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CERN Physicist Says Dark Matter May Be an Illusion
anonymousNR writes "A CERN physicist has a new theory explaining the rotational curves of galaxies. 'The key message of my paper is that dark matter may not exist and that phenomena attributed to dark matter may be explained by the gravitational polarization of the quantum vacuum,' Hajdukovic told PhysOrg.com. 'The future experiments and observations will reveal if my results are only (surprising) numerical coincidences or an embryo of a new scientific revolution.' Given the many theories around explaining various observations in recent times, there seems to be a breakthrough on its way in our understanding of the cosmos."
I hope so. Dark matter is the ugliest kludge to the standard model ever.
It's worse than the Plus upgrade for Windows 98.
Support FSF: Stop thinking with your wallet, and think with your imagination. (cc/non-commercial)
Yay for phlogiston and aether. Dark matter might end up on the list of ideas that physcists turned to in order to explain things that had other explanations. La plus ca change...
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
He gives an example of a dielectric slab being inserted into a parallel plate capacitor, which results in a decrease in the electric field between the plates. The decrease is due to the fact that the electric charges of opposite sign attract each other. But if the electric charges of opposite sign were repulsive instead of attractive, then the electric field would increase. Back to the quantum vacuum scenario, since the gravitational charges of opposite sign are repulsive, the strength of the gravitational field increases.
If the gravitational charge of opposite signs are repulsive, it would mean that the "vacuum gravitational dipole" will have a tendency to separate into matter and antimatter.
As the antimatter is repulsed by the normal matter, wouldn't this require the introduction of another force (the "dark force"?) – that should be even stronger than the strong force – to explain how come we are not seeing flows of antimatter originating from the core of the galaxies?
Questions raise, answers kill. Raise questions to stay alive.
Here's a link to the actual PDF (arxiv version) and not the pay version
http://arxiv.org/ftp/arxiv/papers/1106/1106.0847.pdf
Quick and dirty:
if something "comes and goes" on a quantum level, faster than the universe can usefully notice, and it doesn't violate any of the "conservation (energy, momentum, information (maybe), ...) laws", then it is permitted. In this case, if a positron/electron pair are spontaneously emitted from "empty" space, very, very quickly their opposite charge will attract them to each other and they will annihilate each other paying back the energy that it took to create them, so there's no "law" violated.
The guys hypothesis rests on anti-matter having an opposite gravitational "charge" to "ordinary" matter. In the presence of a galaxy-size gravitational field, there could be a bias for the electron to be nearer to it than the positron, and given the very large amount of space around a galaxy, the average bias to have the gravity field directional could be enough to account for the rotational energy excess of a typical galaxy.
If matter and antimatter are gravitationally repulsive, then it would mean that the virtual particle-antiparticle pairs that exist for a limited time in the quantum vacuum are “gravitational dipoles.” That is, each pair forms a system in which the virtual particle has a positive gravitational charge, while the virtual antiparticle has a negative gravitational charge. In this scenario, the quantum vacuum contains many virtual gravitational dipoles, taking the form of a dipolar fluid.
“We can consider our universe as a union of two mutually interacting entities,” Hajdukovic said. “The first entity is our ‘normal’ matter (hence we do not assume the existence of dark matter and dark energy), immersed in the second entity, the quantum vacuum, considered as a sea of different kinds of virtual dipoles, including gravitational dipoles.”
He goes on to explain that the virtual gravitational dipoles in the quantum vacuum can be gravitationally polarized by the baryonic matter in nearby massive stars and galaxies. When the virtual dipoles align, they produce an additional gravitational field that can combine with the gravitational field produced by stars and galaxies. As such, the gravitationally polarized quantum vacuum could produce the same “speeding up” effect on the rotational curves of galaxies as either hypothetical dark matter or a modified law of gravity.
Basically what this means to me, is that the effect is on a super-massive scale and not easily manipulated by us without the technology to literally change things on super-massive scale.
That brings me to an interesting point, / . is just "the ramblings of socially-inept, technology-literate news-mongers".
Time is an illusion. Dark matter doubly so.
You can detect dark matter. If it exists, we have already indirectly detected it. We have not yet directly detected it, but that is not because it not possible to do so, just that we have not succeeded yet. We are currently trying to do so.
What really surprises me is, despite this, so many physicists have jumped on the bandwagon.
This is because it is the simplest theory which fits available data. There are simpler theories, but they do not fit available data, and thus are of little value.
Average Slashdotters have been more skeptical of they dark matter theory than physicists, from what I've seen.
This is because average Slashdotters do not have even the beginnings of a clue about astrophysics, but think they are expert at every subject they ever heard mentioned on the internet.
