Slashdot Mirror
Good bye Dark Matter, Hello General Relativity
dr. loser writes "The CERN newsletter reports that a new paper by scientists at the University of Victoria has demonstrated that one of the prime observational justifications for the existence of dark matter can be explained without any dark matter at all, by a proper use of general relativity! What does this imply for cosmology and particle physics, both of which have been worrying about other aspects of dark matter?"
...the simplest solution turns out to be the best.
Science never has been definite. The defining characteristic of science is that it accepts that all solutions to problems are tenative, and that some piece of information might turn up in the future that will cause us to doubt what we now believe. Intellectual process can't happen without replacing wrong old ideas with better new ones.
There's no point in questioning authority if you aren't going to listen to the answers.
Always smelled like aether/ether to me anyway.
It should be illegal to say that freedom of speech should be limited.
Note that this is the LaTeX source files for the paper, not source code. What would you do with a GPL scientific paper -- change some things and put your own name on it?
Anyway. I'm surprised it took so long for anyone to do this. Is the an obvious approach, especially if the alternative to postulate entirely new classes of matter. We lesser scientists tend to carry an inferiority complex over the supposed genius of physicists, but I wonder if we've maybe given them too much credit.
What I'm listening to now on Pandora...
What does this imply for cosmology and particle physics, both of which have been worrying about other aspects of dark matter?
The case for dark matter has been built for several decades. There is a mountain of evidence that needs an alternative explanation. I would call these new results tentative at best.
an ill wind that blows no good
I wonder if some scientists might already be so invested in theories of dark matter that they will refuse to accept this position.
Information wants a fueled airplane waiting at the hangar and no one gets hurt.
This may also be a cautionary tale about the use of linear models (Newtonian gravity) versus nonlinear ones -- interactions among masses distort the solution. If one assumes the wrong things and gets an answer that doesn't fit the observations, perhaps its time to change the assumptions, not add unseen dark matter, epicycles, etc.
Two wrongs don't make a right, but three lefts do.
> It'd be nice if we could stick with general relativity without dark matter.
That's neither here nor there for me; I just want the model to match whatever is really out there.
Sheesh, evil *and* a jerk. -- Jade
Comment removed based on user account deletion
Dark matter isn't even that sensational. Suppose you have equations that would be balanced if you have a certain amount of mass in the universe, and you observe less than that amount. There's two simple explanations: you got the equations wrong, or you're not observing the right amount of mass (in other words, there's some stuff out there we can't see.) Neither idea is that fantastical, and dark matter is just the somewhat catchy name for the stuff we can't see.
This paper is just claiming that, in fact, the equations were wrong. (And it's not like no one had checked them before. ^_^ They're just claiming to have done a better job, I guess.)
Dark matter always seemed like it was in the honored high school chemistry tradition of adding a fudge factor. There was no direct observational evidence for it, but tossing it in there made the numbers fit.
Well, doing realistic simulations of a galaxy even with "old" Newtonian physics is very expensive. I mean, imagine simulating 100 billion point masses all acting gravitationally on each other (not counting simulating the hydrodynamics of the gas clouds). So, in the best case you can reduce the number of operations to N log N, or about 2000 billion (per time step). Now simulate the whole galaxy, but also taking into account that your binary stars need a lot smaller time step then your simple stars... And then you have a huge discrepancy of time scales (years for binary stars, millions of years for a star like sun to orbit around the center ONCE).
And then add general relativity into this mess? Very hard with today's computers...
I think it's more accurate to say that it is not the scientists, but the pseudo-scientific press that is the problem. The seminal example was the 'Black Hole', a term which the research team neither wanted nor approved of, but which became the name for that phenomenon.
There are some snake-oil sellers out there, but the majority of scientists and researchers roll their eyes when they see the way the general press (and, worse, places like this site) mash theories and garble messages.
"A little knowledge..."
But what is the SIGnificance?
I noticed you were referring to an article on arXiv.org. While it may certainly be true, these articles have not been peer reviewed by a scientific journal. Also note that this author appears to have only the single article on the site (which may or may not mean anything - draw your own conclusions).
I think arXiv.org is a great idea - a way for physicists to communicate ideas informally before going through the hassle of getting them published. It's still best to take it all with a grain of salt, as papers here may not be as carefully reviewed as other sources.
