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Vast Web of Dark Matter Mapped

Soulskill posted more than 2 years ago | from the here-there-be-dragons dept.

Canada 86

astroengine writes "Astronomers from the University of British Columbia and University of Edinburgh have created a vast cosmic map revealing an intricate web of dark matter and galaxies spanning a distance of one billion light-years. This is the largest map of its kind and demonstrates that this large-scale web stretches across the universe in all directions. The results of this groundbreaking discovery were presented at the American Astronomical Society conference in Austin, Texas on Monday."

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86 comments

You sir. (-1)

Anonymous Coward | more than 2 years ago | (#38643806)

Are a fucking racist..

Re:You sir. (0)

Anonymous Coward | more than 2 years ago | (#38647378)

I bet you're a racist too.

What are the odds... (3, Interesting)

rshol (746340) | more than 2 years ago | (#38643906)

...dark matter eventually turns out to be like luminiferous aether from the 19th century? I don't believe anyone has directly observed dark matter.

Re:What are the odds... (3, Insightful)

na1led (1030470) | more than 2 years ago | (#38643944)

How do they even know it's matter? It could be a sea of graviton waves or something.

Re:What are the odds... (3, Interesting)

stevelinton (4044) | more than 2 years ago | (#38644102)

From the way it clumps around galaxies and clusters of galaxies, I think we know that it isn't moving at or close to the speed of light, which rules out gravitons and a bunch of other things.

Re:What are the odds... (2, Interesting)

Anonymous Coward | more than 2 years ago | (#38644550)

One of the many things that has always bothered me about Dark Matter is how it has gravity but at the same time doesn't seem to be affected by gravity.
 
Case in point, an Astronomer was able to map out the DM field around a pair of colliding galaxies but the DM cloud from one galaxy had just sailed through the DM cloud of the other galaxy without any apparent affect. But at the same time all the visible matter behaved exactly as predicted, swirling together and merging into a larger galaxy.
 
Does anyone know why these big clouds of Dark Matter, each with enough gravity to hold a galaxy together, don't collapse in on themselves. Regular matter gets blown around by light, a cloud of Hydrogen collapses and heats up too fast the heat blows the cloud apart, preventing further collapse. So what keeps DM from collapsing into some kind of super sized uber black hole?

Re:What are the odds... (2, Interesting)

Anonymous Coward | more than 2 years ago | (#38644742)

Lack of friction and no way to dissipate energy or angular momentum. It cannot radiate photons, as doing so would make it not dark.

Re:What are the odds... (3, Funny)

ae1294 (1547521) | more than 2 years ago | (#38644890)

Maybe the dark matter is not really matter at all but dark space fabric with different rules and demons and shit.

Re:What are the odds... (1)

L4t3r4lu5 (1216702) | more than 2 years ago | (#38649574)

Once you've come up with a mathematical proof for your demons, you too can be published in Nature or some such.

The added benefit is that nowadays you won't be burned at the stake for suggesting it!

Re:What are the odds... (2)

ae1294 (1547521) | more than 2 years ago | (#38649716)

Once you've come up with a mathematical proof for your demons, you too can be published in Nature or some such.!

I'm working on it now but my retrieval teams keep coming back .... different .... It's so hard to find good help now days that are immune to the effects of non-euclidean space/time. As far as Nature(tm) they have already agreed to publish my work, proof or no. They said something about shifting paradigms and proofs being over rated and not important to their core market group.

Re:What are the odds... (1)

Anonymous Coward | more than 2 years ago | (#38648254)

Case in point, an Astronomer was able to map out the DM field around a pair of colliding galaxies but the DM cloud from one galaxy had just sailed through the DM cloud of the other galaxy without any apparent affect. But at the same time all the visible matter behaved exactly as predicted, swirling together and merging into a larger galaxy.

That's actually part of why they think it's non-baryonic, IIRC. Normal matter in the colliding galaxies is slowed by friction and electromagnetic forces; the dark matter doesn't interact strongly with baryonic matter, so it just sails past until it's gradually pulled back by gravity.

Re:What are the odds... (1)

Cyberax (705495) | more than 2 years ago | (#38653472)

Particulate dark matter just never gets too cold to be held by its own gravity. Purely gravitational interactions resulting in ejection of fast-moving particles would eventually let it cool down enough to form planet-sized objects but it'll probably take longer than the lifetime of baryonic matter.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38644118)

This man definitely thinks there's no such thing as dark matter.

http://links.gnrpodcast.com/title.php/200/bgaede%27s_Channel_-_YouTube [youtube.com]
http://en.wikipedia.org/wiki/Bill_Gaede [wikipedia.org]

Bill Gaede (November 19, 1952) is an Argentine engineer, programmer, quintessential Cold War industrial spy who worked at Advanced Micro Devices (AMD) and Intel Corporation (Intel)...

