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Science Technology

Missing Matter... Still Missing 370

squidfrog writes "Nature.com, PhysicsWeb, and the BBC all report on the latest results from the Cryogenic Dark Matter Search. 'The most powerful search yet for the Universe's missing matter has come up empty handed, contradicting an earlier study that claimed to have seen new particles.' 'A favoured theory is that the dark matter consists of Wimps (weakly interacting massive particles) about a thousand times more massive than a proton, one of the particles found in an atom's nucleus... on the rare occasions a Wimp strikes an ordinary atom, the effect should be noticeable.' 'Writing in the Physical Review Letters, the team says that while a detection has yet to occur, there is now a better idea of how much dark matter must exist.' They 'hope to improve the sensitivity of the experiment by another factor of 20 over the next few years.' What's 20 times 0? And don't tell me zero!"
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Missing Matter... Still Missing

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  • by erick99 ( 743982 ) * <homerun@gmail.com> on Wednesday May 05, 2004 @05:08PM (#9067534)
    That the sensor has never detected something doesn't tell you that it's working or not working - or am I am missing something here?

    ....Researchers from the Cryogenic Dark Matter Search II (CDMSII) say they are pleased with their first results, which show that their detector is working.

    However since it started running in November last year, the detector has not seen a single WIMP.

    Then they decide to make a more sensitive detector so that they can "not" detect at an even higher level?

    Physicists with the CDMSII experiment say they will now add another 24 crystals to the detector, increasing its sensitivity tenfold.

    Okay, maybe I am being a bit silly, but, I still don't see how they can know the detector is working. I don't even know how the WIMP can make the thing "ring" once it, itself, is subject to the 1/10 degree above absolute Zero conditions. And then, somehow, with no data, they can extrapolate more accurately how much dark matter is in the universe. Well, they would say the lack of WIMPS is data but I'm not buying it. Enough /. folks have worked in research to know better than to buy into those kinds of statistical games (you can prove almost anything with non-parametric statistics).

    Happy Trails!

    Erick

    • by Xandu ( 99419 ) * <matt@@@truch...net> on Wednesday May 05, 2004 @05:13PM (#9067588) Homepage Journal
      No, they don't extrapolate how much dark matter is in the universe. They say, if dark matter is of the 'WIMP' variety, we know that the mass and cross section (aka how easily they interact with other particles, namely the germainium nuclei in their detectors) of of these WIMPS is not in a certain range.
      • by Anonymous Coward

        because there isn't any.

        The astronomers have been seeing something they do not understand, and so they assume it is dark matter. The same result could be gotten by a decaying speed of light.

        Unfortunately, that requires another rewrite of physics, from the ground up. However, looking for something understood gets more grant money.

        • by Profane MuthaFucka ( 574406 ) <busheatskok@gmail.com> on Wednesday May 05, 2004 @05:41PM (#9067826) Homepage Journal
          Nice with the conspiracy theory, AC. Too bad that you're wrong. The first tip-off that there's dark matter is the rotational speed of galaxies. Your decaying speed of light won't explain that.

          • by gewalker ( 57809 ) <Gary.Walker@nOsPaM.AstraDigital.com> on Wednesday May 05, 2004 @06:59PM (#9068534)
            OK, so you don't like decaying lightspeed as an explanation (and I agree, though it could explain some other issues and is given serious consideration by real scientists).

            There is a thery that there is little or no dark matter, and the difference is accounted for by the assumption that the inverse square law for gravity fails at large distances -- based on a theoretical model of graviton particle exchanges that would not follow inverse square -- This just happens to match the observed data pretty well without need for dark matter.

            A second alternative is combines light speed decay along with big change in assumed age of universe, so that spiral galaxies look the way they do because they are quite young compared to the standard model.

            I'll bet there are other non-darm matter models that are explain observed data as well as the dark matter model too.
            • No, I like all those theories, including decaying lightspeed as explanations equally well. That is to say, I have no preference for any of them, except the one that will eventually have the most evidence. Decaying lightspeed is off to a spectacularly bad start...

              But, I don't think that scientists are staying away from that theory because they don't want to rewrite the Physics textbooks.

              Look at the last guy who rewrite the Physics textbooks. He's got one of the most recognizable faces in the world. Everyon
            • by TMB ( 70166 ) on Wednesday May 05, 2004 @11:57PM (#9070487)
              There seems to be a common sense here that all of the evidence for dark matter could be equivalently explained by changing the force law.

