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Dark matter - one mystery solved

  1. Oct 6, 2005 #1
    Hello All,
    Here is an article we have just published on a very interesting development concerning dark matter:
    http://www.isracast.com/tech_news/061005_tech.htm

    Comment are most welcome.

    Iddo
     
  2. jcsd
  3. Oct 6, 2005 #2

    Labguy

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    Not enough detail on the observational data.
     
  4. Oct 6, 2005 #3

    turbo

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    That's a pretty lame statement. The flat rotation curves of spirals do not "prove" the existence of dark matter. Modeling the behavior of stars in an elliptical galaxy cannot "prove" the existence of dark matter, either. Such exercises can show us how inaccurate our GR model of gravity is on large scales, but they do not demonstrate to us the nature of the inaccuracies.
     
  5. Oct 7, 2005 #4

    Chronos

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    Perhaps we could allow for other interpretations, turbo. I think it's too early to give up on them. Labguy suggests other observations suggesting other conclusions. Would you allow that possibility?
     
  6. Oct 7, 2005 #5
    Turbo - it's funny that you point this out to me of all people since I should be the most sensitive to this kind of wording - being a philosopher of science that is.

    Of course Avishai did not give any formal proof - you have to understand that headlines are supposed to be somewhat sensational - I don't believe I actually said anything like that in the article itself.

    Writing popular science is always managing between writing to the GENERAL audience and staying accurate to the facts.

    b.t.w. If I had to guess I would say one of two options regarding dark matter is right - either our theories are wrong (and we don't need dark matter) or there is "dark matter" but it is pretty ordinary stuff like black holes, dust, dead stars etc'.
     
  7. Oct 7, 2005 #6

    Garth

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    Concur on the second option.

    Garth
     
  8. Oct 7, 2005 #7

    Labguy

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    Me too as to dark matter. Dark energy is another whole story, but I have seen a lot of posts that seem to think that they are one in the same (DM & DE). NOT!..:biggrin:
     
  9. Oct 7, 2005 #8

    wolram

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    I have heard that dark matter is a preponderance of black birds .
     
  10. Oct 7, 2005 #9

    Danger

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    If that's true, then they must be evenly distributed throughout the universe. Since their wings won't work in vacuum, they can't fly toward or away from each other.
     
  11. Oct 8, 2005 #10

    Chronos

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    Perhaps there are other options, would you not agree? Can we really rule out non-interacting [dark] matter given the preponderance of evidence? It's not an aesthetically appealing proposition, but, the universe is an even weirder place than we imagine without it.
     
  12. Oct 8, 2005 #11

    Garth

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    Sure, if we can add one epicycle - that of non-interacting DM to explain large structure formation in the time available to the high-z LCDM model then why not add another - some interacting DM - to remove the density cusps at galactic cores that the non-interacting kind must produce?

    Garth
     
  13. Oct 8, 2005 #12
    1 + 1 + 1 = 3 votes

    Emboldening is mine

    Me too.
     
  14. Oct 8, 2005 #13
    Turbo-1 here. First off, I apologize for the change in my user name. I moved recently and had to change ISP's and I neglected to edit my user profile accordingly. Apparently, it was time to update my password, and I never got the notification (my fault entirely!). I have tried to get my password reset for the past couple of days to no avail, so I have created an alter-ego until this can be sorted out. Temporarily I am Turbot - an unattractive creature with an optimistic outlook - always looking up! :rofl:

    I am always open to alternate interpretations, which is why I get into trouble with the concordance cosmologists. I ask only that we regard observation as real and require theory to agree with reality. It is not sufficient that theory can be patched to conform to observation after the fact, a real theory must be able to make predictions.
     
  15. Oct 8, 2005 #14

    Chronos

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    I entirely agree turbo. The observational evidence must be accepted at face value. Explaining it is a separate issue. None of the existing explanations can [or should] be deemed beyond reproach. Patching existing theories to accomodate new data is, however, is second nature to scientists and totally appropriate. If the underlying theory is wrong, it will eventually collapse under it's own weight. Sooner or later it will be boxed into an inescapable corner. This is precisely how formerly revered theories were exposed as imposters. This naturally takes a lot of effort. Not only are we slow to accept new ideas, we stubbornly cling to them once accepted. While an inefficient process, I can't imagine a more effective way to do science properly.

