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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 Update: 10/09 16:06 GMT by Z : A few readers have written in to point out that the article is not peer-reviewed; your mileage may vary.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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  • Re:E=MC^2 (Score:1, Insightful)

    by TruePoindexter (975295) on Tuesday October 09, 2007 @11:08AM (#20912757)
    He'd smile and stick out his tongue.
    Nyah
  • by caramelcarrot (778148) on Tuesday October 09, 2007 @11:14AM (#20912883)
    Physics as we experience it will go to shit, since much of the base derivations are a consequence of a non-spacelike time.
  • "... about to ..." (Score:5, Insightful)

    by dpilot (134227) on Tuesday October 09, 2007 @11:19AM (#20912963) Homepage Journal
    So dpilot was talking with God, and God said, "To Me, a minute is like a million years, and a million years are like a minute." So dpilot said, "In a that vein, is a penny like a billion dollars, and a dollars like a penny?" God replied, "You've got it." Which led dpilot to ask of God, "Can you spare a penny?" "Sure," said God, "in just a minute..."

    When you say "about to" in sports, something generally happens pretty fast.
    When you say "about to" in geology, something generally happens pretty slow.
    Generally speaking, saying "about to" in cosmology is to geology as geology is to sports.

    But not always. At some points in time, the volcano under Yellowstone does go off. Likewise, supernovas happen, and perhaps brane changes too. But to say "about to" or "soon" is just meaningless to human scales of time.
  • by Anonymous Monkey (795756) on Tuesday October 09, 2007 @11:20AM (#20912991)
    No, not at some time in the future. At some POINT in the future. If time is becomes a detention of physical space then future and past will be like left and right. I could never tell my left from my right as a kid.
  • Define "about to"? (Score:5, Insightful)

    by WibbleOnMars (1129233) on Tuesday October 09, 2007 @11:21AM (#20913009)
    I'd like to know how they define "about to flip".

    Are we talking about something they see as imminent -- could happen at any moment?
    Or are we talking about geological time scales -- it'll happen in a few hundred thousand years, give or take?
    Or do they mean cosmological scales -- where 'about to happen' means somewhere in the next ten or twenty million years?

    Or is the whole question of when a silly thing to ask, given that they're talking about the end of time as sequential/chronological?
  • by pclminion (145572) on Tuesday October 09, 2007 @11:22AM (#20913035)

    Isn't "time" only subtlety different from a physical dimension?

    This phrasing suggests that time is not a physical thing. Given that the variable "t" occurs in practically all dynamic equations of physics, I'd have to disagree with the assertion that time isn't physical.

  • Re:Mayan Calender (Score:2, Insightful)

    by mentaldingo (967181) on Tuesday October 09, 2007 @11:58AM (#20913573) Homepage

    Disclaimer: IANAP.

    Seriously, I think this is ridiculous for two main reasons, I think.

    How can the Universe suddenly change like that? Change requires time. It's a logical paradox. You say that in the future, that time will become a fourth spacial dimension, but try writing up a timeline of the events:

    1. Time 0: Universe has time and is normal.
    2. Time 1: Universe suddenly flips and now has 0 time, 4 space.
    3. Time ??: No time, but now where did the past go?

    OK, I'm no good at explaining this, but it clearly doesn't mix at all well with general/special relativity's block time. Not only for that timeline problem above, but also because the difference between space and time is made up by humans: Special relativity can be derived from the starting assumption that there are four dimensions (3 with real displacements, 1 with imaginary displacements) and a whole bunch of spaghetti (particles and stuff moving around). When you rotate the spaghetti through the fourth, imaginary dimension, you get a velocity, and it just so happens, that the rotation becomes hyperbolic, and you get the speed of light as a limit.

  • by king-manic (409855) on Tuesday October 09, 2007 @12:32PM (#20914121)
    The "problem", philosophically, with a purely Newtonian universe, derives from the niggling little detail that free will cannot exist. Every possible action you could ever take will have already happened, just not yet.