              However, that isn't true. One unique test of dark matter is that it is dynamical; it can move. And there are a bunch of tests that have started to be made that show evidence for dynamical dark matter:

              - in order to explain rotation curves without dark matter, models like MOND require force laws that would make the derived "shape" of the dark matter halo spherical at large radius. You can test this by looking at the shapes of clusters using X-ray emitting gas (eg. Buote et al. 2002, ApJ, 577, 183; Lee & Suto 2003, ApJ, 585, 151; Lee & Suto 2004, ApJ, 601, 599) or the Sunyaev-Zeldovich effect (LS03,LS04). You can also look at the shapes of dark matter halos around galaxies using weak gravitational lensing (Hoekstra et al. 2004, ApJ, 606, 67). So far all of the tests indicate that dark matter halos are not spherical, but flattened exactly as predicted by cold dark matter.

              - the bars in barred spiral galaxies should slow down and disperse quickly in a spherical static halo potential, like you'd get from modifying the force law, but they can be maintained for long periods of time if they can exchange angular momentum with the dark matter (Athanassoula 2002, ApJ, 569, L83; Valenzuela & Klypin 2003, MNRAS, 234, 459).

              - there's a weak gravitational lensing observation of a group that is falling into a cluster, where the mass of the infalling group is offset from the light - the gas is moving slower because it's interacting with the cluster gas, while the dark matter has kept moving (Clowe et al. 2004, ApJ, 604, 596).

              [TMB]
            • I like the idea that, once we develop nanotechnology a goal should be to begin to develop Dyson [freshmeat.net] Spheres, [wikipedia.org] so we can capture 100% of each star's output and save it in batteries to be rationed later. We can make the universe last longer that way (a year or two ago it was determined that we won't contract: we were sentenced to a heat death. So we might as well conserve as much as possible; think big.

              So if that's a goal of ours, perhaps it's a goal of another race's. And perhaps they got a head start on

      • by arminw ( 717974 ) on Wednesday May 05, 2004 @06:24PM (#9068222)
        The theory of dark matter is based on the assumption that the basic properties of the Universe have never changed over time. If the intrinsic properties of space itself HAVE changed significantly, then there is no need to postulate such a thing as dark matter. Scientists are very reluctant to accept new data that shakes their preconceived pet ideas to their foundations. It took over 200 years after Roemer first measured a finite light speed, for the majority of scientists to accept the fact that light did not get instantaneously from point A to point B, as was the belief for centuries. In the same way, the majority of scientists today refuse to even consider the idea that some very fundamental "constants" may have changed dramatically since the beginning of time. For example, the cause for the "Red Shift" of distant star light is traditionally attributed to the Doppler effect, and in light of that INTERPRETATION of the cause for an observed fact, (the shifted light) all sorts of cosmological observations are very difficult to explain. Humans (including scientists) like to assume that certain things stay the same for all time, but that is a fervently desired wish based on faith, not observed fact. It seems that in the physical universe, there is nothing as constant as change! AAW
        • Scientist assume things stay the same, unless they have some evidence to the contrary. This is just Occam's Razor (Entities should not be multiplied beyond necessity).

          If you don't have evidence the constants change, and they are called constants becuase they have always been observed to be the same, don't start assuming they have been without evidence. It isn't about faith, you assume it has not changed based on the observed facts that nobody has seen it change. If there is evidence of change, you rethink

    • A possible explanation:

      The detector can measure interactions between protons and strong interactions (collisions with photons or what have you). But is not sensitive enough to detect interaction with WIMPs.
    • by confused one ( 671304 ) on Wednesday May 05, 2004 @05:18PM (#9067629)
      when we built a detector, we put in a mechanism for testing and calibration. So, we could apply artificial pulses to verify everything was working properly; and, because we knew the amplitude of the pulses we applied, we could calibrate the instrumentation.

      I'm sure this is part of thier validation that the detector is working.

    • by Vellmont ( 569020 ) on Wednesday May 05, 2004 @05:21PM (#9067656) Homepage

      That the sensor has never detected something doesn't tell you that it's working or not working - or am I am missing something here?


      Yah, you're missing the scientific paper. This is a one page write-up written by a journalist. The one page write up doesn't describe how they know the detector works, but I'm sure they have _some_ means of testing that it does. Blame the article, but at this point you can't really accuse anyone of doing shoddy science for grant money.
      • by Uber Banker ( 655221 ) on Wednesday May 05, 2004 @05:32PM (#9067747)
        The one page write up doesn't describe how they know the detector works, but I'm sure they have _some_ means of testing that it does.

        Sure they do... the system has a green light on. If the red light were on it would be on standby and no light may mean there is no power, or the light is broken. But as long s the green light is on they know it's working.

        Surely everyone knows that. Now please increase my grant.
        • by Tackhead ( 54550 ) on Wednesday May 05, 2004 @05:53PM (#9067908)
          > Sure they do... the system has a green light on. If the red light were on it would be on standby and no light may mean there is no power, or the light is broken. But as long s the green light is on they know it's working.
          >
          >Surely everyone knows that. Now please increase my grant

          You forgot the third possibility. Suppose the power indicator LED is orange: it's hard to tell if we're in a superposition of states or merely oscillating very rapidly.

