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William
2014-Apr-26, 02:53 AM
This paper by Pavel Kroupa provides a summary of the observational evidence and related analysis (multiple authors, more than one logical pillar to support the assertion) that appears to support the assertion that dark matter does not exist. In addition to the evidence that he provides, the most sensitive experiments to detect dark matter have failed which is expected if dark matter does not exist.

http://arxiv.org/abs/1204.2546v2

The dark matter crisis: falsification of the current standard model of cosmology

This lecture by Kroupa is an overview of his paper.

http://www.youtube.com/watch?v=UPVGDXNSBZM

Kroupa includes a list of all of the major problems associated with the current cosmological theory (22 items), however the scope of his paper and his lecture is limited to evidence to support the assertion that dark matter does not exist. The point of including the long list of problems with cosmological theory, is that one cannot use the faulty logic to defend dark matter that it must be exist as if it did not exist that would spoil a theoretically perfect theory.

Shaula
2014-Apr-26, 05:17 AM
His conjectures have several rather fundamental issues with them.
1) Dwarf galaxies are observed to have large amounts of dark matter in general, making the more likely hypothesis to be that his TDGs are not part of our observed data set (consistent with the idea that they are generally very small and faint objects or very weak bound systems)
2) The dual galaxy conjecture is his own addendum to the current models. The TDGs he talks about are hypothesised but have not been definitively identified, which could be for a number of reasons including average brightness, lifetime etc. He claims that because TDGs 'must' form we can therefore assume that all galaxies we see in the one population he claims 'must' be TDGs because calling them anything else requires you to accept the current standard models to get around this.
3) The Tully Fisher relationship applies to spirals, not dwarf galaxies
4) He asserts that finding so many satellites in polar orbits is impossible with the current model - which is simply false. Anything orbiting in the disk plane is going to be less visible (greater dust path length) and would quite possibly have interacted with the disk itself as it formed.

I sort of started to lose interest there. Kroupa is a MOND proponent and while, personally, I actually quite like the idea it has shown to so far be less powerful a tool than the current model. He does the cause of MOND no favours when he makes claims like 'standard model cosmologists have to fine tune their model to get it to work which is bad' and then sits and fine tunes MOND to get it to agree with each observation individually. His dwarf galaxy work is interesting and does ask some good questions - however he immediately pushes it to be 'yet more proof' for his personal favourite among the alternatives to the LCDM model. This makes the paper heavily biased in tone and content and undermines its scientific value.

Oh and the 'log Confidence vs time' graph is the sort of thing I would expect to see in a graphics rich presentation by someone trying to sell me something.

William
2014-Apr-26, 10:21 AM
His conjectures have several rather fundamental issues with them.
1) Dwarf galaxies are observed to have large amounts of dark matter in general, making the more likely hypothesis to be that his TDGs are not part of our observed data set (consistent with the idea that they are generally very small and faint objects or very weak bound systems)

William: As dark matter has not been detected your statement/assertion that "dwarf galaxies' are observed to have a large amounts of dark matter in general, is a non sequitur. What is the observational evidence that supports the assertion that dwarf galaxies have large amounts of dark matter in general? The dark matter hypothesis was created to explain observational anomalies/paradoxes. It does not follow logically from the fact that there are observational anomalies that dark matter exists and is the cause of the observational anomalies.

I do not understand what you mean by the statement that "tidal dwarf galaxies are not part of our observed data set". Obviously spiral galaxies interact and what forms when spiral galaxies interact is tidal dwarf galaxies. The tidal dwarf galaxies that form when spiral galaxies interact have a spacial/phase relationship. Tidal galaxies are concentrated in a rectangular region that is aligned to the plane of the originating spiral galaxy interaction. As there can be multiple interactions of spiral galaxies there can be more than one rectangular region that has dwarf spiral galaxies in it. Observationally it is a fact that tidal dwarf galaxies exist.



His conjectures have several rather fundamental issues with them.

2) The dual galaxy conjecture is his own addendum to the current models. The TDGs he talks about are hypothesised but have not been definitively identified, which could be for a number of reasons including average brightness, lifetime etc. He claims that because TDGs 'must' form we can therefore assume that all galaxies we see in the one population he claims 'must' be TDGs because calling them anything else requires you to accept the current standard models to get around this.


William: Your second comment is also a a non sequitur. There is observational evidence that spiral galaxies interact and there is observational evidence that what forms when spiral galaxies interact is tidal dwarf galaxies that have a spacial distribution due to their origin. The second sentence of your comment is also a non sequitur. It is a prediction of the standard model of cosmology (SMoC) (which includes dark matter) that the dark matter will cause there to be a large number of DM dwarf galaxies about the spiral galaxy that are spherical distributed. (I would recommend you watch Kroupa's video which provides an explanation of how spiral galaxies are hypothesized to form from mergers of dark matter clouds in accordance with SMoC theory. That is not what is observed. The number of dwarf galaxies observed about spiral galaxies is too few by orders of magnitude and the dwarf galaxies that are observed about the spiral galaxies have a spacial/phase relationship which indicates their origin was spiral galaxy interaction, not combination of hypothesized dark matter dominated clouds of gas.


His conjectures have several rather fundamental issues with them.

I sort of started to lose interest there. Kroupa is a MOND proponent and while, personally, I actually quite like the idea it has shown to so far be less powerful a tool than the current model. He does the cause of MOND no favours when he makes claims like 'standard model cosmologists have to fine tune their model to get it to work which is bad' and then sits and fine tunes MOND to get it to agree with each observation individually. His dwarf galaxy work is interesting and does ask some good questions - however he immediately pushes it to be 'yet more proof' for his personal favourite among the alternatives to the LCDM model. This makes the paper heavily biased in tone and content and undermines its scientific value.

Oh and the 'log Confidence vs time' graph is the sort of thing I would expect to see in a graphics rich presentation by someone trying to sell me something.

William:
Kroupa lists 22 fundamental issues with the standard model of cosmology (SMoC). The 22 fundamental issues include four issues that require the laws of physics to be changed to avoid the collapse of the SMoC. Cosmology is the only field of science where changing the laws of physics is readily accepted to avoid looking at other solutions. The scope of this thread is however limited to dark matter. I will start a separate thread to discuss large scale structure observations and the SMoC's inflation which is also a crisis.

It is helpful to have someone list the problems with a theory and to point out that the problems with the theory (SMoC) are increasing with time as observation data improves.

Shaula
2014-Apr-26, 11:20 AM
William: As dark matter has not been detected you statement/assertion that "dwarf galaxies' are observed to have a large amounts of dark matter in general, is a non sequitur. What is the observational evidence that supports the assertion that dwarf galaxies have large amounts of dark matter in general? The dark matter hypothesis was created to explain observational anomalies/paradoxes. It does not follow logically from the fact that there are observational anomalies that dark matter exists and is the cause of the observational anomalies.
This is a comment that totally misses the point of my argument. He claims that dwarf galaxies should be split into two classes and that the main difference between them should be quantity of dark matter. He then claims that the lack of two groups in his analysis implies that there are no primordial type dwarf galaxies, which would contain far more dark matter. The more parsimonious explanation and one he ignores is that there are no tidal type galaxies of the kind he describes because we see dwarf galaxies of the primordial type according to his definitions.


I do not understand what you mean by the statement that "tidal dwarf galaxies are not part of our observed data set". Obviously spiral galaxies interact and what forms when spiral galaxies interact is tidal dwarf galaxies
'Obviously'. Not at all. There are a number of papers out there that estimate the contribution of tidal tail debris to dwarf galaxy formation. The estimates of its contribution range from something like 5% to 50% for clusters of galaxies. It is not settled at all. We cannot point at these objects and say "That is a galaxy and that formed from the tidal debris" yet - all we can do is estimate how many of them might have done so. Given the uncertainty and the statistical nature of this, and the fact that some of the objects under consideration are not shown to be bound, it is actually very hard to identify them as a unique class of galaxy with any confidence. Then the escape from the tidal debris to form isolated dwarf galaxies - that is also a problem. As generally the models say they don't.

The phase space correlation he talks about is based on a very simplistic assumption. He assumes that the distribution of satellite galaxies must begin and remain spherical around the host galaxy. Kroupa himself is a co-author on a paper which shows that there is a mechanism to produce this anisotropy by having a slightly flattened dark matter halo. Moreover the anisotropy he talks about is present not just in satellite galaxies but on a larger scale - galactic cluster sizes. Therefore to make the claims he has requires us to complicate things by having a different mechanism for this anisotropy at different scales. This is ignored in the paper.


It is a prediction of the standard model of cosmology (SMoC) (which includes dark matter) that the dark matter will cause there to be a large number of DM dwarf galaxies about the spiral galaxy that are spherical distributed.
This is a known issue and can, to a degree, be tuned out by varying the mix of dark matter. This is an area of active research.


The 22 fundamental issues include four issues that require the laws of physics to be changed to avoid the collapse of the SMoC. Cosmology is the only field of science where changing the laws of physics is readily accepted to avoid looking at other solutions.
You mean we still use Newton's physics for everything? I did not know that! This is a ridiculous claim. The models of physics change all the time. They incorporate new phenomena, new forces, new fields. That is how physics advances.


It is helpful to have someone list the problems with a theory and to point out that the problems with the theory (SMoC) are increasing with time as observation data improves.
This is to ignore the fact that actually the scale of the problems with the theory are getting smaller. The gross features of the universe are fairly well explained in this way. The reason you can claim that there are many, many more problems is because we are making ever more detailed and complex models. We have gone from the large scale structure of the universe to trying to understand what are very small scale, in cosmological terms, phenomena.

Ken G
2014-Apr-26, 12:24 PM
I would say that one thing Kroupa does is good science, and one is bad science. It is always good science to increase skepticism, as self-questioning is the crux of all science and when we forget that, and start treating science like a bandwagon, we end up doing things like believing for 1400 years that the Earth is the center of the universe. So let him point to the problems of the theory and the evidence we may be heading the wrong direction, science never gets better than that and no scientist should ever react defensively to such a challenge. It is also valid for proponents of the model to answer the challenges and point out flaws in the argument that there are flaws! All is part of good science. Indeed, Kroupa is a little naive to hold that a theory can be "falsified" by one failed prediction, the truth is we have often needed to "shore up" incomplete theories to fix failed predictions! So his comments should be framed as "if the standard cosmology is to survive as the prevailing theory, it must find a way to fix this." In that light, I think he makes some good points that standard cosmologists should indeed be ready to address, or to explore further.

The bad science is using problems with the prevailing theory to promote an alternative with problems of its own, and here Kroupa appears guilty of an even greater suspension of skepticism than he accuses standard cosmologists of. Instead, let the debate on MOND be focused on its strengths and weaknesses, it has nothing to do with the standard picture. A scientific argument does not look like "my theory must be right because your theory has problems", it looks like "here are the strengths and weaknesses of theory A. Here are the strengths and weaknesses of theory B." Any skepticism directed toward theory A should also be directed toward theory B. It's not a courtroom with a lawyer for theory A and a lawyer for theory B, it's science, and we can all be scientists rather than lawyers or politicians. But perhaps if Kroupa feels voiceless against the din of the prevailing standard cosmology, he is to be forgiven for upping his rhetoric a bit, just to be heard at all.

Shaula
2014-Apr-26, 12:26 PM
I would wholeheartedly agree with Ken on this. Kroupa makes some interesting points worth thinking about. I just think he goes way too far with the conclusions drawn from them.

William
2014-Apr-26, 03:19 PM
This is a comment that totally misses the point of my argument. He claims that dwarf galaxies should be split into two classes and that the main difference between them should be quantity of dark matter. He then claims that the lack of two groups in his analysis implies that there are no primordial type dwarf galaxies, which would contain far more dark matter. The more parsimonious explanation and one he ignores is that there are no tidal type galaxies of the kind he describes because we see dwarf galaxies of the primordial type according to his definitions.

William:
It appears we need to move in logical baby steps, one issue at time. There are two different formation methods to form dwarf galaxies that are associated with disk type galaxies.

Type B dwarf galaxy (labeling consistent with Kroupa's paper) formed from tidal interaction): Kroupa's lecture includes astronomical pictures of spiral galaxies interacting in the process of forming tidal galaxies. There is observational evidence that tidal dwarf galaxies form. Simulations ( Kroupa's assertion in his paper and in his lecture, he includes pictures of the leading authors of the simulation studies) supports the assertion that if dark matter exists, the dark matter remains with the large spiral galaxy/(galaxies) when there is a merger. Simulations in peer reviewed literature supports the assertion that tidal collision formed dwarf galaxies do not have a dark matter halo.

