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Good bye Dark Matter, Hello General Relativity

Hemos posted more than 8 years ago | from the all-einstein-quotes-you-know-are-wrong dept.

Space 688

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?"

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688 comments

i finger my ass (-1, Troll)

Anonymous Coward | more than 8 years ago | (#13756392)

i finger my ass thinking about slashdick and its sexy penis users! I love butt-cum!

Re:i finger my ass (0, Funny)

Anonymous Coward | more than 8 years ago | (#13756401)

Seems perfectly safe, since there is no dark matter.

Re:i finger my ass (0)

Anonymous Coward | more than 8 years ago | (#13756594)

Seems perfectly safe, since there is no dark matter.

Now there is ;-)

So does that mean... (5, Funny)

scsirob (246572) | more than 8 years ago | (#13756404)

.. that Dark Doesn't Matter??

Re:So does that mean... (2, Funny)

FlatCatInASlatVat (828700) | more than 8 years ago | (#13756513)

Don't you mean that "Dark Matter Doesn't"?

----

Sub ubi non contorque (Don't get your knickers in a twist)

Re:So does that mean... (-1, Offtopic)

Sivar (316343) | more than 8 years ago | (#13756641)

Don't you mean that "Dark Matter Doesn't"?

Speak like Yoda he does?

Re:So does that mean... (2, Funny)

Anonymous Coward | more than 8 years ago | (#13756530)

It means that there is no Dark Force!

The white force has won!

I should have known that Star Wars was just an old fairy tale.

Well it clearly matters to some people... (5, Insightful)

Alaren (682568) | more than 8 years ago | (#13756597)

(No pun intended)

I think this is a great article.

See my comment here [slashdot.org] where I wonder if maybe we're getting way too excited about dark matter without having any material reason (other than "this is the only explanation that fits our current expectations of gravity") to believe it actually exists.

Based on the moderation that followed, I would say that "some people" don't like it when popular theories get questioned. Which just goes to show you--once a scientific "fact" has been established, our attachment to it becomes as dogmatic as any theological notion...

Re:So does that mean... (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#13756670)

Why do you not care about black people?

Expectable (1)

ntb (694877) | more than 8 years ago | (#13756406)

Quite expectable, I'd say... just like the nature fear of vacuum or the ether

Neat (2, Funny)

SilverspurG (844751) | more than 8 years ago | (#13756408)

The concept is neat. I'm not about to wade through the math and double-check anything. It'd be nice if we could stick with general relativity without dark matter.

On a side note, they are distributing the source [lanl.gov]. It's possible they may even be GPL friendly.

GPL friendly physicists rule.

Re:Neat (2, Funny)

famebait (450028) | more than 8 years ago | (#13756446)

GPL friendly physicists rule.

Not my country. And to be quite honest, I'm not totally sure I wish they did either.

Except that the "source" is the document source. (1)

AlanKilian (887556) | more than 8 years ago | (#13756452)

Does the GPL even apply to the "source" for a document?

Re:Except that the "source" is the document source (0, Flamebait)

poopdeville (841677) | more than 8 years ago | (#13756580)

You know, I'm not really sure. TeX (and LaTeX) are general purpose programming languages, so a .tex file could be viewed as a program -- much like Perl and the like. But then again, TeX is usually used to capture a document's format specifications. It would be counter-intuitive (and wrong) to apply the GPL to HTML, so by analogy, it should be wrong to apply it to TeX files.

All of this is academic since the author only gives limited distribution rights to arXiv.org and reserves the rest. I'd be really pissed if someone "modified" my source and submitted it to Nature (or Proc. AMS. in my case)

Re:Neat (4, Insightful)

Otter (3800) | more than 8 years ago | (#13756515)

On a side note, they are distributing the source. It's possible they may even be GPL friendly.

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.

Re:Neat (-1, Offtopic)

Otter (3800) | more than 8 years ago | (#13756565)

Sorry, I also hate when people feel the need to post to correct trivial typos but I somehow badly mangled that between Preview and Submit:

I'm surprised it took so long for anyone to do this. Is the math here significantly more difficult than it looks? Considering relativity seems like an obvious approach, especially if the alternative to postulate entirely new classes of matter.

