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Space Science

Time Dimension To Become Space-like 587

Posted by Zonk
from the you're-not-thinking-fourth-dimensionally dept.
KentuckyFC writes "The Universe is about to flip from having three dimensions of space and one of time to having four dimensions of space. That's the conclusion of a group of Spanish astrophysicists who have calculated that observers inside such a Universe would see it expanding and accelerating away from them just before the flip (abstract, full paper pdf on the physics arXiv). 'We show that regular changes of signature on brane-worlds in AdS bulks may account for some types of the recently fashionable sudden singularities. Therefore, the fact that the Universe seems to approach a future sudden singularity at an accelerated rate of expansion might simply be an indication that our braneworld is about to change from Lorentzian to Euclidean signature. Both the brane and the bulk remain fully regular everywhere.'" Update: 10/09 16:06 GMT by Z : A few readers have written in to point out that the article is not peer-reviewed; your mileage may vary.
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Time Dimension To Become Space-like

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  • by Qzukk (229616) on Tuesday October 09, 2007 @12:24PM (#20913053) Journal
    The other one was about a kid who befriends a neighbor working in 4-D stuff. The kid (because he's young and has an open mind or something) learns to move about in that dimension as well, and communicate with creatures living in other dimensions. Don't remember the title of that one, thoguh.

    I believe that's The Boy Who Reversed Himself [amazon.com]. I remember having read that when I was in highschool.
  • Old, old old news (Score:2, Informative)

    by bradgoodman (964302) on Tuesday October 09, 2007 @12:25PM (#20913075) Homepage
    This is nothing new at all.

    Relativity talks of space and time as a single 4-dimensional 'spacetime'.

    M-Theory, Superstrings, p-Branes, and a billion other theories all say there are 10 (or 11) dimensions, including things like two-dimensional "time" and "imaginary-time" dimensions, smaller "curled-up" spacial dimensions, etc.

  • by davidoff404 (764733) on Tuesday October 09, 2007 @12:48PM (#20913425)
    Unfortunately, while the ArXiv is where important results are first published by working physicists, it's also a place where an increasing amount of junk papers are posted. For those who are interested, this is an example of just such a junk paper as it amounts to nothing more than a fancy way to produce a (parameterized) Wick rotation in a braneworld model.

    Of course, let's not even mention the fact that they're proposing that braneworlds and AdS are reasonable approaches to physics...
  • by Anonymous Coward on Tuesday October 09, 2007 @01:03PM (#20913653)
    A few readers have written in to point out that the article is not peer-reviewed

    Not only that, it is based on M-Theory [wikipedia.org] (is that still what they are calling it these days?). M-Theory was the brain child of a bunch of mathematicians; an attempt at building a model that could resolve the conflicts between general relativity [wikipedia.org] and quantum mechanics [wikipedia.org].

    The equations that they produced seem to resolve those conflicts, but do so by proposing the existence of a whole host of previously unobserved (and currently unobservable) entities. Good arguments can be made that this violates the principle of Ockham's Razor [wikipedia.org]. Either way, the bottom line is that the evidence just isn't there.

    So far, M-Theory is not really a Theory, but rather an untested hypothesis. Once the evidence rolls in I will change my tune, but until then I consider it to be little more than idle speculation.
  • by sweetser (148397) <sweetser@alum.mit.edu> on Tuesday October 09, 2007 @01:06PM (#20913679) Homepage
    Silly Spaniards playing bogus number games. Quaternions are numbers, like the reals, but with 4 parts, a scalar one for time, and a 3-vector for 3D space. A scalar ain't never gonna be a vector. Ever. There is no finger pointing for scalars. This is why there is no arrow for time, never will be, but there is an arrow for spacetime, due to the space part of spacetime. If you look up "Standard Model" on YouTube, not arXiv, you can see they symmetries of EM, the weak force, the strong force, and gravity, U(1), SU(2), SU(3), and Diff(M) respectively. Those 4 symmetries are involved in the norm of two quaternions, where q* q' = 1. Play with the quaternion 4D wave equation, and you get competition for GR.

    doug
    barking up a real 4D tree by himself
    instead of making dumb 11D claims
  • Re:Time speeding up (Score:5, Informative)

    by dissy (172727) on Tuesday October 09, 2007 @03:25PM (#20915995)

    The big-bang didn't happen sometime in the limitless void of space, the big-bang was the creation of the space-time continuum itself.
    Not according to current brane and bulk theories. In them, time and space existed forever, and still do. The big bang is just a massive release of energy, that reorders the energy and matter within our brane in a way that appears everything is moving away from that 4d point.

    One suggestion was that two branes within the bulk colided, and all that energy that has to go somewhere goes into a big bang in a 4d brane (the bulk is either 10 or lately 11 dinentions while we are just in 4)

    If those theories are correct, both time and space existed before the big bang, and also at some point in the future our brane will collide with another again and cause another big bang. This happens through out all the branes at different times and repeats forever.

    Note that I word my post as if "this is", when it should be pointed out that my wording is this way "if these theories are right", so please take it as such.

  • Re:Mayan Calender (Score:3, Informative)

    by mhall119 (1035984) on Tuesday October 09, 2007 @03:49PM (#20916345) Homepage Journal
    Look at it this way. We live in a 4 dimensional space, x, y, z and t are our 4 dimensions. x, y and z are space-like, while t is (currently) time-like. You steps go like this:

    1. t=0: Universe has time and is normal
    2. t=1: Universe suddenly flips, dimension t is now space-like
    3. t=2: You now life in a 4d universe with 4 space-like dimensions, and you are at point 2 on the 't' dimension, which you can freely travel on in the positive or negative directions (time travel becomes possible)


    Does that help?
  • Re:Time speeding up (Score:3, Informative)

    by blahlemon (638963) on Tuesday October 09, 2007 @04:42PM (#20917153)
    You read that article http://www.space.com/scienceastronomy/white_hole_030917.html [space.com] too eh?

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