole three-dimensional space is one big 3D brane in a hyperspace, and so on.

    But the significant fact for this discussion is that M-theory is a theory about the parts of the universe - what they are and how they interact. When you ask about the origin of the universe, you are talking about the whole (cosmology). And there is no consensus about cosmology in M-theory - for example, whether there was anything before the big bang. The theory of colliding brane-worlds that you describe must be what is called the "ekpyrotic scenario". So that's a theory in which time goes back forever - the braneworlds fall together, all the little branes attached to them experience a big bang inside the braneworld at the moment of collision, the braneworlds bounce apart, eventually fall back together, and this goes on forever. Hawking's favorite theory is a different one, where time turns into space at the big bang, so there's no real first moment, but there certainly isn't an eternal history like in the ekpyrotic universe. Then there's the theory of "eternal inflation", where the real universe is expanding forever at very high speeds, and the part we see is one of many isolated bubbles which changed to slow expansion. That would be the most popular. The ekpyrotic theory, with the bouncing braneworlds, is definitely a minority view.

    So to sum this up - M-theory at the level of interacting parts is agreed upon. Physicists are still figuring out the equations, but as Kevin_Axion said, M-theory is defined first of all as a particular limit of one type of string theory whose equation *is* known, so it really is a question of figuring out what that implies. M-theory at the level of cosmology is something different. There are various rival ideas for what explains the big bang, and so far the theory itself doesn't tell us which one it favors.

    I should also emphasize that Hawking's something-from-nothing cosmology didn't require M-theory. It was first described in terms of Einstein's theory of gravity and curved space. In the theoretical pathway from Einstein's theory of gravity to M-theory, we passed through "supergravity" (gravity plus supersymmetry) and superstrings (the supergraviton particle revealed to be a string and not just a point). From Hawking's perspective, this theoretical progress clarifies what the parts of the universe are and how they interact, but it doesn't affect his picture of the whole.
    Last edited by a moderator: May 4, 2017
  12. Sep 25, 2010 #11
    "how does M-theory explain the genesis of the HIGHER dimensions"
    It doesn't. Not any more than the Standard Model explains the origin of,say, an electron.
    as noted above string theory and M theory extends point particles to one dimensional vibrational strings..objects with length........branes are a two dimensional extension of point particles.....length and width....also with quantum jitters, energy,etc....

    An excellent read on ekpyrotic origins of the universe, a theory of endlessing colliding branes, is THE ENDLESS UNIVERSE , 2007, by Paul Steinhardt and Neil Turork....not lots of heavy math, good insightful ideas and concepts well explained......

    I'm guessing Hawking, and others, take endlessly colliding branes as a given...that's I believe the take in the above book...they have always existed and have been and will continue to collide endlessly....

    In a nutshell there are 11 dimensions in M theory consisting of innumerable Calabi-Yau manifolds (shapes in space, seven hidden, three visible dimensions) and it seems that number of dimensions is required to limit the string energy vibrations so as to match our observed particles....geometry controls particle characteristics....one type of vibration reflects electric charge, another mass,yet another a force etc,etc) ...a problem is that there is tens of thousands such particles are possible within the tehory and nobody yet has logic to select the small number we observe...

    as Marcus notes, M theory and string theory is incomplete....both the foundational math and the solutions.....so for example, all we have are perterbative (approximate) solutions to incomplete mathematical formulations....the early promise has proven to be far more complicated than originally anticipated.
    Last edited: Sep 25, 2010
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