Re:Neat (1, Funny)

Mr. Bad Example (31092) | more than 8 years ago | (#13756637)

> What would you do with a GPL scientific paper -- change some things and put your own name on it?

Hell yeah, I would. I expect to win next year's Nobel Prize for Mr. Bad Example's General Theory of Why the Ladies Should Be All Up Ons.

Re:Neat (5, Informative)

lgw (121541) | more than 8 years ago | (#13756521)

The paper only concerns itself with the observed rotation speeds of galaxies, for which "maybe there's something we don't understad about gravity" has always been just as convincing an explanation as dark matter. However, the recent cosmic microwave background radiation [uchicago.edu] data *also* implies dark matter, and doesn't have such an easy alternative explanation. The data tells us that (at least, at the moment the univers first became transparant) baryons only account for 20% or so of mass.

Re: Neat (2, Insightful)

Black Parrot (19622) | more than 8 years ago | (#13756575)

> 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.

And in 10 years... (1, Interesting)

takeya (825259) | more than 8 years ago | (#13756412)

And in 10 years, scientists "rediscover" dark matter once again.

Science just isn't definite these days, is it?

Re:And in 10 years... (5, Funny)

moonbender (547943) | more than 8 years ago | (#13756428)

Science just isn't definite these days, is it?

Maybe.

Re:And in 10 years... (1)

Cougem (734635) | more than 8 years ago | (#13756632)

When was it ever definite? They held onto Newton's corpuscular theory of light for years before they listened to Huygens and his wave theory. Then they found the photoelectric effect and went back to thinking it was possibly particular. And then Einstein came along and said it was wave-particle-duality.

Re:And in 10 years... (-1)

Anonymous Coward | more than 8 years ago | (#13756434)

It never was. That's the point.

Re:And in 10 years... (5, Insightful)

rgmoore (133276) | more than 8 years ago | (#13756464)

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.

Re:And in 10 years... (3, Interesting)

OwnedByTwoCats (124103) | more than 8 years ago | (#13756577)

It is worth noting that a new idea surpassing current thinking (and demoting current thinking to wrong, old ideas) is not arbitrary. It is not a matter of the old scientists dieing off.

It is a matter of new ideas (a) explaining all of the old observations and experimental results that supported the old theory, as well as (b) explaining observations and experimental results that the old theory could not.

I am not capable of reviewing the observations and redoing the math to verify whether GR by itself explains the observed rotation rates of distant galaxies. Over the next few months more qualified scientists will look at this and publish what they think. Dark matter may go the way of the luminiferous aether. Once it is gone, it is very unlikely to come back in its original form or for its original purpose.

I wonder if this analysis has an effect on the chain of inferences leading to the conclusion that the galactic expansion is accelerating.

Re:And in 10 years... (2, Interesting)

lgw (121541) | more than 8 years ago | (#13756623)

Particle physics in particular is an interesting exception to the "old scientists dieing off" rule of how science works. From what I hear, it's commonly accepted that the Standard Model is "wrong", in that the fundamental underlying model is false, but it keeps predicting new observations so well that alternative theories can't get any traction.

Re:And in 10 years... (1)

Surt (22457) | more than 8 years ago | (#13756535)

Science is never definite, after all, for all we know, the rules of the universe change over extended timespans.
 

Re:And in 10 years... (0)

8400_RPM (716968) | more than 8 years ago | (#13756610)

No doubt. Funny thing is scientist dont see that trend.
All their theories are FACTS. lol

As usual... (3, Insightful)

lax-goalie (730970) | more than 8 years ago | (#13756415)

...the simplest solution turns out to be the best.

Re:As usual... (0)

Anonymous Coward | more than 8 years ago | (#13756468)

A witty saying proves nothing. - Voltaire

Simple solutions being best require subjective definition of the words 'simple', 'solution', and 'best'. Of course everyone thinks it's true.

