Has Dark Matter's Mystery Finally Been Solved?

AI Thread Summary
Recent discussions on dark matter highlight ongoing debates about its existence and nature. Some participants argue that current models, particularly regarding elliptical galaxies, may not accurately prove dark matter's presence, suggesting alternative interpretations should be considered. Others propose that dark matter could be composed of ordinary materials like black holes or dust, while also acknowledging the limitations of existing gravitational theories. The conversation emphasizes the need for rigorous scientific scrutiny and the potential for new evidence to emerge in the coming years. Ultimately, the mystery surrounding dark matter remains unresolved, with various theories still under investigation.
iddo
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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
 
Astronomy news on Phys.org
iddo said:
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.
 
...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.
 
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 - 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'.
 
iddo said:
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
 
Garth said:
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!..:biggrin:
 
I have heard that dark matter is a preponderance of black birds .
 
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.
 
  • #10
iddo said:
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.
 
  • #11
Chronos said:
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
 
  • #12
1 + 1 + 1 = 3 votes

iddo said:
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

Garth said:
Concur on the second option.

Me too.
 
  • #13
Chronos said:
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! :smile:

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.
 
  • #14
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.
 
  • #15
Chronos said:
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.
 
  • #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 [/color]
 
  • #17
Lapin Dormant said:
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 [/color]
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.
 
  • #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[/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. o:)

LD
Yes, I am joking around, just a little .. .. .. .. but not for all of it[/color]
 
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  • #19
Lapin Dormant said:
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. o:)
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.
 
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  • #20
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
 
  • #21
Lapin Dormant said:
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.

Lapin Dormant said:
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:
Baez page said:
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:
Einstein in "On the Ether" said:
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.
 
  • #22
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
 
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  • #23
but sadly, we are getting off of the thread.

Wasn't there allready 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.
 
  • #24
Lapin Dormant said:
Wasn't there allready 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
 
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  • #25
Garth said:
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
 
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  • #26
Turbot said:
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
 
  • #27
Turbot said:
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.
 
  • #28
SpaceTiger said:
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
 
  • #29
Turbot said:
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.
 
  • #30
Turbo, I am curious. What alternative model do you have in mind that predicted the CMB monopoles?
 
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  • #31
Chronos said:
Turbo, I am curious. What alternative model do you have in mind that predicted the CMB monopoles?
Well, first off, perfect black bodies are the ultimate absorbers and emitters of EM. This is basic optics and basic thermodynamics. If you have spent any time outside on a clear Maine night in February (especially if you forgot your hat!), you will understand very quickly that the night sky (less the shielding effects of the atmosphere) is a wonderful blackbody absorber/emitter. Once you get above the sheilding effect of the atmosphere, "empty" space should be a nearly perfect blackbody absorber/emittor, apart from the embedded emitting masses, like galaxies, clusters, etc.

It is very easy to understand how the temperature of "empty" space is a pure blackbody curve. It is a little tougher to understand why EM emitted, absorbed, and re-emitted throughout the entire recomination era of the BB can appear to us today as a perfect blackbody curve. This is not an insignificant question, and I welcome explanations.

If we believe that the temperature of space is 2.7K, (as predicted pretty closely by any number of astronomers and physicists that adhered to the steady state model), we should be willing to believe that doppler effects due to the motions of the Earth through the Universe will produce anisotropies in the CMB. The largest anisotropy will be a dipole (not a monopole, Chronos:smile:) resulting from the dominant gross movement of our galaxy or group. The remaining anisotropies will be more and more difficult to quantify, as errors in the process of subtracting the major ones multiply, but I firmly believe that they will ultimately be proven to arise from the complex movements of our probes in relation to local space.

If the small angle anisotropies (let's say even as large as 1 degree, to be exceedingly generous, but to remove all doubt) mapped by WMAP2 do not agree with those of WMAP1, the CMP is local, not cosmological. There is no way the casually-disconnected regions of the universe can have conspired to change together over the period of a year.
 
  • #32
Turbot said:
Well, first off, perfect black bodies are the ultimate absorbers and emitters of EM. This is basic optics and basic thermodynamics.

