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Comments: 575 +- Science: New Theory of Gravity Decouples Space & Time on Tuesday November 24, @03:55PM
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kdawson
on Tuesday November 24, @03:55PM
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eldavojohn writes "Petr Horava, a physicist at the University of California in Berkeley, has a new theory about gravity and spacetime. At high energies, it actually snips any ties between space and time, yet at low energies devolves to equivalence with the theory of General Relativity, which binds them together. The theory is gaining popularity with physicists because it fits some observations better than Einstein's or Newton's solutions. It better predicts the movement of the planets (in an idealized case) and has a potential to create the illusion of dark matter. Another physicist calculated that under Horava Gravity, our universe would experience not a Big Bang but a Big Bounce — and the new theory reproduces the ripples from such an event in a way that matches measurements of the cosmic microwave background."
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And FTL, too (Score:5, Interesting)
Special relativity, of course, forbids sending information faster than light. A theory supplanting the space-time unification of General Relativity would also supplant special relativity, and hence might not have that limitation. Here's an inteersting tidbit from the article: "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."
I'd call that a feature, not a bug!
Re:And FTL, too (Score:5, Insightful)
Whether it's a feature or a bug depends on whether it reflects reality.
It's strange to me that Dvali would abandon his model for allowing FTL propagation of information unless he experimentally checked the conditions in question to see if information really could propagate FTL in those cases. I have to assume he did not - lacking clarification on the matter I'm left to assume that the conditions were not something simple he could test no a whim.
Without the experimental results, it's meaningless to call such an artifact in the model "good" or "bad".
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Re:And FTL, too (Score:5, Funny)
I have to assume he did not - lacking clarification on the matter I'm left to assume that the conditions were not something simple he could test no a whim.
Wow. Anyone else see that? From my location, the n arrived before the o; however, the parent clearly typed them in order (o before n) in our reference frame, so I think we've just witnessed information traveling faster than light! Woohoo!
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Re:And FTL, too (Score:5, Funny)
It's strange to me that Dvali would abandon his model for allowing FTL propagation of information unless he experimentally checked the conditions in question to see if information really could propagate FTL in those cases.
Sorry, my bad. I have to be the one who checks for FTL propagation, union rules. I'll get to it after I finish my "get laid" project. I'm particularly hopeful. Just the other day, I made eye contact for 1.3 seconds with what I assume to be the female of our species. I think I can get that up to 10 seconds without breaking any laws of the legal kind. It's very promising progress here.
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Re:And FTL, too (Score:5, Interesting)
"But he abandoned his model because it allowed information to be communicated faster than the speed of light."
I'd call that a feature, not a bug!
Exactly! "Oh no, my theory doesn't match the theory it's replacing!" Well, experiment, dummy! Did Einstein say "oh no, my theory allows light rays to bend and makes C the absolute speed!"? No! He got together with other scientists in 1919 and watched starshine bend around an eclipse.
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Re:And FTL, too (Score:5, Interesting)
Actually, HE DID!
He added the cosmological constant to his general theory of relativity, because if he followed his models...it indicated that the universe was expanding.
Einstein didn't like the idea that it was expanding(because it didn't fit the current thinking), so he added the cosmological constant to his equations to make the universe "static".
so, even Einstein fell prey to conventional wisdom and thinking.
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Re:And FTL, too (Score:5, Interesting)
Actually, faster-than-light transmission of information has already been observed in science. [wikipedia.org]
It's a long way from observing and indirectly influencing quantum entanglement to a Star Trek-esque subspace communication, but the fact that Quantum Entanglement exists in the first place lends credence to the notion that c is not a hard limit, or at least, that it's not a hard limit outside of the 4 dimensions that we can observe.
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Re:And FTL, too (Score:5, Informative)
Actually, faster-than-light transmission of information has already been observed in science. [wikipedia.org]
Well, yes, I suppose... as long as your definition of "transmission" of information is sufficiently flexible. The quantum correlation is "transmitted" faster than light, but you can't get information out of it unless you receive the (slower than light) classical part.
