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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)
Hopefully. Dark matter is a very inelegant solution to observations that don't agree with theory. Even so, working out what properties it must have, should it exist, is a useful exercise because it clarifies the problem more thoroughly.
There seems to be a common misconception that incorrect theories were stupid ideas from the get-go. That's really not the case, until new evidence or new ideas come up the incorrect theories are every bit as valid as the ones that may turn out to be correct and the differences between the various competing theories may point the way to interesting new experiments.
This new theory is probably wrong, but it's founded on an assumption that, while not currently accepted as true, is experimentally verifiable. That's the assumption that anti-matter and matter have gravitation fields of opposite sign. An experiment to determined the truth of that would be very interesting.
So if this is the future...where's my jet pack?
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.
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?
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!).