If you like I will provide Kroupa's list of peer reviewed papers. Kroupa is a senior researcher and has won scientific awards for the number and quality of his scientific papers. I am assuming he is a professional and does not make something up. To break the impasse of what Kroupa states in his peer reviewed paper and in his lecture compared to what you are stating in this forum, you need a link to a peer review paper to support your assertion that tidal galaxies do not form and/or that tidal galaxies have a dark matter halo, i.e that there is only one type of dwarf galaxies. Saying the same comment over and over: the number of times a comment is repeated or how emphatically it is stated, does not make it true.

Type A dwarf galaxy: formed when the universe was young during the formation of the spiral galaxies): During the merger of small gas clouds when the spiral galaxy is formed dwarf galaxies form which do have the theoretical dark matter halos. Simulations however indicate there should be hundreds, if not thousands of the dwarf galaxies. That is not observed which is one of the paradoxes.

Shaula
2014-Apr-26, 03:45 PM
Kroupa's lecture includes astronomical pictures of spiral galaxies interacting in the process of forming tidal galaxies.
No. What it includes is a very famous image, one you see repeated a lot, which shows a series of small condensed objects in a tidal tail. Some of them could be galaxies, some of them may not be. Some of them could have formed from the tail material, some of them may not. I suggest you review the literature on this. As I said I found a range of values with a maximum of 50% (derived from different n-body simulations) probability for the galaxies among them to be these type B dwarf galaxies. I am not denying that they can form, what I am pointing out is that so far we don't have enough insight into them to point at a dwarf galaxy and say "That is a type B". Simulations also show that these galaxies should have low levels of dark matter associated with them, I have not disagreed with that at all. Simulations also show that it is a struggle to get enough of these dwarf galaxies ejected from their formation point to account for the distribution of dwarf galaxies we do see.

As I have said, the logical issue is in his definition of a tidally formed galaxy. Essentially he is claiming that the ONLY way to explain the polar distribution of satellite galaxies is to assume that they are all TDGs (this is the phase space correlation). He then makes the assumption that the type A and B galaxies should have very distinct clusters in brightness/baryonic mass and uses these two facts to claim that in fact all dwarf galaxies are of type B. He then goes on to say that this means that they cannot contain dark matter and the observed galaxies must therefore be behaving MONdianly when they are observed to behave as if they do contain dark matter.


you need a link to a peer review paper to support your assertion that tidal galaxies do not form and/or that tidal galaxies have a dark matter halo, i.e that there is only one type of dwarf galaxies.
I guess you didn't really understand what I am saying then. Because I made none of these assertions.


Saying the same comment over and over: the number of times a comment is repeated or how emphatically it is stated, does not make it true.
Oh? From your threads on the solar cycles I find it hard to believe that you hold this opinion.

For what it is worth I am not repeating myself, I am pointing out a range of issues. None of which emphatically contradict the paper's conclusions. However they do show that what is being asserted and used to reach the conclusion is not always as clear cuts as is stated.


Type A dwarf galaxy: formed when the universe was young during the formation of the spiral galaxies): During the merger of small gas clouds when the spiral galaxy is formed dwarf galaxies form which do have the theoretical dark matter halos. Simulations however indicate there should be hundreds, if not thousands of the dwarf galaxies. That is not observed which is one of the paradoxes
As I said, a well known one that is the subject of active research.

Cougar
2014-Apr-26, 04:01 PM
Indeed, Kroupa is a little naive to hold that a theory can be "falsified" by one failed prediction....

I noticed that too. The invaidity of strict Popperism (especially, in the context of the huge Standard Model of Cosmology) has been discussed on these boards.


So his comments should be framed as "if the standard cosmology is to survive as the prevailing theory, it must find a way to fix this."

Again right. It is Kroupa's framing that I object to. Does his argument create a full-blown "crisis" in the Standard Model of Cosmology because some observations of dwarf galaxies do not conform to "theory" based on computer simulations, or is it more a "problem" with the lack of sufficient observations of dwarfs, or a "problem" with the simulation assumptions? One might recall that the early models of structure formation with dark matter but without a cosmological constant had "problems" reproducing the structure we see. In 1984, Peebles found that a simulated universe with cold dark matter would need a cosmological constant to make up about 80% of the total energy to produce a result similar to the structure observed. Most still saw this as an "implausible" solution, however, to the degree that Michael Turner "faced a barrage of abuse"1 as he argued in 1996 with Gott and Spergel in defense of the cosmological constant. Implausible as it may seem, the naysayers pretty quickly changed their tune when the data came in from Riess and Perlmutter in 1998.


The bad science is using problems with the prevailing theory to promote an alternative with problems of its own, and here Kroupa appears guilty of an even greater suspension of skepticism than he accuses standard cosmologists of.

That is a very applicable criticism.

_______________
1 I'm reading from Pedro Ferreira's The Perfect Theory (2014).

William
2014-Apr-26, 10:07 PM
The following is Kroupa's paper's list of Dark matter and/or SMoc (standard model of cosmology theory) problems. It should be noted that the list of theory problems/paradoxes includes unexplained observed structured anomalies which is very interesting. The SMoc does not provide a physical explanation for the structural anomalies.


17.3.2 A long list of Failures
(William: 1 to 10 of 22 from Kroupa list in this comment, see next comment for 11 to 22).
(1) 1980: Curvature and homogeneity: The BB would imply the universe to be highly inhomogeneous and curved in disagreement with observations.
This is solved by introducing inflation (Guth & Tye 1980). (William: Requires unsolved new physics. The word inflation is a place holder that requires the justification and creation of a special 'field' that has the capability of simultaneously and uniformly expanding the entire universe using some unknown energy source. I will in a month or so, start a separate thread to provide a very brief explanation of what the word 'inflation' must be capable of doing to the physical universe and to provide an overview of the most recent large scale observations, which is a very interesting subject.

(2) 1981: The super-Keplerian galactic rotation curve:
Rotation curves of disk galaxies are observed to remain quite flat (Rubin & Ford 1970; Bosma 1981). This is solved by introducing cold or warm DM (Blumenthal et al. 1984).

(3) 1991: Angular momentum: Disk galaxies forming in the C/WDM cosmological model dissipate too much angular momentum by virtue of the baryons falling into the DM potential wells, ending up being too compact with too little angular momentum in comparison with observed disk galaxies (Navarro & Benz 1991, see also Piontek & Steinmetz 2011; Martig et al. 2012; Dutton & van den Bosch 2012; Scannapieco et al. 2012).

(4) 1991: The cusp/core: CDM haloes have cusps whereas the observationally deduced DM halo profiles have substantial core radii similar to the dimension of the luminous galaxy (Dubinski &Carlberg 1991, see also Gilmore et al. 2007a,b; de Blok 2010; Chen & McGaugh 2010; Jardel & Gebhardt 2012). A possible solution has been suggested by the simulations of Governato et al. (2012) but relies among other assumptions on a bursty star-formation rate (SFR) required to repeatedly blow out gas and a steep Kennicutt-Schmidt exponent (n = 1.5) in SFR ∝ n gas, where SFR is the star formation rate and gas is the local gas density. However, in reality it is not clear if the dSph and UFD satellites experienced bursty SFRs, n = 1 (Pflamm-Altenburg & Kroupa 2008, 2009), the IMF would have had a lack of massive stars at the low SFRs of the MW satellites, as is inferred by Tsujimoto (2011), and the threshold for SF is lower in reality than assumed in the simulations (see further below). Repeated gas blow-out which is required to evolve the cusps to cores is thus not likely to be possible.

WDM models tuned to account for the observed large cores in dwarf galaxies have such long DMparticle streaming lengths that the dwarf galaxies cannot form in the first place (Maccio’et al. 2012).

(5) 1998: Dark energy: The fluxes and redshifts of observed type Ia supernovae (SNIa) do not match the cosmological model (Riess et al. 1998; Schmidt et al. 1998; Perlmutter et al. 1999) unless the universe is assumed to expand at an ever larger rate. To account for the implied accelerated expansion dark energy (DE) is introduced. As with inflation, while mathematically allowed, it remains unclear if DE constitutes physics (see e.g. the discussion in Afshordi 2012). The SNIa flux–redshift data may at least partially be explained with an inhomogeneous universe (Wiltshire 2009; Smale & Wiltshire 2011; Marra et al. 2012) rather than with DE, whereby systematics in SNIa light curve fitting remain an issue (Smale &Wiltshire 2011). Bull & Clifton (2012) find that the “appearance of acceleration in observations made over large scales does not necessarily imply or require the expansion of space to be accelerating, nor does it require local observables to indicate acceleration.” In fact, it might perhaps be surprising that a homogeneous SMoC should lead to a perfect agreement with the observed SNIa data. In other words, the SNIa data that stem from the real inhomogeneous universe (Karachentsev 2012) should show some deviations from a homogeneous SMoC. If none are seen then this may imply an over-constrained model.17 solar [/Fe] values (Thomas et al. 2002). This may be partially alleviated by a prescription for AGN quenching of star formation in massive haloes but not so in the intermediate galaxy-mass regime (Pipino et al. 2009, see also Nagashima et al. 2005; Recchi et al. 2009).

(6) 1999: Missing satellites: Computations with more powerful computers showed that many more DM sub-structures form than observed galaxies have satellites (Klypin et al. 1999; Moore et al. 1999; the problem is somewhat reduced with WDM: Menci et al. 2012).

(7) 2002: Hierachical structure formation: As more massive galaxies are build-up hierarchically from smaller building blocks in the SMoC, their [/Fe]ratios ought to reflect the sub-solar [/Fe] ratios of the building blocks (e.g., dE galaxies have low [/Fe] ratios). In conflict with this expectation, observed massive E galaxies show high near-solar [/Fe] values (Thomas et al. 2002).
This may be partially alleviated by a prescription for AGN quenching of star formation in massive haloes but not so in the intermediate galaxy-mass regime (Pipino et al. 2009, see also Nagashima et al. 2005; Recchi et al. 2009).


(8) 2005: The Disk of Satellites (DoS/VPOS): The observed satellite galaxies of the MW are arranged in a vast polar structure (Kroupa et al. 2005; Metz et al. 2007, 2008, 2009a; Kroupa et al. 2010; Pawlowski et al. 2012b). Of all objects at Galactocentric distances larger than 10 kpc, only 4 per cent are not associated with the VPOS (Sec. 10.1.7). Extragalactic anisotropic satellite systems are common, and Andromeda appears to have a flattened satellite system seen edge-on (Sec. 13.6).

(9) 2007: The TDG mass-deficit: Unexpectedly, observed young TDGs show evidence for DM which however is not possible if the SMoC were true (Barnes & Hernquist 1992) unless they contain undetectable gas (Bournaud et al. 2007, see also Gentile et al. 2007).

(10) 2008: Invariant disk galaxies: Observed disk galaxies are too similar following a simple one parameter scaling law over many orders of magnitude in mass in conflict with the expected variation in the SMoC due to the chaotic formation history of each DM host halo (Disney et al. 2008, see also Hammer et al. 2007; Kroupa et al. 2010).

William
2014-Apr-26, 10:14 PM
William: The following is Kroupa's paper's list of Dark matter and/or SMoc (standard model of cosmology theory) problems 11 to 22 see my above comment for problems 1 to 10.
http://arxiv.org/abs/1204.2546v2

The dark matter crisis: falsification of the current standard model of cosmology

(11) 2008: The common mass-scale: In the SMoC, DM sub-haloes are distributed according to a power-law mass function. But observed satellite galaxies have too similar DM masses (Mateo et al. 1993; Strigari et al. 2008, see also Kroupa et al. 2010 and for Andromeda Tollerud et al. 2012).

(12) 2009: Constant surface density: Considering the matter distribution in observed galaxies within one DM-halo scale radius, Gentile et al. (2009) find “This means that the gravitational acceleration generated by the luminous component in galaxies is always the same at this radius. Although the total luminous-to-dark matter ratio is not constant, within one halo scale-length it is constant”. In the SMoC there is no physical principle according to which the DM and baryonic densities ought to be invariant within this radius.

(13) 2010: The luminous sub-halo mass function: The mass function of observed satellite galaxies disagrees with the predicted mass function of luminous sub-haloes (Kroupa et al. 2010).

(14) 2010: Bulge-less disk galaxies: That the bulge to-disc flux ratios are smaller than those produced by LCDM simulations is pointed out by Graham & Worley (2008). 58-74 per cent of all observed disk galaxies are claimed to not have a classical bulge (Kormendy et al. 2010). This is in conflict with the heavy merging history expected for bright galaxies if the SMoC were true (Hammer et al. 2007). For attempts to produce bulgeless disk galaxies see text below.

(15) 2010: Isolated massive galaxies: In the observed Local Volume of galaxies there are three massive disk galaxies that are too far off the matter filament (Peebles & Nusser 2010).

(16) 2010: The void: The Local Void is observed to be too empty in comparison to the SMoC expectation (Tikhonov et al. 2009; Peebles & Nusser 2010).

(17) 2010: The Bullet Cluster: The observed large relative velocity of the two interacting galaxy clusters is not accountable for in the SMoC (Lee & Komatsu 2010; Thompson & Nagamine 2012).