Gaede would later engage in science related work: namely by creating a critique of mathematical physics and the usage of the scientific method in the disciplines of physics, biology, anthropology and palaeontology.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38651208)

Here's some seemingly accurate comments about him:

Mr Gaede lacks the ability to comprehend new information, especially if it doesn't fit with his whacky ideas! He claims to be some kind of representative of science while demonstrating breathtaking ignorance about the fundamentals of it.

And the following are but two examples.

I want this guy to know that theoretical physics (the part with math) comes AFTER experimental physics. The "mathematicians" use data from experiments.

It's almost unbelievable how absurd this man is...

And that's ignoring the fact this guy was also arrested and convicted for industrial espionase from Intel and AMD, for Cuba, by the FBI. The sad thing is, it looks like both him AND the FBI broke the law and only he went to prison.

Probably best to just ignore this guy. I watched a couple of his videos. For the ignorant masses his videos may hold sway. The problem is, he tells half truths and then refutes them in an attempt to make himself an authority.

Re:What are the odds... (1)

vikingpower (768921) | more than 2 years ago | (#38671996)

There is no such thing as "gravitons". Gravity is the deformation of space-time caused by the presence of matter, as per Einsteins general relativity theory. Gravitons are a fairy tale, sir.

Re:What are the odds... (5, Informative)

stevelinton (4044) | more than 2 years ago | (#38644084)

Looking longer and longer by the day. Aether was invented because people felt it SHOULD exist, but expected consequences of it completely failed to show up. Dark matter was invented because there were observations that are very hard to explain any other way and fit increasingly precisely with one another if dark matter is the cause -- there are several different ways of measuring the distribution of dark matter among various clusters of galaxies, and they are giving remarkably consistent answers.

A better example would be phlogiston, which was invented to explain observations, but eventually failed to explain all observations, so it was replaced by a better theory. The same could happen to dark matter, but there are no signs at the moment,

Re:What are the odds... (1, Interesting)

mark-t (151149) | more than 2 years ago | (#38644376)

Aether was invented because people felt it SHOULD exist.

So was Dark Matter. People felt that the Aether should exist because the existing theories at the time governing the physical laws of the universe predicted that it ought to exist. and its nonexistence would mean that those theories were wrong (and they were). What is particularly interesting about proving the non-existance of the Aether (who says you can't prove that something doesn't exist?) is that it was accomplished without adequately forming another explanation for what was expected to happen... it was simply a blanket disproof that stated that those expectations (in particular, that the wave properties of light would not be possible unless the phenomenon were happening inside of some medium) were simply wrong, with no real explanation as to why. With Dark Matter, if it is disproven, I expect it is much more likely that we will actually discover how our existing theories are wrong at roughly the same time that the existence of Dark Matter is disproven.

Re:What are the odds... (5, Informative)

MozeeToby (1163751) | more than 2 years ago | (#38644544)

The part you're ignoring is that unlike the aether, there is actual evidence for dark matter, quite a lot of it actually. It's true that at the time it was conceived it was little more than a fudge factor, but that time has long since passed. The Bullet Cluster [wikipedia.org] , for example, is probably the stongest single piece of evidence, though by no means the only one. It has a core of regular matter surrounded by a large halo of dark matter which can be observed by measuring the gravitational lensing of light passing through the region.

Fair enough, the same effect could be produced by bending spacetime in some other way, but the only way we know about today is with gravitational mass. Scientists find the assumption that there is a kind of matter we can't see much more readily than they will take the assumption that there is some force other than gravity (or some source of gravity other than mass) that warps spacetime to such a degree over such large volumes of space.

Re:What are the odds... (1)

mark-t (151149) | more than 2 years ago | (#38644794)

I wasn't suggesting that Dark Matter is not a perfectly sound theory, given what we know.

I only point out that the only reason its existence was postulated at all is because we can't currently explain certain observations any other way, based on our knowledge of how the universe works.

Prior to the aether being disproven, all prior observations on waves appeared to necessitate that a medium must exist for the wave to actually propagate.

There's actually quite a lot of similarity, really.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38646900)

The clue that you're not as intelligent as you think is where you seem to believe you have some insight that astrophysicists don't. In attempting to demonstrate your intellectual superiority you reveal the opposite.

What do you think a scientific theory is, other than "We don't have any better explanation"? There are no absolute truths except in religious tomes.

