Slashdot Mirror

← Back to Stories (view on slashdot.org)

Missing Matter... Still Missing

Posted by timothy on from the hey-it's-zero dept.

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!"

3 of 370 comments (clear)

  1. I "detect" a grant money detector at work... by erick99 · · Score: 5, Insightful
    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

    --
    http://www.busyweather.com/
  2. Not completely zero by kyoko21 · · Score: 5, Insightful

    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.

  3. The case for dark matter (abridged) by jpflip · · Score: 5, Insightful

    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...