(18) 2011: The missing bright satellites: The predicted mass function of DM sub-haloes implies that a significant number of bright satellite galaxies is missing (Bovill & Ricotti 2011; Boylan-Kolchin et al. 2011a). Vera-Ciro et al. (2012) suggest this problem does not occur if the DM sub-haloes have Einasto rather than NFW density profiles. Wang et al. (2012) suggest this problem does not occur if the MW DM halo is less massive than about 2×1012 M⊙. But this is unlikely as the large proper motion of the LMC implies the MW to be more massive than about 2×1012 M⊙ and the LMC to be a recent acquisition and on its first passage (Boylan-Kolchin et al. 2011b). Furthermore, if this were the case then the question would need to be posed as to how likely the LMC happens to pass the MW within the VPOS.

(19) 2011: The thin old disk: The MW has a thin disk which has stars as old as 10 Gyr. Such old thin disks have still not been produced in the SMoC (House et al. 2011).

(20) 2012: The Train-Wreck Cluster: The galaxy cluster A520 has been shown to contain what appears to be a DM core with too few galaxies as well as evidence for a cluster–cluster encounter. The C/WDM paradigm cannot account for this separation of DM from the luminous matter, which is the opposite behaviour to the Bullet Cluster (Failure 17 above, Jee et al. 2012, see also Mahdavi et al. 2007).

(21) 2012: Missing Dark Matter: Over spatial scales of 100 Mpc extend the density of matter fluctuates by 10 per cent if the SMoC were valid. By counting up all matter within the local sphere with a radius of 50 Mpc, Karachentsev (2012) demonstrates the actual density to be too low by a factor of 3–4. Most of the missing mass is DM.

(22) 2012 Massive Galaxy Clusters: The most massive most distant galaxy clusters are important constraints on cosmological theory because the rapidity with which mass assembles to galaxy clusters depends on dark matter and/or on modified gravitation (Sec. 16.5). Gonzalez et al. (2012) discover a giant lensed arc near the cluster IDCS J1426.53508 and deduce “For standard LCDM structure formation and observed background field galaxy counts this lens system should not exist.”

Shaula
2014-Apr-26, 10:29 PM
It is a shame you don't copy paste a list of successes of the standard model. There are more than 22.

William
2014-Apr-26, 10:52 PM
It is a shame you don't copy paste a list of successes of the standard model. There are more than 22.

I do not understand your reasoning. A court would not convict a person if there were 22 fundamental problems with the prosecution's case.

A single unsolved issue can invalidate a theory. The crises that required the creation of new physics: 'inflation', 'dark matter', and 'dark energy' would have been sufficient to invalidate SMoC, inflation, dark matter, and dark energy had to be created to avoid changing or replacing the SMoC. Kroupa's list indicates that dark matter does not explain what is observed.

Kroupa's list of SMoC theory problems indicates that dark matter does not work and indicates that are likely one or more very fundamental problems with the SMoC. Inflation, dark matter, and/or dark energy are likely not the solution to the problem.

I completely agree with Ken G.'s comment (http://cosmoquest.org/forum/showthread.php?150846-The-dark-matter-crisis&p=2209960#post2209960) that Kroupa has provided sufficient information/logic to support the assertion that there is a dark matter theory crisis. Kroupa has not however solved the dark matter crisis.

Shaula
2014-Apr-27, 06:02 AM
A single unsolved issue can invalidate a theory.
By that metric we don't have a single scientific theory. There are always unresolved issues - it is how we find refinements to the model or a new model.

Theories are not invalidated and thrown out - they are replaced when something better comes along. And so far no theory has proven to be better. Which leaves us in the position, which is where my comment comes from, that the current best model is the lambda-CDM model. Is it complete? No. And we know that. However it is the current best fit - which is all that is required.


Kroupa's list of SMoC theory problems indicates that dark matter does not work and indicates that are likely one or more very fundamental problems with the SMoC. Inflation, dark matter, and/or dark energy are likely not the solution to the problem.
It really doesn't. It says that the model, as it stands, has problems in some areas. None of those point to the model being totally worthless. Lets go through them.

1) This is basically "I don't like inflation". 1 goes away with inflation so it is not a fatal flaw.
2) This is basically "I don't like dark matter". 2 goes away with dark matter.
3) This is a well known problem - it is believed to be because the current models tend to ignore several quite important factors. The galaxy is not a simple system of gravitationally interacting bodies. Supernovae and other ISM perturbing effects have been shown to help mitigate this issue but not so far conclusively.
4) Assumes we know everything about how dark matter interacts and about its temperature. It could be a problem, it could equally be a signpost to more properties of dark matter.
5) "I don't like dark energy"
6) An open problem that is an interesting probe of dark matter. So far warming the dark matter and understanding structure formation have significantly reduced the issue. And so far nothing contradictory has shown up by doing this.
7) There are a number of reasons that can account for this, it is useful way to probe 2 major factors - observational bias and phased merger history. Both are consistent with observations, more work is needed to test these ideas.
8) I have covered this already. Suffice to say that this is not unique to satellite galaxies, you see it in other systems too. Kroupa and several others have shown a number of ways that this could happen.
9) Assumes we know which are the TDGs and their evolutionary history, also assumes the simulations of how they form are complete.
10) This problem was shown a long time ago to not be a problem, I'd need to chase his papers down to see why he thinks it has been resurrected. Simulations from 1996 show that this can easily be explained by running high resolution models of disc formation.
11) This one assumes that the DM haloes for all galaxies are primordial. Likely not the case for satellite galaxies.
12) http://arxiv.org/abs/1212.6797 points out that this result is disputed.
13) Similar point to 11
14) Similar to 7
15) Implies a more rapid structure formation in this local area than we thought, not that everything is broken
16) Same point as 15
17) The argument is really about the initial velocity of the subcluster. What it is saying is that if you take the X ray results and model the collision simply then the initial infall velocity of the subcluster comes out as way too high if you assume a near Gaussian distribution for the range of infall velocities. The authors themselves have pointed out that they don't have enough data to actually justify this particularly compellingly. So really there are two issues: Is the model used to explain the X ray results right? Is the distribution of infall velocities right?
18) Possibly fixed by changing the DM profile, this could be a really nice way to constrain it.
19) Possibly evidence for late mergers
20) Recent work has shown some hints that this is actually due to a number of filaments crossing in the area - the DM is not actually associated with the colliding clusters
21) Entertainingly this actually points to a need for more dark matter, or at least a slightly less clumped distribution than we have assumed and a less strong correlation between dark and bright matter
22) Again for a simple continuous merger model this is the case, phased models or other more complicated models don't have this issue.

That was a lot of effort. The point is that none of these lead to unresolvable contradictions as you seem to be saying they do. It is a list of problems, past and present, that have challenged simplistic models. It may be that in the end the standard model cannot encompass these results without leading to contradictions - but so far this is not proven by any means. And many of these results break MONDian approaches just as badly (or worse). So until something comes along that replaces the standard model these are interesting challenges to our understanding of it.

William
2014-Apr-27, 08:46 AM
Kroupa's dwarf galaxy satellite theorem and other failures of simulations verses observation (see Kroupa's paper for details) provides strong support for the assertion that Dark matter does not explain what is observed and that dark matter does not exist. Kroupa states in his lecture that he believes the scientific evidence/analysis is sufficiently mature and strong enough, now to discard dark matter as a viable solution. He states that that was not true in 2009.

The attempts to directly detect dark matter have failed. If dark matter does not exist, the concept of dark matter is blocking the resolution of the cosmological puzzle. Modifying an incorrect theory (if it is a fact that dark matter does not exist) does not help one solve a scientific problem. Having no theory to explain what is observed is better than have an incorrect theory as that enables one to relook at the other possible solutions.

There is a physical explanation for what is observed.

This lecture by Kroupa is an overview of his paper.

http://www.youtube.com/watch?v=UPVGDXNSBZM

William
2014-Apr-27, 09:08 AM
I would recommend listening to Kroupa's lecture. Kroupa is the director of the research group on stellar populations and stellar dynamics at the University of Bonn.

As I stated I am going to do some work to prepare for a thread on large scale structures with a very brief overview of 'inflation'.


http://en.wikipedia.org/wiki/Pavel_Kroupa

Kroupa leads the research group on stellar populations and stellar dynamics at the University of Bonn. His research work began in 1987 in Australia with an investigation of Proxima Centauri. Kroupa is well known for his work for the distribution of stellar masses. In Cambridge in 1990-1992 by means of observational data on star counts and on binary stars and with detailed computations of stellar structure with Christopher A. Tout and Gerard Gilmore he deduced the contemporary, generally-used canonical IMF (initial mass function), which describes the distribution of the star masses at their birth. In 2004 in Kiel together with Carsten Weidner he suggested the existence of a physical maximum star mass of approximately 150 solar masses. In Heidelberg he presented the first stellar-dynamic computations in 1993-1995 of star clusters, in which all stars are born as binary stars. He thus solved the problem that field populations have a significantly lower double star rate than star formation areas, because the binary stars are broken up as the star clusters evolve and disperse. He mathematically formulated and applied a theory of the evolution of binary stars (eigenevolution), created the method of dynamic population synthesis, and predicted the existence of binary stars forbidden by previous theory (forbidden binaries). He suggested in cooperation with Ingo Thies and Christian Theis in 2003-2004 in Kiel that brown dwarves and extrasolar planetary systems can develop in circumstellar disks due to passing stars which disturb the disks. Our Solar System is likely to have been shaped by such events.

In Kiel he also theoretically formulated the concept that galaxies ought to be described by stars forming in populations of embedded star clusters. With this he explained in 2002 the observed heating or thickening with age of the disk of the Milky Way, and with Carsten Weidner he formulated the "IGIMF (integrated galactic initial mass function) theory". In 2008 in Bonn together with Jan Pflamm-Altenburg he pointed out that the IGIMF theory implies that disk galaxies have a radial star formation law, in which the star formation density is proportional to the radial gas density. The IGIMF theory implies also that the star formation rates of irregular dwarf galaxies are proportional to their gas masses and must be corrected to clearly higher values as compared to previous theory. Simple star-formation laws for galaxies emerge from this work. The IGIMF theory gives good predictions for the mass distributions of the various metals within galaxies.
In 1997 and in Heidelberg Kroupa, together with Ulrich Bastian, took the first precise measurement of the spatial movement of two extragalactic systems. In 1997 he also discovered stellar-dynamic solutions for the satellite galaxies of the Milky Way without the need for exotic dark matter. His work implies a possible connection of the satellite galaxies with the Bulge of the Milky Way. This connection can be explained by a collision of the early Milky Way with another young galaxy during which the satellite galaxies formed as tidal dwarf galaxies about 11 Gyr ago. This is shown in a series of research papers with Manuel Metz and Marcel Pawlowski.

As a result of this work and since 2010 Kroupa has concerned himself increasingly with cosmology. While the cosmological standard model does not offer a unique solution to the cosmic background radiation and to cosmological expansion, he finds that the observed structures on scales of 10 Mpc and above falsify the standard model.

Shaula
2014-Apr-27, 09:31 AM
Kroupa's dwarf galaxy satellite theorem and other failures of simulations verses observation (see Kroupa's paper for details) provides strong support for the assertion that Dark matter does not explain what is observed and that dark matter does not exist.

Saying the same comment over and over: the number of times a comment is repeated or how emphatically it is stated, does not make it true.
I know who Kroupa is and I have read a number of his papers. I do not accept your simple argument from authority. There are a large number of papers and debates out there that cover this issue, endless repeating the conclusions from one that you happen to believe the most does not build a compelling case. His case is far from proven either. As I have shown above he ignores the proposed or shown fixes for many of these issues he raises. That might be because he feels that they are unjustified, but after watching MOND morph to TeVeS I connt help but feel that this is not a tenable position to hold. I am not claiming he is wrong, I am not claiming that he has no case. I am pointing out that at the moment the balance of evidence is still with the LCDM model. That may change, but nothing he has presented is a deathblow to the theory.


If dark matter does not exist, the concept of dark matter is blocking the resolution of the cosmological puzzle.
Except it is not, as the plethora of papers and theories out there shows.


There is a physical explanation for what is observed.
No there is not. Kroupa uses a MOND-like solution which has been shown to have issues, including several of the ones he throws at the Standard Model. If there were a better model that explained more and predicted more accurately then it would be the mainstream. That really is how simple it is.


