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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.
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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"?
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
Electromagnetism is stronger than gravity. Given that the particles in question also have the opposite charge, and are therefore attracted electromagnetically, it wouldn't make a major difference to them.
'Sensible' is a curse word.
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.
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.
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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
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.
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.
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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!).