It might mean that there is no such thing as dark matter
Actually, I think this is incorrect. 'Dark matter' is simply all the mass of the universe that doesn't emit detectable radiation. All the planets, asteroids, and other chunks of rock floating around in space. The logical conclusion, if this paper is correct, is that there is no need to assume the existence of such enormous amounts of dark matter in order to explain the behavior of galaxies. It's like the modern-day version of man coming to understand there is no such thing as 'ether'. Except that in this case there actually is dark matter, just not as much as we'd misled ourselves to believe.
These people looked deep into my soul and assigned me a number based on the order in which I joined.
Are you sure they didn't use newtonian physics to calculate those values too?
I've dealt with this same issue.
There seems to be, as you put it, a "dogmatic" belief, often from undergrads (I'm guessing), that their now current understanding of physics is "right", and that any questioning of dark matter is an excuse to call the qestioner ignorant.
I've asked numerous times why I should think dark matter is anything other than a mildly promising theory.
The responses questioning my intelligence, calling me names, and generally being assholes outnumber the cogent replies 3 to 1.
Since when did scientists start behaving like fundies?
People tend to snicker sometimes history classes hearing about people who created the strangest "scientific" theories in order to fit their ideas to how the universe actually worked. Epicycles, aether, heavenly spheres...
Dark matter?
Actually, maybe those guys weren't all that laughable or dogmatic as you'd think. Maybe they just needed some time to work out the formula they needed.
Science tells us a lot more than it used to about the universe around us, but I don't think the days of imaginary constructs in science is over yet.
When science teachers started teaching `facts' instead of the simplest hypotheses which were not disproved by any observational evidence.
I am TheRaven on Soylent News
IAAP, and while I see where you're coming from I'd actually make the argument in the opposite direction.
A previous poster has already noted a paper (astro-ph/0508377) which quickly followed this one and refuted its conclusions (I have seen other physicists describe the same point elsewhere). It seems (though I have not yet checked the math myself) that the authors made an honest error, and they weren't modeling the situation they thought they were. In addition to the self-gravitating cloud of gas they were trying to model, the metric also includes a disk-shaped "singularity" - essentially a very thin, very heavy disk in the plane of the galaxy. It is this unphysical disk which is responsible for the effect they observe.
It's also worth noting that dark matter has MANY independent lines of evidence pointing to it (rotation curves, gravitational lensing, the cosmic microwave background, large scale structure, element abundances... see here). Galactic rotation curves were the first such evidence, but arguably they are the weakest today. I'm still more than willing to believe that the dark matter paradigm could be wrong, and this result would be VERY interesting if true, but there would still be lots left to explain. This is how science works, of course - idea gets put forward, it gets checked by others, the community works out what to think of it.
This also makes me think of the current controversy over intelligent design, but in the opposite way to the previous poster. Look at the Slashdot thread around us. Hundreds of people are posting to say how relieved they are that dark matter doesn't exist, since they always thought it was too weird and that those pointy-headed physicists were out of touch with their own good common sense. They feel very confident doing this, even though (1) they admit that they don't understand the evidence and reasoning they are talking about (even as some of them chastise physicists for the "basic error" they were making), and (2) the reasoning itself was later shown to be flawed. Several posters have tried to make follow-up postings showing that this reasoning has been refuted, but they can't hit every discussion thread (and it's not clear it would do any good if they did). As with the anti-evolution "controversy", people latch on to sensational headlines of flaws in basic science and simplistic errors by scientists to believe whatever they felt most comfortable believing to begin with. From there, it's an uphill battle to get the truth out there.
"Maybe it's just me, but the first time I heard about dark matter and how it "must be out there" because it makes the calculations add up nicely...first thing I thought of was the ether."
And Plank thought the same about that quantum physics he invented. He even spent a great part of his life working against quantum physics, and here we are, using computers...
Some times, a completely weard theory that just fits the data is right, there is why people take them seriously.
Rethinking email
The problem, as I see it, is often that those who question the theories don't have anything better to back them up -- they're just presented with skepticism or an alternative answer that has nothing to do with physics.
Of course, I think there's more room for that in astrophysics, given the focus on math and proofs rather than testing (due to rather obvious logistics). A new mathematical proof can come out that completely changes how people view space (or, heck, an appropriate use of an old mathematical proof, as the article shows).
But I can understand why some people would be a trifle edgy nowadays. I'm not saying that you provoked the argument, as I've dealt with scientists (heck, I live with one and hang out with her friends), but I have to ask -- when you said it was a 'mildly promising theory,' did you present an alternative opinion? One thing I learned is that scientists really dislike people saying "I don't believe that" or "I think that theory is wrong" but then don't offer what they DO believe in that's based on science. After all, that doesn't accomplish anything -- it just states a claim of belief, which isn't science.
