Galaxy motions -> hidden superstructure (DM)

[Nereid]

http://www.msfc.nasa.gov/news/news/releases/2004/04-231.html , a Chadra PR, goes on to say: "A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA's Chandra X-ray Observatory. Astronomers think most of the matter in the universe is concentrated in long large filaments of dark matter and that galaxy clusters are formed where these filaments intersect.[/color]" The cluster is Fornax.

 

[polyb]

Perhaps more evidence to revise previous theories?

 

[Vast]

Astronomers think most of the matter in the universe is concentrated in long large filaments of dark matter and that galaxy clusters are formed where these filaments intersect.

If this were correct, it would seem to shed some light on what dark matter really is. Could it simply be that dark matter is ordinary matter, but is of low density so that no stars can form? Thus only where intersections or higher concentrated regions of dark matter come together star production and galaxies eventually form?

Theories of dark matter being dark objects like comets, stars that aren’t luminous, rocks, or black holes, may not actually be what dark matter is…

 

[Chronos]

It is pretty simple to me. Dark matter is the most logical solution to observational evidence.

 

[Nereid]

If this were correct, it would seem to shed some light on what dark matter really is. Could it simply be that dark matter is ordinary matter, but is of low density so that no stars can form? Thus only where intersections or higher concentrated regions of dark matter come together star production and galaxies eventually form?

This is quite close to the generally accepted models Vast! However, the difference is that DM is certainly not ordinary (baryonic) matter - galaxies etc formed at the intersections of the filaments because the overall mass density was high enough that interactions among the baryonic matter quickly resulted in that matter 'cooling' (you can think of it as losing gravitational energy due to emission of photons). Baryonic mass also formed galaxies etc along the filaments, but not at the same rate.

Theories of dark matter being dark objects like comets, stars that aren’t luminous, rocks, or black holes, may not actually be what dark matter is…

In the most popular cosmological models, DM can't be comets, rocks, pebbles, gas, or even BHs ... a) because there's no observational evidence for several of these hypothesised forms (gas, dust, stars), and b) because a model with mass in the form of only baryonic matter doesn't resemble the present day universe at all (there are some alternative models - e.g. Garth's SCC - where this inconsistency might disappear).

 

[sol2]

http://www.msfc.nasa.gov/news/news/releases/2004/04-231.html , a Chadra PR, goes on to say: "A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA's Chandra X-ray Observatory. Astronomers think most of the matter in the universe is concentrated in long large filaments of dark matter and that galaxy clusters are formed where these filaments intersect.[/color]" The cluster is Fornax.

Imagine Neried. A overall geometry that details evrything that we can see with predictability? Okay. So I am dreamer

The isometric relations that one might find in the cosmos, in relation to the orbitals always serves as a nice catelogue reference, when we look at these events. But like the dreamer one has to imagine that there is a geometry that underlines all the basis of exploration that is curently taken from the cosmological pallete to the one we so have a hard time understanding below.

So how shall the quantum geometry of the universe, take us to the one below? Is this possible in your doggone eyes

 

[Chronos]

Dark matter? Come up with a better explanation and collect your Nobel. Nereid correctly points out there is no better explanation. Is anyone happy with dark matter? No. The facts remain. There is no better explanation.

 

[Nereid]

http://www.tmforum.org/browse.asp?catID=2067 is the title of HEASARC's piccie of the week (yes, the same Chandra image of the Fornax cluster).

There are some good sites on the links on this page, good for a fun few hours.

HEASARC: High Energy Astrophysics Science Archive Research Center.

 

[Garth]

The spectra of distant quasars reveal a Lyman Alpha forest - the fingerprint of intergalactic hydrogen in which is also the spectral signature of a relatively high degree of "metallicity" of which only 20% can be explained as galactic outflow. Is not this then the observational evidence for the Dark Matter? In the form of cold gas?

The fact it is normally attributed to something exotic is because the standard BB model produces only a maximum of 4% of critical density in baryonic form, and the density required by cluster dynamics and gravitational lensing is about 20% - 30% critical density. However this higher value is in the range produced by the 'freely coasting ' model.
- Garth

 

[turbo]

It is pretty simple to me. Dark matter is the most logical solution to observational evidence.

Well, you know how I feel about this one. Dark matter is the most convenient way to reconcile GR with observations that cannot be explained by GR. It is hardly the most logical.

There is no plausible explanation of its make-up. There is no logical way to explain how how dark matter can distribute itself so obediently in every circumstance where GR needs it, so GR can stay predictive with observations in galactic rotation rates, cluster structure, etc. Please remember that this powerful stuff is entirely invisible, despite decades of searching by very inventive, talented people.

When a phenomenon is entirely unconstrained by causality, and is entirely undetectable, yet performs in intelligent ways to save GR, we should not celebrate our ignorance. We should ask ourselves "Where is GR broken?" We should ask "What does GR NOT model correctly, that can explain the convoluted behavior of the dark matter needed to fix GR?" I believe that the solution may be found in the places that GR cannot go - QED.

This is not to say that GR may not be found to be predictive and accurate after its deficiencies are explained and corrected. After all, Newtonian dynamics are predictive and accurate for a LOT of real-world stuff. If we look at the progression of theories explaining planetary movements up though Newton, and Einstein, and then declare that GR is the end-all, we are both being presumtuous and inapprorpriately smug. Science is defined by the processes though which theories are expressed, modeled, tested, and refined.

Einstein's theories have already been refined and redefined in many ways. It is interesting to see how many GR folks are willing to accept these modifications, and yet will believe six impossible things before breakfast (regarding dark matter) to keep GR alive. When folks outside the GR field try to model the problems, the GR folks decry their attempts as "fringe" or "unconventional", while clinging to these outrageous "leap of faith" concepts necessary to keep it alive. It's pretty sad.

The conventional GR view is "GR is true, so Dark Matter must exist because if GR is true, we need it to explain the observations." That kind of thinking is wrong in so may ways! Epicycles (like dark matter) are an obvious measure of just how the standard model is broken, and should lead us to challenge the fundamentals of the theory and find a better solution. We can either strive to learn, or we can stagnate. Choose.

The glove is down!

OK, Chronos, it's not like I could be mad at you, but you may have to supply some math.!

 

[Chronos]

We can either strive to learn, or we can stagnate. Choose.

The glove is down!

OK, Chronos, it's not like I could be mad at you, but you may have to supply some math.!

I am reverse engineering this question.

Well, you know how I feel about this one. Dark matter is the most convenient way to reconcile GR with observations that cannot be explained by GR. It is hardly the most logical.

Describe models that are more logical and why they are more logical.

There is no plausible explanation of its make-up.

OK, I will try, how about dark matter is matter that does not emit detectable EM?