Re:What are the odds... (2)

mark-t (151149) | more than 2 years ago | (#38647480)

Where do I claim or imply that I have some insight that astrophysicists do not? It is my understanding that the reason we believe in the existence of Dark Matter is because based on our *CURRENT* understanding how the universe works, that is the only thing that we have thought of so far that fits observed phenomonena.

Dark Matter, in this respect, bears a lot of similarity to the idea of the Aether because before the Aether was disproven, observations had already been made that showed that light propagated like a wave, and all other experience with waves showed that they required a medium to propagate. That light could propagate in absence of a medium was entirely counter to their understanding as the notion today that the gravitational phenomena that we observe today is not attributable to invisible gravitational sources. But ultimately, the only reason for its postulation is simply because, as you put it, "we don't have any better explanation". I'd put a "yet" on the end of that, however. Maybe dark matter does exist... maybe it doesn't. Hopefully, some day, we will find out for sure.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38652332)

based on our *CURRENT* understanding how the universe works

On what else could it or any other theory be based?

Re:What are the odds... (1)

CSMoran (1577071) | more than 2 years ago | (#38657960)

based on our *CURRENT* understanding how the universe works

On what else could it or any other theory be based?

Belief, probably.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38648030)

The idea that astrophysicists already have every insight into everything ever is retarded. If that were true, there wouldn't be any debate around dark matter. They'd already know the truth and be able to prove it beyond a shadow of a doubt.

In attempting to demonstrate your intellectual superiority, you reveal you're an idiot.

Scientific theory isn't "We don't have any better explanation." It's "We got some measurements from a test, and then we ran some other tests to confirm or deny a hypothesis about why we got those measurements, and it turns out that our hypothesis correlates positively with the test results."

And you might want to check out some other religious tomes beyond the Bible. They tend to disagree with each others' "absolute truths".

Re:What are the odds... (-1)

Anonymous Coward | more than 2 years ago | (#38644852)

You are missing the point.
All that 'evidence' for dark matter is based on current models being right. The problem is that without dark matter the current mudels are provably wrong.
Do you see the circle reasoning? Dark matter is an invention to protect current models, current models should not be used to protect dark matter.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38645672)

The problem is without new theory XYZ, the previous models are provably wrong.

Do you see the circular reasoning? By rejecting the new idea that addresses an issue, of course you will end up with an unaddressed issue. That says nothing about how well the new idea addresses the issue versus other new ideas.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38646584)

What? How was this modded insightful? Parent is clearly grossly ignorant about the scientific method, let alone astronomy.

Actually... (0)

Anonymous Coward | more than 2 years ago | (#38648586)

There is plenty of evidence for the aether: http://www.anti-relativity.com/daytonmiller.htm It's just not the party line, and often omitted in physics undergraduate and graduate courses.

Re:What are the odds... (1)

Anonymous Coward | more than 2 years ago | (#38648944)

"We have a useful phrase to describe new fields whose energy warps spacetime: 'dark matter.'" --Sean Carroll
dark matter: just fine, thanks [discovermagazine.com]

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38646082)

Yves Couder's demonstrations of macroscopic quantum-duality-like behavior, with silicone droplets bouncing on a liquid silicone substrate, may indicate that there is an aether after all. Einstein's theory merely provided an alternate explanation, but didn't disprove the aether.

Re:What are the odds... (1)

jc42 (318812) | more than 2 years ago | (#38668130)

People felt that the Aether should exist because the existing theories at the time governing the physical laws of the universe predicted that it ought to exist. and its nonexistence would mean that those theories were wrong (and they were). What is particularly interesting about proving the non-existance of the Aether (who says you can't prove that something doesn't exist?) is that it was accomplished without adequately forming another explanation for what was expected to happen...

In contrast to this, I've read explanations in a number of physics and other scientific textbooks that, strictly speaking, Einstein didn't disprove the existence of the aether at all. His new theory simply ignored the aether. When it turned out that Einstein's equations were better predictors of the universe's behavior than previous equations, physicists didn't insist that there was no aether; they also simply stopped mentioning it. It became irrelevant.

Of course, the distinction here is probably a bit too subtle for most people. In popular/media speech, it makes sense to say that physicists had shown that space was empty, and the aether doesn't exist. But it's more accurate to say that they showed that they didn't need the aether to explain the universe. Something like it might exist, but our measurements aren't yet good enough to detect its effects. It may exist, but it's irrelevant.

The same approach could be used with "dark matter". At the moment, it's a useful concept that works better than previous concepts to explain some observations (such as galactic lensing and the rotation speeds of galaxies). But, as with the aether, someone may come up with an alternate concept (plus appropriate equations) that work better. Or maybe the new concept that works will be a refinement of "dark matter" that supports its existence. We don't know yet, so stay tuned.

