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Time Dimension To Become Space-like
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 Update: 10/09 16:06 GMT by Z : A few readers have written in to point out that the article is not peer-reviewed; your mileage may vary.
So that's whats going to happen when the Mayan calender rolls over in 2012.
Oh, I'm living in a tesseract,
a four dimensional box.
It's bigger on the inside,
what why my four-space rocks!
When you get on the inside,
the outside becomes the in,
Dimensionally speaking,
it's all about the spin.
I've fallen off your lawn, and I can't get up.
"Oh, that was easy," says Man, and for an encore goes on to prove that black is white and gets himself killed on the next zebra crossing.
"Flyin' in just a sweet place,
Never been known to fail..."
where the theories and calculations of the brightest brains in the room become indistinguishable from the random brainfarts of two stoners sitting on a smelly couch in a dorm room at 4:20 AM
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
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.
The living have better things to do than to continue hating the dead.
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?
Lets say I told you we had two spatial dimensions. You would imagine a plane with perpendicular x-y axes everyone knows and loves. If I asked you to draw the set of points that were equidistant from the origin, you would probably assume the geometry was Euclidian and would probably instinctively draw a circle (a good guess!). It is commonplace to hear "time is the fourth dimension." As first pass to visualize this, you might try to draw a two dimensional space-time plot: an x axis and a perpendicular time axis in a plane. If I then asked you to draw all the points equidistant from the origin, you would probably again draw a circle in this x-t plane. It seems to make sense, but is only true of time is a "space-like" dimension like "y" in the x-y plane. This is way Newton thought of things and it seems to be what the authors of the paper are advocating. But, unbeknownst to some people who cite "time as the fourth dimension," according to the theory of relativity, the set of equidistant points from the origin on a x-t graph would actually be hyperbole, not circles. This is because in relativity space-time is a Minkowski geometry, not Euclidian. All the weird stuff in special relativity like time dilation and length contraction come about because of this weird geometry. In fancier language, time has an opposite sign than space in the metric. The metric determines how distances are calculated in a given geometry. If time has the same sign as space in the metric, then space-time becomes Euclidian and one would say that time was a space-like. The article is probably extra confusing to non-physics people because most probably didn't know time wasn't space-like to begin with.
i\hbar\dot{\psi}=\hat{H}\psi
In the future, time will become very confusing...
Dark Helmet: What the hell am I looking at? When does this happen in the movie?
Sandurz: Now, you're looking at now, sir. Everything that happens now is happening now.
Dark Helmet: What happend to then?
Sandurz: We passed then.
Dark Helmet: When?
Sandurz: Just now. Were at now, now.
Dark Helmet: Go back to then!
Sandurz: When?
Dark Helmet: Now.
Sandurz: Now?
Dark Helmet: Now!
Sandurz: I can't.
Dark Helmet: Why?
Sandurz: We missed it.
Dark Helmet: When?
Sandurz: Just now.
Dark Helmet: When will then be now?
Sandurz: Soon.
Dark Helmet: How soon?
Demented But Determined.
Change requires time. It's a logical paradox.
You're assuming that there is only one time dimension. But actually, from a non-linear, non-subjective viewpoint, it's more like a big ball of wibbly-wobbly, timey-wimey... stuff.
When our name is on the back of your car, we're behind you all the way!
When I first heard that the rate of the universe's expansion was actually accelerating, I came up with a weird hypothesis after a few days...
Time in our frame of reference is slowing down.
The only way that seemed possible was if we were traveling at speeds close to c, but that didn't sound feasible since we were observing objects that were moving away from us, in all directions. Then another weird thought occurred to me...
Our observed universe is self-contained within the event horizon of a giant black hole.
We're closer to the singularity, and accelerating towards it faster than objects closer to the edge of the event horizon. Time will move slower for us, and far away objects will appear to speed up. An outside observer (if such a thing could possibly exist) would perceive our universe as shrinking, but in our current frame of reference, we still think of it as expanding.
One other observation that lends to this possibility is the fact that we have not seen evidence of other "Big Bangs" or other "Universes". If the Big Bang happened once, shouldn't it be a repeatable occurrence in the limitless void of space?
Okay, that's my rant. You can slap the straitjacket on me now and ship me off to the funny farm.
Solomon Chang
"Twice half-assed makes an ass whole." --Solomon K. Chang
overlords.
Breaking "time's arrow" will really fuck with our verb tenses.
But I worried about that tomorrow...
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Don't blink, don't turn away, don't close your eyes, and whatever you do, don't blink!
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