There is no logical way to explain how dark matter can distribute itself so obediently in every circumstance where GR needs it, so GR can stay predictive with observations in galactic rotation rates, cluster structure, etc.

Agreed, dark matter always seems to be exactly where it needs to be according to GR.

Please remember that this powerful stuff is entirely invisible, despite decades of searching by very inventive, talented people.

Agreed. That is maddening.

When a phenomenon is entirely unconstrained by causality, and is entirely undetectable, yet performs in intelligent ways to save GR, we should not celebrate our ignorance.

Good question. Why does dark matter just happen to be right where GR predicts it should be?

We should ask ourselves "Where is GR broken?" We should ask "What does GR NOT model correctly, that can explain the convoluted behavior of the dark matter needed to fix GR?"

The evidence GR is not broken appears to be far more convincing than the evidence that it is broken.

I believe that the solution may be found in the places that GR cannot go - QED.

The need for such a solution has not yet been established, so far as I can see.

This is not to say that GR may not be found to be predictive and accurate after its deficiencies are explained and corrected.

What deficiencies?

After all, Newtonian dynamics are predictive and accurate for a LOT of real-world stuff. If we look at the progression of theories explaining planetary movements up though Newton, and Einstein, and then declare that GR is the end-all, we are both being presumtuous and inapprorpriately smug. Science is defined by the processes though which theories are expressed, modeled, tested, and refined.

Agreed.

Einstein's theories have already been refined and redefined in many ways. It is interesting to see how many GR folks are willing to accept these modifications, and yet will believe six impossible things before breakfast (regarding dark matter) to keep GR alive.

Please clarify. What modifications have GR folks accepted and impossibilities believed before breakfast are you referring to?

When folks outside the GR field try to model the problems, the GR folks decry their attempts as "fringe" or "unconventional", while clinging to these outrageous "leap of faith" concepts necessary to keep it alive. It's pretty sad.

What 'leaps of faith'?

The conventional GR view is "GR is true, so Dark Matter must exist because if GR is true, we need it to explain the observations." That kind of thinking is wrong in so may ways!

Dark matter, or something like it, is observational fact. Did the standard model forbid dark matter before it was observed? No. Does dark matter forbid the standard model? No.

Epicycles (like dark matter) are an obvious measure of just how the standard model is broken, and should lead us to challenge the fundamentals of the theory and find a better solution

Assumes facts not in evidence.

 

[Garth]

Describe models that are more logical and why they are more logical.

The freely coasting model does not need DM or Inflation.

Your suggestion that Dark Matter is just that, dark ordinary matter does not fit as the BBN allows only a maximum of 4% baryonic matter when you need over 20%. It must therefore be, according to GR, not only Dark but unknown, some exotic non-baryonic species.

What deficiencies?

1. Inflation - no Higgs boson
2. Dark Matter - see above
3. Dark Energy - what the heck is this supposed to be? Anybody's guess is as good as anybody else’s; there is certainly no shortage of suggestions, all of which of course are completely unsubstantiated.
4. No large angle fluctuations in the CMB WMAP data, is the universe flat and infinite or not? Perhaps we all do live on a football (soccer-ball) then!
5. False vacuum fine-tuned to one part in 10^(102). (Anthropic argument again perhaps?)
6. Densities of Dark matter, energy and baryons all approximately equal (to within an order of magnitude) but why? Oh! I forgot; Anthropic explanation called for!
7. The small value of the false vacuum energy is unstable to quantum corrections - if interpreted as a small positive cosmological constant then it is incompatible with String theory.
8. Galaxy mass profiles predicted by the standard theory have too pronounced a cusp at small angles and a too steep galaxy luminosity function.

Perhaps the claim that we are in the epoch of the 'end of cosmology' is a little premature - just as it was at the turn of the 19th/20th centuries.

- Garth

 

[turbo]

Why does dark matter just happen to be right where GR predicts it should be?

Gotta go to work, but let me give you my take on this point quickly. Dark matter does NOT happen to be right where GR predicted it. GR did NOT predict dark matter - neither its existence, its function, not its distribution. None of this is in GR. It all has to be put in by hand to fix deficiences in GR that cause observations to disagree with its predictions.

"Dark matter" was dreamed up to explain deficiencies in GR. The deficiencies were observed and measured, and then conventional physicists said "what could cause this?" They agreed that extremely large fields of matter might cause the effects, if they were distributed "just so". The problem is that each instance in which "dark matter" is invoked to fix GR has a special "just so" distribution that has to be put into GR by hand to save it. This is not science. It is religion - blind belief.

Dark matter's properties and distributions were tuned to make GR's "predictions" more accurate. Instead of probing these problems, some GR adherents are claiming that this artificially restored predictive ability is proof that dark matter exists! If there is a more glaring example of circular reasoning in "science", I'd love to see it.

 

[selfAdjoint]

"Dark matter" was dreamed up to explain deficiencies in GR.

AFAIK, the problems that dark matter was introduced to solve had nothing to do with GR in particular. The motions of the galaxies were computed from Newtonian approximations, which was fine because they are so slow and spread out. So the animus you apparently direct at GR should be aimed at Newton instead.

 

[Garth]

turbo-1 although we tend to agree on this question I have one niggle..

It is religion - blind belief.

Not all religion is blind belief.
- Garth

 

[Garth]

AFAIK, the problems that dark matter was introduced to solve had nothing to do with GR in particular. The motions of the galaxies were computed from Newtonian approximations, which was fine because they are so slow and spread out. So the animus you apparently direct at GR should be aimed at Newton instead.

I agree - the fact that it is believed that DM exists is down to Newton and it could be cold gas/mini primordial black holes/bricks or whatever. It hasn't been identified and the limits on each form are getting smaller so it is a problem.

The fact that it is believed to be some exotic non-baryonic substance WIMPs etc. is down to GR because, as I said above, BBN requires the baryonic density to be no more than 4% (even that is pushing it) whereas there is a requirement for >20% of DM.

So for GR BBN to be consistent with galactic/cluster rotation rates and gravitational lensing it has to invoke a totally unknown species of matter, a form of mass that has evaded discovery after more than two decades of intense research.

It is in this sense that GR is deficient.

- Garth

 

[turbo]

AFAIK, the problems that dark matter was introduced to solve had nothing to do with GR in particular. The motions of the galaxies were computed from Newtonian approximations, which was fine because they are so slow and spread out. So the animus you apparently direct at GR should be aimed at Newton instead.

You are absolutely right. I should have said the "Standard Model" and not GR, which is only a part of the SM (if an important one). I tend to lump them together mentally because the inapplicability of GR to QED is a blind spot that might hide the mechanism for the "misbehavior" of galaxies and galaxy clusters that necessitated the invention of dark matter. Thank you for the clarification.