I would recommend listening to Kroupa's lecture. Kroupa is the director of the research group on stellar populations and stellar dynamics at the University of Bonn.
Why? I have read his papers.

wd40
2014-Apr-28, 11:42 AM
"Is the Universe playing fair with us? Are the laws of physics and the structure of space-time the same everywhere? It is a fundamental tenet of the Standard Cosmological Model that the answer
is yes. Yet the difficulty of explaining the physics of cosmic acceleration forces a new scrutiny of many of our most cherished assumptions. If the structure of space-time is not the same everywhere, if in fact we occupy a privileged location in space and time at the center of a spherical bulge of matter and curvature, then it may be possible to explain a vast catalog of observational data without the need to invoke new physical effects such as dark energy."

from
Caldwell, R.R., and N. A. Maksimova, 2013. “Spectral Distortion in a Radially Inhomogeneous
Cosmology,” arXiv:1309.4454v2 [asto-ph.CO] 15 Oct 2013. (http://journals.aps.org/prd/abstract/10.1103/PhysRevD.88.103502)

Cougar
2014-Apr-28, 12:57 PM
"...if in fact we occupy a privileged location in space and time at the center of a spherical bulge of matter and curvature...

Why would our little speck of a planet occupy a privileged position?

Plus, our observations of the largest temperature fluctuations of the CMB indicate that the spatial curvature of the observable universe is quite nearly flat.

William
2014-Apr-29, 04:32 AM
This is a link to the arxiv preprint of the paper.

http://arxiv.org/pdf/1309.4454v2.pdf

V. SUMMARY

Solutions to the physics of cosmic acceleration that dispense with dark energy and new gravitational physics are immensely appealing. In a number of recent papers, it has been shown that the expansion history along the past light cone|determined by the luminosity distance, energy density, and number counts|can be built from the LTB metric to match the _CDM Standard Cosmological Model without the presence of a Gigaparsec void [10{12]. That is, a post-decoupling cosmos containing just dark matter and baryons obeying the laws of general relativity can satisfy many of the classical tests of cosmology. The price to pay seems philosophical, since for this to work we must be located at the center of a radially inhomogeneous space-time, contrary to the Copernican and Cosmological Principles.

However, these LTB-based models must also pass a battery of other observational tests before we can discuss the possible meaning.


The authors have the right idea as to how to attempt to solve the problem. The nature of the cosmological problem is it almost impossible to solve it if the observations are viewed from the standpoint of a cosmological model that is fundamentally incorrect. If there is no dark matter or dark energy if inflation did not happen a different cosmological model is required.

In private industry a standard approach to solving complex problems is to force the analysis to consider more than one hypothesis, to carry a second or third hypothesis along, to set up a breakout group to formally consider other hypotheses, in a structured manner with the task of summarizing an alternative solution(s). Re-look at major alternative hypotheses and play with possible solutions at a high level.

Kroupa's lecture included some astute, succinct, very fundamental criticism of the current cosmological model. If inflation did not happen 10,000 years of theoretical work concerning inflation and the current cosmological model will not help to solve the cosmological puzzle. If inflation did not happen, the concept of inflation is blocking the logical next step in the analysis.

Shaula
2014-Apr-29, 05:26 AM
In private industry a standard approach to solving complex problems is to force the analysis to consider more than one hypothesis, to carry a second or third hypothesis along, to set up a breakout group to formally consider other hypotheses, in a structured manner with the task of summarizing an alternative solution(s). Re-look at major alternative hypotheses and play with possible solutions at a high level.
The existence of groups like Kroupa's studying MOND and other ideas shows that a similar approach does happen in scientific circles.


Kroupa's lecture included some astute, succinct, very fundamental criticism of the current cosmological model.
However it tended to present all criticisms as fatal flaws and not give any of options for solving them that are being investigated.


If inflation did not happen 10,000 years of theoretical work concerning inflation and the current cosmological model will not help to solve the cosmological puzzle.
Of course it would. Because if it is wrong eventually in-depth enough study will show it to be irrevocably flawed, a point we are not at yet as I have shown you. After all did the fact that aether theories are wrong stop GR from coming along? Did the Steady State universe theory stop Hubble?

Cougar
2014-Apr-29, 12:46 PM
The existence of groups like Kroupa's studying MOND and other ideas shows that a similar approach does happen in scientific circles.

They have conferences, too. The gripe is about funding. What percentage of proposals for funding are accepted? Alternative theorists aren't the only ones who get their proposals rejected.

Reality Check
2014-Apr-30, 01:33 AM
A court would not convict a person if there were 22 fundamental problems with the prosecution's case.

Wrong analogy: Science is more like an election with multiple sides where the side with the most "votes" (evidence) wins. Your "single unsolved issue" idea invalidates all theories of dark matter :D! In fact it invalidates all scientific theories since they all have at least on unresolved issue.

In this case we have one side
* MOND which as far as I can see could have many of the same "22 fundamental problems" (especially the introduction of new entities explain observations - his first 3 failures!). MOND only works with galaxies where it is actually better than CDM.
and another side
* CDM which works at all scales, has extremely strong evidence for existence (e.g. the Bullet Cluster) but has problems at small scales.

His "A long list of Failures" has some surprisingly "failures"- the introduction of inflation, dark matter and dark energy as if observations are not supposed to change scientific models.

Reality Check
2014-Apr-30, 01:51 AM
For balance:
A unified solution to the small scale problems of the LambdaCDM model (http://adsabs.harvard.edu/abs/2014JCAP...04..021D)
Del Popolo, A.; Lima, J. A. S.; Fabris, Júlio C.; Rodrigues, Davi C.
Journal of Cosmology and Astroparticle Physics, Issue 04, article id. 021, pp. (2014).

We study, by means of the model proposed in Del Popolo (2009), the effect of baryon physics on the small scale problems of the CDM model. We show that, using this model, the cusp/core problem, the missing satellite problem (MSP), the Too Big to Fail (TBTF) problem, and the angular momentum catastrophe can be reconciled with observations.
It looks like some problems need not be problems!

Reality Check
2014-May-01, 02:11 AM
The attempts to directly detect dark matter have failed.
Not quite right, William: The attempts to directly detect specific dark matter candidates have failed so far.
This is more like success, not failure. If you have a wide range of candidates for X (where X has independent evidence for its existence) then experiments that rule out candidates allow future experiments to concentrate on the remaining candidates.
The minus side is that as you run out of candidates for X it may be less likely that X actually exists and then you have to look at the original evidence again.

NoChoice
2014-May-01, 02:26 AM
Not quite right, William: The attempts to directly detect specific dark matter candidates have failed so far.
Your post is an interesting piece of very twisted "logic".
Let's start with your first statement.
The correct statement is "The attempts to directly detect any and all dark matter candidates have failed so far". All evidence so far is indirect.



This is more like success, not failure.
This is where it gets really "interesting"!


If you have a wide range of candidates for X (where X has independent evidence for its existence) then experiments that rule out candidates allow future experiments to concentrate on the remaining candidates.
The minus side is that as you run out of candidates for X it may be less likely that X actually exists and then you have to look at the original evidence again.

So, basically, no direct candidates at all have been found and through elimination it was made "less likely that they actually exist".
How exactly is that a success?

Reality Check
2014-May-01, 02:36 AM
17) The argument is really about the initial velocity of the subcluster. What it is saying is that if you take the X ray results and model the collision simply then the initial infall velocity of the subcluster comes out as way too high if you assume a near Gaussian distribution for the range of infall velocities. The authors themselves have pointed out that they don't have enough data to actually justify this particularly compellingly. So really there are two issues: Is the model used to explain the X ray results right? Is the distribution of infall velocities right?

Multi-Wavelength Simulation of the Bullet Cluster (http://adsabs.harvard.edu/abs/2012AAS...21920703L)
Lage, Craig; Farrar, G.
American Astronomical Society, AAS Meeting #219, #207.03: 1/1012

...A simple initial configuration using two spherically symmetric clusters with NFW dark matter profiles and isothermal beta plasma profiles is found to give a good fit to the current observational morphology of the merging clusters without the need for unconventional physics or extreme infall velocities.
Followed up by Constrained Simulation of the Bullet Cluster (http://adsabs.harvard.edu/abs/2013arXiv1312.0959L)

I suppose that authors concentrate on the Bullet Cluster because it is a well-known cluster with lots of observations. Not because it is strong evidence for the existence of dark matter and so they do not want it to exist :rolleyes:.

Reality Check
2014-May-01, 02:47 AM
The correct statement is "The attempts to directly detect any and all dark matter candidates have failed so far". All evidence so far is indirect.

The correct statement is that "The attempts to directly detect specific dark matter candidates have failed so far".
See Dark Matter - Direct detection experiments (http://en.wikipedia.org/wiki/Dark_matter#Direct_detection_experiments).
No experiment has looked for "any and all" dark matter candidates.
We have not run an experiment for each dark matter candidates in all energy ranges.
We do not know if eliminating some candidates for some energies means that it is less likely that dark matter exists. The very strong evidence that dark matter exists and is non-baryonic says otherwise.
An analogy: We have strong evidence that broccoli exists. We go into a vegetable garden that contains every type of vegetable. Pick one - it is a cabbage. Pick another - it is a carrot. This does not mean that it is less likely that broccoli exists. It means that it is more likely that our next pick will be broccoli. On the other hand if we pick everything in the garden and find no broccoli then that is evidence that broccoli does not exist.
We have not picked everything in the dark matter candidate garden :).

We have direct observational evidence for dark matter - see the Bullet Cluster and other clusters.

In science a null experiment (not finding something) can be a success. The classic example is the Mickelson-Morley experiment that went looking for evidence of an aether and did not find it.
The LHC is doing lots of null experiments - bashing particles together and not finding particles that theorist really like to exist.

borman
2014-May-01, 07:20 PM
The two MOND papers listed in todays fun arXiv papers reflect on this discussion. Milgrom says many MOND theories may never amount to more than effective theories. The Mcgaugh paper looks at both paradigms and sees where both have their successes and failures relative to each other. Important also are those zones where both paradigms fail simultaneously. This suggests both theories are likely wrong and an appropriate theory will need to recover the successes of both and avoid the failures of both paradigms.

wd40
2014-May-01, 09:20 PM
Why would our little speck of a planet occupy a privileged position?



"Many people (myself included) feel that the appearance of such a complex and structured universe from simple laws requires the invocation of something called the anthropic principle, which restores us to the central position we have been too modest to claim since the time of Copernicus." (Stephen Hawking, "On the Shoulders of Giants" p.xi 2002)

Strange
2014-May-01, 10:05 PM
"Many people (myself included) feel that the appearance of such a complex and structured universe from simple laws requires the invocation of something called the anthropic principle, which restores us to the central position we have been too modest to claim since the time of Copernicus." (Stephen Hawking, "On the Shoulders of Giants" p.xi 2002)

Without seeing the context, it sounds as if he means "central position" in a metaphorical sense, not literally.

wd40
2014-May-01, 10:49 PM
Without seeing the context, it sounds as if he means "central position" in a metaphorical sense, not literally.

Here is Hawking's full paragraph:

"It was quite a shift in our view of the universe: If we are not at the center, is our existence of any importance? Why should God or the laws of nature care about what happens on the third rock from the sun, which is where Copernicus has left us? Modern scientists have out-Copernicused Copernicus by seeking an account of the universe in which man (in the old prepolitically correct sense) played no role. Although this approach has succeeded in finding objective impersonal laws that govern the universe, it has not (so far at least) explained why the universe is the way it is rather than being one of the many other possible universes that would also be consistent with the laws. Many people (myself included) feel that the appearance of such a complex and structured universe from simple laws requires the invocation of something called the anthropic principle, which restores us to the central position we have been too modest to claim since the time of Copernicus."

Strange
2014-May-01, 10:57 PM
So, the metaphorical sense, then.

Ken G
2014-May-02, 04:59 AM
Interesting point by Hawking, it's not really the standard way to put it. Many would argue that the "anthropic principle" is actually the opposite of a principle that elevates humanity. A typical way that this principle is invoked is by claiming that there are a spectacularly huge number of different universes, all inflating with different attributes, and different constants of nature. This "landscape" of universes, the "multiverse", then has whatever forms of life it can support appearing in whatever kinds of universes can support them. That picture is then said to "explain" (in a non-traditional sense of the scientific meaning of that term, wherein explanations unite a set of observations, not a set of non-observations) why our universe has the attributes it does. This prescription is often thought of as further downgrading the importance of humanity, as now we are not even in a universe that is specially made for us, we are just in the universe that will have us. But Hawking puts a different spin on the anthropic principle here-- he seems to be focusing on the fact that our universe is the only one we see, and it does appear to be specially made for us, and it does appear to be centered on us, even if both of those things are kinds of illusions. When the illusion is the only thing we can detect or measure, how is it still an illusion? And if other intelligent lifeforms anywhere in the universe are under a similar illusion, again how is that an illusion? Something that everyone sees, and no one can detect anything that is any different, does not seem like the traditional meaning of an illusion in science.

Shaula
2014-May-02, 05:05 AM
The anthropic principle doesn't actually apply to a position in the universe. Simply because there is no need for us be there, we could happily live somewhere else in such a universe and so it is not a case of 'well it has to be so for us to be here observing it'

wd40
2014-May-02, 03:20 PM
Interesting point by Hawking, it's not really the standard way to put it.