          Or I just want a high-speed digital camera for Christmas.

    • by Anonymous Coward
      The lack of WIMPs is data. If they reported "zero" WIMP events, the actual report would have been within some error, zero +/- some amount. Using that, you can set an upper limit to the actual amount of WIMP activity; you can say that the WIMP level must be below a certain amount (if the data is to be trusted).

      You can tell a piece of equipment is working if it sees things you expect and if it behaves the way you expect it to from the theory. Getting "nothing" is not no data. You're being way too cynical
    • Working detector? (Score:5, Informative)

      by Anonymous Coward on Wednesday May 05, 2004 @06:04PM (#9067995)
      CDMS detectors detect heat (vibrational energy) which is deposited in their superconductors when any kind of particle flies in and hits them. The localized heat causes the hit region to go non-superconducting, and as a result they can measure a reduced current as would be expected from a normal conductor.

      All sorts of particles are constantly flying in and creating signals in their detectors. This is how they know that it is working. The trick is to veto the known signals by surrounding their superconductors with other detectors which can detect ordinary matter, but not dark matter. Therefore if the other detectors tell you that some ordinary matter entered the superconductor, then you would reject that signal.

      In the context of a dark matter flux (flow) measurement, greater sensitivity means a greater ability to detect low fluxes. So far they've measured 0 dark matter particles in a few years of running. This means that the flux is less than 1 particle per detector area per few years (also per detector efficiency).

      Suppose the numerical value of their measurement is that the flux is less than 100/m^2/year (just to use round numbers). Then, if the true flux given to us by nature is 1/m^2/year, then they would have to run for another ~100 years in order to detect 1 dark matter event. On the other hand, if they make their detector 100 times larger, then they can detect the 1 dark matter event with only 1 more year of running. This is what they mean by increased sensitivity by building a larger detector. Meanwhile, in the time taken to see the 1 dark matter event, they probably reject several trillion false events which are caused by ordinary matter particles.

      A. Physicist

    • That the sensor has never detected something doesn't tell you that it's working or not working - or am I am missing something here?

      Yes, you're missing something. :-)

      The statement "the sensor has never detected something" is patently false. Figure 1 of the paper [lanl.gov] shows all of their detections - and there are lots of them! WIMPs aren't the only things that interact with Germanium. ;-) However, once you exclude all of the events which are consistent with being cosmic-ray produced interactions with the shie

    • You're missing some physics, allow me to fill you in:

      Particle detectors of these kinds detect all weakly interacting particles. Weakly interacting means that it will generally go strait through matter without "touching" it at all. Thermal equilibrium (temperature) is a non-issue in that weakly interacting particles don't contact enough with "normal" matter to ever come to thermal equilibrium. They cool it down so that stray vibrations don't give a false positive reading. A good example of a weakly inter
  • by Xandu ( 99419 ) * <matt@@@truch...net> on Wednesday May 05, 2004 @05:09PM (#9067547) Homepage Journal
    For much more info, head to the CDMS homepage [berkeley.edu], which includes links to preprints of the mentioned Phys. Rev. Letters article (note, the paper hasn't been published yet), as well as other (published and unpublished) papers, as well as general info.
  • by R2.0 ( 532027 ) on Wednesday May 05, 2004 @05:12PM (#9067573)
    Anyone in high school knows that if a wimp hits anything, no one notices. If someone did notice, he wouldn't be a wimp.
  • Wimp?! (Score:5, Funny)

    by Kjuib ( 584451 ) on Wednesday May 05, 2004 @05:12PM (#9067580) Homepage Journal
    If a Wimp is about a thousand times more massive than a proton - what does that make a proton? a Wuss? or a Nerd?
  • by Nom du Keyboard ( 633989 ) on Wednesday May 05, 2004 @05:13PM (#9067583)
    The real dark matter in the universe is the massive SCO intellectual property rights that no one else has yet seen.
    • Thanks (Score:2, Funny)

      by Anonymous Coward
      I was wondering how this story was going to be tied into SCO or Microsoft.
  • Gravity is wrong (Score:4, Interesting)

    by Ckwop ( 707653 ) * <Simon.Johnson@gmail.com> on Wednesday May 05, 2004 @05:13PM (#9067584) Homepage

    I think the answer to the dark matter problem and the quantum theory of gravity is one in the same. Our description of gravity is wrong. It has recently been discovered [physicsweb.org] that dark matter is 'missing' from three elliptic galaxies. One would think that on the scale of something as big as a galaxy and with WIMPs being so massive that you ought to detect some quite major effect..

    Add that to the fact that the universe's acceleration is getting quicker rather than slowing down and I think we have a strong case for our description of gravity being incorrect.

    Simon.

    • I think the answer to the dark matter problem and the quantum theory of gravity is one in the same.