 

[turbo]

turbo-1 although we tend to agree on this question I have one niggle..

Not all religion is blind belief.
- Garth

I intended no offense to those of faith. My point was that there is an air of 'sanctity' about the Standard Model that allows otherwise logical people to abandon the scientific method in this instance, and believe in dark matter.

 

[Garth]

I intended no offense to those of faith. My point was that there is an air of 'sanctity' about the Standard Model that allows otherwise logical people to abandon the scientific method in this instance, and believe in dark matter.

No offence taken!

The air of 'sanctity' you mention is worrying, it manifests itself by a certainty that the evidence will not bear. "Precision cosmology", "the concordance model", “the end of cosmology”, even "the end of physics" and "knowing the mind of God", have all been banded about.

Of course the WMAP data set is very detailed and rich in information, the question is how should that information be interpreted, as that interpretation is theory dependent?

Garth

 

[Nereid]

I intended no offense to those of faith. My point was that there is an air of 'sanctity' about the Standard Model that allows otherwise logical people to abandon the scientific method in this instance, and believe in dark matter.

Perhaps we should try harder to get to the bottom of the apparent differences of opinion here ...

Perhaps we start with the assertion above that folk like Tegmark have 'abandoned the scientific method' - in what way do you feel they have done so?

Then we could consider 'believe in dark matter' - if we are following the scientific method, then our beliefs are irrelevant (fairies, dark matter, the existence of turbo-1); what counts is whether we can construct hypotheses and theories which are a) internally consistent, b) consistent with QM and GR within the appropriate domains of applicability, and c) {most important} consistent with good observational and experimental results. In these respects, I submit that appropriate hypotheses incorporating cold, non-baryonic dark matter are good hypotheses. Further, AFAIK, no other hypotheses satisfy these three conditions as well; for example, MOND is explicitly inconsistent with GR, and Garth's SCC (or the more general 'freely coasting' cosmologies) has quite some work still to do address the full range of observations and experiments (e.g. large scale structure, the SZE (I'm not 100% sure of this one), and primordial abundance of nuclides (the 'Indian team's paper is, IMHO, far from satisfactory in this regard)).

If you consider that DM hypotheses do not satisfy one or more of these criteria, please say so (and give details); if you are aware of other hypotheses which don't include DM but do satisfy all these criteria as well as the concordance models, please provide details.

Note to Mentors: could you give us an indication please as to whether disagreement with the current state of cosmology - based on personal distaste for certain concepts - is appropriate here? I feel it's similar to some of the posts - since moved to TD - expressing dislike for SR or GR.

 

[Nereid]

The air of 'sanctity' you mention is worrying, it manifests itself by a certainty that the evidence will not bear. "Precession cosmology", "the concordance model", “the end of cosmology”, even "the end of physics" and "knowing the mind of God", have all been banded about.

Ah, hubris, so human.

Of course the WMAP data set is very detailed and rich in information, the question is how should that information be interpreted, as that interpretation is theory dependent?

But what's to stop you, or anyone else, conducting your own analyses of the data, and publishing your own conclusions and interpretations?

 

[Garth]

But what's to stop you, or anyone else, conducting your own analyses of the data, and publishing your own conclusions and interpretations?

A slight matter of funding?
I quote from Eric Lerner's "An Open Letter to the Scientific Community- http://www.cosmologystatement.org/
(Published in New Scientist, May 22, 2004)
signed by Arp, Koch, Bondi, Gold Narlikar and about 160 other scientists and engineers:-
"Supporters of the big bang theory may retort that these (alternative - my addition) theories do not explain every cosmological observation. But that is scarcely surprising, as their development has been severely hampered by a complete lack of funding. Indeed, such questions and alternatives cannot even now be freely discussed and examined. An open exchange of ideas is lacking in most mainstream conferences. Whereas Richard Feynman could say that "science is the culture of doubt", in cosmology today doubt and dissent are not tolerated, and young scientists learn to remain silent if they have something negative to say about the standard big bang model. Those who doubt the big bang fear that saying so will cost them their funding."

The point is that over confidence is not conducive to good scientific method, it makes it difficult to question and positively criticise.

Garth

 

[turbo]

Then we could consider 'believe in dark matter' - if we are following the scientific method, then our beliefs are irrelevant (fairies, dark matter, the existence of turbo-1); what counts is whether we can construct hypotheses and theories which are a) internally consistent, b) consistent with QM and GR within the appropriate domains of applicability, and c) {most important} consistent with good observational and experimental results. In these respects, I submit that appropriate hypotheses incorporating cold, non-baryonic dark matter are good hypotheses.

There is something happening with gravitation that we don't understand, and it is evident at galactic scales. The Standard Model falls apart here (differential galactic rotation, excess cluster lensing, cluster stability with "insufficient" mass...) There is an underlying mechanism for these observations that diverge from the Standard Model.

The insistence on the physical existence of "dark matter" to fix these divergences is a departure from good science for the following reasons:

1) Dark matter has mass, but cannot be detected by any means other than its gravitational effects. Implausible. Huge sheets or strings of massive dark matter (large enough to cause clusters to stream toward it) should be quite visible via lensing of background galaxies.
2) Dark matter distributes itself perfectly in every situation to save the Standard Model. Convenient but impossible - the laws of science do not include inanimate matter that distributes itself intelligently. How can a diffuse entity like dark matter "know" that it is surrounding a spiral galaxy, or assisting in the lensing of a cluster? No mechanism has been suggested that might cause these special distributions - they are just accepted.

The scientific method (and Occam's razor) suggest that we should look for fundamental inaccuracies in our model, using the entities we know to exist, like matter, energy, space-time, gravitation...

I don't have a mathematically-provable model to give you Nereid, and I truly wish that I did, but can you see the logic of 1) and 2)? Does it not follow that DM is "believed" in spite of them, and in spite of the scientific method that requires us to test and prove otherwise illogical assumptions?

 

[marcus]

AFAIK, the problems that dark matter was introduced to solve had nothing to do with GR in particular. The motions of the galaxies were computed from Newtonian approximations, which was fine because they are so slow and spread out...