"All this evidence that the universe looks the same whichever direction we look in might seem to suggest there is something special about our place in the universe. In particular, it might seem that if we observe all other galaxies to be moving away from us, then we must be at the center of the universe.

There is, however, an alternate explanation: the universe might look the same in every direction as seen from any other galaxy, too. This, as we have seen, was Friedmann’s second assumption. We
have no scientific evidence for, or against, this assumption. We believe it only on grounds of modesty: it would be most remarkable if the universe looked the same in every direction around us, but not
around other points in the universe." (Hawking, "A Brief History of Time", 1988)

Shaula
2014-May-02, 03:29 PM
We believe it only on grounds of modesty: it would be most remarkable if the universe looked the same in every direction around us, but not around other points in the universe.
It is not so much modesty as parsimony.

Strange
2014-May-02, 03:41 PM
And what do Hawking's philosophical musings have to do with dark matter, anyway?

"Is the Universe playing fair with us? Are the laws of physics and the structure of space-time the same everywhere? It is a fundamental tenet of the Standard Cosmological Model that the answer
is yes. Yet the difficulty of explaining the physics of cosmic acceleration forces a new scrutiny of many of our most cherished assumptions. If the structure of space-time is not the same everywhere, if in fact we occupy a privileged location in space and time at the center of a spherical bulge of matter and curvature, then it may be possible to explain a vast catalog of observational data without the need to invoke new physical effects such as dark energy."

from
Caldwell, R.R., and N. A. Maksimova, 2013. “Spectral Distortion in a Radially Inhomogeneous
Cosmology,” arXiv:1309.4454v2 [asto-ph.CO] 15 Oct 2013. (http://journals.aps.org/prd/abstract/10.1103/PhysRevD.88.103502)

So, they hope to explain the accelerating expansion with their model. This is dark energy not dark matter.

Also, as "dark energy" is just a name for whatever-it-is-that-causes-accelerating-expansion and their proposed inhomogeneity of space time is a new idea, then they are obviously proposing a "new physical effect" which is [currently called] dark energy.

Ken G
2014-May-02, 07:30 PM
But if we drop the cosmological principle, we might not need any new physics to replace it, so we might not need anything we would call dark energy. That seems to be their goal, to ask if we can just use the physics we already have (plus dark matter), and assert a non-uniform spatial distribution, and see everything we see. That's a hugely significant question, as the cosmological principle is invoked only because of Occam's Razor and the Copernican principle. But it doesn't really satisfy Occam's razor to require new physics to be able to keep the old principles, so it pretty much comes down to the Copernican principle. Drop that, and it might be a more natural scientific assumption to just set out the matter distribution so as to not need any dark energy at all. I don't know if that is true or not (because I don't know how you'd get acceleration of the expansion using a matter distribution, it seems hard to do), but it seems to be the question Caldwell and Maxsimova are asking-- just how badly do we want this Copernican principle anyway?

wd40
2014-May-03, 09:08 PM
just how badly do we want this Copernican principle anyway?

Badly, it would seem:

"The density of the nebular distribution increases outwards, symmetrically in all directions, leaving the observer in a unique position. Such a favoured position, of course, is intolerable; moreover, it represents a discrepancy with the theory, because the theory postulates homogeneity. Therefore, in order to restore homogeneity, and to escape the horror of a unique position, the departures from uniformity, which are introduced by the recession factors, must be compensated by the second term representing effects of spatial curvature. There seems to be no other escape." (Hubble)

Ken G
2014-May-04, 01:26 AM
Yes, one wonders if astronomers long ago used to talk about the "intolerable horrors" of a moving Earth, or more recently, the intolerable horrors of a universe that had a beginning? It's funny what horrors we can tolerate if and when observations require us to.

profloater
2014-May-04, 02:35 PM
I have been reading in this weeks new scientist the interview with physicist Mordechai Milgrom. It contains the statement that the difference in MOND occurs when the acceleration of a star drops below 100 billionth of a G. At that tiny acceleration a new law of gravity or a new law of inertia can explain the faster velocity of stars in the outer parts of galaxies. Is the difference between dark matter and MOND really down to such a tiny value?

Shaula
2014-May-04, 02:59 PM
I have been reading in this weeks new scientist the interview with physicist Mordechai Milgrom. It contains the statement that the difference in MOND occurs when the acceleration of a star drops below 100 billionth of a G. At that tiny acceleration a new law of gravity or a new law of inertia can explain the faster velocity of stars in the outer parts of galaxies. Is the difference between dark matter and MOND really down to such a tiny value?
That is the Vector-Scalar formulation and so far no, it cannot quite explain what we see as it is basically non-relativistic. Which is why they shifted to a Tensor-Vector-Scalar (TeVeS) model.

Reality Check
2014-May-12, 03:35 AM
That is the Vector-Scalar formulation and so far no, it cannot quite explain what we see as it is basically non-relativistic. Which is why they shifted to a Tensor-Vector-Scalar (TeVeS) model.
Which has new problems: The Death of Dark Matter’s #1 Competitor by Ethan Siegel in Starts With A Bang! (https://medium.com/starts-with-a-bang/98edff3a066f)
Observations of a double pulsar "agrees with Einstein’s relativity at the 99.95% level (with a 0.1% uncertainty), and — here’s the big one — rules out all physically viable incarnations of Bekenstein’s TeVeS".

kzb
2014-May-14, 11:29 AM
"Manly" astrophyics.

This group have some interesting ideas about interstellar hydrogen snow, and AU-sized gas clouds. Their ideas have been mentioned on here before I know, but this is the first time I have found their Manly web site. Perhaps others on here will find it interesting also.

http://manlyastrophysics.org/Projects/index.html

John Mendenhall
2014-May-14, 02:52 PM
There is an interesting idea at http://xxx.lanl.gov/abs/astro-ph/0507619v1. I have access only to the abstract. Anybody read the whole thing?

antoniseb
2014-May-14, 04:02 PM
There is an interesting idea at http://xxx.lanl.gov/abs/astro-ph/0507619v1. I have access only to the abstract. Anybody read the whole thing?
That paper is 9 years old... IIRC we had a thread about it here then. I seem to remember that there were a few issues with it, but more broadly it does not address the need for dark matter to account for lensing.

John Mendenhall
2014-May-14, 04:43 PM
That paper is 9 years old... IIRC we had a thread about it here then. I seem to remember that there were a few issues with it, but more broadly it does not address the need for dark matter to account for lensing.

Got it. It's the the 'Whack a Mole' problem. You knock one down, but another one pops up.

Thanks Tony. Good help.

Reality Check
2014-May-14, 10:44 PM
That paper is 9 years old... IIRC we had a thread about it here then. I seem to remember that there were a few issues with it, but more broadly it does not address the need for dark matter to account for lensing.
And its citations (only 35 in those 9 years) include:
Comment on ``General Relativity Resolves Galactic Rotation Without Exotic Dark Matter'' by F.I. Cooperstock & S. Tieu (http://arxiv.org/abs/astro-ph/0604022) (3 Apr 2006)

The general relativistic model of Cooperstock & Tieu, which attempts to fit rotation curves of spiral galaxies without invoking dark matter, is tested empirically using observations of the Milky Way. In particular, predictions for the mass density in the solar neighbourhood and the vertical density distribution at the position of the Sun are compared with observations. It is shown that the model of Cooperstock & Tieu, which was so constructed that it gives an excellent fit of the observed rotation curve, singularly fails to reproduce the observed local mass density and the vertical density profile of the Milky Way.
and
Comments on the Cooperstock-Tieu Galaxy Model (http://lanl.arxiv.org/abs/astro-ph/0601191)(9 Jan 2006)

The recently proposed Cooperstock-Tieu galaxy model claims to explain the flat rotation curves without dark matter. The purpose of this note is to show that this model is internally inconsistent and thus cannot be considered a valid solution. Moreover, by making the solution consistent the ability to explain the flat rotation curves is lost.

Jerry
2014-May-17, 08:13 PM
I would say that one thing Kroupa does is good science, and one is bad science. It is always good science to increase skepticism, as self-questioning is the crux of all science and when we forget that, and start treating science like a bandwagon, we end up doing things like believing for 1400 years that the Earth is the center of the universe. So let him point to the problems of the theory and the evidence we may be heading the wrong direction, science never gets better than that and no scientist should ever react defensively to such a challenge. It is also valid for proponents of the model to answer the challenges and point out flaws in the argument that there are flaws! All is part of good science. Indeed, Kroupa is a little naive to hold that a theory can be "falsified" by one failed prediction, the truth is we have often needed to "shore up" incomplete theories to fix failed predictions! So his comments should be framed as "if the standard cosmology is to survive as the prevailing theory, it must find a way to fix this." In that light, I think he makes some good points that standard cosmologists should indeed be ready to address, or to explore further.

The bad science is using problems with the prevailing theory to promote an alternative with problems of its own, and here Kroupa appears guilty of an even greater suspension of skepticism than he accuses standard cosmologists of. Instead, let the debate on MOND be focused on its strengths and weaknesses, it has nothing to do with the standard picture. A scientific argument does not look like "my theory must be right because your theory has problems", it looks like "here are the strengths and weaknesses of theory A. Here are the strengths and weaknesses of theory B." Any skepticism directed toward theory A should also be directed toward theory B. It's not a courtroom with a lawyer for theory A and a lawyer for theory B, it's science, and we can all be scientists rather than lawyers or politicians. But perhaps if Kroupa feels voiceless against the din of the prevailing standard cosmology, he is to be forgiven for upping his rhetoric a bit, just to be heard at all.
Everyone blew past this, but I cannot. We are constantly being reminded that it is not enough to find fault in the parametric assumptions necessary to hold the standard model together. We must also provide feasible alternatives; preferably ones that do not require new physics.

So I don't understand why 'promoting an alternative' is bad science. No one should expect new models to emerge that do not require 'place holders' where physical laws are not fully understood; as the standard model is full of them. Creative new placeholders need to be allowed, and it may even take more of them. If we do not openly explore alternative concepts, how will we ever know?

Shaula
2014-May-17, 08:48 PM
Everyone blew past this, but I cannot. We are constantly being reminded that it is not enough to find fault in the parametric assumptions necessary to hold the standard model together. We must also provide feasible alternatives; preferably ones that do not require new physics.

So I don't understand why 'promoting an alternative' is bad science. No one should expect new models to emerge that do not require 'place holders' where physical laws are not fully understood; as the standard model is full of them. Creative new placeholders need to be allowed, and it may even take more of them. If we do not openly explore alternative concepts, how will we ever know?
No one is saying promoting an alternative is bad science. No one is saying alternatives are bad. This is part of the narrative you have imposed on the discussion, not part of the actual discussion.

What people are saying is bad science is badly done science. People actively promoting alternatives with more problems than the standard model not by showing their strong points but by harping on about perceived flaws in the standard models.

Edit: Also not sure how me wholeheartedly agreeing with what Ken said there in the post directly after his is 'blowing past this'.

Reality Check
2014-May-18, 11:59 PM
Everyone blew past this, but I cannot. ...
Ok:

I would say that one thing Kroupa does is good science, and one is bad science..
The good science is actually just good literature - a paper trying to list the problems with Lambda-CDM cosmology.
The bad science is the one-sided list of the problems with Lambda-CDM cosmology :p!
* He presents the problems but somehow does not know of the possible solutions to the problems.
* He presents the scientific process as if it is a problem (introduction of dark matter, dark energy and inflation).
* He does not "provide feasible alternatives; preferably ones that do not require new physics". MOND is not feasible, is non-relativistic and involves new physics. TeVeS is new physics and is probably not feasible.

The bad science is not 'promoting an alternative', it is trying to debunk Lambda-CDM cosmology as if it is support for an alternative.

Ken G
2014-May-19, 08:45 AM
We must also provide feasible alternatives; preferably ones that do not require new physics.
And the key word there is feasible. That's what is missing, as Reality Check said. You see, Kroupa's problem is that he provides a list of problems with one theory, and zero such list with another. Why? He comes off as selling snake oil that way. Science is not a debate, it is a set of strategies for moving forward. If Kroupa simply said "the key difference between these theories centers on set of observations S that remain to be done, and if they come out X, then Lambda-CDM is the better theory, and if they come out Y, then MOND is the better theory." That's the actual way that science works, although it is arguable that the observations have already come out X.

Creative new placeholders need to be allowed, and it may even take more of them. If we do not openly explore alternative concepts, how will we ever know?But is he exploring the alternative concept? This is what exploration looks like: alternative concept A predicts alternative observational result X. This motivates looking for X. That would be "exploring alternatives", yet I see zero of that either. Has MOND ever predicted anything before it was seen? Lambda-CDM certainly has.

