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Space Science

Most Detailed View of Dark Matter Mapped By Hubble 93

Posted by CmdrTaco
from the final-frontier dept.
astroengine writes "Building on previous studies by the Hubble Space Telescope, new analysis of gravitational lensing data has revealed the most detailed map of the distribution of dark matter yet. The distribution appears as a beautiful ghost-like or ethereal haze and could have serious ramifications on our understanding as to how galaxy clusters form and evolve."
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Most Detailed View of Dark Matter Mapped By Hubble

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    • Re: (Score:2, Informative)

      by Anonymous Coward
      there's a 25sec advertisement on the front of this linked video and then something fairly average that i couldn't see through to the end. which kind of begs the question of whether there is any decent hubble-related comedy out there?
      • Re: (Score:3, Funny)

        by NatasRevol (731260)

        You're just not looking far enough...

        • Re: (Score:3, Informative)

          by bmo (77928)

          With regards to your sig, it's not Apple you should thank, but the fine folks at KDE.org which did all the heavy lifting. Webkit is a modified version of khtml.

          Just sayin'

          --
          BMO

          • Really? ALL the heavy lifting? You might want to look at what Apple has contributed back to the project since 2002. Which is exactly what open source is all about.

            And then let me know when you see a phone that ships with KHTML on it.

      • Re: (Score:2, Informative)

        by I_Human (781026)
        Raises the question! Begging the question is a logical fallacy that has to do with circular logic.
      • by VShael (62735)

        which kind of begs the question of whether there is any decent hubble-related comedy out there?

        Rule 34, coming right u--

        Oh wait, you said hubble-related *comedy*. My bad.

  • Just a question (Score:4, Interesting)

    by Burnhard (1031106) on Tuesday November 16, 2010 @05:31PM (#34248240)
    I'm just asking the question, because I don't have a great deal of knowledge about this, but could an alternative explanation be that our theory of gravity is wrong?
    • by immakiku (777365)
      Yea. The discovery is that, IF our theory of gravity is correct, this is more evidence for the existence of dark matter.
      • by geekoid (135745)

        well, more correctly: If this isn't caused by some property of gravity we have previously not known about, then it's more evidence of dark matter.

        the Theory of gravity is just our understanding of the properties of gravity, and how to measure it. IT sin't wrong. It's provable correct. That doesn't mean more data won't refine our understanding.

        • Re: (Score:3, Informative)

          by BlackPignouf (1017012)

          You have it backwards : nothing in physics is "provable correct".

          A theory is only useful till it is proven incomplete or incorrect. If it holds a very long time, it is only "probably correct" or "correct enough for today".

          The phenomenon that led scientists to develop the concept of dark matter could very well be hints that our theory of gravity is wrong/incomplete.

        • by sjbe (173966)

          It's provable correct.

          No model in physics is "provably correct". That's not how the scientific process works. Scientific hypothesis and their resulting models can never be proven conclusively correct, they can only dis-proven. You can support a model with vast amounts of evidence and be quite confident that it is a useful and accurate model but it only takes a single piece of evidence to establish that the model is wrong. When we say something is a physical law we are basically saying we have a mathematical model for how thi

        • by symbolset (646467)
          It's not actually proof of anything. It is rather a graphical representation of the where the invisible mass would have to be to explain the difference between observed phenomena and our gravity model. Let us consider it not a proof, but a map of our ignorance. A lovely, mysterious misty map - which just happens to be in the form of Cthulu or the Flying Spaghetti monster, by mere coincidence.
      • Re:Just a question (Score:5, Informative)

        by Fluffeh (1273756) on Tuesday November 16, 2010 @06:27PM (#34248958)

        but could an alternative explanation be that our theory of gravity is wrong?

        Yea. The discovery is that, IF our theory of gravity is correct, this is more evidence for the existence of dark matter.

        It is something more along the lines of this:
        We have a good number of formulas and calculations that work properly with the things we can measure - planets, the sun, cars, planes, kitchen scales.
        One of these might be:
        y + 3 = 5
        Nice and simple for this example. Lets say that the "y" here represents gravity and the formula has been proven in every experiment we have done.
        We therefore assume that this calculation is correct and true. BUT when we try to use this calculation when looking at things like galaxies, we seem to find the wrong answer:
        y + 3 = 7.2
        This is clearly not correct, but as we don't want to throw out all the formulas and understanding we have about how things work, we add another variable to the formula like so:
        y + 3 + x = 5
        The "y" still represents gravity, but now we add the "x" which represents something we don't understand and we don't know where it came from. We call it Dark Matter because we can't see it, don't seem to be able to interact with it and have no real idea of what it is - but with this new addition to the formula, the answer once again comes out at what we know (think) to be true. We just now need to find what this x variable is.