I agree but let us not appear to let GR off the hook.
the Newtonian approximation is included in GR (as a limit when things are "slow and spread out" enough) as we all know.

so if there were no dark matter something would be wrong with GR. the rotation curves would be just as wrong from a GR standpoint as they are from a Newtonian standpoint.

evidence for dark matter is piling up, but IF it doesn't exist, then the theory that badly needs to be fixed is General Relativity (which would also simultaneously fix its Newtonian approximation).

so I can sympathize with turbo's attitude.

also if the Pioneer anomaly is real, GR would need to be modified, would it not? want to keep thinking of these possibilities as open

 

[Nereid]

A slight matter of funding?
I quote from Eric Lerner's "An Open Letter to the Scientific Community- http://www.cosmologystatement.org/
(Published in New Scientist, May 22, 2004)
signed by Arp, Koch, Bondi, Gold Narlikar and about 160 other scientists and engineers:-
"Supporters of the big bang theory may retort that these (alternative - my addition) theories do not explain every cosmological observation. But that is scarcely surprising, as their development has been severely hampered by a complete lack of funding. Indeed, such questions and alternatives cannot even now be freely discussed and examined. An open exchange of ideas is lacking in most mainstream conferences. Whereas Richard Feynman could say that "science is the culture of doubt", in cosmology today doubt and dissent are not tolerated, and young scientists learn to remain silent if they have something negative to say about the standard big bang model. Those who doubt the big bang fear that saying so will cost them their funding."

The point is that over confidence is not conducive to good scientific method, it makes it difficult to question and positively criticise.

Garth

This time it took three glasses of my favourite Sauvignon Blanc ... and I'm not sure I can keep my comments cool and neutral.

How much effort - by a professional, with a good PhD and tenure (and access to sufficient computing resources) - would it take to analyse the first year's results from WMAP (or SDSS, or the whole 2dF, or ...) and write a paper laying out the degree to which those results are consistent with SCC (or any other freely coasting cosmology), and provide 95% CL estimates of the key parameters in SCC? From what I've read so far, not much; certainly it should be well within the capabilities of the 34 original signatories (add summer and PhD candidates and you've got even more resources). Ditto, wrt primordial nuclide abundances, within an SCC ... as I said before, there's *no new physics*, all that's required is an application of stuff that's probably mostly already in textbooks that many of the PhDs actually used.

I looked for Davis and Bahcall's signatures on this statement, I wasn't the least bit surprised to find they're not there. Why? At one level, this whole statement is equivalent to "you two guys should never had been given funds to pursue the 'solar neutrino problem', it's just an epicycle"; or "Fermi's crazy idea of the neutrino, in 20 years of research not a trace of this epicyclic hypothetical particle has been found". Speaking of Bahcall, how about one of the signatories comes up with a research proposal that has the clarity and simplicity of his 'galactic halo blank field red dwarf HST single image search' (to constrain the baryonic parameters of DM), or his 'variations in alpha over cosmological time'? In both cases, most (or all) the raw data could be obtained from existing archives; in both cases, big advances were made in constraining popular models. With all the creativity of the >160 signatories, there's no one who can write a similarly 'big step forward' research proposal?

Apart from Bahcall, which respected astrophysicists have shown maverick or iconclastic tendencies in their careers? Have any of the 34 signatories asked these people for assistance? I mean, the picture painted by this statement is one of suffocating conformity within a scientific community; I'll grant you that debate can at times be robust (shall we say), but the kind of dogmatism implied by this statement seems quite at odds with the personalities of a sizable minority (at least) of the community being chastised.

I almost feel like Evo, 'I don't want to hear any more whining or excuses, go to your rooms and don't come out until you've finished your homework!'

 

[Nereid]

There is something happening with gravitation that we don't understand, and it is evident at galactic scales.

Aren't you imposing your beliefs onto the data? The *data* don't say anything about gravitation; I feel a more accurate statement would be something like 'the amount of mass, and its distribution, required to account for the observations is greater than that we estimate from analysis of the EM'; whether it's a problem with our theories of gravitation, or something completely different, the data doesn't say.

The Standard Model falls apart here (differential galactic rotation, excess cluster lensing, cluster stability with "insufficient" mass...) There is an underlying mechanism for these observations that diverge from the Standard Model.

This is, IMHO, a serious misrepresentation; apart from leaving out several important classes of observation (in the three dots, I presume; examples include lensing by masses considerably smaller than clusters), there's all the work done to constrain 'invisible' forms of ordinary matter - the MACHO and OGLE work, the search for faint stars and failed stars, rogue planets, IGM dust, low metallicity gas clouds, ... IOW, it's not that 'there is an underlying mechanism'; it's that there are masses of good data that need to be accounted for!

The insistence on the physical existence of "dark matter" to fix these divergences is a departure from good science for the following reasons:

1) Dark matter has mass, but cannot be detected by any means other than its gravitational effects. Implausible. Huge sheets or strings of massive dark matter (large enough to cause clusters to stream toward it) should be quite visible via lensing of background galaxies.

I assume you can back this up - how large are the expected lensing effects for these sheets and strings? What are the current constraints on the mass in these sheets, from null results of lensing searches?

IIRC, the observational results are, in fact, consistent with the cosmologically estimated mass in the sheets and strings.

2) Dark matter distributes itself perfectly in every situation to save the Standard Model. Convenient but impossible - the laws of science do not include inanimate matter that distributes itself intelligently. How can a diffuse entity like dark matter "know" that it is surrounding a spiral galaxy, or assisting in the lensing of a cluster? No mechanism has been suggested that might cause these special distributions - they are just accepted.

My goodness, I wonder how many of the papers you've actually read? For example, the HST (+Chandra) cluster study I referenced some time ago *derived* a distribution of DM which was *consistent with* that expected from cosmological models, in which DM is assumed to be a cold, collisionless 'gas' that interacts with ordinary matter only via gravitation. IIRC, this too is consistent with models of galaxy mass distribution, where the components are DM (as above) + baryonic matter (which can collapse, as it loses 'gravitational' energy via EM cooling) - look at all the work done by folk like King, look at the NFW profiles and how they can arise ... this is just what Ockham ordered - minimal sets of assumptions, rich predictions which match detailed observations quite well.

The scientific method (and Occam's razor) suggest that we should look for fundamental inaccuracies in our model, using the entities we know to exist, like matter, energy, space-time, gravitation...

It's perfectly OK to look for these fundamental inconsistencies; the trouble with GR is that it seems to fit all the observations and experiments to date, and some with extraordinary accuracy. Further, these aren't just 'local', binary pulsars and SMBH seem to behave just as Uncle Al said they would. To make this point more strongly, if a galaxy's nucleus seems to harbour a many-billion sol BH*, and a multi-billion sol galaxy looks like it has lots of DM (in the halos), why abandon GR for the latter but accept it for the former?

I don't have a mathematically-provable model to give you Nereid, and I truly wish that I did, but can you see the logic of 1) and 2)? Does it not follow that DM is "believed" in spite of them, and in spite of the scientific method that requires us to test and prove otherwise illogical assumptions?

I hope my clarifications have illustrated that DM is quite consistent with the scientific method. Let's continue the discussion, with reference to observational data?