But that's just an assertion. It may not exist. It's currently our best way of explaining certain phenomena, but there may be a better explanation coming. It's far from "detection"
Then quantum phenomena must really get your panties in a twist.
I realize this isn't a group of physicists here, but most of the arguments people here are positing against dark matter more or less boil down to "it's unintuitive". Seriously, welcome to modern physics guys.
This new idea may be the start of something (and I must say this guy certainly doesn't lack in the self-esteem department), or it may fall apart as it fails to get further developed. But until it - or another alternative idea - gain some traction with the scientific community, it's a bit premature to start writing off dark matter. At the moment, it's the best solution we've got.
#DeleteChrome
From TFP: "Let us end by pointing that the rotational curves of galaxies are not the only phenomenon
which is currently explained by Dark Matter. For instance, CMB data are apparently in favor of
the presence of dark matter as a key for understanding of density fluctuations and the structure
formation in the Universe (see review of Einasto, 2010). While our Letter gives indices that the
gravitational vacuum polarization could be an alternative to dark matter in the explanation of the
galactic rotational curves, a tremendous work would be needed, to reveal if the other phenomena
could be alternatively explained by the vacuum polarization."
In other words, it's just another MOND theory, of which there have been many over the years. Wake me when MOND proponents write a theory that explains *all* the evidence for dark matter, CMB, nucleosynthesis, rotation curves, etc., not the particular phenomena they've cherry-picked. Until then, dark matter, whether that's WIMPs, MACHOs or axions, is the only explanation that fits all the evidence thusfar.
Yes. It doesn't exist because we currently can't detect it! I know this because I said so.
Filthy, filthy copyrapists!
Dark matter isn't undetectable, it's just difficult to detect because it doesn't interact with normal matter much. There's experiments, such as the cryonic dark matter search, underway attempting to detect it.
upon the advice of my lawyer, i have no sig at this time
You can detect dark matter. If it exists, we have already indirectly detected it. We have not yet directly detected it, but that is not because it not possible to do so, just that we have not succeeded yet. We are currently trying to do so.
Using similar methods, there was a time when you could "detect" epicycles, too. Like dark matter they were a theoretical fudge factor designed to prevent a cherished theory from falling apart due to its lack of successful predictions and explanatory power. In the case of epicycles, the cherished theory was geocentrism. You would have been ridiculed extensively (and quite possibly be in danger of the Inquisition) for questioning it, not because your own theory wasn't viable or couldn't also explain the observed results but because "everybody knew" how "well-established it is" that the earth is the center of the solar system...
If they teach scientists about the history of these things as part of their normal training, they don't do a very good job. At all.
It is a miracle that curiosity survives formal education. - Einstein
So what's your idea? Given that the observed behaviour of the universe is inconsistent with what we expect, there are basically two possibilities:
1) Our understanding of gravity is wrong.
2) Our understanding of the matter in the universe is wrong.
Despite lots of effort, nobody has come up with a satisfactory theory of gravity which fixes the problem. And a new theory to fix the problem is not really more satisfactory in itself than a new type of matter - they both would be fudges to fit the data until some independent test came along. And it's not as if the scientists said "it must be dark matter, right, problem solved", there are active efforts to determine dark matter's characteristics and independently test for it.
There's been talk about phlogiston, but what about the neutrino? When the energy of electrons from beta decays didn't appear consistent with known laws of physics, someone (Pauli IIRC) said "there must be a new particle that we (so far) can't detect, which has properties X, Y and Z"... not unlike dark matter. And lo and behold, he was right.
This is because it is the simplest theory which fits available data.
But it doesn't fit the data -- the dark matter theory is constantly being revised. First it's "90%" of the mass of the universe, then it's "70%", then we're back to "98%", then there's dark energy, then the fractions change again, and again, and again.
That's not a fit! It's not like we started at, say, 80%, then refined the fit to 82.5%, then an additional data helped us narrow it down to 82.515%, and so on. It's just jumping all over the place.
Secondly, it's not "fitting to the data", it's fitting to the difference between a theory and the data. There's a huge difference. And it's particularly galling that the "theory" used is Newtonian gravity, when it's been known to be wrong for a century! Several papers have been released that show that it's possible to make the need for dark matter vanish by using relativistic mechanics. Not exactly surprising that the "difference" is affected by the theory chosen!
Every research paper about dark matter reads something like "we use a simplified theory of gravity because of [excuse], and then oh look, we find that our hugely simplified model doesn't agree with observations, so clearly there's an invisible something out there". The excuses vary between: "The other paper did it too", "Relativistic equations are hard, and I'm lazy", "I don't understand relativity so I don't know how it could possibly apply to galaxy sized masses thousands of light years in size", and "my computer is too slow to do this properly".