    Free will is just an idea. It isn't some essential observed bit of the universe. From all scientific evidence we are complicated finite state machines. We are entirely physical, deterministic machines.
  • Consequences (Score:4, Insightful)

    by xPsi (851544) * on Tuesday October 09, 2007 @12:43PM (#20914331)
    Ok, as others have pointed out, this "paper" is not peer reviewed. I want to make it clear that I don't personally feel slashdot is the place to debate random physics papers on the arXiv. But, being slashdot, I will ignore my own pleas for sanity. What would be the physical consequences of time suddenly becoming space-like? First, on most mesoscopic scales in our everyday life, time already appears like a spatial dimension. Newton certainly thought so and our (incorrect) intuition tells us this is the case. The degree to which special and general relativity play a role in your everyday life is a measure of how "time-like" time feels. Probably not much. Nevertheless, if time suddenly physically became space-like, physicists all over the world would know it right away. All the weird stuff in relativity like time dilation and space contraction and so on, comes from time having an opposite metric sign as space. These effects all go away if time is space-like. For example, in a typical advanced undergraduate physics lab, you might measure the lifetime of a muon that is sitting in the lab as opposed to one that is crashing down from the sky. The one coming from above (at a large fraction the speed of light) lives longer in the frame of the ground because of time dilation. Easily verified in an afternoon. But I guess no more (at least after next Thursday or whenever this is supposed to happen). Similarly, all the special relativity equations required to perform basic momentum, energy, and lifetime calculations at colliders like Fermilab, CERN, and Brookhaven would suddenly stop working. That would be a big deal and it wouldn't be a subtle thing. IMHO, it makes for great science fiction, but I'm not sure where these guys are going with it.
  • by Anonymous Coward on Tuesday October 09, 2007 @12:58PM (#20914625)
    You forgot a few:

    CONSPIRACY: We HAVE made contact. Now that you know, I have to kill you.

    PHASE SHIFT: We're looking for signals in radio waves, but due to relativistic differences in velocity between us and other intelligent civilizations, their broadcasts are arriving in deep infrared.

    ACTIVE JAMMING: They don't want us to look, and they've developed sufficient FTL technology to get between their early signals and us.

    EARLY TO THE PARTY: Somebody had to be first...

    GAH LAK TUS: 'Nuff said, true believer.
  • Re:E=MC^2 (Score:1, Insightful)

    by Anonymous Coward on Tuesday October 09, 2007 @01:02PM (#20914683)
    Both, obviously.
  • Re:Mayan Calender (Score:3, Insightful)

    by tm2b (42473) on Tuesday October 09, 2007 @01:36PM (#20915223) Journal
    How can the Universe suddenly change like that? Change requires time. No... this change requires time before it, not after it. It's a phase transition.

    What was time like before the (4-space) big bang?

    That said, this is probably a junk paper, but what you identify isn't a problem.
  • by Anonymous Coward on Tuesday October 09, 2007 @01:48PM (#20915441)
    FTFA:

    It don't . . . they got . . . this ain't . . . yep . . . ain't got . . . we're all starin' down the barrel . . .

    Nuthin' detracts from scientific journalism more 'n talkin' like a fsckin' hillbilly.

  • by PRMan (959735) on Tuesday October 09, 2007 @05:53PM (#20918839)

    Actually, strangely enough, this exact sort of logic is used by Creationists to explain how starlight could be billions of years old on a 3 day old earth. One theory is that the universe was created out of a white hole, and the earth was in a 4 space dimension 0 time dimension position while billions of years of star formation and travel were happening (by the earth's reference clock).

    http://www.answersingenesis.org/docs/405.asp

    I have the book. It's very interesting. The most interesting thing of all is that the math supports his premise and has gone unchallenged, meaning that it is physically possible that starlight could be billions of years old when the earth was only 3 days old, as long as earth was near the center of the white hole and exited toward the end.

"If that makes any sense to you, you have a big problem." -- C. Durance, Computer Science 234

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