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Re:And FTL, too (Score:5, Interesting)
You have two things quantumly entangled. You tickle either one, they both laugh. But if can only observe one at a time, if one laughs without being tickled, you don't know whether it was because the other was tickled or if it laughed spontaneously until you observe the other being tickled. There's no way to confirm the laughter as FTL information from the future unless and until you observe the future.
It may be that they only both laugh when you can observe them both. Your observation entangles them and bridges the FTL transmission classically.
I'd like to see the experiment where they're entangled, one is dropped through a black hole's event horizon, and you observe the result on the other. Time compression should have an interesting effect on the half-life of the retained entangled one until it crosses the EH.
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Re:And FTL, too (Score:5, Interesting)
Remember, faster than light means time travel (&, thus, causality violations), so I can understand caution. But, I bet in reality his theory had more serious problems.
If his theory is correct and space and time are decoupled then faster than light travel wouldn't allow you to travel back in time.
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So help me out here. (Score:5, Funny)
Does this theory suck or is there some pull to it? It just seems so weighty to me.
Much more mathematical detail... (Score:4, Informative)
Re:Much more mathematical detail... (Score:5, Funny)
It's a PDF version of a PowerPoint deck, so it's not exactly easy to read.
Indeed, informative link but I think your signature should be at the start of your post. I was doing pretty good right up until they plugged the ansatz into the Horava’s action to produce the reduced Lagrangian.
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Re:Much more mathematical detail... (Score:5, Funny)
... until they plugged the ansatz into the Horava’s action to produce the reduced Lagrangian.
Huh. I didn't get that far. And I'm pretty sure that whatever it that is, it's illegal in Texas.
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Re:Much more mathematical detail... (Score:5, Insightful)
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String Theory (Score:5, Interesting)
Re:String Theory (Score:4, Informative)
"String theory" is actually a collection of several competing theories and this theory appears to be another version. I can't really say for sure as the presentation on the theory seemed to me to be rather limited.
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ZZZTTT ! (Score:4, Informative)
it fits some observations better than Einstein's or Newton's solutions. It better predicts the movement of the planets (in an idealized case)
Oh. In an idealized case. Imaginary physics. Of course, in the actual case, it does not (it requires patching to allow for non-spherical planets).
At any rate, there are at present no known relativistic measurements that are not consistent with General Relativity, so I am not clear where the "better than" comes from.
And, from the standpoint of a General Relativist, the stubborn desire of the particle physicists to have a flat spacetime at high enough energies, no matter what, seems, well, quaint.
some modest hypotheses (Score:4, Funny)
2. I don't think time, as in "time lines" or some kind of unidirectional movement through a medium exists. Now exists, hypostatized out of a past (which stops existing when it stops being now) and which in turn hypostatizes the future (which does not exist.)
3. Electromagnetism is the dominant force in the heavens as it is on Earth.
4. Stars are organisms and they reproduce through fission.
5. Galaxies are powered by vast electric circuits; beads on a string.
Theory or Hypothesis? (Score:4, Interesting)
Sounds to me like this is just an hypothesis as there doesn't appear to much experimental evidence supporting it. This is an extraordinary claim and so need extraordinary proof.
And, the interchanging of hypothesis and theory by scientific magazines is a bad thing. If scientists, science fans, and science writers do not use the words correctly how are we to defend the difference when creationists come around misusing the words?
Ow! (Score:4, Insightful)
Ow! My brain hurts.
I have a hypothesis about gravity. (Score:4, Funny)
My hypothesis about gravity:
Everything is growing. We can't see anything growing, because our rulers and tapemesures and everything is growing. That's gravity: Just the growing earth pushing against your growing feet. Gravity at a distance is just objects growing towards each others (the void doesn't grow). Come to think of it. It's probably a bad hypothesis. It couldn't explain a slingshot effect, could it? Nevermind.
Re:Not again (Score:5, Insightful)
Behold, science.