Re:As usual... (3, Insightful)

GoofyBoy (44399) | more than 8 years ago | (#13756470)

Um.. define "the best"?

The "Truth"?

The "most elegent"?

The "one that majority of scientists can most willingly accept"?

The "one that my mind can most willingly accept"?

Re:As usual... (1)

sholden (12227) | more than 8 years ago | (#13756595)

The one that describes the most observations, and whose predictions have been verified.

Ties are broken with simplicity - so Relativity trumps my "fairies push things around" theory even though they equally fit the observations due to it being simpler.

Simple means requiring less made up stuff - like fairies and dark matter and electrons.

Re:As usual... (0)

Anonymous Coward | more than 8 years ago | (#13756487)

Yup, right on. Totally insightful - go with the simplest solution.

I *told* them this, over and over: "Dear scientists, I said, listen to me: the *simplest* solution - go for the *simplest* solution. There *has* to be a *simpler* solution than dark matter. Read EINSTIEN for crying out loud! Its all in the GENERAL RELATIVITY - *SIMPLIFY* man. Do the math, man - its all there".

But did they listen? Noooo, they just acted like I was some sort of lunatic ...

Re:As usual... (1)

YU Nicks NE Way (129084) | more than 8 years ago | (#13756514)

The simplest correct solution turns out to be the best. This would be (as a comment further down [slashdot.org] points out) a head-slappingly obvious thesis -- which leads me to wonder if the authors have their calculations right.

Re:As usual... (2, Interesting)

lawpoop (604919) | more than 8 years ago | (#13756576)

This has always struck me as an anthropocentric, 'faith-based' element in modern physics. Why should the universe be simple and elegant? Because it's 'beautiful'? Because we don't like doing hard math problems?

I'm not against it, but it seems to be taken on faith that the universe should be simple and elegant. So far the track record is pretty good, but that doesn't mean that it's a scientific belief. Don't get me wrong, I'm not against a simple-and-elegant universe; I just haven't heard any scientific explanation why it should be so.

Re: As usual... (3, Interesting)

Black Parrot (19622) | more than 8 years ago | (#13756604)

> ...the simplest solution turns out to be the best.

Surely GR & QM are better than the super-simple Newtonian/Euclidian model that went before.

Re:As usual... (0)

Anonymous Coward | more than 8 years ago | (#13756622)

why is the dept. saying einstein quotes are wrong if they used relativity? shouldn't it say "from the don't-believe-people-who-go-against-einstein-dept. "?

Re:As usual... (0)

Anonymous Coward | more than 8 years ago | (#13756638)

the simplest solution turns out to be the best

That's why I'm a creationist. Gravity is God's angels with their little tug boats.

PS> General relativity is not simple. Newton mechanics is the "simple" solution! Not many high schools teach General Relativity in their regular physics courses. Also, a big "duh", the simplest correct solution is the best one. Had dark matter been proven to defy general relativity, we'd need some other solution that will be the best one. And then it'll be called simple.

Re:As usual... (4, Funny)

lgw (121541) | more than 8 years ago | (#13756645)

As any engineer knows: every problem has a simple, easy to understand, wrong answer.

Re:As usual... (1)

Mr. Bad Example (31092) | more than 8 years ago | (#13756667)

> ...the simplest solution turns out to be the best.

I had a witty reply ready to go for this, but the bowling ball failed to make it down the ramp onto the bellows, which would have blown the balloon across the room carrying the mouse to the cheese on the Enter key, whose weight would have submitted my post.

                                                                                              --Rube Goldberg

Damn.. (4, Funny)

Druox (911165) | more than 8 years ago | (#13756425)

Geeze science, make up your mind - Think of the poor sci-fi writers for those made-for-tv movies! Have you considered THEM before publishing research findings??

Re:Damn.. (1, Funny)

dcphoenix (528517) | more than 8 years ago | (#13756617)

As a matter of fact, yes - yes they did consider the scifi writers. Now, with this new report, those very writers can start talking about the vast government conspiracy to cover up the truth about dark matter and those big bad aliens hiding in it until they attack us.