      I agree.

      A friend and I read The Elegant Universe and both came to the same conclusion - "dark matter" doesn't exist. The gravitational effects are due to gravitons entering our universe either from another brane, or from our own brane folded over in a higher dimension.

      For those who haven't read it, according to string theory all particles except the graviton are bound to their "home" brane. Gravitons may m
    • I think the answer to the dark matter problem and the quantum theory of gravity is one in the same.

      Why, exactly?

      Our description of gravity is wrong.

      Assuming that you're referring to general relativity, then no, you're absolutely incorrect. GR is perhaps the most well-tested physical theory yet developed and, as such, you can't say that it's "wrong". It plainly isn't once you remain within its field of reference.

      It has recently been discovered that dark matter is 'missing' from three ell
      • by Ckwop ( 707653 ) *

        GR is perhaps the most well-tested physical theory yet developed and, as such, you can't say that it's "wrong". It plainly isn't once you remain within its field of reference.

        You miss the point.. I'm citing the effects as evidence the theory is incorrect.

        Simon.

        • No, you made a statement claiming that our "description of gravity is wrong." Trust me on this, our description of gravity in terms of general relativity is quite obviously *not* wrong. If you think it is, give me one example of an experimentally observed physical process which violates general relativity. Just one.
    • Well, if it is... (Score:5, Informative)

      by Pi_0's don't shower ( 741216 ) <ethan@@@isp...northwestern...edu> on Wednesday May 05, 2004 @05:29PM (#9067723) Homepage Journal
      I hate to say it, but CDMS II (this experiment) was SUPPOSED to not find WIMPs in this range. There was an experiment called DAMA which had found a modulation in their noise consistent with their being WIMP dark matter, and they claimed detection. The whole purpose of this press release is to say that DAMA's claimed detection is now *ruled out*.

      As for the description of gravity being incorrect, I hate to tell you this, but general relativity solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else. Gravitational lensing, bending of light by masses, binary pulsar decay, Mercury's perihelion precession... etc. etc... NO other theory of gravity explains any of this, unless it starts with General Relativity and expands on it.

      As for your proof that there is no dark matter because it's there in small quantities in three (out of ~250,000) galaxies, give me a break. Normal matter clumps and interacts with itself, so it's quite reasonable to expect we will get some cases where we have more normal matter than dark matter.

      On average, though, Dark Matter is well known (see my comment history for examples) to exist in about 6-7 times the abundance of normal matter.

      Sorry if this is a rant, but talk about throwing the baby out with the bath water...
      • by websensei ( 84861 )


        general relativity solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else

        while I agree that the case for GR is pretty compelling, this same line of thought is why it took so long for ptolemy's ridiculous (in hindsight) orbits to be debunked. "but they solve so many problems that cannot be solved otherwise that it's preposterous to consider anything else"... ditto for many other "givens" (sun circles the earth, etc) in history. my point

      • by blincoln ( 592401 )
        As for the description of gravity being incorrect, I hate to tell you this, but general relativity solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else.

        Newton's physics accurately describe a lot of things - and are still very useful - but they are *not* a correct description of the way the universe really works.

        General Relativity is the same way. It accurately describes many things, but eventually it will be superceded by a more complete
    • You can always tweak gravity to give ANY answer you want, BUT whenever you do it tends to break other things or look really strange. Case in point, if we change gravity to account for the missing mass we "see"(we notice that things don't rotate as they should given the light we see) then you can break other systems, like black holes, or the acceleration of the universe. Which brings us to your statement about the accleration of the universe: Einstein's theories predict solutions with an accelerating expa
    • Re:Gravity is wrong (Score:2, Informative)

      by Abcd1234 ( 188840 )
      Uhh, did you read that article? That article only showed that three elliptical galaxies didn't have as much dark matter in them as expected. It did this by showing that these galaxies rotated in the exact fashion they should *in the absence of dark matter*. So, this study does not deny the existence of dark matter. It only poses the question "why do some galaxies have dark matter and others don't?"

      As for cosmic acceleration, there's no particular reason to believe that that phenomenon has anything at a
    • Re:Gravity is wrong (Score:2, Interesting)

      by citdude ( 671496 )
      The fact that dark matter is "missing" in eliptical galaxies means nothing. The amount of gravitational mass in young (or close) spiral galaxies is much higher than the visible mass that makes up the stars and the dust clouds around the galaxy. At some point, whenever my project gets approved, I will conduct similar research on older, farther away spiral galaxies that may give us some insight as to how spiral galaxies and the dark matter in them evolved together.
      In other words, it a bit early to say that
  • Maybe - (Score:3, Funny)

    by Black Parrot ( 19622 ) on Wednesday May 05, 2004 @05:15PM (#9067604)


    What if software bugs emit gravitons? Wouldn't that explain the apparent extra mass in the universe?