It has been argued that the above approach is also a good explanation of scientific attitudes towards God (or gods). Science hasn't shown that there's no god in our universe. Rather, they have shown that they can get better explanations of the universe's behavior if they simply ignore the concept of gods, and only work with things like photons, electrons, quarks, etc. Adding a god (or an aether) to scientific theories adds no further explanatory power, so it's best to just put such concepts on the shelf of history and ignore them. They're irrelevant to understanding the universe. At present, we don't have a better concept than dark matter, so it's sitting on the "active hypotheses" shelf.

Re:What are the odds... (2)

Hentes (2461350) | more than 2 years ago | (#38645170)

there are several different ways of measuring the distribution of dark matter among various clusters of galaxies, and they are giving remarkably consistent answers.

Those ways (like this one) measure gravitational anomalies. They are not proof that these anomalies are caused by some kind of non-radiating matter.

The main problem with dark matter theories (mind you, there are many of them that each have a different candidate for the role of dark matter), is that they are not full theories. They don't tell anything about how this matter would behave, so no predictions can be based upon them. If some of those theories got refined to the point where a prediction on the distribution of the matter could be made, they could be compared with the observations. That would be the true test of these theories.

Still, it seems to be the most logical explanation at the moment, at least most of these theories don't require a change in physical laws. It might be the case that GP merely confused this with another set of dark matter theories that aim to explain the galactic rotation curves [slashdot.org] , those have much more problems.

Re:What are the odds... (1)

Livius (318358) | more than 2 years ago | (#38644866)

Don't be silly. The luminiferous aether is dark *energy*.

Seriously, once you starting talking about vacuum having curvature, geometry, pressure, energy, etc., then you pretty well have gone back to the luminiferous aether hypothesis, just with a bit better math.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38645130)

The problem is simply that Google hasn't taken the Beta off the Universe yet because they haven't gotten all bugs worked out. Once they feel it is ready for production use they will take it off and all these strange anomalies will be [mostly] sorted out.

Re:What are the odds... (1)

davewoods (2450314) | more than 2 years ago | (#38650846)

I find this to be the most believable theory out of all of these. I mean... Gravitational lensing? Seriously? That was the best we could come up with?

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38645262)

^^^ mod parent up, plz.

I have been thinking this for quite some time.

Actually, it is taught in certain mystery and occult schools (of back then and continuing to this day) that yes, aether = dark matter.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38645912)

Yep! Seeing's believing, that's why Rutherford didn't believe in atoms.

Re:What are the odds... (3, Insightful)

Black Parrot (19622) | more than 2 years ago | (#38647522)

...dark matter eventually turns out to be like luminiferous aether from the 19th century? I don't believe anyone has directly observed dark matter.

We don't "directly observe" much of anything. Is that any reason to doubt the existence of x-rays? That our sun is a huge ball of gas undergoing fusion inside? That dinosaurs were actually living creatures?

Even if you run an experiment in your lab, all you "directly observe" is the photons striking your eyes and the sound pressure waves impinging on your ears.

Science is in the business of making inferences from evidence. We have a curious constellation of astronomical/cosmological evidence, for which dark matter is currently the best inference going. Yeah, we may have to throw it out... but the same can be said about *any* conclusion scientists have ever reached.

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38648302)

We have observed gravitational effects being caused by apparently nothing.
We have observed galaxies clustering around and being attracted to apparently nothing.
We have observed light being distorted by apparently nothing.

*Something* is causing those effects. You can make up any name for it you wish, but something is causing those effects.

How else do you describe unknown quantities? Especially when you deny variables exists?

Re:What are the odds... (0)

Anonymous Coward | more than 2 years ago | (#38648526)

To me it looks like Perlin Noise! :)

Re:What are the odds... (1)

Urkki (668283) | more than 2 years ago | (#38649022)

...dark matter eventually turns out to be like luminiferous aether from the 19th century? I don't believe anyone has directly observed dark matter.

Well, we haven't observed directly very many things, we've just observed side effect [of side effects [of side effects [...]]] of many things we "know" to exist.

I think it's pretty safe to think "dark matter stuff exists", much like it's safe to think "there's stuff inside Jupiter". We don't know what it is, we can only make educated guesses, but we know there must be "something", and we even have pretty tight conditions for what this "something" can or can't be like.

And, apparently we've made maps of dark matter density. That's one thing setting conditions on what it can be. Like, if it lumps together like that, it must be bound together, probably gravitationally, but we probably can't rule out some yet-unknown natural force which only affects dark matter stuff.