From the Abstract (5, Interesting)

poopdeville (841677) | more than 8 years ago | (#13756440)

A galaxy is modeled as a stationary axially symmetric pressure-free fluid in general relativity. For the weak gravitational fields under consideration, the field equations and the equations of motion ultimately lead to one linear and one nonlinear equation relating the angular velocity to the fluid density.

That's really interesting. It makes sense to model a galaxy as a fluid on a very large scale. After all, gravity is a relatively weak force. I haven't gone through the paper, but if their math is right, since the assumption is relatively benign, this seems like it would be experimentally verified.

Since the model assumes that a galaxy is a fluid (on a large scale), the model would predict fluid-like phenomena. What I wonder is if there is a galactic analogue to solitary waves. How would these manifest? (A friend wrote his thesis on solitons)

Re:From the Abstract (0)

Anonymous Coward | more than 8 years ago | (#13756497)

Spiral arms? ;-) Actually, spiral arms aren't solitons, AFAIK, but there's some similarities. Might be an avenue you want to look into.

Re:From the Abstract (2, Informative)

Xilman (191715) | more than 8 years ago | (#13756541)

Since the model assumes that a galaxy is a fluid (on a large scale), the model would predict fluid-like phenomena. What I wonder is if there is a galactic analogue to solitary waves. How would these manifest? (A friend wrote his thesis on solitons)

Yes there are analogues and easily visible manifestations are spiral arms.

Treating galaxies as fluids has been done for many years and the models have been quite successful. I think it was found back in the 70's that spiral arms could be modelled rather well as density waves in a rotating disc of fluid.

Paul

Re:From the Abstract (1)

JasonKChapman (842766) | more than 8 years ago | (#13756562)

Since the model assumes that a galaxy is a fluid (on a large scale), the model would predict fluid-like phenomena.
Hmmm. So the higher the density of matter is in a given volume of space, the more "viscous" the fluid-model becomes?

Re:From the Abstract (1)

ArsonSmith (13997) | more than 8 years ago | (#13756642)

So you're saying the galaxy is just dirty bath water circling the drain of the universe? I get it now.

That sound you heard... (5, Funny)

OakDragon (885217) | more than 8 years ago | (#13756441)

...was physicists around the world collectively slapping their foreheads.

Re:That sound you heard... (1)

Brad1138 (590148) | more than 8 years ago | (#13756520)

And I thought it was that Simpsons episode with all the Homers falling off the cliff. DOH!

Scientists flunking general relavity? (2, Funny)

Anonymous Coward | more than 8 years ago | (#13756458)

Aha, but the Electric Universe theory offers a solution as to why much dark matter is replacing the grey matter that used to be important to our society.

Shocking News (1)

moonbender (547943) | more than 8 years ago | (#13756462)

Sadly, Brig. Gen. Harold Relativity was not available for comments.

Re:Shocking News (-1)

Anonymous Coward | more than 8 years ago | (#13756624)

Luckily we wera able to get a comment from his nephew... Pvt. Parts

And then refuted virtually instantaneously... (5, Interesting)

Anonymous Coward | more than 8 years ago | (#13756498)

The great thing about the speed of communication these days is that whenever a moronic story hits the web, it can be refuted immediately. See, in this case, Singular disk of matter in the Cooperstock and Tieu galaxy model [arxiv.org], which says:
Recently a new model of galactic gravitational field, based on ordinary General Relativity, has been proposed by Cooperstock and Tieu in which no exotic dark matter is needed to fit the observed rotation curve to a reasonable ordinary matter distribution. We argue that in this model the gravitational field is generated not only by the galaxy matter, but by a thin, singular disk as well. The model should therefore be considered unphysical.

No magic pixie dust after all (2, Interesting)

lheal (86013) | more than 8 years ago | (#13756501)

I always thought "dark matter" was a kind of special pleading, an appeal to magic in the face of the unknown.

