Has Dark Matter's Mystery Finally Been Solved?

[iddo]

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

 

[Labguy]

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

Not enough detail on the observational data.

 

[turbo]

...an Israeli cosmologist showed that the existing model of elliptical galaxies was wrong, proving that dark matter was there all along.

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.

 

[Chronos]

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?

 

[iddo]

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'.

 

[Garth]

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'.

Concur on the second option.

Garth

 

[Labguy]

Concur on the second option.

Garth

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!..

 

[wolram]

I have heard that dark matter is a preponderance of black birds .

 

[Danger]

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.

 

[Chronos]

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'.

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.

 

[Garth]

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.

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

 

[Lapin Dormant]

1 + 1 + 1 = 3 votes

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'.

Emboldening is mine

Concur on the second option.

Me too.

 

[Turbot]

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?

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!

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.

 

[Chronos]

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 accommodate 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.

 

[Turbot]

Patching existing theories to accommodate 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.

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. ...For the time being, it still deserves the benefit of the doubt.

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.

 

[Lapin Dormant]

Personally I suspect that the current Theory of Gravitational Activity is somewhat Short on the "Completeness" that is required to address 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 [/color]

 

[Turbot]

Personally I suspect that the current Theory of Gravitational Activity is somewhat Short on the "Completeness" that is required to address 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 [/color]

So you're the sleepy hare that lost to the tortoise!

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.

 

[Lapin Dormant]

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[/url] @ math. edu. ucr. edu[/color]

{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.

LD
Yes, I am joking around, just a little .. .. .. .. but not for all of it[/color]

 

[Turbot]

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

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.

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.

 

[Lapin Dormant]

Good answer, had read of several items in things like my University physics book about how he had been sort of 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

 

[Turbot]

Good answer, had read of several items in things like my University physics book about how he had been sort of 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.

An important question, indeed.

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

Yes, I have read that page and probably most of the others on that site. I have to take exception to his statement:

Albert Einstein, in his essay On the Aether (1924), made some injudicious comments to the effect that relativity theory could be said to ascribe physical properties to spacetime itself, and in that sense, to involve a kind of "aether". He clearly did not mean the kind of "aether" which had been envisioned by Maxwell and others in the nineteenth century, but his remarks have been seized upon ever since, by various cranks and other ill-informed persons, as evidence that "gtr is an aether theory".

Einstein did not make what anyone should construe as casual or injudicious comments anywhere in that paper. (Please find it in print and read it - it is not available on-line anywhere to my knowledge.) Quite to the contrary, his entire article was devoted to arguments showing that GR requires the existence of a real ether with real physical characteristics. After discussing experimental tests of quantum physics, such as Compton scattering and Bose's derivation of the Planck formula, he concludes:

But even if the these possibilities should mature into genuine theories, we will not be able do do without the ether in theoretical physics, i.e. a continuum which is equipped with physical properties; for the general theory of relativity, whose basic points of view physicists surely will always maintain, excludes distant action. But every contiguous action theory presumes continuous fields, and therefore also the existence of an ether.

Bolding mine, of course.

Please get a copy of "The Philosophy of Vacuum" (Saunders & Brown ed.) and read "On the Ether" by Einstein. You will see that contrary to the statement on Baez's pseudo-science page, Einstein did not make an incautious remark that is seized on and misinterpreted by those of us who are too misguided to see the truth. Instead, he spent the entire essay laying out the history of the concept of the ether (and the motivations for its various incarnations) and spelling out in very clear and unambiguous language why GR demands the existence of a real dynamical ether with physical properties.

 

[Garth]

The question about the aether is not whether or not the space-time continuum with its "continuous fields" has physical properties, but whether or not it can be used to select out a preferred inertial frame of reference.

GR requires that it cannot be so used, and as such is not compatible with Mach's Principle.

The aether that is relegated to the historical dustbin by Baez and others is that in which a preferred frame of reference may be defined.

Given that GR is a testable scientific theory the question of whether or not preferred frames may actually be defined is still open; GR may yet be falsified, say by the Gravity Probe B experiment now in its data analysis phase. We wait and see!

Garth

 

[Lapin Dormant]

but sadly, we are getting off of the thread.

Wasn't there already measurements by two satellites (lagos?) that demonstrated that there was a growing separation between them, over time, indicating a Drag in the medium, just above the Earth?

I seem to recall having seen that one, grav b will simply be a Confirmation of that, if successfull.

I would agree with Turbot that there is a "Need" for one, just what, as Space-time is an erroneous, and misleading {assumptive} conclusion.

 

[Garth]

Wasn't there already measurements by two satellites (lagos?) that demonstrated that there was a growing separation between them, over time, indicating a Drag in the medium, just above the Earth?