*large mass determined from doppler shifts (lines in the optical), gravitational reddening (X-ray line profiles), brightness profiles, and (for the MW) stellar orbits; small volume determined by similarly ... ergo, BH.

 

[turbo]

Note to Mentors: could you give us an indication please as to whether disagreement with the current state of cosmology - based on personal distaste for certain concepts - is appropriate here? I feel it's similar to some of the posts - since moved to TD - expressing dislike for SR or GR.

Dear Nereid, I do not "dislike" SR or GR. They are wonderful models. I have a profound respect for Einstein, as well as Newton (who had to invent calculus to model gravitation, though some might argue that Archimedes had done so almost 2000 years earlier), and for Feynman (perhaps my favorite character of all - and the consummate teacher/communicator - thanks to his dad!).

My point is that each of these great gentlemen had the work of others to build on, and NONE of them felt that their works were the end of scientific development. Scientific theory cannot be sacrosanct. If observation disagrees with theory, observation wins, and the theory MUST be re-examined. If the theory disagrees with observation on several accounts, and each divergence has a similar theme (apparent gravitational anomalies in differential galactic rotation, apparent excess gravity causing high cluster lensing, apparent excess gravitation causing low-mass cluster to stick together, even with high apparent motions) then the model is seen to have a systemic problem in that regard. (Gravity? hint, hint, hint?) Any logical person would try to figure out what simple fundamental problem with GR/Standard model could cause all those disagreements. Each of the physics giants cited above would INSIST on rigorous examination of previous or their own theories under such circumstances.

The invocation of dark matter to "solve" all of these problems, with special gravitational properties, with fine-tuned distributions in each circumstance, and with built-in "stealth" technology is a bit hard to swallow. It is in fact contrary to good science.

I have tried to present my math-poor but hopefully cogent arguments as well as I can. I'm not a tenured professional, and I've got a cheesy 4-year-old personal computer at my command, but I do have a brain, and my brain (where I store all this stuff) says that we've got to re-examine gravitation to fix the standard model.

 

[Chronos]

Oh well, it is only my neck.

The big bang today relies on a growing number of hypothetical entities, things that we have never observed-- inflation, dark matter and dark energy are the most prominent examples. Without them, there would be a fatal contradiction between the observations made by astronomers and the predictions of the big bang theory. In no other field of physics would this continual recourse to new hypothetical objects be accepted as a way of bridging the gap between theory and observation. It would, at the least, raise serious questions about the validity of the underlying theory.

1] No inflation? I was not aware the Hubble constant had been refuted.
2] No dark matter? I look forward to the observational evidence that makes it go away.
3] No dark energy? See above.

But the big bang theory can't survive without these fudge factors. Without the hypothetical inflation field, the big bang does not predict the smooth, isotropic cosmic background radiation that is observed, because there would be no way for parts of the universe that are now more than a few degrees away in the sky to come to the same temperature and thus emit the same amount of microwave radiation.

Fudge factors? Please elaborate on the theory that explains the CMBR without a 'big bang'?.

Without some kind of dark matter, unlike any that we have observed on Earth despite 20 years of experiments, big-bang theory makes contradictory predictions for the density of matter in the universe. Inflation requires a density 20 times larger than that implied by big bang nucleosynthesis, the theory's explanation of the origin of the light elements. And without dark energy, the theory predicts that the universe is only about 8 billion years old, which is billions of years younger than the age of many stars in our galaxy.

Agreed. Is it just me, or do I fail to see where you offered a better alternative theory?

What is more, the big bang theory can boast of no quantitative predictions that have subsequently been validated by observation.

You have got to be kidding.

The successes claimed by the theory's supporters consist of its ability to retrospectively fit observations with a steadily increasing array of adjustable parameters, just as the old Earth-centered cosmology of Ptolemy needed layer upon layer of epicycles.

Perhaps the theory's supporters are merely deluded by decades of observational evidence.

Yet the big bang is not the only framework available for understanding the history of the universe. Plasma cosmology and the steady-state model both hypothesize an evolving universe without beginning or end. These and other alternative approaches can also explain the basic phenomena of the cosmos, including the abundances of light elements, the generation of large-scale structure, the cosmic background radiation, and how the redshift of far-away galaxies increases with distance. They have even predicted new phenomena that were subsequently observed, something the big bang has failed to do.

1] Plasma cosmology? Why discard that model just because it fails to match observational evidence?
2] Steady state? See above.
3] Elaborate on how they can explain anything that you claim they explain and how it fits observation. Last time I checked, they were discarded because they do not fit observation.

Supporters of the big bang theory may retort that these theories do not explain every cosmological observation. But that is scarcely surprising, as their development has been severely hampered by a complete lack of funding.

Perhaps they have not been funded because they lack credibility given observational evidence.

Indeed, such questions and alternatives cannot even now be freely discussed and examined. An open exchange of ideas is lacking in most mainstream conferences. Whereas Richard Feynman could say that "science is the culture of doubt", in cosmology today doubt and dissent are not tolerated, and young scientists learn to remain silent if they have something negative to say about the standard big bang model. Those who doubt the big bang fear that saying so will cost them their funding.

They should be reluctant to theorize without observational evidence.

Even observations are now interpreted through this biased filter, judged right or wrong depending on whether or not they support the big bang. So discordant data on red shifts, lithium and helium abundances, and galaxy distribution, among other topics, are ignored or ridiculed. This reflects a growing dogmatic mindset that is alien to the spirit of free scientific inquiry.

1]What discordant red shifts?
2]What discordant lithium and helium abundance?
3]What discordant galaxy distributions?
4]What other topics?
5]This reflects a mindset that has learned to recognize and resist funding bad science.

Today, virtually all financial and experimental resources in cosmology are devoted to big bang studies.

Translation: real science.

Funding comes from only a few sources, and all the peer-review committees that control them are dominated by supporters of the big bang.

Who are these mysterious 'supporters'?

As a result, the dominance of the big bang within the field has become self-sustaining, irrespective of the scientific validity of the theory?

Scientific validity? Offer some and you might get some support.

Giving support only to projects within the big bang framework undermines a fundamental element of the scientific method -- the constant testing of theory against observation.

Since when and whom has constrained the gathering of observational evidence?

To redress this, we urge those agencies that fund work in cosmology to set aside a significant fraction of their funding for investigations into alternative theories and observational contradictions of the big bang. To avoid bias, the peer review committee that allocates such funds could be composed of astronomers and physicists from outside the field of cosmology. Allocating funding to investigations into the big bang's validity, and its alternatives, would allow the scientific process to determine our most accurate model of the history of the universe.