        THAT is why finding/understanding Dark Matter (and on that note, Dark Energy) is so important. We know (think we know) the right answers, but our formulas just don't seem to fit so well when applied to certain really, really, really big things (like clusters, superclusters etc). When we find this "x" in the formula, it will once again work perfectly for all our calculations.

        • That is the most elegant explanation of dark matter that I have ever seen or heard.
          • by hitmark (640295)

            Indeed. And it reminds me of how when Einstein first presented his theory of relativity, he had a constant (somewhat like that X) in there to maintain a steady state universe. But soon after new observations favored a expanding universe. So the constant was removed and the theory have been found to be highly accurate since then. So sometimes a X is not added, but removed, because it was put there based on either unreliable data or assumptions by the scientist(s) working on it. Such assumptions show up in va

            • by Fluffeh (1273756)

              That is the most elegant explanation of dark matter that I have ever seen or heard.

              Indeed. And it reminds me of how when Einstein first presented his theory of relativity, he had a constant (somewhat like that X) in there to maintain a steady state universe.

              I know this is off topic, but thank you. Those two comments on my post just made my day! :)

    • Re: (Score:3, Informative)

      by Anonymous Coward

      Dynamical studies of our own galaxy show there's a lot of invisible matter in it. This means that something has to happen with gravitational theory within a region much smaller than the observable universe, at speeds of only a few hundred kilometers per hour. The modified theory also has to conform to the known motions of solar system objects, which are known to extremely high accuracy. These conditions are very hard to meet.

    • Re:Just a question (Score:5, Interesting)

      by Monkeedude1212 (1560403) on Tuesday November 16, 2010 @05:43PM (#34248450) Journal

      I'm just asking the question, because I don't have a great deal of knowledge about this, but could an alternative explanation be that our theory of gravity is wrong?

      Kind of.

      In all other experiments, our understanding of Gravity works just fine. In this one situation however, it does not. Someone proposes the idea of Dark Matter - which fits the bill almost perfectly, as it accounts for what we've seen.

      Alternatively, our understanding is wrong. We don't know how its wrong, or why its wrong, it's just not working. When we look at hundreds of other examples, it works. When we look at this one, it doesn't.

      Is it more plausible to discount our theory based on the 1 case where it doesn't hold up, or assume there is something special about that one case that seperates it from the others.

      Thats why Dark Matter holds some water. But - by all means, it is entirely possible that we don't have it quite right, we could be missing some variables that simply are negligable at a non-cosmic scale.

      • I consider the possibility of an incomplete model of gravity as sort of like newtonian physics. We do all sorts of local observations and the models work fine, but then under 'fantastic' scenarios beyond our ability to observe or reproduce things don't work out right, i.e. extremely fast speeds. Then Einstein provides us with relativity and it provides a factor that makes it all work and even fits cleanly into Newtonian models as a term that is immeasurably small to explain how things appear to act differ

        • Re: (Score:3, Interesting)

          As someone who has studied algebraic geometry quite a bit I find the jump from classical mechanics to relativity to be very beautiful mathematically. The former is still useful as the approximation is close enough for the majority of situations, but it did unwittingly make some assumptions which turned out to be wrong. To me dark matter and dark energy seem like a kludge and I do hope we just unwittingly made some assumptions about the system that turn out to be false. Of course that's just the mathematicia
          • by hitmark (640295)

            I guess we can say that when it comes to the universe, perfection is highly overrated.

      • by mark-t (151149)
        I consider it more probable that our theory of gravity is simply not complete, even though we can only find very limited cases where it doesn't seem to work without the introduction of dark matter. I consider even this admittedly implausible notion to be vastly more likely than the existence of dark matter because using dark matter to explain it is too similar to the conspiracy theory fallacy.
        • Than you surely wouldn't like much of quantum physics either. It'll all seem like a bunch of straw man arguments because you simply have to take their word that what they're saying is happening is actually happening.

      • by k.a.f. (168896)

        Kind of.

        In all other experiments, our understanding of Gravity works just fine. In this one situation however, it does not. Someone proposes the idea of Dark Matter - which fits the bill almost perfectly, as it accounts for what we've seen.

        Alternatively, our understanding is wrong. We don't know how its wrong, or why its wrong, it's just not working. When we look at hundreds of other examples, it works. When we look at this one, it doesn't.

