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Splitting Time from SpaceŚNew Quantum Theory Topples [sic] Einstein's Spacetime
ScientificAmerican ^ | Dec 2009 | Zeeya Merali

Posted on 11/25/2009 12:25:53 AM PST by Daffynition

Was Newton right and Einstein wrong? It seems that unzipping the fabric of spacetime and harking back to 19th-century notions of time could lead to a theory of quantum gravity.

Physicists have struggled to marry quantum mechanics with gravity for decades. In contrast, the other forces of nature have obediently fallen into line. For instance, the electromagnetic force can be described quantum-mechanically by the motion of photons. Try and work out the gravitational force between two objects in terms of a quantum graviton, however, and you quickly run into trouble—the answer to every calculation is infinity. But now Petr Hořava, a physicist at the University of California, Berkeley, thinks he understands the problem. It’s all, he says, a matter of time.

More specifically, the problem is the way that time is tied up with space in Einstein’s theory of gravity: general relativity. Einstein famously overturned the Newtonian notion that time is absolute—steadily ticking away in the background. Instead he argued that time is another dimension, woven together with space to form a malleable fabric that is distorted by matter. The snag is that in quantum mechanics, time retains its Newtonian aloofness, providing the stage against which matter dances but never being affected by its presence. These two conceptions of time don’t gel.

The solution, Hořava says, is to snip threads that bind time to space at very high energies, such as those found in the early universe where quantum gravity rules. “I’m going back to Newton’s idea that time and space are not equivalent,” Hořava says. At low energies, general relativity emerges from this underlying framework, and the fabric of spacetime restitches, he explains.

Hořava likens this emergence to the way some exotic substances change phase. For instance, at low temperatures liquid helium’s properties change dramatically, becoming a “superfluid” that can overcome friction. In fact, he has co-opted the mathematics of exotic phase transitions to build his theory of gravity. So far it seems to be working: the infinities that plague other theories of quantum gravity have been tamed, and the theory spits out a well-behaved graviton. It also seems to match with computer simulations of quantum gravity.

Hořava’s theory has been generating excitement since he proposed it in January, and physicists met to discuss it at a meeting in November at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario. In particular, physicists have been checking if the model correctly describes the universe we see today. General relativity scored a knockout blow when Einstein predicted the motion of Mercury with greater accuracy than Newton’s theory of gravity could.

Can Hořřava gravity claim the same success? The first tentative answers coming in say “yes.” Francisco Lobo, now at the University of Lisbon, and his colleagues have found a good match with the movement of planets.

Others have made even bolder claims for Hořava gravity, especially when it comes to explaining cosmic conundrums such as the singularity of the big bang, where the laws of physics break down. If Hořava gravity is true, argues cosmologist Robert Brandenberger of McGill University in a paper published in the August Physical Review D, then the universe didn’t bang—it bounced. “A universe filled with matter will contract down to a small—but finite—size and then bounce out again, giving us the expanding cosmos we see today,” he says. Brandenberger’s calculations show that ripples produced by the bounce match those already detected by satellites measuring the cosmic microwave background, and he is now looking for signatures that could distinguish the bounce from the big bang scenario.

Hořava gravity may also create the “illusion of dark matter,” says cosmologist Shinji Mukohyama of Tokyo University. In the September Physical Review D, he explains that in certain circumstances Hořava’s graviton fluctuates as it interacts with normal matter, making gravity pull a bit more strongly than expected in general relativity. The effect could make galaxies appear to contain more matter than can be seen. If that’s not enough, cosmologist Mu-In Park of Chonbuk National University in South Korea believes that Hořava gravity may also be behind the accelerated expansion of the universe, currently attributed to a mysterious dark energy. One of the leading explanations for its origin is that empty space contains some intrinsic energy that pushes the universe outward. This intrinsic energy cannot be accounted for by general relativity but pops naturally out of the equations of Hořava gravity, according to Park.

Hořava’s theory, however, is far from perfect. Diego Blas, a quantum gravity researcher at the Swiss Federal Institute of Technology (EPFL) in Lausanne has found a “hidden sickness” in the theory when double-checking calculations for the solar system. Most physicists examined ideal cases, assuming, for instance, that Earth and the sun are spheres, Blas explains: “We checked the more realistic case, where the sun is almost a sphere, but not quite.” General relativity pretty much gives the same answer in both the scenarios. But in Hořava gravity, the realistic case gives a wildly different result.