Did I miss... (0)

Anonymous Coward | more than 2 years ago | (#38643940)

...the story where they discovered/detected Dark Matter?

Re:Did I miss... (1)

Manos_Of_Fate (1092793) | more than 2 years ago | (#38644042)

They're just measuring the known affects of dark matter, as opposed to measuring the dark matter itself.

Re:Did I miss... (1)

sFurbo (1361249) | more than 2 years ago | (#38648410)

But then, that has been the case since shorty after the invention of fire and the wheel. Seriously, what physical phenomenon are we directly observing? We can't see atoms, we can't even see the circuits making up computers anymore. All we ever did was meassuring the effects of stuff, and conclude that stuff (probably) exists and have certain characteristics.

Re:Did I miss... (4, Informative)

newcastlejon (1483695) | more than 2 years ago | (#38644198)

...the story where they discovered/detected Dark Matter?

No, there was no discovery story to miss. We have yet to directly observe dark matter. I'll try an analogy with one caveat: like models, all analogies are wrong. Still, some can be useful...

Picture a ball hanging from a ceiling by an invisible thread. Through various methods you are fairly certain how much the ball weighs, and your knowledge of how gravity works gives you an idea of what it should be doing (i.e. falling), yet it does not. You are faced with two ways to explain this discrepancy: your understanding of gravity is faulty or there is something preventing the ball from falling.

Dark matter is the latter sort of explanation. We think there is a string, and we can infer some of its properties from what we see the ball do but we cannot see it. At the risk of incurring the wrath of cosmologists everywhere I'll give another analogy, even more wrong than the first: one cannot see the air or the winds, but one can deduce their existence from their effects on things one can see.

N.B. The string used in the example above has nothing to do with any of the string theories.

Re:Did I miss... (3, Interesting)

MozeeToby (1163751) | more than 2 years ago | (#38644636)

There's a bit more too it than that though, dark matter is no longer just a guess, there is more direct evidence to back it up. To extend your analogy, lets say instead of a single ball hanging you have hundreds of them. A follower of the string theory (pun definitely intended) might make a prediction: some of the balls should have a detectable periodic motion from past disturbances. A thorough survey of the floating balls shows that yes, some of them are swinging like pendulums. It doesn't prove that the balls are hanging from strings, but it means that there's yet another effect that a modified theory of gravity has to take into account, which can be explained very easily by positing the strings. Similarly, there have been a host of indirect observations which show that either there is large amounts of matter that we can't detect or there are dozens and dozens of gravitation effects that are not only not included in current theory but in some cases appear to be mutually exclusive.

Re:Did I miss... (1)

Urkki (668283) | more than 2 years ago | (#38649042)

N.B. The string used in the example above has nothing to do with any of the string theories.

Of course it does. If you do the math right, that string will surely pop out of the sea of String Theories!

Re: Einstein's Telescope (1)

opentunings (851734) | more than 2 years ago | (#38649946)

Einstein's Telescope, by Evalyn Gates, has a very good entry-level discussion of how gravitational lensing of galactic clusters and superclusters is being used to investigate dark matter. She wrote the book so that it'd be accessible to people without a science background. Friends who aren't scientists have read it and learned a lot from it, although they may have had to read some sections two or three times for some of the concepts to sink in.

Re: Einstein's Telescope (1)

davewoods (2450314) | more than 2 years ago | (#38650880)

If gravitational lensing was how we discover black holes, dark matter, etc... Then why are they not lit up like a floodlight? The lensing that should occur around something that is infinitely dense (Such as a black hole) should also be an infinite amount of lensing, therefore curving all the light in the universe around it, to point back at us. That should (According to my small brain) make black holes the brightest point in any universe.

I once drew a diagram of this for some friends, but none of them really understood it. Am I crazy, or do I just not understand fully how gravitational lensing works?

I suppose I could buy the book and find out, but I would rather ask /..

Re: Einstein's Telescope (1)

stevelinton (4044) | more than 2 years ago | (#38651876)

Black holes are not infinitely dense (caveat, volume may not make too much sense for a black hole if you get pedantic). A black hole with the same mass as the sun would (roughly speaking) be a sphere about 4 miles in diameter. Any light actually hitting that sphere would be absorbed. Light just barely missing it will be bent through large angles. Light passing a few miles away will be bent through smaller angles and so on. If you're in the right place, this can make make something behind the black hole look a bit brighter, because more of the light from it gets to you.

Dark matter is not especially dense anywhere (we think). It's spread throughout galaxies and clusters of galaxies like a sort of background haze. Actually, given the relative amounts it's better to say the Universe is full of a web of sheets and filaments of dark matter. At a few places where this is especially dense it has attracted (by gravity) enough normal matter to form a large black hole and its accompanying galaxy.