  • The Answer (Score:4, Funny)

    by theraccoon ( 592935 ) * on Wednesday May 05, 2004 @05:15PM (#9067607) Journal
    What's 20 times 0? And don't tell me zero!

    Zero.

    Opps. I meant, seven.

    • Zero.
      Opps. I meant, seven.

      How about 42?

    • Re:The Answer (Score:5, Interesting)

      by infinite9 ( 319274 ) on Wednesday May 05, 2004 @05:42PM (#9067835)
      Opps. I meant, seven.

      IBM may agree with you! Try this code on AIX:

      #include"stdio.h"

      int x,y,z;

      int main() {

      x=1;

      y=0;

      z=x/y;
      printf("%d", z);

      }

      On most unix implementations you get floating point exception since the divide operator takes floating point operands. On AIX, when the denominator is cast to a float, it's a zero approximation rather than the official floating point zero. The result is that instead of a core dump, you get... 15.
    • Do you work for Enron? If not, want a job?

      We have an excellent "culture" for a person possessing your skillsets.

  • Forgive my ignorance (Score:2, Interesting)

    by jm92956n ( 758515 )
    A favoured theory is that the dark matter consists of Wimps (weakly interacting massive particles) about a thousand times more massive than a proton

    My training in physics is quite elementary, but I was led to believe the proton is relatively massive on the atomic level, especially when compared to an electron. How could a wimp be so large and yet unnoticed?
    • by Mr. Bad Example ( 31092 ) on Wednesday May 05, 2004 @05:30PM (#9067734) Homepage
      > How could a wimp be so large and yet unnoticed?

      You just described my entire high school career.
    • How could a wimp be so large and yet unnoticed?

      Proton-proton interactions are governed in a large part by their electromagnetic interaction; the fields produced by each couple to each other. WIMPs, on the other hand, interact with other types of particles only through gravitational interactions. Now, by construction, the gravitational interaction is many, many times weaker than other interactions so it becomes more difficult to detect them.
    • by stox ( 131684 ) on Wednesday May 05, 2004 @05:34PM (#9067767) Homepage
      The Top quark was only discovered in 1995, and it is around 200 times the size of a proton.
    • by jmtpi ( 17834 )
      > > A favoured theory is that the dark matter
      > > consists of Wimps (weakly interacting massive
      > > particles) about a thousand times more massive
      > > than a proton

      > My training in physics is quite elementary, but
      > I was led to believe the proton is relatively
      > massive on the atomic level, especially when
      > compared to an electron. How could a wimp be so
      > large and yet unnoticed?

      The key is the "weakly interacting" in the name. At the microscopic level, these pa

    • Part of the issue is that some of these particles are extremely short-lived. Combined with their weak interactions, it is hard to determine that they exist. For example, the Higgs Boson is theorized to be the most massive. It has yet to be actually observed.
    • by radtea ( 464814 ) on Wednesday May 05, 2004 @06:00PM (#9067957)
      Size, mass and interaction strength are unrelated. For example, imagine trying to detect clouds by throwing rocks at them. Clouds are big, but they only interact with rocks very weakly.

      --Tom
  • The Cryogenic Dark Matter Search uses equipment at the bottom of a Minnesota mine to filter out all interference.

    The underground observatory is some 1,000m beneath the surface. It is only from such an isolated place that scientists believe they have a chance of catching their quarry.

    Excellent location choice! Even if they don't find any dark matter, at that depth they at least have a chance at locating the remnants of ex-Gov. Jesse Ventura's political career.

    • The observatory is at one of the lowest levels of the Soudan Mine in Northern Minnesota. It's open for tours, including a mine tram ride to an ore extraction site, and a quick glimpse of part of the CDMS labs at the bottom of the mine. I wish they offered more extensive tours of the labs, and maybe they do, but not on the weekend I was there.

      If you're in the Ely area, it's definitely worth a quick side trip to see the mine.

  • Horn, funnel, whatever shape it was. Maybe the dark matter is really the "nothingness" that exists beyond the shape of the universe.

    • IAKAP, but I do have access to a dictionary, and the universe, as defined, is EVERYTHING. Nothing exists outside the universe, by definition.

      From dictionary.com:

      universe (yn-vûrs)
      n.

      1. All matter and energy, including the earth, the galaxies, and the contents of intergalactic space, regarded as a whole.
        1. The earth together with all its inhabitants and created things.
        2. The human race.
      2. The sphere or realm in which something exists or takes place.