I seem to recall having seen that one, grav b will simply be a Confirmation of that, if successfull.

I would agree with Turbot that there is a "Need" for one, just what, as Space-time is an erroneous, and misleading {assumptive} conclusion.

This discussion may well be right on thread, as the DM detection is by gravitational effects therefore the interpretation of those effects is dependent on the gravitational theory used to analyse them.
GP-B is a significantly different experiment to that of the LAGEOS satellites. They measured the geodesic orbits of two 'test' particles and determined that there was a frame-dragging, gravitomagnetic, effect on their orbits as predicted by GR. GP-B measured the actual precession of four physical gyroscopes to measure both the gravitomagnetic precession and also the geodetic one (caused by the gyros 'leaning into the slope' of space-time curvature). A couple of theories, Moffat's Nonsymmetric Gravitational Theory and my Self Creation Cosmology predict the same gravitomagnetic precession as GR but different geodetic precessions; in the case of SCC 5/6 that of GR or 5.5120 arcseconds/yr.
Furthermore SCC identifies DM as largely baryonic.
The case is still wide open!

Garth

 

[Turbot]

Furthermore SCC identifies DM as largely baryonic.
The case is still wide open!

Garth

In this paper on how small-angle CMB anisotropies constrain BB models, (Kindly supplied by Space Tiger in another thread) Holtzman seems to leave hope open for only one model - one with about equal parts of massive neutrinos and non-baryonic DM. The other variants that he modeled resulted in temperature differentials in the CMB anisotropies that were too large. This included baryon-dominated models.

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1989ApJS...71...1H&data_type=PDF_HIGH&type=PRINTER&filetype=.pdf

 

[Garth]

Holtzman seems to leave hope open for only one model - one with about equal parts of massive neutrinos and non-baryonic DM.

Yes that was an important paper, however we now know that neutrinos are not significantly massive and account for less than 1% closure density, so Holtzman will have to think again.
His analysis is theory (GR) dependent but SCC does not follow the Friedmann scale factor expansion, so the analysis will have to be carried out using a strictly linear expansion.

Garth

 

[SpaceTiger]

In this paper on how small-angle CMB anisotropies constrain BB models, (Kindly supplied by Space Tiger in another thread) Holtzman seems to leave hope open for only one model - one with about equal parts of massive neutrinos and non-baryonic DM. The other variants that he modeled resulted in temperature differentials in the CMB anisotropies that were too large. This included baryon-dominated models.

Turbo, that paper is 15 years old. Although I'll grant that it's newer than most of the papers you cite, it's still woefully out of date for this discussion. I gave you the reference because you asked for pre-COBE predictions of the CMB anisotropies.

 

[Turbot]

Turbo, that paper is 15 years old. Although I'll grant that it's newer than most of the papers you cite, it's still woefully out of date for this discussion. I gave you the reference because you asked for pre-COBE predictions of the CMB anisotropies.

I understand that, ST. You understood that I was asking for predictions of the nature of the CMB prior to high-resolution mapping of the CMB and you supplied some. The reason I asked is so you would give me the best, most predictive papers you knew of, so I could see if there were in fact accurate predictions of what we came to understand about the CMB.

Its possible (especially if your theory has lots of adjustable parameters) to supply almost any given level of accuracy of explanation for an observed phenomenon after it has been observed. It is quite another to predict it ahead of time. The reason that I quoted the old paper is that you supplied it, and although presumably it has been superseded by newer studies that have been better informed (by better observations) the fundamentals (model-dependent constraints) are likely somewhat valid and they have not been fine-tuned after the fact in light of better observations.

I have been digging up more modern papers, too, especially those dealing with quadropole polarization, so I'll have a better grasp of what I'm reading when the results of WMAP2 are released.

http://arxiv.org/abs/astro-ph/9706147

 

[SpaceTiger]

Its possible (especially if your theory has lots of adjustable parameters) to supply almost any given level of accuracy of explanation for an observed phenomenon after it has been observed. It is quite another to predict it ahead of time. The reason that I quoted the old paper is that you supplied it, and although presumably it has been superseded by newer studies that have been better informed (by better observations) the fundamentals (model-dependent constraints) are likely somewhat valid and they have not been fine-tuned after the fact in light of better observations.

If you acknowledge that the paper is not the most accurate because of updated observations, why did you post it in this thread? If you wish to challenge the accuracy of the prediction that was provided by CDM, it would seem more sensible to do it in the thread in which the topic is being discussed. The Holtzman paper did have the fundamentals correct, but they didn't even consider some of the things that are now taken as standard (including dark energy). Given what they knew, their analysis is consistent with the modern picture.

 

[Chronos]

Turbo, I am curious. What alternative model do you have in mind that predicted the CMB monopoles?