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New Theory of Gravity Decouples Space & Time
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."
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!
http://www.geoffreylandis.com
So does this compete with string theory or have a chance modifying it to an eventual theory of everything?
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?
There is no "-1 offended" or "-1 you don't agree with me" mod options for a reason.
Sounds like this guy's saying "Let us assume the speed of light is not necessarily the fastest anything can travel. If we assume this, then..."
The reason for Einstein's initial assumption is that we have never to date observed anything which has moved faster than light. Then again, would we know such a thing if we observed it, and have we actively looked for such a thing? If so, how have we looked?
From the linked article, it seems the theory both predicts the heat death of the universe (continued accelerated expansion) and that our universe started from a "Big Crunch" scenario (gravity had pulled everything back again). This seems quite strange (although of course nature can be quite strange at times). Anyone know this theory any better and can provide some enlightenment?
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?
Free Martian Whores!
There are really 42 quarks.The LHC should probably be able to test this...
(God but I love that guy's cartoons!)
Free Martian Whores!
Yep. It's called the Correspondence Principle when applied to quantum/classical mechanics. Basically, Newton's equations 'fall out' of Einstein's when you assume the speed of light is a big number relative to all other speeds.
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.
So let's say our universe is expanding (doesn't matter if it's this theory or mainstream Big Bang). We already know there's volume beyond the visible edges of our universe. What if there's another universe expanding towards us, accelerating into heat death, and then its edges hit our own? Wouldn't that Big Smack be a Big Crunch? And thus another universe is born?
Here's to hot beer, cold women, and Glaswegian kisses for all.
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.
It's easy to get Newtonian physics from Relativity. The hard part was to get Relativity knowing just Newtonian physics. Ergo, things are not just built on top of one another, but it's more like building beneath of what you don't know.
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.
How do we know for sure that it's impossible? How can we test against it to conclude it's definitely an impossibility? We surely haven't found any way to achieve that, but given that all theories are still in the balance, how do we know for sure there's no way we possibly could?
This being said, nice to see a theory that's more intuitive than usual, that attempts to explain dark matter and dark energy by revising how things work rather than claiming there's a bunch of invisible mysterious things at work, and that does so without adding a bucketload of new unperceptible dimensions and weird vibrating strings that no one can prove. Ah, and give an alternative to the ailing theory of Big Bang.
And nice to see that it took SciAm's commenters less time than Slashdot users to make the discussion drift into some crap about religion. Maybe we're not that bad after all.
You just got troll'd!
I prefer to say one will prove to be a better model. I suppose "more accurate" works too, although it begs the question of what "accurate" means in the context. Scientists of course understand that means it produces correct predictions more often, but laymen are likely to interpret it to mean something more vis a vie it's status as a "description" of reality. Which may indeed be true, but ultimately that's a philosophical question, not a scientific one. In science, the "better description of reality" is "better" only in the sense that it produces better predictions. "Closer to the truth" is a question outside the scientific realm. "Right" is right out...
"Convictions are more dangerous enemies of truth than lies."
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'm no math nerd either, but what I remember is that since it has no end (infinite), you can't add or subtract from it because it still has no end after that. That's all fine, but irrational numbers don't exist, yet we use them in arithmetic. I don't know why we just can't use infinity the same way and do magic tricks like:
oo - oo = 0
oo / oo = 1
etc.
(Note: oo = infinity. ∞ and ∞ not supported on Slashdot.)
Any math lord reading this thread?
http://dilbert.com/2010-12-13
http://mndl.hu/works/fractalcow
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
Religions, which is what you're talking about when you say faith, are software that runs in a cluster of human beings. They mutate all the time... you turn your head, there's another one popping up, the bastard stepchild of a few predecessors. Some religions will destroy the hardware they run on before they ever propagate. The Davidians, for example. Others will propagate through a population quickly, but lead that population to extinction in a few generations. A few will endure, supporting their populations growth and infecting or destroying the populations running another religion.
This is not made up airy-fairy bullshit that some simpleton believes for no reason. This is evolution at work. These old religions have demonstrated their reliability, because the people who believe in them are not dead.
The evidence indicates that the vast majority of ideas that are "modern" and "novel" and "progressive" will lead the population that embraces them to extinction.
http://en.wikipedia.org/wiki/Evolutionary_psychology
-1 Uncomfortable Truth
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.
Uh, because that would be incorrect? One infinity is not necessarily equal to another, not to mention infinity isn't a number, nor is it a constant or variable. It's a concept, and you can't add, subtract, multiple or divide concepts, so you can't do anything like that to infinity.
There's a calculus theory whose name escapes me that allows you to solve for what X/Y equals when X and Y are both infinite functions using their derivatives. I remember taking tests where we basically had lim (x->oo, y->oo) of (x+10)/(y^2) and we had to determine what it equaled. Sure you could simplify that to oo/oo and then say it equals 1, but you'd get that question wrong.
There are two kinds of fool One says 'This is old therefore good' Another says 'This is new therefore better'- Dean Ing
Thanks for making the point more clear. We can't predict the future so we can't know if in ten feet the road will vanish beneath me or that my electrons won't go flying off into space. Fair enough.
Haven't we proven enough of our theories about this world that we know for certain things are stable to a known degree? Or is it like the "law" of gravity, not proven but correct according to a large body of evidence? Do you mean to say that we know no absolutes?
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.
Who must what?
That is, you--who who exist and are persistent in time with a unique personal identity and live in a causal world that is persistent in time and full of a diversity of phenomena that are identifiable by you and persistent in time--must, to engage in the act of disagreeing with the self-consistency and sturdiness of the logical foundations of empiricism, must presuppose--as a condition of entering into the discourse--the very conditions that you for some reason want to say must be uniquely presupposed by empiricists.
That is, you are saying, "I completely accept these conditions without dispute and can raise no argument or question against them, but I demand that empiricists justify them, even though I don't demand the same thing of anyone else, including myself."
What you are claiming is a problem with empiricism is actually nothing more than a universal and rather uninteresting form of scepticism, and anyone who raises it seriously immediately rules themselves out of bounds by the simple fact of not having applied their own argument to their own utterance first.
Blasphemy is a human right. Blasphemophobia kills.
Your use of argumentum ad ignorantiam is... interesting. Would you, perhaps, claim that agnostics use argumentum ad ignorantiam when they say that we cannot prove or disprove the existence of God?
- Francis Ocoma
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Assuming, of course, that Einstein's theories are actually incorrect. This particular theory, for example, sets of my bullshit detector because it claims that the nature of reality suddenly changes totally in large enough energies - not just some field, but space and time itself.
Frankly, yes: I don't think that Einstein's theories will ever be proven wrong. They fit too many phenomenom perfectly, predict too much, and when you really come down to it, are too fundamentally simple: General Relativity is really just taking the notion that all observers are equal and examining the logical consequences.
The only reason these "Einstein was wrong" -theories keep on popping up is because it's difficult to get the math of quantum mechanics and General Relativity to work together. I suspect that's mainly because of our insufficiently advanced mathemathics, rather than physics, and possibly also inappropriate use of Heisenberg uncertainty principle (which is why you get infinite energies input into GR in the first place). It could also be that the universe simply is chaotic in the fundamental level, and only looks stable at large scale because uncertainty becomes averaged out.
In any case, since the article doesn't bother to actually describe the theory, it's impossible to say for sure. But I'm not holding my breath.
Forget magic. Any technology distinguishable from divine power is insufficiently advanced.