The catch is, eventually one will be right, and explain things that are out of the scope of Einstein's theories or more accurately explain in-scope things.
Or do you believe we are at the pinnacle of the field, and can achieve no more?
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Re:Not again (Score:5, Funny)
We have reached enlightenment. We shall now call ourselves Q.
(huuummmm)
Man this is dull.
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Re:Not again (Score:5, Funny)
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Re:Not again (Score:5, Funny)
Then I shall be Fah Q 2!
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Re:Not again (Score:5, Funny)
Well Fah Q both then
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Re:Not again (Score:5, Funny)
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Re:Not again (Score:5, Funny)
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Re:Not again (Score:5, Funny)
I believe they will all be right, but it will only be from the perspective of the observer/believer which is right at the moment. However when it isn't being observed it will be both right and wrong until observed again. Therefore there are multiple pinnacles and it won't matter which are right or highest. Just have your towel ready because on top of the pinnacle is a little man who is only going to apologize for the inconvenience.
Always have a towell ready.
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Re:Not again (Score:4, Interesting)
There are really 42 quarks. [angryflower.com]The LHC should probably be able to test this... [angryflower.com]
(God but I love that guy's cartoons!)
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Re:Correction: (Score:5, Funny)
Or maybe you actually meant the theory would be better than 'Reletivity'. That could work.
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Re:Not again (Score:5, Insightful)
Yeah: http://yfrog.com/b9sciencevsfaithbigp [yfrog.com]
This sentiment is rather old, I'm sure before and when Einstein came about, people were saying the same thing about Newtonian physics. Skepticism about new theories are fine, but I'm sure the science will come to a point where we do discover something better than Einstein's formulas in some areas.
BTW, my physics is really rusty, doesn't one of Einstein's equations devolve into a newtonian equation at slow speed? Which just shows that things are truly built on top of one another.
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Re:Not again (Score:5, Insightful)
BTW, my physics is really rusty, doesn't one of Einstein's equations devolve into a newtonian equation at slow speed?
Wouldn't be correct if it didn't. Newton wasn't *wrong*, he just didn't specify the parts he couldn't see. Same with Einstein, same with this.
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Re:Not again (Score:5, Interesting)
Recently, paradigms in physics have been interesting in this respect as the new perfectly subsume the prior in their limits. I am not sure that this is a tautology of science, but it is an elegant means of progression.
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Re:Not again (Score:5, Informative)
Same thing in Quantum Mechanics. They devolve into classical equations, if you set Planck's Constant to 0.
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Re:Not again (Score:5, Insightful)
Not so. You cannot prove that repeatedly making a measurement in the past is any indication that it will hold in the future. Pointing out that it's worked before is just begging the question, and therefore reproducing the results doesn't help, for it does not mean you'll reproduce the results *again*.
You *must* presuppose that the future is relevantly like the past for empiricism to have any meaning in any context; it's pretty much an irreducible problem.
With that said, such "faith" is, I would argue, essentially to daily living and doesn't really deserve to be categorized as "faith" except in the most pedantic of senses. Without acting under this presupposition, you cannot learn. Anything. I suspect that biologically this presupposition cannot be unlearned since it appears to be intrinsic to learning even in some of the stupider members of the animal kingdom.
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Re:Not again (Score:5, Insightful)
"You cannot prove that repeatedly making a measurement in the past is any indication that it will hold in the future."
Flip side, you can't prove that it won't hold true in the future either. In essence, your argument is a case of argumentum ad ignorantiam.
The bottom line is that you're engaging in fancy footwork trying to get to him to use the word "faith", in which case you then have a basis for moving on to a discussion of "true faith", a belief in God or some such. Faith is belief without proof.
But... if you have proof then you don't need faith. Past personal observation, history, science, math, and orbital mechanics all say that the sun will come up tomorrow. Faith is not needed.
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Re:Not again (Score:5, Insightful)
Belief without evidence is called blind faith, science rests on the faith that the universe is ultimately predictable and will continue to exist even if we don't (in other words it believes that the proverbial tree in a forest does indeed make a noise).
