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Canada Space Science

Vast Web of Dark Matter Mapped 86

Posted by Soulskill
from the here-there-be-dragons dept.
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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Vast Web of Dark Matter Mapped

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  • What are the odds... (Score:4, Interesting)

    by rshol (746340) on Monday January 09, 2012 @06:08PM (#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: (Score:3, Insightful)

      by na1led (1030470)
      How do they even know it's matter? It could be a sea of graviton waves or something.
      • by stevelinton (4044) <sal@dcs.st-and.ac.uk> on Monday January 09, 2012 @06:23PM (#38644102) Homepage

        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: (Score:2, Interesting)

          by Anonymous Coward

          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.

          Do

          • Re: (Score:2, Interesting)

            by Anonymous Coward

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

          • by ae1294 (1547521) on Monday January 09, 2012 @07:20PM (#38644890) Journal

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

            • 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!
              • by ae1294 (1547521)

                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.

          • by Anonymous Coward

            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

          • by Cyberax (705495)

            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.

      • 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.
    • by stevelinton (4044) <sal@dcs.st-and.ac.uk> on Monday January 09, 2012 @06:21PM (#38644084) Homepage

      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: (Score:2, Interesting)

        by mark-t (151149)

        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 a

        • by MozeeToby (1163751) on Monday January 09, 2012 @06:51PM (#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.

          • by mark-t (151149)

            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.

          • by Anonymous Coward

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

        • by jc42 (318812)

          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 bi

      • by Hentes (2461350)

        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 dist

    • by Livius (318358)

      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.

    • by Black Parrot (19622) on Tuesday January 10, 2012 @12:08AM (#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.

    • by Urkki (668283)

      ...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

  • .... look like demo scene?

    • by Deus.1.01 (946808)

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

  • 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.
    • 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.
  • 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 als

    • by pantaril (1624521)

      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.

    • by stevelinton (4044)

      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.

  • by Whiteox (919863)

    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.

    • 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.
      • by Whiteox (919863)

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

  • 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?

    • by stevelinton (4044)

      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.

    • by physburn (1095481)
      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

  • 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.

    • by c6gunner (950153)

      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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