They're blinding us with science... (2, Interesting)

KidCeltic (130804) | more than 8 years ago | (#13756503)

It has seemed in recent years that scientists have shunned the scientific method in exchange for sensationalism. As someone else alluded to, it seems that scientists are more interested in concocting incredible theories rather than addressing the more simple facts that are staring them in the face. Science community: please return to hard science, not fantasy.

Re:They're blinding us with science... (2, Insightful)

starwed (735423) | more than 8 years ago | (#13756612)

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.)

Re:They're blinding us with science... (1)

LeonGeeste (917243) | more than 8 years ago | (#13756631)

That's a good point. Have you ever considered how few eyeballs are invested in checking the work of physicists? Maybe 1,000 people worldwide a capable of truly discussing cutting edge theoretical physics. (Compare that with the Linux source code checkers.) With so few people - and the good-ol'-boy nature of professors - errors can easily persist for decades.

This is why I actually like creationists: they force biologists to rigorously prove all aspects of evolution. While otherwise they would content themselves with hand-waving excplanations of things like irreducible complexity, now they have to deal with such issues. Imagine if the Bible talked about quantum physics!

Re:They're blinding us with science... (3, Insightful)

ubera (107426) | more than 8 years ago | (#13756669)

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..."

Re:They're blinding us with science... (0)

Anonymous Coward | more than 8 years ago | (#13756679)

We cannot perform experiments on a cosmological scale - if you have a suggestion about how else scientists could possibly work, other than "concocting incredible theories" please let them know. I'm sure they will tip their hats to you in grateful thanks.

I'm going back to jesus (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#13756516)

You know what , I'm sure mad about this. I left my church because science said it had proven that Steven Hawking could talk.

Does this mean... (0)

Anonymous Coward | more than 8 years ago | (#13756522)

that the theory of General Relativity is no longer a theory?

What, no Gaffer Tape? (5, Funny)

Morgaine (4316) | more than 8 years ago | (#13756523)

TFA is just plain silly.

Every teccie knows that the universe is held together by gaffer tape, and the only problem has been to find the link between gaffer tape and dark matter.

If relativity does away with dark matter, well fine, but the cosmologists are missing the key issue here. All this means is that now we have to find the link between relativity and gaffer tape.

Tentative results (4, Insightful)

amightywind (691887) | more than 8 years ago | (#13756533)

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.

Interesting (3, Insightful)

andrewman327 (635952) | more than 8 years ago | (#13756538)

I wonder if some scientists might already be so invested in theories of dark matter that they will refuse to accept this position.

Re:Interesting (1)

promatrax161 (913597) | more than 8 years ago | (#13756608)

I wonder if some scientists might already be so invested in theories of dark matter that they will refuse to accept this position.

I would not worry too much about that... They will easily adapt, using their results as "boundary" cases of whatever currently popular new theory. Investing in theories is never futile...

But what about Nibblers output? (1)

DocTillo (615220) | more than 8 years ago | (#13756539)

There's clearly proof of the existance of dark matter in the futurama series. How can a serious scientist ignore these?

Experiment... (1)

bmfs (467488) | more than 8 years ago | (#13756540)

Ahh, this would explain why my undergraduate WIMP detector failed to detect anything ;)

WYSIWYG universe (4, Insightful)

G4from128k (686170) | more than 8 years ago | (#13756555)

Perhaps it is a WYSIWYG universe, we just don't understand how to properly see what we see.

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.

Rationality .vs. Creationism (-1, Flamebait)

ElitistWhiner (79961) | more than 8 years ago | (#13756583)

Good Day for the Scientists reaffirming belief in Mind over Matter (i.e. Dark). We live in a rational Universe, today, complete with rules and predictable behaviors.

Bad Day for the Creationists sullying belief in Matter over Mind (i.e. Mythology). Their lives are winnowed by one fewer dark unknowns to support their irrational behaviors and flaunting the rules of the known World.