But I don't think I need to explain why an "accepted theory" will have people assume that it's accurate and "true" and be reluctant to drop it just at some new information or test or mathematical proof. That older theory generally has plenty of evidence to back it up -- the new theory has none. So people will look at the new theory, run through the math or tests on their own, and confirm, therefore changing the general understanding. That's how science works. The reluctance to accept just any new information without seeing a lot more proof is one of the reasons science tends to add to a base of knowledge, rather than jumping down any old path.
Dark matter always seemed like it was in the honored high school chemistry tradition of adding a fudge factor. There was o direct observational evidence for it, but tossing it in there made the numbers fit.
But that's how you usually discover things: Make predictions from your current theories, collect data and compare it to the predictions, make up new theories that explain it better, use the data to chose between theories and tell you where to look for more data to make better choices, and iterate.
Sometimes people take shortcuts or make errors in calculation and you have to check their work. And there's valuable science to be done there. But it's more "scientist fun" (and funding) to come up with "George's theory of dark matter" than "George's proof that Sam blew his calculations and Einstien was right after all". So sometimes it takes a while.
Now we wait for "Larry's proof that George blew HIS calculations and Sam was closer to the real world" or "Larry's confirmation that George's model has fewer/smaller holes than Sam's."
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
> Anyway. I'm surprised it took so long for anyone to do this.
Yeah, it seems very weird to me that no one had tried running the numbers taking GR into account...
IMO, what seems to separate the really great physicists from the good ones is a very good gut instinct. Being able to wisely guess what's important (and needs to be kept in the equation) and what's negligible (doesn't affect the solution much, so factor it out to allow a simpler solution).
Maybe, up 'til now, most physicists just assumed that General relativistic effects were negligible for this class of problem, but the instincts of F. I. Cooperstock and S. Tieu told them otherwise...
Which just goes to show you--once a scientific "fact" has been established, our attachment to it becomes as dogmatic as any theological notion...
Perhaps for some people, but not for the overall scientific community. This article being the most obvious example. And I need not note the difficulty one would encounter trying to debunk a theological notion...
I have often mentioned my disbelief in common astronomical theories to my fellow students at the Niels Bohr Institute here in Copenhagen, and not once have I been meet with an attitude like the one you describe. (For instance I don't believe such a thing as a GR-black hole actually exists..)
In my oppinion your fellow students are seriously lacking in their scientifical education if they are unable to accept that alternative theories should be considered seriously but critically.
Perhaps with quantum mechanics as the only possible exception (because QM is true and that's just the way it is.. :), I have never had the experience that any scientific theory has been considered unquestionably true.
This is a very interesting discussion for me, since I took General Relativity from Dr. Cooperstock when I was at UVic 6 years ago. He was a great teacher, but he always had slightly... unconventional ideas? Such as he doesn't believe in the existence of black hole singularities. It doesn't surprise me that he would write a paper refuting the existence of dark matter, but knowing him, I'm not sure I would trust it.
Now, I'm not saying he won't turn out to be right. But I'm not holding my breath on this one.
I don't know that they put theologians and politicians to shame, per se. I've seen ugly fights there too :) But you're right, science is no bastion of open-mindedness either.
There are certainly evolutionists that hold the view you describe, but they are not so monolithic in their attitudes (see the NCSE website, for instance). Bear in mind that the evolution fight for the past several years has been to keep evolution in the classroom, or to prevent it being watered down by indirect attacks (e.g. intelligent design theory). In other words, it's been largely a defensive fight. But that said, I think what you would find, were you to speak to evolution proponents, is that they do not object, per se, to religion in schools. You want to have a religion/philosophy/epistemology course? Go for it. Just don't put it in a science classroom. It's not science and it has no place there. If this isn't absolutely clear, then maybe we need to do a better job teaching what science is in the classroom.A valid criticism of science teachers, but not of scientists. A difference sometimes overlooked.
Socialism: a lie told by totalitarians and believed by fools.
There aren't any competing scientific theories outside of evolution so I'm not sure what else a biology class could teach. Obviously, evolution is not cut dried, it's science, its a living thing that is being updated constantly. That's why we have journals.
Maybe you're thinking of Creationism/ID? I guess you could hold it up as pseudo science (what not to do) but that's more pertinent to a philosophy class.