This is because average Slashdotters do not have even the beginnings of a clue about astrophysics
Yeah, well, I studied Physics at a university level, and I think dark matter smacks of hubris, laziness, and weak logic. It sounds an awful lot like chasing the error terms in Epicycles a century too late.
The latest attempts to explain dark matter are an ever bigger joke, like Modified Newtonian dynamics. Here's a hint... we already have a "modified" theory for motion -- it's called relativistic dynamics!
Until some physicist demonstrates that dark matter is still required to explain measurements when the theory used is the full general relativistic model with speed of light delay included, I'm just going to automatically assume that dark matter is bullshit.
This kind of thinking is all too common in Physics. A classic example is the double-slit experiment. Every textbook states a formula for the spacing of the interference fringes that disregards a bunch of things, handwaving them away as "unimportant". A math-geek friend of mine in my physics class was upset by this lack of rigor, walked up to the whiteboard, and demonstrated that the simplifications can result in errors as large as ten percent or more in real-world scenarios!
Imagine someone basing a new theory of light based on the difference between observed interference fringe spacing and the simplified theory. That would be stupid, wouldn't it? Why is it then acceptable for gravity?
Disclaimer: I'm a lay person when it comes to things like quantum physics.
From my understanding of the arguments and analogies given in the article, the explanation is that vacuum does has a digravitational constant (the gravitational equivalent of the dielectric constant) greater than 1 in strong gravitational fields.
But, by the same quantum fluctuations getting polarized argument, shouldn't vacuum also have a dielectric constant greater than 1 in strong electrical fields?
Can't we test that last hypothesis pretty easily? Is it already known?
The crux of the article's hypothesis, that anti-matter has opposite-sign gravity, seems like an attractive idea and one that should also be easily testable once sufficient anti-matter can be manufactured and contained.
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
Go to a fundamentalist church group some time and tell me you really think they are more capable of understanding when they are wrong.
Would you want someone to base their opinion of Americans based on trip to a US insane asylum? If not then why would you think a visit to a fundamentalist church would be a good way to judge a religion as a whole? Both are only fractions of their respective societies and both are filled with people who have a tenuous grasp on reality. It is bad science to use a biased sample like that on which to base your judgements.
And some types of dark matter are observed aka neutrinos.
Neutrinos are too light to be Dark Matter. Their low mass means that they are produced moving at almost the speed of light so, if they were the Dark Matter, the "wrinkles" we see in the Cosmic Microwave Background would be far more blurred out than they are.
If free neutrons didn't have such a short decay time, I'd consider that option as well.
Sorry but neutrons interact via the strong nuclear force and so cannot be dark matter otherwise we would see it interacting with atomic nuclei.
Without electrons the photon interaction with a neutron seems considerably hindered
Electrons have nothing to do with photon interactions with neutrons. Neutrons are made of quarks so photons of sufficient energy can directly interact. Electrons can interact with neutrons either via EM (photon) or weak nuclear interactions.
How can you possibly not know about the Bullet Cluster? That is pretty much blatant evidence that there appears to be something there which is both dark and massive. Wouldn't a theory of dark matter be appropriate when presented with such evidence? (and, by the way, structures like the Bullet Cluster were predicted by the theory of dark matter - people said "well if it doesn't interact electromagnetically, we should be able to see places where normal matter got pushed but dark matter didn't, like when two clusters collide" - so they set out to look for something like that, and lo and behold they found it!)
And that's not even going in to the other things that dark matter predicts and nothing else does, like the Cosmic Microwave Background.
Or you could just read Starts with a Bang, Ethan Siegel is a lot better at explaining this stuff than Slashdot is.
About the changing numbers, I'd like to see citations.
Dark energy is a completely different concept than dark matter, completely independent of it, and used to explain completely different phenomena. The only thing dark matter and dark energy have in common is the adjective "dark".
Note that we already know particles which have exactly the properties needed for dark matter: neutrinos. They are not massive enough to explain the observations, but they are a proof that particles of that kind can exist. It is of course not a proof that they do exist, but it shows that the idea is not as stupid as you want to make us believe.
99% of all descriptions of the double slit experiment (and 100% of those in textbooks) are for explaining the properties of quantum mechanics, not for a quantitative description of an actual experiment. The unimportant parts are unimportant for understanding. It's like complaining that text books introducing free fall don't take into account air friction in their equations, despite the fact that air friction can even dominate a free fall.
The Tao of math: The numbers you can count are not the real numbers.
Dark Matter is not like the luminiferous aether.
The luminiferous aether is a substance that was invented to explain something that seemed missing from our theories (specifically, what it is that the speed of electromagnetic waves given by Maxwell's Equations is relative to). It made predictions, those predictions were tested, and so the idea was tossed out.