    Everybody should be suspicious of invoking 'invisible' entities, like dark matter. The problem is the dang stuff just won't go away on its own. It keeps popping up all over the place. Alternative explanations [e.g., MOND], fully deserve investigation. But it takes time for them to gain traction, and that's a young persons game. Veteran researchers have too much time invested in their work to nurse a new idea to maturity. It's really no different than wagering on horses. Most of the money goes down on the favorites. Dark horses must win a few races before they strart drawing attention. I am, however, convinced compelling evidence, one way or the other, will be found within the next decade. If DM is wrong, I'm supremely confident a smoking gun will be found. For the time being, it still deserves the benefit of the doubt.
     
  16. Oct 8, 2005 #15
    Unfortunately, the DM concept is not going away, despite NO evidence that it is real. It does not deserve the benefit of the doubt. It either is real, testable and falsifiable (along with the model that requirees it) or it is bogus.
     
  17. Oct 9, 2005 #16
    Personally I suspect that the current Theory of Gravitational Activity is somewhat Short on the "Completeness" that is required to adress all of the Observations, currently known, something, or somethings are still missing, perhaps.

    LD
    .. .. .. Hops off .. .. .. Looking for Turtle's return, he should be back, Soon
     
  18. Oct 9, 2005 #17
    So you're the sleepy hare that lost to the tortoise! :rolleyes:

    Yes, there is something missing in GR. If you can borrow a copy of "The Philosophy of Vacuum" (it is very expensive at $120 US!), read Einstein's article "On the Ether". In it he explains that GR is a good approximation, but that it is incomplete because it is a mathematical model only and does not properly address the mechanics of the dynamical ether, nor does it help explain the EM phenomena produced by the interaction of matter and energy with that ether. By 1924 he had concluded that the ether is conditioned by the matter embedded in it and that it was not absolute, but varied in its properties in accordance with the distribution of masses within it. He had also concluded that the ether confers both inertia and gravitation on embedded masses. His GR ether was by then both polarizable and interactive - if he could have envisioned then that the vacuum field effects resulting from polarization could give rise to self-attraction of the ether as well, I think our theory of gravity would today be much different. The simple inverse-square relationship that seems to work so well with simple n-body systems would have to give way to a more complex model in which self-attraction of dense gravitational fields must be taken into account.
     
  19. Oct 9, 2005 #18
    what an Æther? who'da thunk it?

    Uh-oh I think you've broken a rule, or two, there-here, {@ PF} so go, please and read this threads' link.

    The Thread it's in these forums, and it links to this Link @ math. edu. ucr. edu

    {S p a c e d to de-link it}

    But, By the way, I would sort-of agree with the rest of what you said, happy though, that it was you who said it, not me. o:)

    LD
    Yes, I am joking around, just a little .. .. .. .. but not for all of it
     
  20. Oct 9, 2005 #19
    It seems pertinent at times to point out that Einstein did not regard the 1916 version of GR as finished. Many mainstream cosmologists would be surprised to know how he was modifying GR in the years after its initial publication. In 1924 when he published "On the Ether" he was 45 years old and may have been at the height of his talents. He had come to believe that gravitation and inertia are emergent forces arising from the interaction of mass with the GR ether. Gravitation in this version of GR is not a fundamental force. This view was echoed by Sakharov 4 decades later although he specifically identified the field as the quantum vacuum and not as an aether or ether - terms more likely to be misunderstood, as people might equate them with the "luminiferous aether" and other incarnations that had fallen out of favor.
     
    Last edited by a moderator: Oct 9, 2005
  21. Oct 9, 2005 #20
    Good answer, had read of several items in things like my University physics book about how he had been sorta pushed into the concluding expression "No preffered frame of reference" as it couldn't be found, at that time.

    As for there being something there, I would agree, just what though, is what is at question, nowadays.

    Did you read the "GR is not an Ǽther theory" at that second link?

    I suspect it had been slightly modified since the last time I had read it, I had sent the writer an e-mail after I had read it, pointed out one or two things that are, now, known about Space/time.....and that one Space/time Such a flawed description
     
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