        Is it more plausible to discount our theory based on the 1 case where it doesn't hold up, or assume there is something special about that one case that seperates it from the others.

        Isn't that exactly the same situation as with classical mechanics? It worked really, really well in each every case, except you observed utterly insane speed values. It turned out that it was wrong and you had to include a factor for speed, which happened to be neglegible in all other cases. Now, as fas as I understand it, we have another theory that works really, really, well except when observing astronomical masses and distances. Why shouldn't that require another modification to the formula itself? (I've always had the suspicion that physicists are so keen on detecting new elementary particles to explain gaps in our explanations because you can at least experiment with them, just by upping the energy involved... whereas you can't do experiments on distant galaxies at all, you can just observe them.)

    • by boristdog (133725)

      Well, that will make flying cars a lot easier to build.

    • by Abcd1234 (188840)

      The evidence doesn't support any kind of modified gravity theory at this point. Hit Wikipedia on the Bullet Cluster and related results.

    • by jovius (974690)
      You mean the theory that compares apples and oranges?
    • Re: Just a question (Score:4, Informative)

      by Black Parrot (19622) on Tuesday November 16, 2010 @06:05PM (#34248712)

      I'm just asking the question, because I don't have a great deal of knowledge about this, but could an alternative explanation be that our theory of gravity is wrong?

      Yeah, that or a lot of other things. There was a popular explanation called MOND - Modification of Newtonian Dynamics - but AIUI the evidence shot it down. However, I think there's some MOND variants still out there. But most cosmologists apparently lean toward DM as the best explanation for the available observations.

    • How do we know that general relativity isn't wrong and we're not just "seeing" objects moving faster than the speed of light?
    • Re: (Score:1, Informative)

      by Anonymous Coward

      That's what the MOND [wikipedia.org] theory is all about

    • Short answer: No (Score:5, Informative)

      by Velodra (1443121) on Tuesday November 16, 2010 @06:38PM (#34249072)

      Long answer: Dark matter wasn't invented just because someone saw some anomalous behavior that didn't agree with theory, and said to themselves: "Oh, there has to be something mysterious at work here, we'll call it dark matter.". There are several reasons for believing in dark matter, for example that when measuring gravity we notice gravity coming from directions where we can't see any matter. However, the source of this gravity behaves a lot like matter would. For example we can observe these "invisible gravity sources" being thrown around when two galaxies collide. Because these "invisible gravity sources" acts a lot like matter, except for the fact that we can't see it, it's called dark matter.

      If you're not yet convinced, take a look at this recent blogpost by a professional astrophysicist: http://scienceblogs.com/startswithabang/2010/11/the_simplest_argument_for_dark.php [scienceblogs.com] In this post, he basically explains how we can derive the existence of dark matter from: A) Assuming that the theory of general relativity is valid, B) assuming that the big bang theory is valid, and C) our observations of the cosmic microwave background.

    • Alternate hypothetical:

      Proportional displacement. Gravity is a push, not a pull on matter. Think Casimir Effect on a huge scale.

    • In regards to dark energy....According to a physicist who posted on here a couple of years ago (I'm too lazy to find it and link to it), the expected expansion rate of the universe is based on a solution to Einstein's equations that makes a homogeneity assumption that is now known to be false. Nobody has redone the solution using what is now known to be a more realistic matter distribution, because its hard, and because there's a disconnect between the theoretical and observational physics disciplines. An

    • Re: (Score:2, Informative)

      by symbolset (646467)

      In a word: yes.

      In a bunch of other words: yes, but... The standard model for gravity is used for a number of reasons, first among them that it fits better than the others. It's only off by about a factor of five (working with a universe of 20% normal matter, 80% dark matter). It doesn't devolve into some easily disprovable logical contradictions like most of the others. It's easy to say "yes, but..." It's much harder to propose a theory of gravity that stands up to close inspection of the world's physi

    • by radtea (464814)

      could an alternative explanation be that our theory of gravity is wrong?

      Sure.

      An alternative explanation could also be that elves are holding the galaxy together. Seriously. There are an infinite number of alternative explanations. It's just that some of them are far more plausible than others.

      General relativity is a beautiful theory that has been tested over a ridiculous range of field strengths and range, from orbiting black holes to galaxy clusters to GPS corrections here on Earth.

      The only anomaly we've found so far are at large distance scales, where everything from Newto

    • by Coren22 (1625475)

      Dark Matter isn't the big deal there. Dark Matter is just Matter that doesn't emit energy, it could be just dust out in space. Dark Energy however is the stuff I can't get my head around.