Blackbodies are a simplifying assumption and a limiting case for thermodynamics. There are many things in the universe that are not in thermodynamic equilibrium, and therefore do not emit as blackbodies.


If you have spent any time outside on a clear Maine night in February (especially if you forgot your hat!), you will understand very quickly that the night sky (less the shielding effects of the atmosphere) is a wonderful blackbody absorber/emitter.

No, I don't understand. The spectrum of the "night sky" is not that of a blackbody. I certainly don't understand how you can ascertain that the vacuum absorbs and emits by spending time outside on a "clear Maine night".


It is very easy to understand how the temperature of "empty" space is a pure blackbody curve. It is a little tougher to understand why EM emitted, absorbed, and re-emitted throughout the entire recomination era of the BB can appear to us today as a perfect blackbody curve. This is not an insignificant question, and I welcome explanations.

Light being absorbed and re-emitted many times is exactly the condition needed to form a blackbody spectrum. You can't form it from nothing, the absorbers/emitters must reach a statistical equilibrium before a blackbody curve can be produced.



If we believe that the temperature of space is 2.7K, (as predicted pretty closely by any number of astronomers and physicists that adhered to the steady state model), we should be willing to believe that doppler effects due to the motions of the Earth through the Universe will produce anisotropies in the CMB. The largest anisotropy will be a dipole (not a monopole, Chronos:smile:) resulting from the dominant gross movement of our galaxy or group.

This is correct in both pictures, but relatively trivial.


The remaining anisotropies will be more and more difficult to quantify, as errors in the process of subtracting the major ones multiply, but I firmly believe that they will ultimately be proven to arise from the complex movements of our probes in relation to local space.

If this were true, then different CMB experiments would give different results (particularly the ground-based vs. space-based ones). They don't. There are no statistically significant inconsistencies between WMAP, COBE, Boomerang, etc.


If the small angle anisotropies (let's say even as large as 1 degree, to be exceedingly generous, but to remove all doubt) mapped by WMAP2 do not agree with those of WMAP1, the CMP is local, not cosmological. There is no way the casually-disconnected regions of the universe can have conspired to change together over the period of a year.

Why do you need WMAP2? There have been several experiments that have already produced CMB maps on those scales.
 
  • #33
SpaceTiger said:
Blackbodies are a simplifying assumption and a limiting case for thermodynamics. There are many things in the universe that are not in thermodynamic equilibrium, and therefore do not emit as blackbodies.
Blackbodies are classical examples of heat-sinks (EM-sinks) that can absorb any wavelength of EM and will emit EM with a curve appropriate to their temperatures. Pretty basic. The area under the BB curve is dependent on the temperature of the emitting body and the shape of the curve is very well-defined. We do not have to worry about whether empty space can exhibit black-body behavior. "Empty" (non-radiating with respect to us) space is a pure black body.

As for the CMB, why might we believe that the echo of the big bang can express itself as a black body, since the "echo" should express itself over a fairly large redshift span and over a large span of temperatures?

SpaceTiger said:
No, I don't understand. The spectrum of the "night sky" is not that of a blackbody. I certainly don't understand how you can ascertain that the vacuum absorbs and emits by spending time outside on a "clear Maine night".
I was pointing out that the night sky is a powerful heat sink. Any astonomer can explain this to you. A telescope pointed at the dark sky will cool far more rapidly that you would expect by considering the ambient temperature alone. This is pretty basic.

SpaceTiger said:
Light being absorbed and re-emitted many times is exactly the condition needed to form a blackbody spectrum. You can't form it from nothing, the absorbers/emitters must reach a statistical equilibrium before a blackbody curve can be produced.
Not true. The EM need only be absorbed once and emitted once to produce a black-body spectrum based on the temperature of the emitter. An object can exhibit a black-body spectrum at one temperature, and then can exhibit a different (based on its temperature) black-body spectrum after being heated or cooled to a different temperature.

SpaceTiger said:
If this were true, then different CMB experiments would give different results (particularly the ground-based vs. space-based ones). They don't. There are no statistically significant inconsistencies between WMAP, COBE, Boomerang, etc.
I am not predicting "statistically" significant inconsistencies of gross effects. I predict gross inconsistencies at small angles between WMAP1 and WMAP2.