Astronomers and physicists from outside the field of cosmology? Great idea. Let people unfamiliar with the body of knowledge direct research. We already have that, they are called politicians.

Why am I not surprised that Halton Arp tops the list of endorsers for this whining diatribe?

 

[turbo]

Why am I not surprised that Halton Arp tops the list of endorsers for this whining diatribe?

Dear Chronos, Mr. Arp is a true gentleman. He is also a giant in the field of observational astronomy. He worked closely with Edwin Hubble. Some ignorant people deride him because he believes that redshift does NOT strictly equate to cosmological expansion. That is unfortunate, because although redshift is a very simple concept, it may arise from a more complex set of causes.

Chip Arp's contribution to astrononomy/cosmology cannot be ignored. His photographic studies of galaxy interaction and morpholgy are fundamental. Would you like to take a breath and tell us why his work and his opinions should be dismissed? I'm all ears.

It is very easy to dismiss the work of a man who has been branded as a maverick or a "fringe" researcher. Just pile on, and enjoy the glow... Indulge me this one time and please show me where he is wrong, and give some examples.

 

[Garth]

Surely the basic point is that while the Higg's boson, DM and DE are elusive other approaches to cosmology ought to be encouraged, and funded, for the sake of good scientific practice?

Garth

 

[Garth]

Nereid - Please keep cool! The issue is serious not belligerent!

How much effort - by a professional, with a good PhD and tenure (and access to sufficient computing resources) - would it take to analyse the first year's results from WMAP (or SDSS, or the whole 2dF, or ...) and write a paper laying out the degree to which those results are consistent with SCC (or any other freely coasting cosmology), and provide 95% CL estimates of the key parameters in SCC? From what I've read so far, not much; certainly it should be well within the capabilities of the 34 original signatories (add summer and PhD candidates and you've got even more resources). Ditto, wrt primordial nuclide abundances, within an SCC ... as I said before, there's *no new physics*, all that's required is an application of stuff that's probably mostly already in textbooks that many of the PhDs actually used.

Working on it! But if you look at my public profile you'll see I'm an "Independent researcher" - without easy access to sufficient resources- that is why I will be glad of some cooperation!

I looked for Davis and Bahcall's signatures on this statement, I wasn't the least bit surprised to find they're not there. Why? At one level, this whole statement is equivalent to "you two guys should never had been given funds to pursue the 'solar neutrino problem', it's just an epicycle"; or "Fermi's crazy idea of the neutrino, in 20 years of research not a trace of this epicyclic hypothetical particle has been found".

Surely the point is that the neutrino has been discovered and the solar neutrino problem has been resolved, neutrinos have a small mass*, whereas the problem identifying the Higg's bosons, DM and DE hasn't been resolved?

- Garth
*But unfortunately not enough to solve the DM problem too.

 

[turbo]

Aren't you imposing your beliefs onto the data? The *data* don't say anything about gravitation; I feel a more accurate statement would be something like 'the amount of mass, and its distribution, required to account for the observations is greater than that we estimate from analysis of the EM'; whether it's a problem with our theories of gravitation, or something completely different, the data doesn't say.

No, I am not imposing my beliefs on the data, and your "more accurate statement" is overly simplistic. To restate: 'the amount of mass required to account for observations is greater (far, far greater!) than we estimate from analysis of the EM AND the distribution of that mass must be fine-tuned to account for observations in each relevant circumstance.'

The three glaring problems I cited (differential galactic rotation, excessive cluster lensing, and anomalous cluster binding) all need "dark matter" for one reason only - to provide additional gravitational force to make observations agree with the Standard Model. Right now, the ONLY thing that "Dark Matter" does is provide extra gravitational force. It is not a leap of faith to consider that perhaps the Standard Model does not model gravity properly, especially on large scales, where these problems become especially troublesome.

To address your statement, the data indeed does say something about gravitation, and it's coming through loud and clear. Gravitation is the ONLY thing that "Dark Matter" provides. As a bookkeeping convention "Dark Matter" is tolerable, and it keeps the Standard Model usable at large scales, but we should regard it as a measure of the failing of the SM at galactic scales, not as a real entity.

 

[Nereid]

Nereid - Please keep cool! The issue is serious not belligerent!

I'll try; is 'robust' OK?

Working on it! But if you look at my public profile you'll see I'm an "Independent researcher" - without easy access to sufficient resources- that is why I will be glad of some cooperation!

How many of the 34 have tenure? Access to PhD and summer students? university broadband internet and computing resources?

Surely the point is that the neutrino has been discovered and the solar neutrino problem has been resolved, neutrinos have a small mass*, whereas the problem identifying the Higg's bosons, DM and DE hasn't been resolved?

- Garth
*But unfortunately not enough to solve the DM problem too.

My point isn't that we *now* know 'all about' the neutrino, it's that there was a many decades gap (2?) between its prediction and the first direct observations, and many more decades (4?) before anomalous behaviour was nailed down; to say that no one has a DM particle in their SQUID, despite 20 years of looking, therefore it's all epicycles is equivalent, at some level, to saying SelfAdjoint, Bahcall, Davis etc should never have been given any funds to waste looking for neutrinos!

 

[Garth]

My point isn't that we *now* know 'all about' the neutrino, it's that there was a many decades gap (2?) between its prediction and the first direct observations, and many more decades (4?) before anomalous behaviour was nailed down; to say that no one has a DM particle in their SQUID, despite 20 years of looking, therefore it's all epicycles is equivalent, at some level, to saying SelfAdjoint, Bahcall, Davis etc should never have been given any funds to waste looking for neutrinos!

I think you have got it the wrong way round. I'm not saying the standard model shouldn't be funded, on the contrary it needs all the ongoing research available, however it should not be treated as the only show in town and beyond criticism when these questions still remain.

What I am saying is, for the sake of good scientific practice, and in order to give alternatives against which the standard model can be fairly tested, the cosmological community should also support these other approaches until they are falsified. That has not happened yet with SCC, nor apparently with some other theories suggested by serious researchers and published in reputable journals.

For example I have published SCC originally in GRG, from which there were over 45 citations, and the revamped theory in Astrophysics and Space Science and now by Nova Science Publishers. As a challenge to the standard model I would have thought others, from an academic point of view at least, would have welcomed another alternative and criticised it. Yet so far silence. I am grateful that by chance GPB is going to test it against GR -the result is still open and it seems we will have to wait until 2006 to obtain the result, ah well patience is a virtue!.
- Garth

 

[Nereid]

I think you have got it the wrong way round. I'm not saying the standard model shouldn't be funded, on the contrary it needs all the ongoing research available, however it should not be treated as the only show in town and beyond criticism when these questions still remain.