There is no way to "prove" that the universe behaves like this but rational people take it as an indisputable fact because the evidence of ones own perceptions is very difficult to ignore particularly when they match the perceptions of other humans. So yes, science is based on faith as is all knowledge that goes further than "I think therfore I am".
"The bottom line is that you're engaging in fancy footwork trying to get to him to use the word "faith"
No he is not, the "bottom line" is that basic scientific philosophy confuses the hell out of people who subscribe to the popular but incorrect notion that science is in the bussiness of "proof". We wouldn't even be having this discussion if epistemology [wikipedia.org] was taught in modern high schools.
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Re:Not again (Score:5, Insightful)
This is healthy. Science can only progress if we accept that thinking outside the box is admissable. If the idea works ehen it will be testable.
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Re:Not again (Score:5, Insightful)
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Re:Not again (Score:5, Insightful)
Can you send me an example where Jesus accurately predicts known experimental results?
(I'm not sure if your stay on rejection was genuine or troll-bait, but it's caught momentum and I thought I'd provide an honest response rather than leave the question hanging.)
There's the golden rule, for starters. He didn't invent it, but he was instrumental in the widespread use of its positive statement ("Do unto others as you would have them do unto you" as opposed to "Do not to your neighbor what you would take ill from him"). And the result of following that rule, the rule of initiating kindness, you are statistically more likely to be treated kindly in return. Common sense and anecdotal evidence bear this out as well.
Then there's a bunch of other stuff he said, including things about the Kingdom of Heaven being here and now, forgiveness, faith, and love, that has unfortunately been so steadily downplayed and cloaked in tradition and dogma that it gets lost in the "war" to "win souls" for God. I think the historical Jesus would get along just fine with good-hearted atheists, Muslims, Hindus, Krishnas, Christians, Buddhists, and followers of most any other creed that you can imagine--and he probably had more in common with the Buddhists than we tend to think. He might not agree with all of the beliefs in those various systems, but he was more interested in disciples, people who would emulate his way of living, than converts to his religion, which didn't even exist during his lifetime. In other words, I think he'd be an excellent person to discuss philosophy and religion with, and he'd probably be the first to quell any budding flame wars.
This is of course only my understanding of Jesus. I've put a lot of thought and a decent amount of study into it, so I have a nuanced view not shared by most Christians, but I prefer to simply act in a manner I think he would approve of than to talk about it. It's more challenging and more effective to act, and I lack the agenda to convert people so dislike being perceived as having it. It is still disheartening to see his teachings rejected out-of-hand because of the centuries of stupid, un-Christlike actions of his followers, not to mention the (in my opinion) corruption of his words within the Bible. I hope to change that by trying to live up to the way I think he did. Even if most people who learn from me never find out my source, it is a good way to live.
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It is also not a complete and consistent theory (Score:5, Insightful)
Horavec's formulation works for certain (perfectly spherical) cases of the stress-energy tensor, not in other cases. In fact it produces some wildly inaccurate results in more realistic cases. Nor is he the first to try this kind of thing. Still, it sounds interesting and further refinements could produce a fully consistent theory which can match observation. When and if that happens then it will be a really major advance. It certainly seems like we're edging closer to something.
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Re:Oh no... (Score:5, Funny)
If you reverse the polarity, inject some chroniton particles, and rub Patrick Stewart's head for good luck, it'll still work.
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Excellence: Biography of Petr Hoava (Score:4, Informative)
Yet, who is Petr Hoava? He maintains a Web page [berkeley.edu] that offers the following biography.
"Petr Horava received his Ph.D. in 1991 at the Institute of Physics of the Czech Academy of Sciences in Prague. He was awarded the Robert McCormick Research Fellowship at the Enrico Fermi Institute at the University of Chicago, worked as a Research Associate at Princeton University, and won a Sherman Fairchild Senior Research Fellowship at Caltech, before joining the New High Energy Theory Center at Rutgers University in 2000 as an Associate Professor. In 1997, he was awarded the Junior Prize of the Czech Learned Society, and in 1999 he appeared on the list of top three scientists of the Czech Republic of the 90's. He joined the Physics Department at UC Berkeley in 2001."
