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Thread: Dark Matter Exists!!

  1. #1 Dark Matter Exists!! 
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    This article http://<a href="http://www.sciencene...6/fob1.asp</a> from Science News Online says scienctist have proven dark matter exists. Thier "proof" seems a little sketchy to me. What do you think?


    "As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality. " Albert Einstein

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    Hi Cheeseman,
    Why does the 'proof' seem sketchy?


    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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    I understand the theoretical proof that dark matter exists and understand the theory. This article says the prrof that it exists is in the way the gas is spread out in the picture. I don't see how this relates to dark matter. They say it is like this because the dark matter went right through the galaxy. My understanding of dark matter is that it isn't made of atoms. It just doesn't seem to me that it would appear as a purple gas.

    Cheese
    "As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality. " Albert Einstein

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    In these science articles, the science writers try their best to generalize this stuff for the general public. But they end up leaving a bulk of the science out.

    The scientific article by Clowe can be found here
    http://xxx.lanl.gov/abs/astro-ph/0608407
    but you'll see it is written by astrophysicists, for astrophysicists....

    I haven't read it myself, but I may print it and give it a browse.

    Cheers,
    william
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  6. #5  
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    Howdy,
    So here is my synopsis of the
    http://xxx.lanl.gov/abs/astro-ph/0608407
    article;

    Clowe et al. observed the merging of the cluster named '1E0657-558'. From the rotational curves and observed composition of galaxies, it is inferred that ~1-2% of the galactic mass is made up of stellar components (stars and such), ~5-15% is made up of plasmas (gas), and the rest is 'something' that has mass but is otherwise non-detectable (dark matter). In a collision between clusters, the stars are basically collisionless (i.e., they'll pass by each other and not collide with the exception of a very VERY rare event where two stars may collide), but the gas is not collisionless (it is strongly interacting - the gas particles will collide). This is well established and observed in this system in that the two groups of stars are are seen spatially separated while the gas has for the most part formed a large clump near the center which is not spatially separated as much.

    Okay... 'so what?' one might say.

    Well, what Clowe et al. did was observed the gravitational lensing of more distant objects due to the mass of the merging cluster. You would expect to see the greatest lensing effect where the most mass is located. If there were no dark matter, you'd expect to see the strongest lensing effect where the gas is located as opposed to where the stars are located as that is where the bulk of the mass lies (recall, gas makes up ~5-15% while stars make up ~2% of the galactic mass).

    However, what Clowe et al. observed was that the greatest lensing effect was near the location of the stars! This indicates that there is more mass where the stars are located and not what we'd expect if there were only stars and gas making up the cluster! So whatever the source of this extra mass is, it must be collisionless, and is otherwise non-detectable (else we would see it by other means). By the very nature that it is non-detectable (other than the effect its mass has), and possesses the property of mass, this constitutes the definition of 'dark matter'.

    So here we have direct empirical evidence of the existence of dark matter!

    Furthermore, this throws a wrench in the machinery of competing theories involving modified gravity such as MOND etc.


    And it is with GREAT pleasure to announce to 'Mike NS' that this also decapitates his hypothesis that the source of the dark matter is charged particles/ions as these are not collisionless (and are detectable)! And we all know how much Mike NS likes to rely on 'EMPIRICAL' observations!

    Cheers,
    william
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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    Quote Originally Posted by william
    So here we have direct empirical evidence of the existence of dark matter!
    Not everyone else seems to agree with you.

    Taken from the latest issue of New Scientist:

    Moffat claims that his MOG theory can explain the Bullet cluster without an ounce of dark matter. In MOG, gravity acts as predicted by Newton's inverse square law up to a certain distance from the gravitating mass, after which it gets a little stronger. In the Bullet cluster, the complex arrangement of galaxies and hot gas combines to make gravity strongest in the lobes, so that is where the lensing would be most apparent. Moffat has worked this out for the Bullet cluster using a one-dimensional model, and is now trying to extend this to two dimensions. If he succeeds, it will contradict Clowe's claims that the cluster's lensing can be cited as direct evidence of dark matter.

    Moffat is not the only researcher claiming that a modified gravity theory does away with the need for dark matter. Two months before Clowe made his claim, HongSheng Zhao of the University of St Andrews in the UK and his collaborators applied a theory of modified gravity called TeVeS to the Bullet cluster. In TeVeS, an extra field kicks in when the gravitational field falls below a threshold strength, which is equivalent to the gravity of a sheet of paper. TeVeS boosts gravity in places such as the outskirts of galaxies and has an effect on lensing. "We noticed that even where there is no matter there is [bending] of light," Zhao says (www.arxiv.org/astro-ph/0606216).