William
2014-May-19, 05:06 PM
And the key word there is feasible. That's what is missing, as Reality Check said. You see, Kroupa's problem is that he provides a list of problems with one theory, and zero such list with another. Why? He comes off as selling snake oil that way. Science is not a debate, it is a set of strategies for moving forward. If Kroupa simply said "the key difference between these theories centers on set of observations S that remain to be done, and if they come out X, then Lambda-CDM is the better theory, and if they come out Y, then MOND is the better theory." That's the actual way that science works, although it is arguable that the observations have already come out X.
But is he exploring the alternative concept? This is what exploration looks like: alternative concept A predicts alternative observational result X. This motivates looking for X. That would be "exploring alternatives", yet I see zero of that either. Has MOND ever predicted anything before it was seen? Lambda-CDM certainly has.

What are ineffective or effective methods to solve the cosmological problem? How deep is the cosmological theory problems?

It is the nature of the cosmological theory problem that if one or more fundamental theoretical components or the theory itself is incorrect, then the analysis will diverge (more anomalies will be identified), rather than converge. How basic is the fundamental theory problem? Are certain theory problems unthinkable, unimaginable? Why is that so? Does that make it impossible to solve the problem, as the people in the field do not formally scientifically re-look at discarded theories?

A systematic problem of modern science is it possible to develop very complex models that match the data and that make correct predictions that have no basis in reality (the model and process is a complex type of curve fitting), if there are sufficient free parameters in the model or if the laws of physics are incorrectly changed to enable the model in question to avoid catastrophic paradoxes.

The cosmological field is interesting as there are piles upon piles of anomalies and structural/linked anomalies and exceptional comprehensive observational data (particularly large structural data) which appears to point to missing mechanisms.

The nature of the cosmological theory problem is that it is necessary to view the observations in question from the prospective of the correct fundamental theory to solve the problems. If for example dark matter and dark energy do not physically exist, then theoretical models that use dark matter and dark energy to explain the observational anomalies are purely theoretical, have no physical basis and are a barrier to making any progress to finding the true physical answer. I brought up the question of inflation, as if inflation did not happen, then options as to what causes the anomalies that the posited dark matter and dark energy are required to explain changes.

I find it astonishing that there is almost no discussion that inflation requires what based on recent observational data appears to be an infinite universe to expanded at millions of times faster than the speed of light roughly 14.7 billion years ago. Where was the universe at say 16 billion years ago? Why are there massive voids without galaxies and peculiar links/ribbons of gas between clusters?

Shaula
2014-May-19, 05:58 PM
Does that make it impossible to solve the problem, as the people in the field do not formally scientifically re-look at discarded theories?
As has been pointed out many, many times on this board there are people out there, in the scientific community, who are investigating alternatives, looking back at old models and re-testing current models all the time. A fair bit of this is never publicised, however, because a paper saying "This idea still doesn't work" is not really front page science magazine news.


the model and process is a complex type of curve fitting
However what you are missing in your rush to rubbish the current models is that there are many different ways to probe the free parameters. So what you usually see happening is a parameter is refined by one method then tested against an independent mechanism. So it is far more than curve fitting, there are cross checks you can make. What doesn't happen is a sort of global fit. There are always checks.


The cosmological field is interesting as there are piles upon piles of anomalies and structural/linked anomalies and exceptional comprehensive observational data (particularly large structural data) which appears to point to missing mechanisms.
Actually there are fewer mysteries than there are successes. Which is why the models we use are held to be reasonable. The anomalies are actively studied to see if they invalidate the current model or point to new parts of it.


The nature of the cosmological theory problem is that it is necessary to view the observations in question from the prospective of the correct fundamental theory to solve the problems.
If that were the case then we would have to give up now. We simply do not have the lab based equipment to test energies that existed in the early universe. So the only way to tackle them is to build theories, test them, extend them and from this come up with ways to refine fundamental theory. We are not going to suddenly trip over a user's guide to absolutely everything - we have to work it out ourselves. And that means observing and modelling things we don't fully understand.


Where was the universe at say 16 billion years ago?
Our models break down before that. Well known. Hopefully a quantum gravity theory will help, as of now we cannot model conditions before a certain time.


Why are there massive voids without galaxies and peculiar links/ribbons of gas between clusters?
Most of this structure is pretty well modelled using current LCDM theories, modelling two fluids interacting gravitationally. There are most issues at the galactic level to be honest.

You are not really bringing much to the debate here that is not either wrong or not well known by the scientific community. We know our models are at best incomplete and possibly wrong. We know that we may have to change everything we think we know. We know that simplistic models don't replicate exactly what we see (we also know how hard it is to simulate things in high fidelity on the scale of the universe!). The more mundane explanations were tried first, and are still tried. No one actually wants to have things like inflation, dark energy and dark matter as placeholders (although dark matter is probably far less of a placeholder than it was a decade ago). But observations lead us to the conclusion that they are needed.

Cougar
2014-May-19, 07:44 PM
Why are there massive voids without galaxies and peculiar links/ribbons of gas between clusters?

If the only matter in the Universe was baryonic, then there is not enough time in the history of the Universe to create the structures we see from the slight density perturbations in the surface of last scattering. If 5 to 10 times more mass is added to the model in the form of dark matter, the evolutionary result is galaxies, clusters, superclusters, voids... much like what is observed. There are several independent lines of evidence supporting the existence of dark matter. It took nearly half a century for the astrophysical community to accept what Zwicky discovered in the 1930s, by the way, which was that due to the speeds of the cluster galaxies, there must be a lot more matter in clusters than the luminous matter and gas that we can detect, otherwise the clusters would not stay clustered.

William
2014-May-19, 09:37 PM
As has been pointed out many, many times on this board there are people out there, in the scientific community, who are investigating alternatives, looking back at old models and re-testing current models all the time. A fair bit of this is never publicised, however, because a paper saying "This idea still doesn't work" is not really front page science magazine news.

Our models break down before that. Well known. Hopefully a quantum gravity theory will help, as of now we cannot model conditions before a certain time.

Most of this structure is pretty well modelled using current LCDM theories, modelling two fluids interacting gravitationally. There are most issues at the galactic level to be honest.

You are not really bringing much to the debate here that is not either wrong or not well known by the scientific community. We know our models are at best incomplete and possibly wrong. We know that we may have to change everything we think we know. We know that simplistic models don't replicate exactly what we see (we also know how hard it is to simulate things in high fidelity on the scale of the universe!). The more mundane explanations were tried first, and are still tried. No one actually wants to have things like inflation, dark energy and dark matter as placeholders (although dark matter is probably far less of a placeholder than it was a decade ago). But observations lead us to the conclusion that they are needed.

It is a fact that the most sensitive dark matter detector ever constructed has confirmed dark matter does not exist within the 'parameter' space of the standard model.

You miss my point. If the current cosmological theory is incorrect at its foundations we can spend 10,000 years working on it and make no progress. For example, if it is a fact that there is only one universe, the theoretical work on multiverses does not advance science. If inflation did not happen, one of the 100,000 string theory papers published every year (there is no 'string theory' string theory is the name for a mathematical field of work were the objective is to develop a theory, so far there is no theory, which would indicate a pure mathematical approach may never advance fundamental physics or cosmology) will never answer the question what caused inflation. Allowing the possibility that inflation did not occur validates the re-look at the discarded cosmological models. If inflation did not occur there is a catastrophic set of anomalies between observations and the current cosmological model. It is possible that it is physically not possible for an infinite universe to expand at more than a million times faster than the speed of light for a fraction of a second to save the standard theory and then billions of years later to start to expand again, to explain the super nova anomaly. What is changing billions of years later to cause the expansion? What was the energy source 14.7 billion years ago to cause the millions of times faster than the speed of light expansion?

I am asserting that the current methodology to investigate cosmological theory is not effective. It does not address the possibility that there could be and that there appears to be errors at the foundation of the theory. A model that is incorrect at its foundation will create paradoxes which only exist due to the analysis been made with a model that is incorrect at its foundation. These are the type of fundamental anomalies that led to the discover of quantum mechanics. i.e. In the case of quantum mechanics, different approaches were tried to solve the problem rather than just beating the existing theory to death. The resultant change is a breakthrough not a small change to the theory.

I have never seen a formal review of the old competing cosmological models with the modern observational data. There has been no attempt to organize large scale observations to point out the patterns, as there is no explanation for why there are patterns which points to a different cosmological model.

It is a fact that are piles of anomalies and observations that appear to point to different mechanisms and possibly to a different cosmological model. For example:

CMB Large Scale Anomalies


"The temperature fluctuates more" in half the sky than in the other half, and there’s a cold spot, and some sign of alignment of large-scale distortions that were expected to be randomly distributed. But interpreting something like this is tricky — it could just be a statistical fluke, and since there’s only one universe, you don’t get to improve your statistics with better measurements. (That last point is called the problem of “cosmic variance”.) So if something interesting is going on in the overall shape or structure of the universe, I suspect we’re going to need an additional and different type of measurement to convince ourselves. And I’m not sure what that would be.

http://profmattstrassler.files.wordpress.com/2013/03/planckvswmap.jpg?w=500

http://profmattstrassler.com/2013/03/21/the-universe-according-to-planck-the-satellite/

WayneFrancis
2014-May-20, 03:52 AM
William you seem to be asking to throw out the baby with the bath water and you seem to be trying to justify this with inaccurate and/ or ignorant arguments. Are there problems with the standard model? Yes but there are problems with every model because models are, by their very definition not an accurate representation of the actual system. If they were they wouldn't be called models. IE If I have a 1/12 model of my favorite car then the model isn't an accurate representation of my favorite car. If I didn't build it to a 1/12 scale but built it full scale and everything was just like my favorite car then it wouldn't be a model of my favorite car it would BE an instance of my favorite car.

You seem to keep trying to point out problems with the standard model. Some that aren't even problems but something you, and many other people, just don't like at a gut level. It doesn't matter if you, me, Stephen Hawking or any other person doesn't like a part of the explanation. Arguing that you need to completely discard the explanation to investigate a more fundamental explanation is a non sequitur. All a model does is provide one explanation of an observation and allow us to make predictions. The better the model the more accurate the predictions. You can have 2 different models about the same phenomena that explain the phenomena in entirely different ways and both make accurate predictions. If they make the same predictions then normally the more simple model will be adopted. If they make predictions in different areas then you'll often see both models used even though they are in conflict with their explanations. We even keep using models when more accurate models have been discovered if they are easier to use. An existing model does NOT prevent other models from being developed. Sure many scientists will continue down the path of the existing models because they tend to have a more proven track record of producing valid results.

You seem to be implying that the existing models need to be ditched so all scientist are forced to look for new answers because you believe certain things will never be explainable under the current set of models. That isn't how science works. You don't get to force all scientist to pursue what you deem as important. Pointing out gaps in a theory also will not steer scientist away. In fact they'll often try, and do, figure out how to fill those gaps within a existing models framework. Does that mean that is how the phenomena actually works? No but it does strengthen that model.

Using inaccurate representations of a model doesn't bolster your position and isn't a good practice. Most, more likely all, of the people involved in this discussion understand the models and their domains of applicability very well. So you using a straw man, whether you know it or not, of the model doesn't work. It might make your argument sound better to those that don't understand the model in question but those are not the people that will probably ever do any real science or influence science in any way. You might as well go try and convince some third graders that the standard model is completely flawed and needs to be thrown out in hopes that actual scientists will then change the focus of their research based on the third graders statements.

Let us take some of your comments and look at them.


If inflation did not occur there is a catastrophic set of anomalies between observations and the current cosmological model.

Well no duh. If you take out a major component of a model then there will be anomalies. That is why they are components of the model, because they are useful and essential in the models. A good model shouldn't have components that aren't actually needed for the model to actually work. So your initial "If" is flawed. Even if inflation never actually happened the model still uses that as a basis for not only observations that have been made but making predictions on future observations. And to date there have numerous predictions that have been made based on inflation happening that have later been observed. Like a jigsaw puzzle they predicted, if inflation occurred in this manner then we should observe x with the value y. Every time those predictions are later observed then our confidence in the model is strengthened. Did inflation never happen? I don't know but I know that something that seems to produce the same effects of inflation happened that is why inflation is such a strong component to the models.



It is possible that it is physically not possible for an infinite universe to expand at more than a million times faster than the speed of light for a fraction of a second to save the standard theory and then billions of years later to start to expand again, to explain the super nova anomaly. What is changing billions of years later to cause the expansion? What was the energy source 14.7 billion years ago to cause the millions of times faster than the speed of light expansion?


Well there is a straw man. First off I'll point out that there is no problem with GR with space expanding "faster then light". There was no problem with this concept back in 1916 when Einstein proposed GR and there is no problem with it today. Again a lay person might read that statement and think "I was always told nothing can travel faster then light! William must be right!" sorry didn't mean to rhyme. Everyone in this discussion knows this isn't a problem in the slightest and many of us have explained why it isn't a problem more times then we have fingers and toes on these forums alone.