SpaceTiger said:
Why do you need WMAP2? There have been several experiments that have already produced CMB maps on those scales.
See above. If the same probe cannot give OOM-consistent temperatures on angular resolutions of a degree or so (again, I think I'm being very generous), we must admit that the CMB is local and not cosmological. We need to compare WMAP1 and WMAP2 to settle this. We cannot compare results from probes with different altitudes, different sensors, or even different stabilization techniques. We are looking at differentials on the order of 10 ppm or less in magnitude and perhaps 1 ppm in terms of polarization. If the small-angle anisotropies of WMAP2 do not agree with those observed in WMAP1, there is no possible way (absent instrument error) that the CMB can be cosmological. Huge portions of the Universe that are non-causally-connected cannot possible conspire to change together over a period of one Earth-year.
 
  • #34
Turbot said:
Blackbodies are classical examples of heat-sinks (EM-sinks) that can absorb any wavelength of EM and will emit EM with a curve appropriate to their temperatures. Pretty basic. The area under the BB curve is dependent on the temperature of the emitting body and the shape of the curve is very well-defined. We do not have to worry about whether empty space can exhibit black-body behavior. "Empty" (non-radiating with respect to us) space is a pure black body.

If it's not radiating or absorbing, it isn't a blackbody. That follows from what you said above.


As for the CMB, why might we believe that the echo of the big bang can express itself as a black body, since the "echo" should express itself over a fairly large redshift span and over a large span of temperatures?

Because a redshifted blackbody spectrum retains its blackbody shape. That's all there is to it. I'd prove it to you, but you don't know any math.


I was pointing out that the night sky is a powerful heat sink. Any astonomer can explain this to you. A telescope pointed at the dark sky will cool far more rapidly that you would expect by considering the ambient temperature alone. This is pretty basic.

This is pretty wrong. The "night sky", as you're describing it, does not absorb radiation from the telescope, the telescope just emits the radiation and gets no feedback from its environment. In this sense, the night sky is not a heat sink, but rather the lack of a heat source. Any object left to itself will cool with time because it radiates its energy away. If, at the same time, the environment is giving feedback in the form of radiation, then the cooling process will be slower. That's why your telescope cools more slowly when pointed at a radiating source.


Not true. The EM need only be absorbed once and emitted once to produce a black-body spectrum based on the temperature of the emitter. An object can exhibit a black-body spectrum at one temperature, and then can exhibit a different (based on its temperature) black-body spectrum after being heated or cooled to a different temperature.

I think you need to pick up a good book on statistical mechanics. Equilibrium is not obtained as a result of one event, but is instead the end result of the many complicated interactions in a body (photon absorptions, collisions, etc.). An electromagnetic wave that is emitted from, say, the sun, will impact on the surface of a body (for example, you) and deliver energy to your surface. The particles on your surface will then have higher energies than the particles in your interior. However, because of collisions, vibrations, photon exchanges, etc., the energy will be redistributed throughout your body. A process like this can take a split second, a year, a millenium, or it might not occur at all. We can, however, calculate the approximate time for this process to occur and determine that the early universe should have had no trouble obtaining thermal equilibrium.


I am not predicting "statistically" significant inconsistencies of gross effects. I predict gross inconsistencies at small angles between WMAP1 and WMAP2.

If I understand you, you're saying that the anisotropy on one part of the sky will be inconsistent with the anisotropy on the same part of sky when viewed by a different experiment. However, I'm asking why you're singling out WMAP1 and WMAP2 when the CMB has already been observed at small angles by multiple experiments. For example, you can look at the CMB maps from COBE and WMAP:

http://qonos.princeton.edu/nbond/wmap_cobe.jpg"

Notice how the anisotropies are the same (not just one average) on the scales resolved by COBE. The same is true of the other experiments (such as BOOMERANG) that go to smaller angles.


If the same probe cannot give OOM-consistent temperatures on angular resolutions of a degree or so (again, I think I'm being very generous), we must admit that the CMB is local and not cosmological. We need to compare WMAP1 and WMAP2 to settle this. We cannot compare results from probes with different altitudes, different sensors, or even different stabilization techniques.