Along with Sergei M. Sibiryakov, also at EPFL, and Oriol Pujolas of CERN near Geneva, Blas has reformulated Hořava gravity to bring it back into line with general relativity. Sibiryakov presented the group’s model in September at a meeting in Talloires, France.

Hořava welcomes the modifications. “When I proposed this, I didn’t claim I had the final theory,” he says. “I want other people to examine it and improve it.”

Gia Dvali, a quantum gravity expert at CERN, remains cautious. A few years ago he tried a similar trick, breaking apart space and time in an attempt to explain dark energy. But he abandoned his model because it allowed information to be communicated faster than the speed of light.

“My intuition is that any such models will have unwanted side effects,” Dvali thinks. “But if they find a version that doesn’t, then that theory must be taken very seriously.”


TOPICS: Science
KEYWORDS: cosmology; physics; quantumphysics; science; spacetime; stringtheory; theoreticalphysics
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1 posted on 11/25/2009 12:25:54 AM PST by Daffynition
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To: Daffynition

bump


2 posted on 11/25/2009 12:33:51 AM PST by tophat9000 (Obama plans to fix America like he fixed his dog)
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To: Daffynition

3 posted on 11/25/2009 12:39:45 AM PST by Berlin_Freeper (Barney Frank is the most disgusting person I can think of. I been thinking about it for months now.)
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Comment #4 Removed by Moderator

To: Daffynition

I LOVE reading articles like this, even though I don’t understand a word of it.


5 posted on 11/25/2009 12:43:19 AM PST by Bullish
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To: Daffynition

Einstein is stupid


6 posted on 11/25/2009 12:52:05 AM PST by woofie
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To: tophat9000

Cut to the chase!

Does this mean we can expect FTL travel in our lifetimes?


7 posted on 11/25/2009 1:06:07 AM PST by Ronin (Better an avowed enemy in front of me than a potential traitor beside me. NO RINOS!)
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To: Daffynition

But does it explain why the climate models don’t predict global cooling?


8 posted on 11/25/2009 1:07:31 AM PST by dila813
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To: Daffynition

I am reading this and honestly am thinking this is too simple, I can’t believe they overlooked this before.

It seems an obvious thing to test.

Maybe the problem was, group think prevented someone from presenting it because they were afraid of retribution from other scientists?


9 posted on 11/25/2009 1:15:46 AM PST by dila813
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To: Berlin_Freeper

10 posted on 11/25/2009 1:53:34 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: Daffynition

http://www.youtube.com/watch?v=t_4NrkEGNBM


11 posted on 11/25/2009 1:58:39 AM PST by happinesswithoutpeace (Its almost over. Its always over. Its almost always over.)
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To: Daffynition

You have looked. But you have not seen.

http://www.youtube.com/watch?v=_jvqPvDUEW8

RIFK


12 posted on 11/25/2009 2:00:40 AM PST by happinesswithoutpeace (Its almost over. Its always over. Its almost always over.)
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To: Daffynition

http://www.youtube.com/watch?v=G7T7wsX5BH0

Yiff


13 posted on 11/25/2009 2:07:04 AM PST by happinesswithoutpeace (Its almost over. Its always over. Its almost always over.)
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To: dila813
Link to Spectral Dimension of the Universe in Quantum Gravity at a Lifshitz Point - Petr Horava

Link to the math: Solutions to Horava Gravity - H. Lu, Jianwei Mei, C.N. Pope

"........ Petr Horava introduced an intriguing idea - that one of the physical principles at the heart of general relativity might be violated. The principle is called Lorentz symmetry (or Lorentz invariance) and it is the principles that physics is the same in any reference frame. The Lorentz violation would only happen at very small scales, of course, which is why it's never been observed to be violated, but if Horava's theory is correct then a theory which doesn't include Lorentz invariance at small scales might still give rise to Lorentz invariance at large scales. The great benefit of this theory, if it can be fully worked out, is that it would be much easier to introduce quantum mechanics into the theory. (General relativity and quantum mechanics are not currently able to work together easily in the same theoretical frameworks.)

A team out of Texas A&M University have now investigated how Horava's theory would affect generic solutions of general relativity, such as those that are spherically symmetrical. Another physicist, Horatiu Nastase, has taken this work and believes that, as it currently exists, the scales are off and Lorentz invariance would only be replicated on scales larger than the observable universe. "Modifications of the detailed balance action, within Hořava theory, can cure this problem," explains Nastase. He also points out, "It is still not known if the quantum Hořava theory makes sense, and more work in that direction is needed."