  • Luckily this story is a dupe and we know from the previous one that there's a unicorn in there [slashdot.org].

    Those colors come from the unicorn farting.

    • by mcgrew (92797) * on Tuesday November 16, 2010 @05:43PM (#34248444) Homepage Journal

      TFA is firewalled off, but I found a better FA [nasa.gov] -- straight from NASA's JPL. here [nasa.gov] is a hi-res photo of the "dark matter" lensing.

      • here [nasa.gov] is a hi-res photo of the "dark matter" lensing.

        Thanks, that picture is much better. I can see the dark matter up there in the corner now. ;-)

        But seriously, since we can't see dark matter why would they post a picture of, well, non-dark matter?

        • by Jesus_666 (702802)
          Because the way NASA etc. see the more distant regular matter indicates gravitational lensing while they can't see enough near matter to account for the neccessary mass. IANAAstronomer but I think the distorted galaxies we see in the GP's second image is either an actual image of such lensing or an exaggerated depiction of the same to get the message across.
  • Paste an image of Bender into that dark matter image, and it would look like the episode of Futurama, where Bender meets the God Entity.

    "You were doing well until everyone died."

    So who copied who?

    • by Bozzio (183974) on Tuesday November 16, 2010 @06:00PM (#34248650)

      God: Bender, being God isn't easy. If you do too much, people get dependent on you, and if you do nothing, they lose hope. You have to use a light touch. Like a safecracker, or a
      Bender: Or a guy who burns down a bar for the insurance money!
      God: Yes, if you make it look like an electrical thing. When you do things right, people won't be sure you've done anything at all.

  • by Anonymous Coward on Tuesday November 16, 2010 @05:52PM (#34248558)

    Building this map may result in the shortening [arstechnica.com] of the life span of the universe.

    • Re: (Score:3, Interesting)

      by MozeeToby (1163751)

      I understand the science journalist not understanding, but does the qualified physicist really not understand the difference between an 'observer' in the traditional sense and an observer in the quantum sense? All of the things that we detect with our advanced technology effect things throughout the universe whether we are looking at them or not, the things that they effect are observers. A grain of dust around a star that is given an every so slightly different orbit because of quantum effects is just as

    • by AC-x (735297)

      Understanding of quantum physics fail. That supernova is being "observed" by every single atom that the light from it hits, it doesn't make any difference whether it's a piece of inert rock or a telescope CCD.

  • Allan Sandage (Score:5, Informative)

    by bhodikhan (894485) * on Tuesday November 16, 2010 @06:02PM (#34248672)
    I just learned that Allan Sandage died this weekend. He was a giant among astronomers and did a lot of work with the Hubble. Take some time and learn about him if you care about astronomy http://en.wikipedia.org/wiki/Allan_Sandage [wikipedia.org]
  • It looks like a giant cosmic brain! I think they are onto someone.
  • by Caerdwyn (829058) on Tuesday November 16, 2010 @06:44PM (#34249148) Journal

    It seems that "dark matter" is by far the most common type of matter in the universe; what we call "normal matter" is very much in the minority.

    You realize what this means?

    WE are the "Goatee Universe [wikipedia.org]".

    CmdrTaco... your agonizer, please.

  • Anyone remember 70 column text on an Apple ][ graphics screen? It worked best on a monochrome monitor. I forget the name of the program, but I think it was by the Beagle Bros.

  • This reminds me of something that has puzzled me for a while:

    * The energy of a photon is proportional to its frequency.
    * Photons are redshifted due to the expansion of space.

    So the energy of the photons, e.g. from CMB, is lower. Where did the energy go? It must be connected to expansion somehow, but how? And on a second note, Einsteins famous equation tells us that energy is proportional to mass, so does this influence mass somehow?

    This is probably obvious for you physicists out there, so I thought I'd ask.

    • by CXI (46706)
      I have similar questions that make we wonder about how these types of calculations are made. Like you indicate, are the theories considering all the energy of all wavelengths inside and emanating from a galaxy or a cluster when calculating its mass? We only "see" a tiny fraction of that energy. Are they calling the rest of it dark energy (which to me makes it sound unnecessarily mysterious) instead of just regular energy we can't observe? It should be possible to estimate this energy and how its mass compar
  • Isn't it wonderful how science uncovers the nature of god's universe for all to marvel at?

    This really illustrates intelligent design's truly blasphemous form.

"You know, we've won awards for this crap." -- David Letterman

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