Quantum physics has plugged a lot of holes in the initial models and it wasn't even that they were trying to. It also provides and explains the initial inflation and why it "turned off" which, as I understand it, is independent from expansion. Characterizing it as an adhoc explanation to super nova light curves or even calling it an anomaly is either based on ignorance or disingenuous. Expansion was observed long before the super nova light curves also provided supporting evidence for expansion. There are multiple lines of independent evidence for expansion which "dark energy" is the current label for the driving force of. It also fits very nicely within the models by filling in some of the open questions.

This isn't all new either. Some of these predictions and models came about shortly after GR and were just thought of, at the time, as mathematical curiosities and not really useful. Much like imaginary numbers were thought to be just maths with no real application then we've found they have very real implications and applications.

So if you want to promote an idea promote it. You don't promote your idea by pointing out gaps in another model. You promote your idea by showing what questions it answers. Our ignorance isn't evidence for your idea just as absence of evidence is not evidence of absence. Just because we have open questions doesn't mean the answers will or will not be filled in using the existing frame work just as open questions in a frame work does not bolster ANY other model's validity. Suggesting that scientist need to drop everything that has gotten us this far and just all go in another direction isn't how science works and if it was well...you and I wouldn't be sitting here at computers because there are orders of magnitude more ideas that are completely flawed then there are working models. Some day a new model may replace current cosmological model or the current model might just be tweaked. At some point we hopefully will unify gravity and quantum physics withing current theories or we might find a more accurate theory that is completely different. But because the current models work as well as they do my bet is for the former. Because it would be very strange in deed if the current models just happen to get such good answers if the underlying assumptions were totally baseless. That would be incredible.

Shaula
2014-May-20, 04:23 AM
It is a fact that the most sensitive dark matter detector ever constructed has confirmed dark matter does not exist within the 'parameter' space of the standard model.
Citation please. I would question anyone's claim to understand the interactions of dark matter well enough to make this claim.


If the current cosmological theory is incorrect at its foundations we can spend 10,000 years working on it and make no progress.
Obviously false - we have made plenty of progress in all scientific fields using theories which turned out to be wrong.


there is no 'string theory' string theory is the name for a mathematical field of work were the objective is to develop a theory, so far there is no theory, which would indicate a pure mathematical approach may never advance fundamental physics or cosmology
Absurd generalisation (up know there are theories other than String Theory in development, right?). Very much like saying in 1930 that experiments have not detected the neutrino and so experimentation will never advance particle physics.


Allowing the possibility that inflation did not occur validates the re-look at the discarded cosmological models.
People do keep looking at alternatives including inflation free models. You just don't see so much of it published as it rarely gets anywhere.


I have never seen a formal review of the old competing cosmological models with the modern observational data. There has been no attempt to organize large scale observations to point out the patterns, as there is no explanation for why there are patterns which points to a different cosmological model.
I've never seen an Okapi, does that mean they don't exist? This is simply argument from ignorance. There are many scientists out there with their own pet model, or who are trying to get away from current models. Some at a hobby level, some as a research project.


CMB Large Scale Anomalies
As he says - they could be important or they could be a fluke. And you are deluding yourself if you think people are not using data like this to attack or modify the current models.

So basically more general complaints that scientists are doing it wrong, no substantial arguments showing that this is the case, lots of "If I can't see it it ain't there". Lots of sweeping (and wrong) generalisations and hints that the answer is obvious and that all the data points to it. If that is the case then publish. Show us all where we are wrong, show us the answer.

Ken G
2014-May-20, 02:49 PM
What are ineffective or effective methods to solve the cosmological problem? How deep is the cosmological theory problems?
Those are research questions, and will be resolved by experiment-- not rhetoric. That's good science. If Kroupa is saying "don't overlook experiment X in your zeal to believe theory A", then that would be fine-- but what is experiment X? This is what is missing from his remarks that would make them valuable. Don't get me wrong, as a "contrarian" Kroupa is performing an important scientific function, as skepticism is at the heart of science. But he applies his skepticism highly unevenly!



It is the nature of the cosmological theory problem that if one or more fundamental theoretical components or the theory itself is incorrect, then the analysis will diverge (more anomalies will be identified), rather than converge. How basic is the fundamental theory problem? Are certain theory problems unthinkable, unimaginable? Why is that so? Does that make it impossible to solve the problem, as the people in the field do not formally scientifically re-look at discarded theories?I don't see the point, these are just the kinds of questions people ask all the time, no one needs Kroupa to get them to ask these questions.


A systematic problem of modern science is it possible to develop very complex models that match the data and that make correct predictions that have no basis in reality (the model and process is a complex type of curve fitting), if there are sufficient free parameters in the model or if the laws of physics are incorrectly changed to enable the model in question to avoid catastrophic paradoxes.Physics always just uses as many free parameters as it needs, that's what physics does. If someone has a theory that satisfies all the same experiments but with fewer free parameters, their theory is always accepted overnight, that's also what physics does. Kroupa is not doing that, he is not suggesting a theory that satisfies the data with fewer free parameters, so his objections about how many free parameters are in lambda-CDM are irrelevant to how physics works.


The cosmological field is interesting as there are piles upon piles of anomalies and structural/linked anomalies and exceptional comprehensive observational data (particularly large structural data) which appears to point to missing mechanisms. Absolutely, that is exactly what makes cosmology so interesting. So what is needed is, theories with the fewest possible free parameters, and suggestions of new observations that can advance these theories. Both of those are supplied by lambda-CDM, which is why it is the mainstream theory. It's not a reason to reject all other theories, but all other theories will be held to that same standard.


The nature of the cosmological theory problem is that it is necessary to view the observations in question from the prospective of the correct fundamental theory to solve the problems. If for example dark matter and dark energy do not physically exist, then theoretical models that use dark matter and dark energy to explain the observational anomalies are purely theoretical, have no physical basis and are a barrier to making any progress to finding the true physical answer.Not so. No physical theory ever has a requirement that its elements "actually exist", that simply is not how physics works. It couldn't work that way, we never have any idea what exists, all we ever have are our theories, how many free parameters they have, what data they satisfy, and what new observations they suggest.


I brought up the question of inflation, as if inflation did not happen, then options as to what causes the anomalies that the posited dark matter and dark energy are required to explain changes.Again, whether or not inflation "actually happened" is inaccessible to science. The scientific questions there are, what does inflation allow us to understand that we cannot understand otherwise? What does it predict that we have not yet seen and would have no reason to expect to see if we did not apply the inflation theory? What observations does it suggest to advance our understanding? Those are the only questions science ever asks, everything else has left the building of science.


I find it astonishing that there is almost no discussion that inflation requires what based on recent observational data appears to be an infinite universe to expanded at millions of times faster than the speed of light roughly 14.7 billion years ago.There is no discussion of it because we have no basis to discuss it. It violates no current theory or any observational data, and is certainly consistent with relativity, as it uses relativity in the theory.
Where was the universe at say 16 billion years ago? It is unclear that such a question is well founded. How would you answer it, observationally? Requiring a theory to answer a question that does not suggest any experiment is unscientific.


Why are there massive voids without galaxies and peculiar links/ribbons of gas between clusters?Simulations of gravitational instabilities produce those things within the current theory, the only issue is whether the voids and ribbons have the nature we would expect from the theory, or if they have unusual characteristics suggesting missing physics. Those are not easy questions, and are certainly research issues that people are trying to figure out observations and simulations that could answer. In other words, nothing is broken there, science is being science and yes, it could lead to big surprises, as it has so often done in the past. But the theories we have now are doing a fine job of focusing and organizing the necessary research to answer those questions, it's not clear that MOND is doing anything that would help with those issues.

Strange
2014-May-20, 09:35 PM
Don't get me wrong, as a "contrarian" Kroupa is performing an important scientific function, as skepticism is at the heart of science. But he applies his skepticism highly unevenly!

Contrast this with Einstein's dislike of quantum theory. He didn't just grumble about it and say that "someone should find something better". He used the theory to propose experiments that (he believed) would show the theory to be incomplete or contradictory. (In the end, this criticism actually strengthened the theory by forcing others to consider these implications and develop the experiments.)

Reality Check
2014-May-21, 12:44 AM
It is a fact that the most sensitive dark matter detector ever constructed has confirmed dark matter does not exist within the 'parameter' space of the standard model.

Sorry, William, but that is incorrect: It is a fact that the most sensitive dark matter detector ever constructed has confirmed dark matter does not exist within the 'parameter' space of that detector.
No detector or detectors has explored the entire 'parameter' space of the standard model.

The point is that the non-detection of specific dark matter candidates is good science - it allows us to concentrate on the other dark matter candidates.

The theoretical work on multiverses does advance science like all theoretical work! Specifically this work should allow predictions to be made that will distinguish between a single universe and multiverses.
If inflation did not happen this would have no effect on string theory papers because inflation has little to do with string theory. String theory is an alternative to inflation.
It is physically possible for an infinite universe to expand at more than a million times faster than the speed of light for a fraction of a second.
There are galaxies now that are receding from us at a speed faster than the speed of light: Can objects move away from us faster than the speed of light? (http://www.astro.ucla.edu/~wright/cosmology_faq.html#FTL)

And what does The Universe According to Planck (The Satellite) (http://profmattstrassler.com/2013/03/21/the-universe-according-to-planck-the-satellite/) actually say:
"◾On small angular scales, the universe looks about as simple and as consistent with current understanding as you could ask for (or not ask for). Many speculative notions about how the universe might have developed in its earliest stages are now out of the question."
"◾The idea that cosmic inflation (a period where the universe was cold and expanding at a spectacular rate, following which the hot dense period we usually think of as the classic “Big Bang” began) may have occurred, making the universe so large and uniform, is unchallenged (one might even say supported) by the data at small and medium angular scales)"
"◾Planck’s predecessor, the WMAP satellite, found that there are some funny non-uniformities, a bit larger than you’d expect, at very large angular scales — and Planck sees them too, confirming their existence and allowing more precise study of them (The temperature fluctuates more in half the sky than in the other half, and there’s a cold spot, and some sign of alignment of large-scale distortions that were expected to be randomly distributed.). But interpreting something like this is tricky — it could just be a statistical fluke, and since there’s only one universe, you don’t get to improve your statistics with better measurements. (That last point is called the problem of “cosmic variance”.) So if something interesting is going on in the overall shape or structure of the universe, I suspect we’re going to need an additional and different type of measurement to convince ourselves. And I’m not sure what that would be."

William
2014-May-21, 02:09 AM
Sorry, William, but that is incorrect: It is a fact that the most sensitive dark matter detector ever constructed has confirmed dark matter does not exist within the 'parameter' space of that detector.
No detector or detectors has explored the entire 'parameter' space of the standard model.

The point is that the non-detection of specific dark matter candidates is good science - it allows us to concentrate on the other dark matter candidates.

Yes or to move (perhaps it might be advisable for a few souls to move on, as we will wait forever to solve this problem if dark matter does not exist) on as dark matter does not physically exist.



Sorry, William,

And what does The Universe According to Planck (The Satellite) (http://profmattstrassler.com/2013/03/21/the-universe-according-to-planck-the-satellite/) actually say:
"◾On small angular scales, the universe looks about as simple and as consistent with current understanding as you could ask for (or not ask for). Many speculative notions about how the universe might have developed in its earliest stages are now out of the question."
"◾The idea that cosmic inflation (a period where the universe was cold and expanding at a spectacular rate, following which the hot dense period we usually think of as the classic “Big Bang” began) may have occurred, making the universe so large and uniform, is unchallenged (one might even say supported) by the data at small and medium angular scales)"
"◾Planck’s predecessor, the WMAP satellite, found that there are some funny non-uniformities, a bit larger than you’d expect, at very large angular scales — and Planck sees them too, confirming their existence and allowing more precise study of them (The temperature fluctuates more in half the sky than in the other half, and there’s a cold spot, and some sign of alignment of large-scale distortions that were expected to be randomly distributed.). But interpreting something like this is tricky — it could just be a statistical fluke, and since there’s only one universe, you don’t get to improve your statistics with better measurements. (That last point is called the problem of “cosmic variance”.) So if something interesting is going on in the overall shape or structure of the universe, I suspect we’re going to need an additional and different type of measurement to convince ourselves. And I’m not sure what that would be."


A picture is worth a thousand words. We are discussing the CMB large scale features (see the picture of the CMB large scale anomalies). At large scales the CMB is not symmetrical from hemisphere to hemisphere from our view point. There are massive large scale anomalies. Yes or no? (i.e. The massive anomalies are not due to instrument error or due to contamination of the CMB from local heat sources. The massive large scale CMB anomalies are real.