Perhaps I misread; didn't you (and turbo-1?) sign a statement which reads, in part "The successes claimed by the theory's supporters consist of its ability to retrospectively fit observations with a steadily increasing array of adjustable parameters, just as the old Earth-centered cosmology of Ptolemy needed layer upon layer of epicycles.[/color]"? Could not a similar set of words have been written about parts of physics, before the 'oscillatory' nature of the neutrino was nailed down recently? Is not this statement which you have signed a rather pointed accusation of those do research following the concordance model(s) as doing bad science?

What I am saying is, for the sake of good scientific practice, and in order to give alternatives against which the standard model can be fairly tested, the cosmological community should also support these other approaches until they are falsified. That has not happened yet with SCC, nor apparently with some other theories suggested by serious researchers and published in reputable journals.

Before you introduced that New Scientist letter, that's what I understood your position to be; having read that letter, I'm curious as to why you think you needed to be so belligerent towards folk such as Tegmark.

For example I have published SCC originally in GRG, from which there were over 45 citations, and the revamped theory in Astrophysics and Space Science and now by Nova Science Publishers. As a challenge to the standard model I would have thought others, from an academic point of view at least, would have welcomed another alternative and criticised it. Yet so far silence. I am grateful that by chance GPB is going to test it against GR -the result is still open and it seems we will have to wait until 2006 to obtain the result, ah well patience is a virtue!.
- Garth

Hey, we at PF love to have you here just the same
(just don't go 'crackpot' on us, OK?)

 

[Garth]

Perhaps I misread; didn't you (and turbo-1?) sign a statement which reads, in part "The successes claimed by the theory's supporters consist of its ability to retrospectively fit observations with a steadily increasing array of adjustable parameters, just as the old Earth-centered cosmology of Ptolemy needed layer upon layer of epicycles.[/color]"? Could not a similar set of words have been written about parts of physics, before the 'oscillatory' nature of the neutrino was nailed down recently? Is not this statement which you have signed a rather pointed accusation of those do research following the concordance model(s) as doing bad science

Nereid - I have read the statement again carefully, the only accusation it makes of the present cosmological community is the generally unacknowledged tentative nature of the standard model's additional "hypothetical entities".

Inflation, DM, DE are treated as 'hard science' is that not the situation?
Now once these have been discovered the situation will change, however, until then the history of adding first Inflation then DM then DE to make the observations fit the theory speaks of getting the scientific cart before the horse. I thought the theory had to fit the observations.

Before you introduced that New Scientist letter, that's what I understood your position to be; having read that letter, I'm curious as to why you think you needed to be so belligerent towards folk such as Tegmark

I was not aware that is was belligerent, just speaking its mind. Its key recommendation: "To redress this, we urge those agencies that fund work in cosmology to set aside a significant fraction of their funding for investigations into alternative theories and observational contradictions of the big bang." is motivated by a desire for good scientific practice - but also, I must admit, probably a little resentment that such funding hasn't already been forthcoming.

Hey, we at PF love to have you here just the same
(just don't go 'crackpot' on us, OK?)

Keep your sharp points coming; I find them invaluable.

Oh! I have been a crackpot all my life!

- Garth

“Blessed are they that can laugh at themselves, for they shall never cease to be amused”

 

[turbo]

Perhaps I misread; didn't you (and turbo-1?) sign a statement which reads, in part "The successes claimed by the theory's supporters consist of its ability to retrospectively fit observations with a steadily increasing array of adjustable parameters, just as the old Earth-centered cosmology of Ptolemy needed layer upon layer of epicycles.[/color]"? Could not a similar set of words have been written about parts of physics, before the 'oscillatory' nature of the neutrino was nailed down recently? Is not this statement which you have signed a rather pointed accusation of those do research following the concordance model(s) as doing bad science?

Dear Nereid, the letter is not an "accusation" aimed at people whose research is aimed at bolstering the standard cosmologies. It is a statement of principal that funding should not be denied nor professional resources withheld from people whose lines of inquiry diverge from the "concordance models", lest potentially valuable insights go unexplored.

This is not a revolutionary idea, but when funding is sought and fought over as vigorously as it is today, that idea can be very threatening to the status quo. Any real paradigm-shift in physics (like Newtonian gravitation, Special and General Relativity) will likely come from a creative intelligent person "pushing the envelope", and not from someone studiously "coloring within the lines" of the Standard Model. If that person cannot get support for his research, and is denied access to the instrumentation that might flalsify his/her models, we all lose. Fair enough?

 

[Chronos]

Shall we discuss Arp's 'white hole' at the center of galaxies to explain galactic morphology? Shall we talk about quantized red shifts? Do galaxies 'expel' quasars and proto-galaxies? Care to discuss the mechanism explaining that process? Shall we embrace the LaSage ['push gravity'] model that Arp endorses? Do galaxies [and stars] increase in mass and become less red shifted as they age [as Arp claims]? Does the universe, and stars, increase in mass by converting the ZPE into mass [as Arp claims]? Dr. Halton 'Chip' Arp may be a fine gentleman and respected astronomer, but, he is a lousy theorist and mathematician. Do you really want to go there?

 

[Garth]

Shall we discuss Arp's 'white hole' at the center of galaxies to explain galactic morphology? Shall we talk about quantized red shifts? Do galaxies 'expel' quasars and proto-galaxies? Care to discuss the mechanism explaining that process? Shall we embrace the LaSage ['push gravity'] model that Arp endorses? Do galaxies [and stars] increase in mass and become less red shifted as they age [as Arp claims]? Does the universe, and stars, increase in mass by converting the ZPE into mass [as Arp claims]? Dr. Halton 'Chip' Arp may be a fine gentleman and respected astronomer, but, he is a lousy theorist and mathematician. Do you really want to go there?

Chronos - No mention of Arp's particular ideas was made in the "cosmologystatement", his theory is not the only alternative show in town; the key point of that statement is more general than that.

However there may be some value in some of his ideas and each ought to be weighed on its merits and not arbitrarily ignored; for example the question of whether particles secularly gain mass, or not, depends on the method of defining and measuring mass over cosmological distances. In general a particle's four-momentum cannot be parallel transported in GR, the required Killing vectors do not in general exist. So the issue is not simple or resolved, only defined by convention to be so.

- Garth

 

[Chronos]

Chronos - No mention of Arp's particular ideas was made in the "cosmologystatement", his theory is not the only alternative show in town; the key point of that statement is more general than that.

However there may be some value in some of his ideas and each ought to be weighed on its merits and not arbitrarily ignored; for example the question of whether particles secularly gain mass, or not, depends on the method of defining and measuring mass over cosmological distances. In general a particle's four-momentum cannot be parallel transported in GR, the required Killing vectors do not in general exist. So the issue is not simple or resolved, only defined by convention to be so.