Other alternative gravity theories, such as those discussed in John Moffat's Reinventing Gravity: A Physicist Goes Beyond Einstein, have been bouncing around in some form or another pretty much since before Einstein even completed general relativity in the first place. The difference between these other theories and the Horava theory, according to Nastase, is that "Hořava['s] theory presents the tantalizing possibility that we have a well-defined quantum theory at short distances, without the need for additional fields."

14 posted on 11/25/2009 2:16:38 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: Daffynition

Tell your husband.

At this point in time i am convinced beyond all reasonable doubt that the one and only reason I am still alive is because i have remained undetected. Trapped In this house, in this place.


15 posted on 11/25/2009 2:18:44 AM PST by happinesswithoutpeace (Its almost over. Its always over. Its almost always over.)
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To: Daffynition

http://www.youtube.com/watch?v=7ZuP2sXwKNQ

^_^


16 posted on 11/25/2009 2:20:10 AM PST by happinesswithoutpeace (Its almost over. Its always over. Its almost always over.)
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To: happinesswithoutpeace

HAHAHA! I love the Stephen King cameo!


17 posted on 11/25/2009 2:27:35 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: happinesswithoutpeace
I have one for you....

Big Science by Laurie Anderson

18 posted on 11/25/2009 2:36:31 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: Daffynition

lulz...proxychecker...

daffy...


19 posted on 11/25/2009 2:37:18 AM PST by happinesswithoutpeace (Its almost over. Its always over. Its almost always over.)
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To: arbooz

20 posted on 11/25/2009 2:39:48 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: happinesswithoutpeace
You're on your own. I'm all set. I have my gravy separator for the holiday and beyond.


21 posted on 11/25/2009 2:42:49 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: happinesswithoutpeace
BWAHAHAHA! Don't be late for class!


22 posted on 11/25/2009 2:45:07 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: dila813
It's being worked on.


23 posted on 11/25/2009 2:54:03 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: Daffynition
... And then the experimentalists (that "Scientific Method" thingy) step in, maps the sphere into an airfoil (viz., Complex Analysis), multiples by zero (an essential step), and then adds the answer (The Crucial Moment).

Problem(s) solved - of course, your mileage my vary.

24 posted on 11/25/2009 3:22:37 AM PST by jamaksin
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To: Daffynition

bfl


25 posted on 11/25/2009 3:25:07 AM PST by Skooz (Gabba Gabba we accept you we accept you one of us Gabba Gabba we accept you we accept you one of us)
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To: jamaksin

I’m wondering what Brian Greene has to say about this. I’m pressed for time right now, but will search later. ;)


26 posted on 11/25/2009 3:27:29 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: Daffynition

lulz


27 posted on 11/25/2009 3:28:28 AM PST by happinesswithoutpeace (I thought about it. It has been several months since i last went out into the street)
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To: Daffynition

http://www.youtube.com/watch?v=rBJbzYxCC5I


28 posted on 11/25/2009 3:35:45 AM PST by happinesswithoutpeace (I thought about it. It has been several months since i last went out into the street)
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To: Daffynition

And he turned to the class, exclaiming “See how simple it is?”


29 posted on 11/25/2009 3:36:18 AM PST by R. Scott (Humanity i love you because when you're hard up you pawn your Intelligence to buy a drink)
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To: R. Scott

Wrong.

http://www.youtube.com/watch?v=_e39UmEnqY8


30 posted on 11/25/2009 3:39:42 AM PST by happinesswithoutpeace (R. Scott stfu or ddos)
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To: Daffynition

ping


31 posted on 11/25/2009 4:01:28 AM PST by 4Speed
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To: Daffynition

I wonder what these guys talk about when they get together on Super Bowl Sunday?


32 posted on 11/25/2009 4:01:32 AM PST by Hot Tabasco
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To: tophat9000
F=ND3
The next step.
33 posted on 11/25/2009 4:16:16 AM PST by UnbelievingScumOnTheOtherSide (IN A SMALL TENT WE JUST STAND CLOSER! * IT'S ISLAM, STUPID! - Islam Delenda Est! - Rumble thee forth)
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To: happinesswithoutpeace

I’m a big Cohen fan, thanks


34 posted on 11/25/2009 4:16:44 AM PST by Hot Tabasco
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To: Hot Tabasco

http://www.youtube.com/watch?v=IasKqCQYIrg


35 posted on 11/25/2009 4:21:53 AM PST by happinesswithoutpeace (you are receiving this broadcast as a dream)
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To: Daffynition
Along with Sergei M. Sibiryakov, also at EPFL, and Oriol Pujolas of CERN near Geneva, Blas has reformulated Hořava gravity to bring it back into line with general relativity. Sibiryakov presented the group’s model in September at a meeting in Talloires, France.