Why? If your theory is correct (that the anisotropies are due to movements of the instrument), then these different probes should give different anisotropies for exactly the reasons that you've cited. If the anisotropies aren't different, then your theory is wrong.


If the small-angle anisotropies of WMAP2 do not agree with those observed in WMAP1, there is no possible way (absent instrument error) that the CMB can be cosmological. Huge portions of the Universe that are non-causally-connected cannot possible conspire to change together over a period of one Earth-year.

This is true, and it'll only be about another month before we see this data. However, I don't see any reason why you feel the need to wait. Your theory is already disproven.
 
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  • #35
Blackbodies are classical examples of heat-sinks (EM-sinks) that can absorb any wavelength of EM and will emit EM with a curve appropriate to their temperatures. Pretty basic. The area under the BB curve is dependent on the temperature of the emitting body and the shape of the curve is very well-defined. We do not have to worry about whether empty space can exhibit black-body behavior. "Empty" (non-radiating with respect to us) space is a pure black body.

If it's not radiating or absorbing, it isn't a blackbody. That follows from what you said above.
Sorry for the imprecision (I left you a pretty good opening there) - when I said that "empty" space is a pure black body, I pute quotes around empty because as the Hubble deep-field exposure show us, it will be impossible to find any direction in space from which we are not receiving radiation from embedded sources in addition to the background temperature of space itself (no matter how slight).

As for the CMB, why might we believe that the echo of the big bang can express itself as a black body, since the "echo" should express itself over a fairly large redshift span and over a large span of temperatures?

Because a redshifted blackbody spectrum retains its blackbody shape. That's all there is to it. I'd prove it to you, but you don't know any math.
Well, I do know a "little" math. I also understand that if all the radiation that escaped during recoupling escaped at one time and at one average temperature, the redshifted spectrum of that source would retain its blackbody shape, albeit flattened with its peak shifted redward. The question I have arises from my understanding that in the BB model, recombination happened over a long period of time, with the plasma medium becoming more and more transparent to EM as time went on.

If the CMB is a perfect blackbody, and the peak of its spectrum is not smeared out (broadened) we are left with the uncomfortable concept that the surfact of last scattering is a rigid boundary that "winked off" everywhere in the Universe simultaneously. This clashes (in my feeble mind) with the concept that the BB universe became transparent to EM gradually over an OOM of z.

Gotta work - more later.
 
  • #36
In these forums, this page seems to offer something .. .. .. I'll go post there, perhaps.
 
  • #37
I was pointing out that the night sky is a powerful heat sink. Any astonomer can explain this to you. A telescope pointed at the dark sky will cool far more rapidly that you would expect by considering the ambient temperature alone. This is pretty basic.

This is pretty wrong. The "night sky", as you're describing it, does not absorb radiation from the telescope, the telescope just emits the radiation and gets no feedback from its environment. In this sense, the night sky is not a heat sink, but rather the lack of a heat source. Any object left to itself will cool with time because it radiates its energy away. If, at the same time, the environment is giving feedback in the form of radiation, then the cooling process will be slower. That's why your telescope cools more slowly when pointed at a radiating source.
The telescope is radiating EM to the night sky and is receiving EM from the night sky. The difference is that the net exchange results in the temperature of the 'scope going down very quickly - radiative cooling. The scope will cool much faster if it is pointed at the night sky than if it is left sitting out in the cold with a dew cap on or without a dew cap, but pointing at a building, a row of trees, etc.

Not true. The EM need only be absorbed once and emitted once to produce a black-body spectrum based on the temperature of the emitter. An object can exhibit a black-body spectrum at one temperature, and then can exhibit a different (based on its temperature) black-body spectrum after being heated or cooled to a different temperature.