- Garth

No ideas should be discarded. That was not the point. I realize some of my objections to Arp tread upon the toes of SCC. My main objection to Arp is his sloppy generalizations. He has a history of using selective observations and bad math to leap to 'spectacular' conclusions. And then he whines when people don't take him seriously... duh? The SCC model is a much better example of the scientific method.

 

[turbo]

Do galaxies 'expel' quasars and proto-galaxies?

Here is a nice picture of M51 (the wallpaper on my PC).

http://housefly.astro.princeton.edu/~rhl/PrettyPictures/M51.jpg

As you look at the picture, notice the "shredded" appearance of the arms near the companion, and the prevalence of hot blue star-forming regions in that area. Now look at the other side of M51, and see how smooth and undisturbed it appears. Does this not look like an ejection event to you?

There are many spiral galaxies with smaller companions embedded in their arms, attached to their arms, or lying outside the host with filaments between the two. Conventional cosmologists always characterize these either as "collisions" or "mergers", never as ejections. Do you wonder why?

Arp has studied galaxy morphology for decades longer than most cosmologists have been alive. You may disagree with many of his ideas, but you might want to pay attention to this one.

 

[meteor]

Do galaxies 'expel' quasars and proto-galaxies?

By no means, this is only an imaginative process proposed by Chip Arp in his Variable mass theory
But nobody takes seriously Arp (well, practically nobody)

 

[Chronos]

Here is a nice picture of M51...
As you look at the picture, notice the "shredded" appearance of the arms near the companion, and the prevalence of hot blue star-forming regions in that area. Now look at the other side of M51, and see how smooth and undisturbed it appears. Does this not look like an ejection event to you?

The appearance of M51 is nicely explained by this paper
http://cc.oulu.fi/~hsalo/M51_I_SL_2000.pdf.
An ordinary collision model accounts for observation. The prevalence of the young star forming regions is due to gas cloud collisions. This paper confirms prior studies [as referenced in the paper] where the same conclusions were reached. The case against ejection appears to be pretty solid.

 

[turbo]

By no means, this is only an imaginative process proposed by Chip Arp in his Variable mass theory
But nobody takes seriously Arp (well, practically nobody)

Please keep an open mind on galactic ejection. Whether or not you can accept gravitational mass as variable or not, please keep galactic ejection as a possiblity. You will thank me for this.

Arp's methods and theories have fallen out of favor as cosmological mathemeticians have come to dominate astronomy, but he is no dummy. His work in galactic morphology is seminal, and there are WAY too many examples of obvious ejection (as opposed to "collision" or ""capture") to be rejected.

Please browse this:

http://nedwww.ipac.caltech.edu/level5/Arp/frames.html

Then tell me that all these interactions are "collisions" or "captures". I'll try not to laugh.

 

[turbo]

The appearance of M51 is nicely explained by this paper
http://cc.oulu.fi/~hsalo/M51_I_SL_2000.pdf.
An ordinary collision model accounts for observation. The prevalence of the young star forming regions is due to gas cloud collisions. This paper confirms prior studies [as referenced in the paper] where the same conclusions were reached. The case against ejection appears to be pretty solid.

Dear Chronos, please re-read that paper. The convolutions that "explain" that multiple-encounter model are laughable. The universe is complex, but the underlying mechanisms are simple. Theories that invoke complex mechanisms to explain a single observation are wrong almost every time. Occam's Razor.

 

[Chronos]

Please keep an open mind on galactic ejection. Whether or not you can accept gravitational mass as variable or not, please keep galactic ejection as a possiblity. You will thank me for this.

Arp's methods and theories have fallen out of favor as cosmological mathemeticians have come to dominate astronomy, but he is no dummy. His work in galactic morphology is seminal, and there are WAY too many examples of obvious ejection (as opposed to "collision" or ""capture") to be rejected... Then tell me that all these interactions are "collisions" or "captures". I'll try not to laugh.

Has anyone has rigorously examined and demonstrated [i.e., a published paper] that any of these interactions cannot be explained by collision or capture events?

 

[Chronos]

Dear Chronos, please re-read that paper. The convolutions that "explain" that multiple-encounter model are laughable. The universe is complex, but the underlying mechanisms are simple. Theories that invoke complex mechanisms to explain a single observation are wrong almost every time. Occam's Razor.

It seems rather cavalier to dismiss such a rigorous study without voicing specific objections. Were the papers referenced, where similar conclusions were reached using different approaches, also too convoluted to be palatable?

 

[turbo]

Has anyone has rigorously examined and demonstrated [i.e., a published paper] that any of these interactions cannot be explained by collision or capture events?

Dear Chronos, if you can rigorously examine and demonstrate that any of these interactions ARE collision or capture events, I wil be happy to review your work. You can start with the M51 system.

 

[meteor]

I still believe that the bridge connecting M51 with the other galaxy is a tidal arm. The Toomre brothers demonstrated in 1972 that gravitational interactions can cause these filamentary bridges to occur, so case closed
It's like going to a castle by night in search of phantoms. if you are suggestive to see them, you will see one behind each corner. If you want to see ejections in images that can be explained other way you will see ejections. But I prefer to follow the mainstream, the truth uses to be always with the point of view of the majority

 

[turbo]

It seems rather cavalier to dismiss such a rigorous study without voicing specific objections. Were the papers referenced, where similar conclusions were reached using different approaches, also too convoluted to be palatable?

Your are kidding about the "rigorous study, right?"

I hope so. That paper is lame in so many ways. The more complex the "explanation" for a particular observation, the more certain you can be that it is absolutely wrong. In this case, the obvious distortions of M51 are "explained away" as if its companion has made a concerted but very complex multi-pass attack on it. There is a relatively simple explanation for M51's appearance, and it does not involve a "Kung Fu" battle between the host and the companion. The companion was ejected, and it distorted the arms of the host in the process.

You may not like this, but Arp's Atlas of Interacting Galaxies will give you enough examples to refute to keep you busy for the rest of your life (assuming you will not simply nay-say every one). If you have not browsed that work, you should spend a few hours on it:

http://nedwww.ipac.caltech.edu/level5/Arp/frames.html

As I have said, Arp has been studying galaxy morphology for decades longer than most cosmologists have been alive.

Look at the examples, and try to think how these galaxies connected by filaments or obviously skewed by tidal distortion could possibly exhibit these abnormalities in "anticipation" of future interaction. The lame half-witted "capture" model dies here, OK?

Now, is it even possible in your estimation that any of these interactions are the result of an ejection phenomenon, or must every single one of them be a result of a collision? You don't have to reply right away, and I'm not going to demand math. Please think before answering, though, and go with your gut.