      If WIMPS were outside the universe, I'd thin

  • Dark Matter (Score:3, Interesting)

    by dustmote ( 572761 ) <fleck55&hotmail,com> on Wednesday May 05, 2004 @05:17PM (#9067623) Homepage Journal
    I don't know, even though science has a track record of proving (at the time) absurd claims, dark matter just seems.....silly. (I typed darl matter here as a typo, that would have led to yet another SCO thread I'm sure) What are the other theories about the missing mass? I'd like to shop around and see if I can find one a little more reasonable-sounding. :)
  • Massive wimps, huh? Never knew there was dark matter at my high school ...
  • Missing Matter (Score:4, Insightful)

    by Detritus ( 11846 ) on Wednesday May 05, 2004 @05:18PM (#9067627) Homepage
    I thought the usual rule in science was, if your theory conflicts with your observations, there is something wrong with your theory. Maybe there is no "missing matter", just an incomplete or defective theory of gravity.
    • Re:Missing Matter (Score:3, Insightful)

      by k98sven ( 324383 )
      Well, for one: It's the only theory of gravity we've got really. If you can come up with one from as few (or fewer) postulates, which fits as well into the what we already know, and make the same predictions, I'm certain people will listen.

      It's not as if everyone here has 'decided' that dark matter simply exists. There are plenty of people at work with alternative explanations.

      However: If the theory is correct, and dark matter does exist, how are you supposed to find it without looking?
    • Re:Missing Matter (Score:2, Interesting)

      by Anonymous Coward
      That's what dark matter/dark energy always sounds like at first glance. However, it's not quite so simple, and cosmologists are not quite so stupid.

      Actually, the "dark matter" hypothesis agrees with practically every observation you can think of: x-rays from galaxy clusters, the rate of formation of large-scale structure, the formation of deuterium/helium/lithium in the Big Bag, the cosmic microwave background, gravitational lensing by large clusters, AND (of course) the familiar argument that 'the outer

  • by nicodaemos ( 454358 ) on Wednesday May 05, 2004 @05:18PM (#9067628) Homepage Journal
    Missing Matter ... still missing

    Did anyone check under the cushions on the couch?
  • 20 times 0... (Score:2, Insightful)

    by aaribaud ( 585182 )
    ... would be the efficiency of the experiment (assuming it would fail the same way as this one), not the sensitivity of the equipment used.
  • by fiannaFailMan ( 702447 ) on Wednesday May 05, 2004 @05:20PM (#9067648) Journal
    All they have to do is reverse the polarity of the anti-proton injectors in the warp core, re-route the resulting subspace pulse through the plasma conduits, synchronise the comm-system to transmit the frequency of the subspace distortion field to the deflector dish and emit a sub-tachyon particle scan over a wide area. That'd surely reveal what they're looking for!
  • by Animus Howard ( 643891 ) on Wednesday May 05, 2004 @05:24PM (#9067681)
    Dunno. But 20 divided by zero is &)%*$%*_))[LOST CARRIER]
    • by Barryke ( 772876 )
      It took me a while but i found it, its halfway down.
      2writer: You freak! you actualy looked up the episode # cq webpage?

      [snip] Bart: But I have 52 million shares! What's 52 million times zero? AND DON'T TELL ME IT'S ZERO! [snap]
  • ObBart (Score:2, Funny)

    by sharkey ( 16670 )
    1:00 - Still just a potato.
    2:00 - "
    3:00 - "
  • by kyoko21 ( 198413 ) on Wednesday May 05, 2004 @05:29PM (#9067720)
    I am not a physics/math expert, but assuming that dark matter does exist, it only proves that the equipment currently used has a sensitivity that is approaching zero, but not zero. But anyone who has seen a graph of an asymptope, it is not very promising especially if you push x approaching infinity. Even if you were to multiply x by 20, while you are out to infinity, by not knowning where exactly they are relative to the origin on the graph, a factor of 20 may not be all that significant... :-/

    But at least they are still trying... and trying... and trying some more.
  • by Shurhaian ( 743684 ) <veritas@@@cogeco...ca> on Wednesday May 05, 2004 @05:29PM (#9067727) Journal
    Wow, what a suprise, hyperbole in the Slashdot summary.

    The fact that the detector hasn't found the thing it was designed to detect doesn't mean that it has a zero sensitivity or that the hypothesis is bogus(you can't readily prove a negative except by proving a contradictory positive), just that, in the finite time it's been running, it hasn't been sensitive ENOUGH to detect anything. 20 x 0.00000000000000000(you get the picture)001 is still an improvement, and may be enough to make progress.
  • Unusual science (Score:5, Interesting)

    by Control Group ( 105494 ) * on Wednesday May 05, 2004 @05:32PM (#9067753) Homepage
    I freely admit to not being a physicist, cosmologist, or astronomer. However: when Einstein formulated general relativity, he discovered that his model demanded either an expanding or a contracting universe. Since he "knew" the universe to be static, he introduced the cosmological constant to "fix" the model. Later, of course, when Hubble (I think?) demonstrated the universe to be expanding, the cosmological constant was dropped, and Einstein referred to it as his greatest mistake.