I think you need to pick up a good book on statistical mechanics. Equilibrium is not obtained as a result of one event, but is instead the end result of the many complicated interactions in a body (photon absorptions, collisions, etc.). An electromagnetic wave that is emitted from, say, the sun, will impact on the surface of a body (for example, you) and deliver energy to your surface. The particles on your surface will then have higher energies than the particles in your interior. However, because of collisions, vibrations, photon exchanges, etc., the energy will be redistributed throughout your body. A process like this can take a split second, a year, a millenium, or it might not occur at all. We can, however, calculate the approximate time for this process to occur and determine that the early universe should have had no trouble obtaining thermal equilibrium.
You missed my point entirely. The complexity of the reactions by which a blackbody attains its temperature has no relation to the spectrum of its radiation. If it is a true blackbody, its spectral curve is defined, and that curve will look the same no matter how many interactions and energy transfers caused the blackbody to have its current temperature, and no matter what the wavelength of the EM that heated it to its current state.
 
  • #38
Turbot said:
Sorry for the imprecision (I left you a pretty good opening there) - when I said that "empty" space is a pure black body, I pute quotes around empty because as the Hubble deep-field exposure show us, it will be impossible to find any direction in space from which we are not receiving radiation from embedded sources in addition to the background temperature of space itself (no matter how slight).

We do indeed see some light at every point that we look, but you can't simply say that the light is coming from space itself, you have to show it. Your argument as it stands right now is circular.


Well, I do know a "little" math. I also understand that if all the radiation that escaped during recoupling escaped at one time and at one average temperature, the redshifted spectrum of that source would retain its blackbody shape, albeit flattened with its peak shifted redward. The question I have arises from my understanding that in the BB model, recombination happened over a long period of time, with the plasma medium becoming more and more transparent to EM as time went on.

I already answered this concern in another thread, but you ignored it. I've noticed that you do that a lot. If you don't understand my explanation, then ask me to elaborate, don't pretend it didn't happen.
 
  • #39
Should one really be taking advice from a 25 year old, with 34 years of experiance?

Albeit an Intelligent 25 year old, but 35 years of experience in 25 years seems, well, way past anyones ability, even if they started at DAY one! there Birthday.
 
  • #40
Turbot said:
The telescope is radiating EM to the night sky and is receiving EM from the night sky. The difference is that the net exchange results in the temperature of the 'scope going down very quickly - radiative cooling. The scope will cool much faster if it is pointed at the night sky than if it is left sitting out in the cold with a dew cap on or without a dew cap, but pointing at a building, a row of trees, etc.

The only difference between this and your previous incorrect argument is that you allowed the night sky to radiate a little bit. I assure you that it still doesn't support your theory that the vacuum is absorbing radiation from the telescope and obtaining a temperature.


You missed my point entirely. The complexity of the reactions by which a blackbody attains its temperature has no relation to the spectrum of its radiation.

Well, of course that depends on how one defines "complexity", but the interactions have to be "complex" enough such that collisions occur throughout the entire gas and for a long enough time that the energy can be smoothly distributed. If these conditions are not met, the spectrum won't be a blackbody.


If it is a true blackbody, its spectral curve is defined, and that curve will look the same no matter how many interactions and energy transfers caused the blackbody to have its current temperature, and no matter what the wavelength of the EM that heated it to its current state.

Actually, no, that's not true. If I start with a blackbody at, say, 300 K, and change its environment such that it's not absorbing the same amount and/or spectrum of radiation, then its temperature will change. This transition takes a finite amount of time (sometimes a very long time) and, in the meantime, the spectrum of the body will not have the usual characteristic shape.
 
  • #41
Lapin Dormant said:
Should one really be taking advice from a 25 year old, with 34 years of experiance?

What "advice"? I'm showing him that his science is wrong. If you see a problem with my arguments, please share with us your wisdom. Otherwise, I don't see what that has to do with anything.
 
  • #42
SpaceTiger said:
I already answered this concern in another thread, but you ignored it. I've noticed that you do that a lot. If you don't understand my explanation, then ask me to elaborate, don't pretend it didn't happen.
That is advice, so please to help me, and any other reader{s} of this, tell me {us?} where you have previoulsy answered his question?

Thank you.

Have you ever done any studies of statistical propensities of Falsifications?
 
  • #43
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  • #44
Thank you.

The other part, no, no more on that, it is simply a sort of Hobby of mine, people studies, and analysis.
 

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