Good point. It's also worth noting that even General Relativity doesnt quite get Mercury's orbit right, or the position of those distant probes (Pioneer? the ones past Pluto), so there's clearly something we still don't understand about gravity.
Socialism: a lie told by totalitarians and believed by fools.
Funny, I call it "the best hypothesis so far".
Sometimes "we don't know what causes that" is a better answer than "the fairies cause it with their magic". Maybe the latter is the "best hypothesis" but, more importantly, it's crap.
In my experience, undergraduate science students, at least in the US, are usually of the belief that they are being taught "facts". Maybe in an introductory class more emphasis is placed on the unknowns, but as they move into their specialties all but the most controversial or speculative ideas are presented as facts.
Generally as they move into graduate studies there is more emphasis on the quest for knowledge as opposed to the memorizing and understanding of facts.
As one of my professors said my first year of graduate school, "You're graduate students now...you're allowed to have opinions."
IMO, all science degrees should include a class in Philosophy of Science. Most undergraduate students I've talked to about this idea say something along the lines of "Philosophy has nothing to do with science."
-pete
However, because the people talking about 'Dark Matter' are actually scientists, they loathe this 'solution'. They quite rightly say 'Saying there's just some stuff out there we don't know about is not 'science'. Either it's there, and we need to find it, or it's not, and we need another theory.'
Everyone who thinks scientists are scoffing at 'Intelligent Design' because they are all evil athiests need to look at how they are treating dark matter. This is what happens where a perfectly good theory has a huge crack in it. Scientists run around wildly trying to prove both sides, usually ending up somewhere in the middle, which is probably what's going to happen here:
'Okay, so it turns out only 10% of the universe is invisible, according to these new equations we've figured out. And there it is, over there. See? Well, of course not, but look at these models we've prepared, which clearly demonstrate what must be there. Whew. Okay, we solved that one, we can all stop looking like idiots.'.
And the rest of the world goes...um, okay. Is this important?
If corporations are people, aren't stockholders guilty of slavery?
Doesn't this mean that the speed of gravity would be related to gravity at that point? i.e. in the same way that the speed of light is observed to slow down near a gravity well (such as a black hole).
Doesn't this therefore mean that the speed of gravity at a black hole would also tend to zero in the same way the speed of light would tend to zero?
Or have I missed something fundamental here?
"The weirdest thing about a mind, is that every answer that you find, is the basis of a brand new cliche" -
I think that overall this is a good point, but I've seen many people who make their living doing hard science who, once they open their mouths, start putting their personal credibility where it does not yet belong.
Although I don't do it for a living, I'm dedicated to science and it's progress and I have a real love for both the process and the results. But I'm afraid that one of the biggest factors that has made science vulnerable to inroads by fundamentalists is that scientists have, of late, embrace three (admittedly hastily constructed) levels of credibility on scientific subjects:
1) We very strongly believe this is true because it has been repeatedly verified through controlled experimentation.
2) We very strongly believe this is true because it can be strongly inferred from existing verified data.
3) We understand that we don't have all the facts, but we are critical thinkers for a living and our theories are worthier than your theories.
Number 1 is where scientists should be, but in debates, articles, and various other discussions on the battle between religion a science I have seen prominent and credible scientists arguing 2 and sadly, much more often 3. I understand it, but many scientist should reign themselves in.
Understand, I'm not saying don't fight, just that we should fight from our position of greatest strength, which is being "fundamentalist" about the scientific method. If we can teach kids, or anyone, how it works and why we're devoted to it, all the while showing by example how to be scientific in thought, then we win. There's plenty of room for religion in the world even with hard science, and there's plenty of amazement and wonder to be had in science too. I just don't want to see scientists try to expand their own role in human exploration way beyond the data.
The only acceptable defense of scientific results is to say that they were the product of the Scientific Method.
[T]his article does not at all dispute the observations of global warming.
And, in fact, it says, "Greens say, rightly, that the best scientific assessment today is that global warming is occurring."
More below.
Otherwise, this is not an article that discusses specific scientific observations
You only found one instance of a specific scientific observation? The first sentence gives a specific instance of low temperature observations. The second paragraph discusses a span of recent large-scale global cooling. The sixth paragraph makes a general observation about the accuracy of global climate models. There are still more direct observations in the article.
Let's step back a minute. The point of bringing this article to light was to illustrate that the recent attention about global warming, and its proposed anthropogenic source, may be a bit precipitous, given the accuracy of the predictive modelling of global climate simulations. While I've seen results of global climate simulations that extend out 150 years, I've yet to see any good data that give me confidence that our accuracy is high enough to say more than "global warming is not much than a mildly promising theory." And specifically "global warming" = "anthropogenic causation of global warming". This was the claim that I was attempting to bolster.