Good on ya, Boys! That's what Albert would think, too;-)

Re:Rationality .vs. Creationism (0)

everphilski (877346) | more than 8 years ago | (#13756673)

I'll have to check my bible but I'm pretty sure it doesn't say "and on the eighth day God created Dark Matter"

In fact I'm pretty sure it says "In the beginning God created the heavens and the earth"

*cough*troll*cough*

-everphilski-

Maybe. However, dark energy... (3, Interesting)

promatrax161 (913597) | more than 8 years ago | (#13756584)

...is going to become the major worry. Data from supernovae distance measurements indicate that the Universe has been expanding for some time already. That means that there has to exist a sort of anti-gravity (called dark energy by astrophysicists). Now, that is hard to explain by conventional means (although it is possible), and may involve either a "beyond Einstein" type of theory (e.g., an improved general relativity) or some exotic form of energy (or both). So, although general relativity alone might account for the rotational curves of galaxies, it does not account for the large-scale properties of the universe.

Re:Maybe. However, dark energy... (1)

Rinzai (694786) | more than 8 years ago | (#13756672)

"...has been expanding for some time already."

???

How about--the whole time?

Einstein has once again, Powned modern physicists. (4, Funny)

doublem (118724) | more than 8 years ago | (#13756592)

How many of us have done as much?

Hell, even Hawking has never shaken up the ideas of science and physics to anything near the degree Einstein has.

How long has he been dead? And he's STILL stirring up trouble!

Personally, I think his statue in Washington DC needs to be bigger. He's done far more for this country and the world at large than most of the people with bigger statues. It's just not fair!

Still uses dark matter (4, Interesting)

marcosdumay (620877) | more than 8 years ago | (#13756606)

The poster title is misleading, the paper still leaves a place for dark matter, but on very smaller amounts and far from the halo. So, this matter could easily be barionic (paper's conclusion).

What is really interesting is that the third galaxy didn't fit the model as well as the others. It may be because of the inacuracy of the calculations (is the inacuracy measurable? The paper should have said that) or because there is something different on this one, maybe a smaller concentration of dark matter near the center.

Have they been using Newtonian physics?! (2, Interesting)

Henriok (6762) | more than 8 years ago | (#13756615)

Really?! I'm interessted in astronomy and physics at a hobbyist level, and have always assumed that the simulations of gravity and galaxy formation was done with relativistic mathematics. Instead they have used approximations using newtonian theories? WTF? No wonder they came out wrong!

I can live with newtonian approximations on a solar system level, but doing cosmology on the scale of galaxies, the age of the universe it self and so forth they really should have used the sharpest tool in the tool box.

If I had the knowledge and the machine power to do simulations my self I would've done so, but I don't so I trusted the astronomers. They really shuldn't have taken the shortcuts, escpecially after their scientific profgress went boink and they started devicing exotic new models just to cover up their seemingly faulty theories! Shouldn't they have done a simmulation without the approximations just to evaluate how good their approximations was?

I'm dissapointed!

Re:Have they been using Newtonian physics?! (2, Insightful)

promatrax161 (913597) | more than 8 years ago | (#13756661)

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...

Dark Fudge (2, Insightful)

LukePieStalker (746993) | more than 8 years ago | (#13756621)

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.

Luminiferous Ether of our times (2, Interesting)

Weaselmancer (533834) | more than 8 years ago | (#13756655)

What does this imply for cosmology and particle physics, both of which have been worrying about other aspects of dark matter?

I think it implies that we can stop chasing for something that probably doesn't exist, and get about the business of finding out what's really going on 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. For a long time we needed an ether to explain radio waves, light propogation, etc. Turns out the truth of the matter is something totally other. And it's a far more facinating other, IMHO.

I'm guessing that hundreds of years from now, physics students will be reading about dark matter and chuckling. Same way we do today when we read about the luminiferous ether [wikipedia.org].

Is this evidence *against* dark matter? (2, Interesting)

ebcdic (39948) | more than 8 years ago | (#13756658)

Before this paper, it seemed that the rotation of galaxies was inconsistent with the amount of visible matter.

Now it is consistent. But is it consistent with the visible matter plus any significant amount of dark matter? That is, does the GR calculation show that there can't be much if any dark matter?
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