    This research, though, seems to be taking the same route: rather than questioning the model, they continue a so-far fruitless search for the "missing matter." If the model demands something the existence of which we are completely unable to verify, shouldn't we be questioning the model? Doesn't the very fact that there's all this "missing" matter indicate that perhaps our understanding is flawed?

    Or am I just displaying rampant ignorance of the current state of physics and cosmology by asking this?

    • Re:Unusual science (Score:4, Interesting)

      by rblum ( 211213 ) on Wednesday May 05, 2004 @05:52PM (#9067901)
      You might want to read up on VSL theories. They do make sense of the cosmological constant, and they solve several other problems. Homogeneity amongst them, which, AFAIK, is a rather big deal to cosmologists :)

      It's not proven or anything, and it competes with inflation theory. But it looks like it might be experimentally verifiable, as opposed to inflation.
    • Re:Unusual science (Score:3, Interesting)

      by stand ( 126023 )

      This research, though, seems to be taking the same route: rather than questioning the model, they continue a so-far fruitless search for the "missing matter." If the model demands something the existence of which we are completely unable to verify, shouldn't we be questioning the model? Doesn't the very fact that there's all this "missing" matter indicate that perhaps our understanding is flawed?

      We know the missing matter is there because we can verify it. One example of how we know is that we can measu

  • Sorry, all this just sounds like wayyyyy to much Star Trek. Or too much herb...
  • by eljasbo ( 671696 ) * on Wednesday May 05, 2004 @05:34PM (#9067769)
    I am not a physicist, but I think the dark matter is a totally false idea fabricated to explain things we cannot explain with our current perception and knowledge of physics. It is similar to the aether idea that was fabricated to explain Maxwell's equations on a cosmological scale so they did not collide with Newton's theories. The more we figured out about the properties of the aether, the more magnificent it needed to be. Einstein realized that Newton's common sense laws were actually different than we perceived and rewrote physics by determining that the existance of the aether was incorrect, and what we observed was caused by relativity. I think the same holds true with dark matter. What we are observing is the effect of gravity traversing dimensions other than the four we normally encounter. The other eletromagnetic forces do not cross into these dimensions, but gravity does. This would also explain why gravity seems so much less powerful than the electromagnetic forces, it is spread out through multiple dimensions. We know there is a force somewhere and lots of it, but can see no evidence of it because it is beyond our perception. We only see the effect of gravity particles (gravitons) that are traversing into our dimension from the others. Perhaps there really is the aether all around us, and it is more spectacular than ever imagined. This aether would be multidimensional and be everywhere. We cannot see or cross the dimensions we are in into another one. But they are there on the other side of the aether. The gravitons pass right through it and that is what we observe.
  • by MoxCamel ( 20484 ) * on Wednesday May 05, 2004 @05:41PM (#9067827)
    What's 20 times 0? And don't tell me zero!

    I'd just like to be the first to say that it's an honor, Mister President, to count you amongst the Slashdot readership.

  • Wow (Score:2, Interesting)

    I find this quote interesting...

    [Dark matter] is thought to come from a variety of heavy particles that rarely interact with regular matter and can pass through conventional objects unseen.

    That sounds like another phenomena of a less scientific nature... ghosts! In some belief systems spirits or souls are more massive or dense then normal matter as well.

    If this were true, I would suggest the reason that this experiment didn't find any "dark matter" is because there wasn't any in the vicinity, becaus
  • But wait a minute (Score:3, Interesting)

    by Billly Gates ( 198444 ) on Wednesday May 05, 2004 @05:44PM (#9067854) Journal
    Only according to some sources 1/4th of the matter in the universe is dark matter. How can it not be undectable then if its this massive particle 1000x more dense then a proton?

    I personally think its a lack of understand of space/time that creates the illusion of dark matter. The string theory could also prove that bends in the time/space contium alot like threades of lint in carpet exist. When light passes through them they amplify when they reach the bend.

    There is alot of stuff in the 4th, 5th, and other dimensions that we do not know about.

  • the search for "ether." [drphysics.com]

    Lemme know when someone figures out what is really going on.
  • by Jagasian ( 129329 ) on Wednesday May 05, 2004 @06:04PM (#9068003)
    Maybe there is no dark matter. Science only describe predicted observations. Reality doesn't necessarily obey the laws of science. Belief in such is similar to belief in a deity. Maybe the universe is governed by the laws of science, but then again, maybe it is governed by such-n-such a deity.

    So if a theory isn't cutting it, then create a new model of whatever observation that you are trying to describe. It seems silly to try to fit nature to the theory, and not the theory to nature.
  • BBC Got it Wrong (Score:5, Informative)

    by Roger W Moore ( 538166 ) on Wednesday May 05, 2004 @06:31PM (#9068285) Journal
    Just in case you got as far as the BBC article they got the dark matter percentage way off. It's actually about 23% that is dark matter. The 70% number is for dark energy which is a completely different beast which nobody yet really understands (at least to my knowledge) since it is actually gravitationally repulsive and is what is thought to be causing the Universe's expansion to accelerate.