I've never trusted this whole bandwagon regarding both dark matter and dark energy. It just seems like all of a sudden, with very little to actually invoke by way of proper observational evidence, everybody got on the dark matter/energy bandwagon and we were off to the races with it, despite continued objections from various and sundry quarters to the effect that we really do not have any actual evidence for any of this stuff. Instead, we have a bunch of "unexplained" things that then get "explained" using dark matter/energy. Sounds more like religion than science if you ask me. So it's nice to see some substantial cracking in the edifice, and I'll be quite pleased if the whole dubious enterprise comes crashing down and we revert to science that's either grounded on more substantial claims or is man enough to admit it doesn't know.
Is it fascism yet?
I've been suggesting for years that "dark matter" is an unnecessary idea which only exists as a transitional kludge until we can uncover some more fundamental error in the theory of gravity, like planetary epicycles or what not. I have made this suggestion both on the internet and in person to some people I hang around with from my college's physics department.
While generally people have not agreed with me, I have never encountered what I would call "dogmatic" resistence; I never felt that people were upset at my suggestion or disrespected my opinion that this was a possibility.
Perhaps the reason why you have met with poor results expressing the same idea have more to do with the way in which you expressed the idea?
I find a lot of people seem to believe that if people disagree with them, it is automatically because of dogmatic resistence. Not necessarily, maybe it's just because you've not made your case very well, or because there are other factors to the discussion you aren't considering (for example, that asking a physicist to abandon the idea of dark matter would-- in the absence of a better explanation for anomolies in gravitational theory-- effectively require them to accept the idea that the galaxy is the wrong shape for no reason whatsoever).
Irritable, left-wing and possibly humorous bumper stickers and t-shirts
I've seen this sort of thing happen occasionally in widely used reference books and been guilty of it myself. With computer modeling so much more widely available and easy to use these days, there's less excuse for not being thorough.
Contribute to civilization: ari.aynrand.org/donate
Within the jargon of science, "true" means "useful and predictive". Scientists sometimes forget that they have a nonstandard meaning for "true", especially if speaking casually. It's worth noting that this jaron definition of "true" is more useful and predictive than the standard meaning. :)
Socialism: a lie told by totalitarians and believed by fools.
If it is indeed the case that all of the estimates of dark matter up until now were based on incorrectly calculated galactic rotational rates, then this was a monumental screwup. So noone was using general relativity for these calculations, and were relying on Newtonian physics? I am speechless. Just a quick Google search turns up about 10 experimental collaborations comprising about 200 physicists looking for dark matter, a topic which is funded so highly **because** of the galactic observations and not because of "gee whiz it would be neat to find dark matter". Assuming a cool $15M per experiment, that's $150,000,000.00 spent worldwide. And you'd a thunk some funding agency somewhere would have paid 0.01% of that for a study of galactic rotations in the full GR before plunking that down.
In GR gravity is not a wave or a particle. gravity is curvature of space and time. thus the question speed of gravity is a non starter, it is like asking the speed of a stationary hill. The common way to illustrate this is to use a sheet and a bowling ball. Stretch the sheet taught, place the bowling ball in the middle then roll a tennis ball at a tangent. The ball will follow the contour of the sheet. Pretty simple and no big deal.
Now when you start talking about gravitational waves you're actually talking about the waves induced when something with sufficient mass is disturbed. what people are wondering is how fast the waves generated by the perturbance are travelling not the speed of gravity.
Or think of it as a lake. The lake has no speed (we have chosen our frame of reference carefully) toss a rock in and measure the result of the waves. You're not measuiring the speed of water...
If the only way we observe Dark Matter has now been explained by something else, and it interacts with the rest of the universe in NO OTHER WAY, surely we can just assume it doesn't exist, whether it actually does or not? If it does exist it's not making any difference so everything is occurring in the same way as if it didn't.
I think the bigger question in my mind is why hadn't someone tried to do this before now?
Science isn't truth, and it isn't fact. It's a process that, over time, results in a gradual and constant tendency towards truth.
If you get into a debate with religious folk about "creationism" versus "evolution", one of the tactics almost invariably tried is to disprove some facet or other of evolution through some form of deductive reasoning. The basic idea is to prove that Science is somehow wrong, and then assume that creationism wins by default once that's done.