The writer was making a joke when he suggested that the large scale CMB anomalies were due to a statistical fluke. Small scale anomalies could be created by statistical flukes. There are no papers to discuss the CMB large scale features as there is no explanation. The universe is not expected to differ massive region to massive region (region from which the CMB originated from.)

http://profmattstrassler.files.wordpress.com/2013/03/planck_anomalies.jpg

The CMB is very, very uniform at small scales. Too uniform (i.e. the universe has massive voids and sheets of clusters that are connected by the weird 'filaments of gas', which is one of the reasons the inflation hypothesis was created. Curiously the voids contain a few galaxies that are also connected by filaments of gas. Makes a person think. How many galaxies are typically in a cluster? How do the galaxies evolve? Why are there so many bulgeless spiral galaxies? How and why do spiral galaxy's bulges develop. What do we observe in the local cluster?



CMB Large Scale Anomalies
"The temperature fluctuates more" in half the sky than in the other half, and there’s a cold spot, and some sign of alignment of large-scale distortions that were expected to be randomly distributed. But interpreting something like this is tricky — it could just be a statistical fluke, and since there’s only one universe, you don’t get to improve your statistics with better measurements. (That last point is called the problem of “cosmic variance”.) So if something interesting is going on in the overall shape or structure of the universe, I suspect we’re going to need an additional and different type of measurement to convince ourselves. And I’m not sure what that would be.


http://profmattstrassler.com/2013/03...the-satellite/

Reality Check
2014-May-21, 02:40 AM
Yes or to move (perhaps it might be advisable for a few souls to move on, as we will wait forever to solve this problem if dark matter does not exist) on as dark matter does not physically exist

No, William.
We know the dark matter "physically" exists because it has physical effects. We will always have to account for those effects. There is a remote possibility that we can account for them by a change in theory but so far all attempts to do this have failed. There is a good possibility that we can detect dark matter particles with current technology. There is a small possibility that dark matter particles are such that we cannot detect them with current technology.
Either way scientists will not give up on looking for theory changes or actual DM particles just because you think DM does not exist :).
And as for "a few souls" - there are more than a few scientists researching DM!

And no - in science a picture is basically useless except for illustrations.
The author was not joking :
URL="http://profmattstrassler.com/2013/03/21/the-universe-according-to-planck-the-satellite/"]The Universe According to Planck (The Satellite)[/URL]

Planck’s predecessor, the WMAP satellite, found that there are some funny non-uniformities, a bit larger than you’d expect, at very large angular scales — and Planck sees them too, confirming their existence and allowing more precise study of them (The temperature fluctuates more in half the sky than in the other half, and there’s a cold spot, and some sign of alignment of large-scale distortions that were expected to be randomly distributed.). But interpreting something like this is tricky — it could just be a statistical fluke, and since there’s only one universe, you don’t get to improve your statistics with better measurements. (That last point is called the problem of “cosmic variance”.) So if something interesting is going on in the overall shape or structure of the universe, I suspect we’re going to need an additional and different type of measurement to convince ourselves. And I’m not sure what that would be
William - we know the large scale CMB anomalies are real (see above)! It is the cause of the anomalies that is unknown.

The universe is "expected to differ massive region to massive region" - that is what the fluctuations in the CMB are all about. The point of the anomalies is that the fluctuations at large scales do not match expectations.

Shaula
2014-May-21, 05:31 AM
William - you have basically said the same thing over and over again for the last few posts. Can we just take it as read that we all know your opinions and move on to some substantive points?

As for the CMB anomalies being real... Jury is actually still out on some of them. The cold spot mentioned in the blog, for example, is contentious since it only appears with certain methods of processing and there is every chance it has had its significance massively inflated due to a filter kernel match between the background models and the foreground smoothing. The large scale asymmetry is more interesting and some of the angular distributions are also of note. They may point to new physics, or they may point to background model problems. There is actually quite a strong variation in significance for some of them depending on how you do your background modelling.

Also - a picture may speak a thousand words, but unless you know far more than is given to you by just a picture you may well misunderstand them. As is shown by the fact that the picture rates the cold spot as far more significant than it might be. Unless you have a fairly strong grasp of how they have processed that data then you will be unable to evaluate what those thousand words mean.

Squink
2014-May-21, 12:50 PM
I'm just not seeing the crisis here. Sure, something's going on that we don't understand, and when we finally get a handle on it, a whole bunch of scientists are going to be surprised and enlightened. Some might get egg on their face; the resolution might even have everyday consequences for the rest of us.
That's not a crisis, it's how scientific discovery works.

Ken G
2014-May-25, 05:19 AM
Contrast this with Einstein's dislike of quantum theory. He didn't just grumble about it and say that "someone should find something better". He used the theory to propose experiments that (he believed) would show the theory to be incomplete or contradictory. (In the end, this criticism actually strengthened the theory by forcing others to consider these implications and develop the experiments.)Good point, for example the EPR paper gets quoted all the time because it was so important for promoting understanding of entanglement, even though Einstein was in some sense on the wrong side of the "paradox."

Decckie
2014-May-26, 10:49 PM
If dark energy is nothing more than a mathematical construct for a hypothetical form of energy that is supposed to permeate all of space and accelerate the expansion of the universe, I think it points to a more radical conclusion that goes beyond mere modelling behaviours in mathematics according to our earth-bound views of how the universe should work. My theory is that the missing mass doesn't permeate all of space, it's actually all contained in a super-massive 'Dyson sphere' that surrounds the whole universe. The mass of this 'super-sphere' is what's causing the expansion of the universe to accelerate. We can't detect its gravitational field because everything in the universe is in free-fall towards it. And what's on the other side you may well ask? Well the super-sphere is actually an elementary particle in a higher universe that operates on a completely different time-frame due to as yet undiscovered laws. It could be a short life particle like a muon that lasts for only microseconds which would be the life of the universe in our time-frame. The particle would have been created in a high-energy interaction in the higher universe which would explain the Big Bang.
Ok I can't prove this theory but can anybody dis-prove it? It may be too fantastic to accept but the truth could be equally fantastic, dismissed forever and relegated to the realms of fantasy while the search for an acceptable truth continues in vain.

Reality Check
2014-May-27, 04:33 AM
If dark energy is nothing more than a mathematical construct ....
Luckily it is not, Decckie :D.
Dark energy is the observation that the expansion of the universe is accelerating.
It has nothing to do with any "missing mass" (that is dark matter).
The gravitational force within a hollow sphere is zero: Shell theorem (http://en.wikipedia.org/wiki/Shell_theorem).

Sorry but you do not have a theory so it is not possible to say anything about it. In any case this is not the place for ATM ideas.

NoChoice
2014-May-27, 04:47 AM
Luckily it is not, Decckie :D.
Dark energy is the observation that the expansion of the universe is accelerating.

There is an observation that the universe is accelerating.
DE is a fictional mathematical construct to try to explain that observation.
It is entirely fictional. DE (so far) was never observed.


In any case this is not the place for ATM ideas.
It seems to me it is you who needs to take his mischaracterization of DE to ATM.

Shaula
2014-May-27, 06:15 AM
Ok I can't prove this theory but can anybody dis-prove it?
Easily. http://en.wikipedia.org/wiki/Shell_theorem. So it wouldn't explain DE or expansion.

Cougar
2014-May-27, 01:26 PM
There is an observation that the universe is accelerating.
DE is a fictional mathematical construct to try to explain that observation.
It is entirely fictional.

How do you know it's "fictional"? I think it would more accurately be termed a hypothesis. It's not even a "mathematical construct" at this point. But the Sne Ia observations require an explanation. There are some constraints on what that explanation could be. As pointed out, Decckie's explanation cannot be right since a "supermassive sphere surrounding our Universe" would have no gravitational effect on anything inside our universe, as shown by Newton a few years ago.

Strange
2014-May-27, 04:58 PM
How do you know it's "fictional"? I think it would more accurately be termed a hypothesis.

It is more like a catch-all term for several hypotheses.

Hlafordlaes
2014-May-27, 07:58 PM
As a recent indication of dark matter at work, wasn't there something in the news about a large hydrogen cloud (failed small galaxy) having passed through the MWG at high speed a few m.y. ago, with the only way possible to do so was with a DM sheath of sorts?

Amber Robot
2014-May-27, 08:40 PM
Ok I can't prove this theory but can anybody dis-prove it?

Until it makes some predictions to compare to observations there's no reason to consider it let alone to attempt to disprove it.

Reality Check
2014-May-28, 12:55 AM
There is an observation that the universe is accelerating.

DE is a placeholder for whatever is causing that acceleration. The simplest explanation is a positive cosmological constant which is General Relativity, not a part of any "fictional mathematical construct".
This is a "hypothetical form of energy" as in Dark energy (http://en.wikipedia.org/wiki/Dark_energy) (there is also quintessence and other options).

borman
2014-May-28, 04:18 PM
Testing LCDM
There is a new paper out today that may have a bearing on this thread:
Particle ejection during mergers of dark matter halos
http://arxiv.org/abs/1405.6725
Some possible evidence in favor:
A filament of dark matter between two clusters of galaxies
http://arxiv.org/abs/1207.0809
Less secure support for a DM bridge:
Weak lensing evidence for a filament between A222/A223
http://arxiv.org/abs/astro-ph/0403656

Bullet groups to search for more evidence:
The abundance of Bullet-groups in LCDM
http://arxiv.org/abs/1404.5636
And:
Dark matter-baryons separation at the lowest mass scale: the Bullet Group
http://arxiv.org/abs/1404.5633



Possible evidence against is a lack of tidal tail of DM in the Bullet Cluster coming from the smaller cluster (the Clowe et al paper):
Weak lensing mass reconstruction of the interacting cluster 1E0657-558: Direct evidence for the existence of dark matter
http://arxiv.org/abs/astro-ph/0312273
And:
A direct empirical proof of the existence of dark matter
http://arxiv.org/abs/astro-ph/0608407


Also:
Catching a bullet: direct evidence for the existence of dark matter
http://arxiv.org/abs/astro-ph/0611496

Can inter cluster DM filaments really be seen?:
Is Gravitational Lensing by Intercluster Filaments Always Negligible?
http://arxiv.org/abs/0710.4935

The a priori assumption in invoking DM particles is that they do not violate the principle of equivalence. Today’s paper does not assume friction or DM-DM interaction, but just ejection by GR gravity.

antoniseb
2014-May-28, 04:26 PM
... Some possible evidence in favor:
A filament of dark matter between two clusters of galaxies
http://arxiv.org/abs/1207.0809
Less secure support for a DM bridge:
Weak lensing evidence for a filament between A222/A223
http://arxiv.org/abs/astro-ph/0403656

...

If I understand most recent universe simulations, if there is a filament between two clusters, our usual models suggest that the filament was there first, and the clusters formed after matter traveled from the filament into the clusters.

borman
2014-May-28, 04:45 PM
Perhaps there is some ambiguity in the use of "filament". On the largest scales we see filaments which enclose galaxies and clusters and superclusters at nodal points. the small scale filaments or DM bridges suggested here are as evidence of the aftermath of a collision, not preceding it, due purely to ejection via GR gravity, The use of filament may have used to convey thinness.

Jerry
2014-Jun-03, 03:34 PM
Luckily it is not, Decckie :D.
Dark energy is the observation that the expansion of the universe is accelerating.
Dark energy is an interpretation of observations of the spectral shift and light attenuation from distant sources that there is an accelerating expansion of the known universe. This interpretation is based upon one primary line of evidence: the luminosity of a peculiar type of supernova. We are finding much more variability in the magnitude of these events than anyone suspected in 1998; and as the database grows, there is less, not more; certainty in the precision of these conclusions.

http://xxx.lanl.gov/abs/1101.2396

That said, holding to the current 'accelerating expansion' interpretation is still reasonable; because the data lean even harder towards acceleration when additional factors, such as reddening, are considered.

Amber Robot
2014-Jun-03, 05:02 PM
We are finding much more variability in the magnitude of these events than anyone suspected in 1998; and as the database grows, there is less, not more; certainty in the precision of these conclusions.

http://xxx.lanl.gov/abs/1101.2396

From this paper:


While the trends are weak, fitting for the trend can improve SN Ia distances by 5%

Is 5% a large enough issue to cast any doubt on the overall supernova results? The light curves shown in this paper's Figure 2 look pretty good for showing how well supernovae fit the template.

Reality Check
2014-Jun-04, 12:48 AM
Dark energy is an interpretation of observations of the spectral shift and light attenuation from distant sources that there is an accelerating expansion of the known universe.

That we are in an expanding universe is supported by overwhelming evidence.
That this expansion is accelerating has strong evidence.
That acceleration has a cause.
That cause has a label - dark energy. Dark energy is thus a placeholder for whatever is causing the observations - and yes this is under the assumption that the universe is expanding and so the term is an interpretation.

I would consider UV Properties of Type Ia Supernova and their Host Galaxies (http://xxx.lanl.gov/abs/1101.2396) as a step toward more precise measurements of distances via Type Ia supernova by looking at their environment rather than an indication that the existing distances are so wrong that the evidence for dark energy is in doubt.