Re: Einstein's Telescope (1)

opentunings (851734) | more than 2 years ago | (#38651992)

They're not infinitely dense. After all, if they were, they would've already sucked the entire universe in. And density may be the wrong way to think about it.

Instead think of them as having high, but not infinite, gravitational fields due to high (not infinite) quantities of mass. That can be achieved with even a "low" density (i.e. mass per volume) - such as galactic superclusters. The amount of bending that occurs when the light passes one of these strong gravitational fields depends on how strong the gravity field is, and the angle of approach for the light.

A couple of examples:

Light pointing at a black hole's event horizon will be pulled in and disappear. It wouldn't make a U-turn and come back toward us.

Light going near a black hole - but never crossing the event horizon - will be bent. How much bending depends on how close to the event horizon the light comes. Someone more knowledgeable than me can advise whether it could make a U-turn, but I guess that's possible.

On the other hand,

Light pointing toward the center of mass of a galactic cluster could go straight through, assuming no one in that galaxy pulls down a curtain that blocks the way.

Light going near a galactic cluster would be bent, once again proportionally to how close it was to the center of mass of the cluster.

All this is from memory from my bachelor's, which was a long time ago. I apologize in advance if I got something wrong.

hth.

Re:Did I miss... (1)

Black Parrot (19622) | more than 2 years ago | (#38644262)

...the story where they discovered/detected Dark Matter?

Apparently. But if you googlize cluster dark matter

you can start catching up on your reading.

Re:Did I miss... (4, Informative)

lgw (121541) | more than 2 years ago | (#38645756)

In a sense, yes. Dark matter was just one hypothesis among many for galaxy rotation speeds before the CMBR studies.

But the CMBR studies were really the "discovery" of dark matter. At the point where the universe took a snapshot of itself, the distribution of matter was still fairly uniform: alternating areas of slightly-denser and slightly-less-dense matter as sound waves rolled through the universe. By measuring the size and magnitude of these compression waves, one thing that we know - by direct observation - is that only 20% or so of matter was interacting with photons, directly or indirectly.

The universe at that time was dominted by 2 forces, gravity and light pressure. Gravity would compress slightly denser patches until light pressure would cause them to "bounce". We know the force of gravity and light pressure quite precisely, and the mechanics of compression waves, and so we can measure the ratio of mass that interacts with each force. And there's abot 5 times as much mass that reacts to gravity as mass that reacts to light pressure.

So, yeah, direct measurement of dark matter, and the exact measurement (which was 2 or 3 significant digits) was just what the dark matter hypothesis had predicted based on completely unrelated measurements of galaxy rotation speeds. Of course, that gives few clues about the nature of dark matter, but we know most matter in the universe is dark.

Re:Did I miss... (2)

TheTurtlesMoves (1442727) | more than 2 years ago | (#38648946)

You know this is falling on deaf ears don't you. The group think on /. is that dark matter is silly and they have a much better alternative... On no wait... they don't even propose an alternative.

In other news everyone knows that you should only listen to real climatologists.

Re:Did I miss... (1)

tinkerton (199273) | more than 2 years ago | (#38650480)

This bothers me too. When you take a bunch of measurements, whatever their interpretation or value, and you make a nice visualization with them, it all becomes more real.

Re:Did I miss... (1)

hutsell (1228828) | more than 2 years ago | (#38660712)

...the story where they discovered/detected Dark Matter?

If there is to be a story [wikipedia.org] that resulted in the idea of missing matter, it should be attributed to Louise Volders discovery in the late 1950's and Vera Rubin's [wikipedia.org] additional work in the 1970's about the rotational speed of galaxies being faster than the observed mass of the galaxies--contradicting the acurate results observed when applying the same classical mechanics to the rotational speed of our solar system. Vera Rubin argued convincingly that Fritz Zwicky's [wikipedia.org] unrelated work [wikipedia.org] in the 1930's (for accurately calculating missing matter in star clusters) was a viable solution [wikipedia.org] .

universe... y u ... (1)

decora (1710862) | more than 2 years ago | (#38644238)

.... look like demo scene?

Re:universe... y u ... (1)

Deus.1.01 (946808) | more than 2 years ago | (#38645080)

*thumb down* Shitty perlin noise texture, can't belive you needed Pixel Shader 2 hardware for this!

Discovery? (0)

Anonymous Coward | more than 2 years ago | (#38644504)

This in no way constitutes a "discovery". It's something they designed and built. That's like saying the Wright Brothers "discovered" airplanes.

The article itself does not use that word. Why was it put in the summary?