Dark Matter is a substance that was explained something that seemed missing from galaxies and clusters of galaxies (specifically, there wasn't enough mass there to explain why they held together given how fast things were moving). The idea of Dark Matter made predictions, those predictions were tested, and they *confirmed* Dark Matter.
There's nothing magic about Dark Matter. And the lines of evidence are more than just some equations that don't balance out.
More here: http://365daysofastronomy.org/2010/06/26/june-26th-dark-matter-not-like-the-luminiferous-ether/
This is because it is the simplest theory which fits available data.
But it doesn't fit the data
Well, I am a physicist (doing my PHD, although not in astrophysics), and I can tell you that it certainly looks like the simplest theory that fits the data. I highly recommend Ethan's blog, who explains this very well, particularly http://scienceblogs.com/startswithabang/2011/03/good_ideas_bad_ideas_mond_and.php and
http://scienceblogs.com/startswithabang/2009/09/dark_matter_part_i_how_much_ma.php. Notice, also, that theory predicts that the percentage of darks matter and energy changed during the history of our universe.
Of course, the theory is not complete, and there should be further experimental confirmation, but it looks pretty good for now.
This kind of thinking is all too common in Physics. A classic example is the double-slit experiment. Every textbook states a formula for the spacing of the interference fringes that disregards a bunch of things, handwaving them away as "unimportant". A math-geek friend of mine in my physics class was upset by this lack of rigor, walked up to the whiteboard, and demonstrated that the simplifications can result in errors as large as ten percent or more in real-world scenarios!
Imagine someone basing a new theory of light based on the difference between observed interference fringe spacing and the simplified theory. That would be stupid, wouldn't it? Why is it then acceptable for gravity?
Well, I work in optics, and I have no clue what you are talking about here... Is it because the usual derivation uses tan(alpha) ~ sin(alpha) ~ alpha? Or because it disregards the polarization of light? I can assure you that both of those approximations are very good "in most cases". But that doesn't mean you can't use the correct formulas, if needed. More likely, your teacher was oversimplifying the problem to get accross the most important concepts without his students being drowned by little details.
But much, much more importantly, physicists know that arriving to the simplest model that explains all your experimental data is very important, because it lets you understand what's going on, instead of just making blind calculations. I can assure you that this is not an easy skill to learn, specially for math-loving students who are irritated by approximations (I know this from first-hand experience!).
First it's "90%" of the mass of the universe, then it's "70%", then we're back to "98%", then there's dark energy, then the fractions change again, and again, and again.
This is not a correct characterization of the history of Dark Matter.
First of all, if you really studied Physics in university, then you ought to know something about uncertainties. If not, then, shame on the people who gave you your degree.
The history of dark matter includes observations on different scales that include different amounts of "missing mass". On some of those scales, we have accounted for some of the "missing mass" with different things-- e.g. some (smallish) fraction of the missing mass in galaxy clusters turned out to be in very hot intracluster plasma (which can be seen in X-rays) (and, even though it's a smallish fractoin, it's more mass than all the stars in the galaxies!). Something like 2/3 of the "missing mass" from cosmology-- which, incidentally, was always considered one of the weakest constraints on dark matter, since the uncertainties on the most basic parameters like the Hubble Constant were HUGE until the end of the 20th century -- turned out to be Dark Energy (which in fact might not be a thing, but a pointer to a flaw in our physics).
The numbers changed, yes. But uncertainties were huge to start with, so there's no surprise that the numbers changed. Trying to claim that the changing of the numbers indicates that the theory isn't making sense is a standard rhetorical technique that somebody who claims to know something about science should be ashamed to use.
Until some physicist demonstrates that dark matter is still required to explain measurements when the theory used is the full general relativistic model with speed of light delay included, I'm just going to automatically assume that dark matter is bullshit.
Go look up the Bullet Cluster.
The gravitational lensing values used in the calculations of where the mass is in that cluster come out of General Relativity.
Using similar methods, there was a time when you could "detect" epicycles, too. Like dark matter they were a theoretical fudge factor designed to prevent a cherished theory from falling apart due to its lack of successful predictions and explanatory power. In the case of epicycles, the cherished theory was geocentrism.
Not to be too pedantic, but the history is more complicated than that. The "cherished theory" in this case also depended on other assumptions that led to epicycles, perhaps the most notable being circular orbits.
In case you didn't know, Copernicus's theory contained a lot of epicycles too. It wasn't that much less complex than the Ptolemaic theory, despite being heliocentric. Why? Because he assumed circular orbits. It wasn't until Kepler came along with his ellipses that the epicycles disappeared.