The liberation of Eastern Europe in 1989 has unleashed an intellectual force that will advance human knowledge by leaps and bounds. 2009 is the 20th anniversary of that liberation.
Buddha bless the Eastern Europeans.
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Re:Excellence: Biography of Petr Hoava (Score:5, Funny)
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Re:Excellent! (Score:4, Interesting)
i read that some of the theory used math from helium super-fluids.
As I'm no math nerd, perhaps someone who is can explain why infinity is disallowed? I finally figured out why you can't divide by zero; 10/2=5, 5/2=2.5, but if you use numbers smaller than one it is reversed; 1/.5=2, 1/.05=20, so anything divided by zero would be infinity. Is the universe infinite? If so, how can it be studied mathematically?
I found this intrigueing:
I'm no physicist, but that occurred to me when I first herd of the big band theory. If so, would it bounce an infinite number of times?
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Re:Just wondering out loud... (Score:5, Informative)
Wrong.
Special relativity is built on two principles:
(actually, if you take Maxwell's equation into account, the first is just a special case of the second). Especially it does not postulate that there's nothing faster than light. Rather,
However, you can describe hypothetical faster-than-light particles in SRT (so-called tachyons; those cannot be decelerated to below the speed of light), and AFAIK there have been experiments to look for them. Note however that as soon as you add quantum mechanics to the picture, even with tachyons no information can be transmitted faster than light (local disturbances in he quantum tachyon field only propagate with light speed).
General relativity adds the equivalence principle (locally you cannot distinguish between gravitation and acceleration) and the demand of general covariance (the equations must look the same regardless of choice of coordinates, even if those don't correspond to an inertial system).
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Re:Just wondering out loud... (Score:5, Informative)
Then we need a new theory.
Well, "the same in all systems" in the post above didn't refer to "at different places in the universe", but "as seen/described by different observers in the same part of the universe".
That doesn't mean we don't also assume that the laws of nature are always and everywhere the same. Indeed, that's basically always assumed.
By applying the laws we found locally to observations of distant objects, and seeing if they fit. For example, we can look at the spectra of distant stars and look if we get the same atomic spectral lines as on earth. This works great; so we know that atomic physics obviously works the same in distant stars. Also we can observe the 21cm hydrogen line everywhere in space, so atomic physics seems to apply also in between the stars.
Where we do have some problems is with large scale gravitation (what we describe with dark matter and dark energy). However, the local effects of those deviations are small enough that we couldn't measure them directly anyway, so it's also no evidence that the local laws of physics are different than the distant ones, even if those effects are to be described with modified theories.
No, it's much too small for that. To be an indication for different physics "outside" it would have to be such a large deviation that we would have to have detected the difference if it applied to Earth.
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Re:Spooky action at a distance? (Score:5, Interesting)
Spooky action at a distance doesn't need any finagling to get around lightspeed, because spooky action at a distance doesn't involve any communication. It's already compatible with general relativity (at least, insofar as any quantum theory is compatible with relativity).
A flawed, but illustrative example that should explain why this is so: imagine you have a friend who is flipping a coin... if it comes up heads, he writes an X on two sheets of paper, if it comes up tails, he writes a checkmark on both instead. Both are immediately sealed inside envelopes and mailed to opposites sides of the planet. If you open one letter and see an X, you instantly know the other has an X also. That doesn't require any communication.
A slightly less flawed, and still illustrative extension: Now instead of a coin flip, you have a machine do it based on the decay of a mass of cesium, and you have a perfect envelope which protects against quantum decoherence. The same situation applies, as soon as you open one envelope you know what is contained in the other. The only difference this time is that the letters were entangled and in a superposition of states. However, it's the same mechanism, and no communication is required.
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