Space-Time mapping indeed (0)

Anonymous Coward | more than 2 years ago | (#38644714)

Accounting for the relative motions of system-objects as complex as galaxies over the course of billions of years of history, the intervening matter which the light is passing through -- but more importantly, the gradation of time between the farthest objects in the field and the nearest (because the volume being studied means there is also a time lag between discrete parts of it)... accounting for all the little things just seems a little bit... far fetched. It's just mind bogglingly complex.

No such thing. (-1, Troll)

cshark (673578) | more than 2 years ago | (#38644868)

Dark energy and dark matter are simply lazy science. The problem is that physics is wrong, or at least incomplete, not that there's some invisible force guiding matter to do strange things that leave only highly questionable evidence behind.

Re:No such thing. (3, Insightful)

Anonymous Coward | more than 2 years ago | (#38645108)

This or something similar seems to come up every time there is discussion of dark matter: "Dark matter was a lazy fix, instead physicists should realise theories were lacking and come up with a new one instead."

Physicists did see physics was incomplete, they did come up with a new theory: dark matter. Dark matter is a new theory and is a way of saying previously physics was incomplete. Physicists also came up with dozens of other theories, but in the end they haven't been doing as well at matching evidence as dark matter.

Way too often people seem to yell that they needed a new theory. But what is really going on, is dark matter is that new theory, and those people just don't like it. That is ok, a lot of people studying or promoting dark matter don't like it either, but still see it as the best of current theories. At least they are trying to look at actual evidence unlike most random armchair scientists on the internet complaining how lazy physicists are, by what amounts to a very lazy and unfounded argument of their own.

Re:No such thing. (2)

Black Parrot (19622) | more than 2 years ago | (#38647554)

This or something similar seems to come up every time there is discussion of dark matter: "Dark matter was a lazy fix, instead physicists should realise theories were lacking and come up with a new one instead."

He's probably posting from the USA, where everyone knows more than the experts.

Re:No such thing. (1)

Urkki (668283) | more than 2 years ago | (#38649048)

Dark energy and dark matter are simply lazy science.
The problem is that physics is wrong, or at least incomplete, not that there's some invisible force guiding matter to do strange things that leave only highly questionable evidence behind.

I think and hope above post was aiming for "funny", not for "troll"... And I certainly hope it was not aiming for "In*" moderation...

Yeah but... (1)

wbr1 (2538558) | more than 2 years ago | (#38645370)

All this extra proof of dark matter is going to prevent me from making the Kessel run in less than 12 parsecs. Damn extra mass.

Re:Yeah but... (1)

opentunings (851734) | more than 2 years ago | (#38649910)

Please. Parsecs are a unit of length, not of time. It'll be 18 parsecs (something upwards of 10^17 meters) until expansion of the universe makes it something else.

Extradimensional matter (0)

Anonymous Coward | more than 2 years ago | (#38646368)

My favorite explanation will continue to be proximity to extra dimensional matter. Much simpler than a new thing - just the same old thing somewhere unexpected.

Re:Extradimensional matter (1)

jbp1 (1179795) | more than 2 years ago | (#38646878)

none of this matters

Stop reading magic and SF into it (1)

dbIII (701233) | more than 2 years ago | (#38647008)

Dark matter is just stuff we can't see directly at the moment mostly becuase it isn't glowing extremely brightly. It's interesting enough without bringing magic into the picture.

Re:Stop reading magic and SF into it (4, Informative)

TheTurtlesMoves (1442727) | more than 2 years ago | (#38649000)

Dark matter does not interact electromagnetically. In other words is *can't* glow, it *can't* absorb light or microwaves or anything. We can see dark stuff, it blocks the CMB and other things. The fact that it does not interact except via gravity also means that is its very diffuse.

Consider a non interacting particle falling from 1 light year out towards the sun. It falls right thought and out the other side and comes to a stand still 1 light year away. It will do this forever since its does not interact with anything that can slow it down. Now consider a say consider about 9x the mass of the sun of these particles, they will always occupy a massive volume and hence be very very diffuse... but in the large scale (galactic) are a large effect with their combined gravity. The are Dark in the sense that they *only* interact via gravity.

Re:Stop reading magic and SF into it (0)

Anonymous Coward | more than 2 years ago | (#38650882)

Would a 4 dimensional object shifted such that only 3 dimensions (2 if you ignore time) are apparent to us reflect light but still have mass?

Re:Stop reading magic and SF into it (0)

Anonymous Coward | more than 2 years ago | (#38653360)

Do they interact with EACH OTHER? Can two of these particles of Dark Matter collide? Can they "clump" together in any way?
Can they be detected locally? Earth has gravity, so some must surely be attracted to it?