    The numbers come from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) which measured fluctuations in the Cosmic Microwave background (afterglow of the Big Bang). There's a good review of their results in hep-ph/0308251 accessible from the LANL preprint server [lanl.gov] though it might be a bit technical for most.

  • by ifwm ( 687373 ) on Wednesday May 05, 2004 @06:34PM (#9068313) Journal
    but my bullshit detector has been pinged since this dark matter nonsense started. I have yet to see a single piece of credible evidence that shows the dark matter hypothesis is anything more than a hastily concocted attempt to explain why some physicists theories don't jive with experimental results. Just admit that you don't know why, rather than attempting to pass off a clearly inferior piece of intellectual flotsam as the next great thing. Show me some evidence, ANY evidence, and then you'll get my money.
    • by jpflip ( 670957 ) on Wednesday May 05, 2004 @06:56PM (#9068509)
      The thing that makes the dark matter explanation compelling is that it makes so many different observations work. We don't have to fine tune things so much - it all fits together. Here are some examples.

      1. Galaxy rotation curves - you can watch the orbits of stars in a galaxy to determine the distribution of matter in the galaxy. This shows that there is a lot more matter than can be accounted for by the stars and that it is distributed differently.

      2. Gravitational lensing - you can see how light is bent by distant galaxies to map out their matter distributions. Again, there's a lot more matter than the stars can account for, distributed differently.

      3. The cosmic microwave background - this one is complicated, but the idea is that you look at the "afterglow" of the big bang, released when the universe was as dense and hot as the surface of a star. We understand the physics of matter at these temperatures very well, and by studying the signatures of vibrations in this hot plasma, we can measure the properties of the early universe. We can see from this that the universe contains a lot of matter, and that the large majority of this matter is not composed of ordinary atoms (hard to explain, but fairly rock solid).

      4. Light elements - Most of the universe's helium, deuterium, lithium and beryllium were created in the early universe, not in stars (the conditions aren't right). Again, the physics is very well-understood, nothing fancy. By studying the relative ratios of these elements, we can figure out the properties of the plasma in which they were formed (a bit hotter and you get less deuterium, the temperature falls too quick and you get less helium, stuff like that). Again, the universe has a lot of matter, and most of it isn't made of atoms.

      5. Structure formation - if you work things out on supercomputers, you find that (if the universe containst only ordinary matter) the universe hasn't been around long enough to form the galaxies and galaxy superclusters that we see. Adding dark matter to the mix makes galaxies form faster - just enough faster!

      And the beautiful thing is that all of these different arguments give essentially the same answer for the amount of dark matter and its basic behavior. You can tweak your theories to explain some of these observations, but no one has been able to explain them all - except with dark matter, the SIMPLEST explanation!!

      Before you say something is "clearly inferior intellectual flotsam", learn what you're talking about...
  • Well (Score:3, Funny)

    by Lord Kano ( 13027 ) on Wednesday May 05, 2004 @07:22PM (#9068765) Homepage Journal
    The most powerful search yet for the Universe's missing matter has come up empty handed,

    No kidding? I guess that's why it's referred to as MISSING matter!
  • by Phragmen-Lindelof ( 246056 ) on Wednesday May 05, 2004 @09:41PM (#9069744)
    The assumption that "dark matter" exists is a common one based on (some of) the observations of the universe. Dark matter does not explain the increased rate of expansion of the universe at great distances. This requires another assumption - "dark energy" (or a positive "cosmological constant").
    There are versions [sciamdigital.com] of M-theory which do not require one or both of these. There is also a theory [arxiv.org], as yet unpublished (since it upsets physics journal editors), which eliminates the "clock hypothesis" and accounts for inflation and accelerated expansion. (One has to be careful to take each new (and old) theory in physics with a big grain of salt.)

    Just as the biological community "sold" the human genome project as THE ANSWER (one gene = one protein) and is trying to sell the protein folding problem as the NEW ANSWER (and it is an important problem), the (majority of) the (astro)physics community is trying to sell "dark" (matter or energy). "Dark" may well exist. I believe that it is important to allow a variety of views in the physics community to be heard (i.e. published) and let scientists design experiments to test various hypotheses. The "popular" theory may (or may not) correspond to observations.
  • Socks (Score:3, Funny)

    by shadowbearer ( 554144 ) on Wednesday May 05, 2004 @10:04PM (#9069874) Homepage Journal

    The should be concentrating on where that missing sock always goes when you do laundry at a laundromat. Find that, they'll probably find the missing matter. At least the research should be cheaper :)

    SB

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