It's easy to see the fallacy: disproving evolution (even if they can) doesn't prove creationism.
But, scientific theory is always undergoing review and clarification. Newtonian gravity works, in limited scopes. It was revised and improved with relativity theory, which is itself being revised and improved today with multidimensional, superstring theory. It's this recursive process of deduction, testing, and review that advances science.
We should be ecstatic! Despite our incredible efforts to find it, we've uncovered NO evidence that this has ever happened before in the multi-billion year history of the universe!
People are stupid, and we have to acknowledge that. Our intellect barely rises above our other urges, the urge towards sex, the blindnesses caused by our tendency to suspend reason (A.K.A. "Faith") and follow the leader 'cause it's easy. And, truly fresh/new approaches to problems are rare, and hard to find. Most any "new" thought is merely an extension of a previous thought. We're creatures of habit. But, so long as we continue to try, so long as we continue to be willing to challenge our assumptions, and take the time to do so when somebody DOES come up with something new, then the process of Science progresses, and life continues to get better.
Schools today don't teach science. They teach "facts", like "water vapor absorbs light, but absorbes blue light the least, and thus makes the sky blue". They don't ever teach the method of science, the passion of science, beyond making you recite the "gather facts, form hypothesis, test hypothesis, draw conclusion" which is only minimally how science works.
Children are BORN scientists. As they explore with their hands, and their minds, the world around them, they perform hundreds of experiments a day, every day. Where do you find frogs? What bug is making that buzzing noise? What happens if you clap your hands near a grasshopper? How many blocks can I stack up before they fall over?
So, what do we do? We lock them up in a sterile environment, where they're told not to question the teacher, and never to talk to the kids next to them. We prevent their natural curiousity, and instead, browbeat them into performing tricks like a circus animal. The apathy of the schoolchild is both detrimental and obvious.
And after that's done, after the child's natural, scientific curiousity has been conquered, that's when we introduce the wonders of science in the most boring, unimaginably unflattering way possible, by forcing him/her to regurgitate "facts" that they'd be ridiculed to question.
The real wonder? How does science advance at all in the face of this educational travesty?
It's pretty obvious that scientific curiosity is built into the very fiber of humanity, or how else could still be advancing despite our incredibly expensive social efforts to prevent it?
I have no problem with your religion until you decide it's reason to deprive others of the truth.
I've read a bunch of comments on this thread, and noticed that many of the highly rated ones share a common theme:
"Maybe it's just me, but when I first heard about dark matter, my immediate thought was the ether. I'm ever-so-smart."
Listen, morons:
History of the Ether: "Light travels. Anything that travels has got to travel through something. Let's call it ether."
History of Dark Matter: "Direct observation consistently reveals more gravitation than is explainable by plugging the currently detectable mass into the current equations. Either our current equations are wrong, or there's more mass than we can currently detect."
One of these is science. The other is a conclusion based on a false assumption which in turn was made with no backing evidence. Can you, being ever-so-smart, tell which is which?
Get over yourselves. You're not smarter than the physics community, no matter how many Slashdot nerds think that your post is "+5 informative".
I know there's a problem with Pioneer, but it may or may not be related to gravity.
As far as mercury is concerned, there's no issue associated with its orbit. We can explain the changes of its orbit within 0.3 arc seconds per century. I don't think it gets much better than that.
I think the comparison between Luminiferous Aether and Dark Matter is one of the most prudent ones I've heard in a long while. Making something up to force your data to fit is a pretty bad idea. We can't be wrong.
Except this has happened many times in physics with successfull results. The neutrino was a predicted particle that interacts weakly with normal matter. It was predicted in 1931 by Wolfgang Pauli to explain the result of experiments measuring beta decay. The particle wasn't actually detected until 1956. Does this mean Dark Matter must exist? Obviously no, and if this new calculation pans out it most likely doesn't exist. But that doesn't mean that proposing something new to fit your data is bad science. It obviously is good science, just make sure your prediction can be falsified.
AccountKiller
Ah but "we don't know" is true, but not testable. Saying, "the fairies cause it with their magic dust", allows you to test whether there are correlatiions between color of pixie dust and outcomes. The bullshit theory is bullshit, but it is a step towards developing a Law, whereas saying, "well, it's a mystery" is just standing still.
Just to remind, at the beginning of the last century, many people considered atoms and their particles a mere abstraction, not necessarily representing the way things actually work, but rather serving as a model close enough to do meaningful calculations. You could say the same about dark matter here.