Sounds like Michael Mann and his bunch's approach.

Gia Dvali, a quantum gravity expert at CERN, remains cautious. A few years ago he tried a similar trick, breaking apart space and time in an attempt to explain dark energy. But he abandoned his model because it allowed information to be communicated faster than the speed of light.

“My intuition is that any such models will have unwanted side effects,” Dvali thinks. “But if they find a version that doesn’t, then that theory must be taken very seriously.”


Oh, geez. Let's make sure that it doesn't result in telling us something that we don't want to know or believe or is different from what we expected, like experimental results that demonstrate the speed of gravity is many times that the speed of light.
36 posted on 11/25/2009 4:23:12 AM PST by aruanan
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To: R. Scott

37 posted on 11/25/2009 4:44:23 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: Daffynition

lulzing

http://www.youtube.com/watch?v=ZnnDG2k_NDU


38 posted on 11/25/2009 4:46:26 AM PST by happinesswithoutpeace (you are receiving this broadcast as a dream)
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To: Daffynition

http://www.youtube.com/watch?v=b-1BmZAbicE


39 posted on 11/25/2009 4:48:18 AM PST by happinesswithoutpeace (yiff in hell)
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To: Daffynition
Umm ... nothing like a plucked string, albeit a very small and vibrating string, messing with "branes" in Riemann Space.

I sense a whole lot of tensors a'comin! -;}}

40 posted on 11/25/2009 4:50:52 AM PST by jamaksin
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To: Hot Tabasco

41 posted on 11/25/2009 4:59:41 AM PST by Daffynition (What's all this about hellfire and Dalmatians?)
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To: Daffynition

Hope rides alone.


42 posted on 11/25/2009 5:07:41 AM PST by happinesswithoutpeace (yiff in hell)
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To: Daffynition

Hope rides alone

http://www.youtube.com/watch?v=McsWKczU6wc


43 posted on 11/25/2009 5:09:14 AM PST by happinesswithoutpeace (yiff in hell)
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To: Daffynition
The picture is exactly correct. Time is a human perception and has been assigned a value by humans. Consequently time is an imperfect tool to use to try and understand space. While time does reflect a measure of change the universe may not care about our efforts to assign it a value that may or may not be relevant to understanding space. Einstein seemed to be obsessed with time and therefore his projections are probably skewed.
44 posted on 11/25/2009 5:15:17 AM PST by mad_as_he$$ (Beneath this mask there is an idea, Mr. Creedy, and ideas are bulletproof. V for victory)
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To: Daffynition

ya idiot

http://www.youtube.com/watch?v=7WUxlXpZ5eM


45 posted on 11/25/2009 5:16:46 AM PST by happinesswithoutpeace (yiff in hell)
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To: Ronin
What makes you think it does not already exist? FTL actually probably not in our lifetime. Wormhole will be the first FTL technology developed.
46 posted on 11/25/2009 5:17:23 AM PST by mad_as_he$$ (Beneath this mask there is an idea, Mr. Creedy, and ideas are bulletproof. V for victory)
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To: Daffynition; dila813

>>>paper published in the August Physical Review D, then the universe didn’t bang—it bounced. “A universe filled with matter will contract down to a small—but finite—size and then bounce out again

About five years ago there was a calculation discussed that suggested the temperature of the “universe” would make sense only if there had been a series of prior “big bangs”. By their arithmetic, something like five prior progressively cooling universes would be required to form the current state of physics.

Maybe they were on the right track.


47 posted on 11/25/2009 5:22:16 AM PST by tlb
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To: Daffynition

ping


48 posted on 11/25/2009 5:44:42 AM PST by BrandtMichaels
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To: Daffynition
But now Petr Hořava, a physicist at the University of California, Berkeley, thinks he understands the problem. It’s all, he says, a matter of time.

It's About Time!

49 posted on 11/25/2009 5:55:48 AM PST by Willie Green (Go Pat Go!!!)
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To: Daffynition

Still trying after all these years to understand the secrets of the Universe.


50 posted on 11/25/2009 6:56:22 AM PST by Leftism is Mentally Deranged
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