    Unlike MOG, TeVeS requires the presence of heavy neutrinos to explain lensing, though Zhao does not see this as a problem. "We know neutrinos exist and we know they have mass," he says. Measurements of the neutrino's mass put it at between 0.02 and 2.2 electronvolts; Zhao assumes it to be 2 electronvolts.

    So are fast-moving "hot" neutrinos a good substitute for the dark matter that Clowe's team claims to have found? "I'm guessing that when they really look at it, they will need much more dark matter," Clowe says.

    Zhao says that his team is about to publish fuller details of their explanation of the Bullet cluster, which will show no dark matter is needed. "This bullet did not hurt TeVeS that much," he says. "It placed no additional constraints on modified gravity theories because it didn't add anything we didn't already know."

    From issue 2568 of New Scientist magazine, 09 September 2006, page 12
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  8. #7  
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    Another beautiful example of multple theories....

    Which is why ol' billco advises you all NOT to accept new theories but just 'note' them.
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  9. #8  
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    Hi 'Its All Relative',
    Hmmm...
    I shall keep my eye on this....

    wm
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  10. #9 Particles 
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    I do not ever see WIMPs or MACHOs mentioned in this article. Studying collisions that happened a 100 million years ago and using gravitational lensing is important in discovering dark matter but it does not actually PROVE that it exists.

    Does anyone know if anyone has tried to calculate a theoretical and actual value for the amount of gravity, exerted by a relatively close celestial body, and then compare them to see if there is a significant difference in gravitational forces? I am not sure how the "actual" would be calculated but using a star that is close to that massive body to calculate it could be another method of getting those figures.
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  11. #10  
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    Quote Originally Posted by william
    And it is with GREAT pleasure to announce to 'Mike NS' that this also decapitates his hypothesis that the source of the dark matter is charged particles/ions as these are not collisionless (and are detectable)! And we all know how much Mike NS likes to rely on 'EMPIRICAL' observations
    Willy, you should know that the establishment elite likes to make things as complicated as possible to eliminate the general public views about their science.

    This proof of 'dark matter' has been done previosly by the Chandra(?) x-ray telesecope when it 'observed' x-rays in the central regions of clusters to prove that there was unseen matter present in these cluster regions.

    So why do these scientists claim that 'they' have the proof?
    Obviously, they do not read all the other research that is done.

    Vera Rubins research on spiral galaxies is another proof that the spiral velocities do not conform to the 'virial theorum' of diminishing velocities according to the gravity distances from the souces.
    So this DM is present around the spiral galaxies and in the central regions of the galactic clusters.

    NS
    Real science is objective, not subjective
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  12. #11  
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    finally!!! I KNEW THAT DARK MATTER EXIST
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  13. #12  
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    is there anything anyone knows about what dark matter is composed of???
    No man was ever wise by chance.
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  14. #13  
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    There are probably a lot of things we can't see, Dark matter is one of them
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  15. #14  
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    This is an intresting article.
    I know what dark matter and dark energy are but I'm still a little sketchy on what MACHOS and WIMPS are. Can someon care to explain to me?
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  16. #15  
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    Quote Originally Posted by Time Master
    This is an intresting article.
    I know what dark matter and dark energy are but I'm still a little sketchy on what MACHOS and WIMPS are. Can someon care to explain to me?
    You know? I thought the search for it was still on?
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  17. #16  
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    Quote Originally Posted by Time Master
    This is an intresting article.
    I know what dark matter and dark energy are but I'm still a little sketchy on what MACHOS and WIMPS are. Can someon care to explain to me?
    Cute names aye?

    Well, do a search on wikipedia.org and you'll get a good explanation, but in brief, MACHO stands for "massive compact halo objects" and WIMP stands for "weakly interacting massive particles".

    The "halo" refers to the halo of a galaxy, and "weakly interacting" basically means "a bitch to detect" and also that they may only interact with other particles/matter via the gravitational and weak forces.

    These MACHOs and WIMPs may contribute to the solution to the dark matter problem.

    Again, I recommend wikipedia for more details on this.

    Cheers,
    william
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  18. #17  
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    Well I mean what are the theories of MACHOS and WIMPS???
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  19. #18  
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    thanks for the info and the explinations

    Just to let you know and stuff, Wikipedia isn't a great resource because people could make up information there. I'm just giving you a hint.

    Anyways thanks.
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  20. #19  
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    Wiki's ok for a quick ref, and people mostly try to put accurate stuff on there but I always try to check it from a 'reliable' source, NASA, or some uni, I treat all other 'science' sites with some reservation.
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