Re:Stop reading magic and SF into it (1)

TheTurtlesMoves (1442727) | more than 2 years ago | (#38668168)

They interact mostly only via gravity, even with each other. They are so diffuse or dilute that yes they interact with earth via gravity but not in a currently detectable way, but we have detected it around clusters, in particular the bullet cluster.

Possible model bias (1)

Required Snark (1702878) | more than 2 years ago | (#38646998)

After reading the article, I wonder if there is not an inherent bias in the approach.

What they measured was the deflection of light from galactic sources that were 6 billion light years away. Using a method not described in the article, they were able to measure the amount of gravitational deflection between the light sources and our current observation position. I believe this is a composite measure of gravitational lensing.

I assume that their measurements are accurate. To my understanding, there is also an assumption that a specific portion of the lensing is due to dark matter. This has an appearance of circular logic. One of their assumptions about measuring the effect of dark matter is that they know how much effect dark matter has.

Have I gotten something wrong here? It's always a guessing game using an article intended for the general public when trying to understand scientific findings. Is there anyone out there with meaningful credentials who can clear this up? (I promise that I will ignore all the self appointed "experts" who don't actually have any more knowledge then I do.)

Re:Possible model bias (2)

pantaril (1624521) | more than 2 years ago | (#38648634)

The effect of gravitational lensing can be computed precisly from general theory of relativity. The experimental observation is just verification of it.

One of the reason we introduced dark matter is that some gravitational lenses bended the light more then the theory expected.

But we have also other observations which hints us toward dark matter - unusualy fast rotation of some galaxies and the structure of CMB to name two.

Re:Possible model bias (1)

stevelinton (4044) | more than 2 years ago | (#38651932)

The amount of lensing measures the mass, since mass is what determines gravity.
We don't know how many dark matter particles there are per kilogram, or anything like that, so we only
know the amount in one sense, mass, but that we do get from the lensing.

PBS (1)

Whiteox (919863) | more than 2 years ago | (#38648008)

Pure bullshit. I have actually nothing to back that up, but the whole Dark Matter/Energy thingy sounds to weird to be true.
More likely the physicists made some kind of wrong assumption early on, painted themselves in a corner and this is what they came up with.
Same with the BB theory. They reckon that in the first few nano-secs there were no physical laws? Therefore the BB could do whatever it wanted to (if I'm allowed to add consciousness to that :) Forget rationality or believability.

Re:PBS (2)

f()rK()_Bomb (612162) | more than 2 years ago | (#38648858)

Dark matter doesn't sound even remotely as weird as quantum mechanics. Yet quantum mechanics works incredibly well. You wouldn't have been able to type that comment without us understanding quantum mechanical effects that seem like magic. How uninituitive a theory sounds is a ridiculous judge of whether it is useful or accurate.

Re:PBS (1)

Whiteox (919863) | more than 2 years ago | (#38649038)

Yeah, you're probably right. I think I'll take an aspro and lie down for a while.

Sigh! (0)

Anonymous Coward | more than 2 years ago | (#38648794)

What's the bloody point?

Can we know the temperature now? (1)

marcosdumay (620877) | more than 2 years ago | (#38649922)

Does that map make it possible to calculate the temperature of the dark matter?

As far as I can understand it, if we know the spatial distribution we can infer how much kinetic enery each particle have. But I'm not so sure about that, there may be something I'm overlooking, or the current map may be less precise than the infered values from computer simulations. Do anybody knows the answer?

Re:Can we know the temperature now? (1)

stevelinton (4044) | more than 2 years ago | (#38651954)

We can probably get an idea of the typical velocity spread of the dark matter from the extent to which it is clumped. That's sort of like temperature.

Re:Can we know the temperature now? (1)

physburn (1095481) | more than 2 years ago | (#38656500)

Yes, by measuring the infrared light (oh wait, it doesn't radiate, its dark) we can know the temperature. We can measure the volume, and the mass. To get the temperature we have to notice dark matter holding its up from gravity by pressure and not angular momentum, and also know the masses of the particles in dark matter, then PV=nRT.

---

a href = whoops brooken

Low density plasma (1)

curious.corn (167387) | more than 2 years ago | (#38650416)

But what if the Big Bang never happened [amazon.com] ?

Every time I read about webs of matter spanning across such distances, considering the time required to form these I remember the refreshing perspective put forward by this beautiful little book.

Re:Low density plasma (1)

c6gunner (950153) | more than 2 years ago | (#38654748)

Heh. Was that published by the Flat Earth society? It's about as "refreshing" as the Copernican model of the universe.

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