|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Galaxy mix: No dark matter required
On Feb 19, 3:00*pm, YKhan wrote:
On Feb 19, 2:35*am, Eric Gisse wrote: If someone finds a theory that explains the large scale structure of the universe, properly fits the CMBR, suggests a credible theory for galaxy formation, galactic rotation curves, and replicates observed results for colliding galaxies, but does not involve dark matter or dark energy - I'll honestly consider it. Unfortunately every 'alternative' works in one of two aspects and none of the others, MOND and such. And those problems are equally a problem working against Dark Matter, isn't it? If you're saying DM describes more scenarios and examples, that's simply not true. Some colliding clusters seem to be described by DM, while others seem to have DM in all of the wrong places. Since when? The only example I've seen is Abel 520 [from memory, it's close] in which it is an /unlikely/ prospect that the cluster formed via a DM model. However, 'unlikely' is the order of the day when considering how unlikely that Earth would get a plane-on view of a cluster of galaxies colliding. View the events with respect to the whole, not just in isolation. Cherry picking is bad. And making a case that DM describes the CMBR any better than any other theory is pointless. Considering I am yet to hear of a reasonable alternative that does so, I'm gonna disagree. And of course DM completely falls apart in every case of dwarf galaxies, cannot begin to describe them, but the alternatives can. The current model of galaxy formation appears to fall apart. There's a difference. Again - cherry picking. Grabbing the corner case and using it as represenative of the whole isn't a good idea. What this result tells me is that we really have no idea how dwarf galaxies form and that our ideas on how galaxies themselves form may be wrong. Which if you think about it, then you're damning Dark Matter models implicitly. If you say we have no idea how dwarf galaxies and galaxies in general form, then that's a damnation of all Dark Matter models. All models, not just DM models. Because all of Dark Matter's competitors can easily describe how dwarf galaxies form, and they can also describe how galaxies of any and all sizes can form without the asterisks, fine print, or footnotes. So? The Ballmer formla can easily describe the spectra of Hydrogen. Explaining one particular thing in isolation is not a major accomplishment! * Yousuf Khan |
#2
|
|||
|
|||
Galaxy mix: No dark matter required
On Feb 20, 7:59*pm, Eric Gisse wrote:
And those problems are equally a problem working against Dark Matter, isn't it? If you're saying DM describes more scenarios and examples, that's simply not true. Some colliding clusters seem to be described by DM, while others seem to have DM in all of the wrong places. Since when? The only example I've seen is Abel 520 [from memory, it's close] in which it is an /unlikely/ prospect that the cluster formed via a DM model. However, 'unlikely' is the order of the day when considering how unlikely that Earth would get a plane-on view of a cluster of galaxies colliding. View the events with respect to the whole, not just in isolation. Cherry picking is bad. Abel 520 is an example of cherry picking against DM, but the Bullet Cluster is also an example of cherry picking for DM. The vast majority of clusters so far can be explained by either DM or DM-alternatives equally. And making a case that DM describes the CMBR any better than any other theory is pointless. Considering I am yet to hear of a reasonable alternative that does so, I'm gonna disagree. I think most DM-alternative theories also lay claim to being able to explain the CMBR variations, just as much as DM lays claim to it. Really, it's a wash, many of the theories can explain the CMBR variations just as well as DM does. Like for example, in the following link, they are showing how TeVeS can explain the CMBR data pretty well too: The Third Peak in TeVeS "One can see, by inspection, that the scalar field plays the role usually ascribed to CDM of providing a driving term in the oscillations. " http://www.astro.umd.edu/~ssm/mond/CMB6.html And of course DM completely falls apart in every case of dwarf galaxies, cannot begin to describe them, but the alternatives can. The current model of galaxy formation appears to fall apart. There's a difference. You mean like the current model of galaxy formation, involving Dark Matter? Again - cherry picking. Grabbing the corner case and using it as represenative of the whole isn't a good idea. snip Which if you think about it, then you're damning Dark Matter models implicitly. If you say we have no idea how dwarf galaxies and galaxies in general form, then that's a damnation of all Dark Matter models. All models, not just DM models. How is it damning of /all/ models? The DM alternatives seem to be able to explain the dwarf galaxy formations pretty well, it's only the DM models that fail. Because all of Dark Matter's competitors can easily describe how dwarf galaxies form, and they can also describe how galaxies of any and all sizes can form without the asterisks, fine print, or footnotes. So? The Ballmer formla can easily describe the spectra of Hydrogen. Explaining one particular thing in isolation is not a major accomplishment! If it were only one isolated example of explaining something well, but the DM alternatives can explain all cases that DM explains well, and then gets the stuff right that DM gets wrong. Yousuf Khan |
#3
|
|||
|
|||
Galaxy mix: No dark matter required
On Feb 28, 4:33*pm, YKhan wrote:
On Feb 20, 7:59*pm, Eric Gisse wrote: And those problems are equally a problem working against Dark Matter, isn't it? If you're saying DM describes more scenarios and examples, that's simply not true. Some colliding clusters seem to be described by DM, while others seem to have DM in all of the wrong places. Since when? The only example I've seen is Abel 520 [from memory, it's close] in which it is an /unlikely/ prospect that the cluster formed via a DM model. However, 'unlikely' is the order of the day when considering how unlikely that Earth would get a plane-on view of a cluster of galaxies colliding. View the events with respect to the whole, not just in isolation. Cherry picking is bad. Abel 520 is an example of cherry picking against DM, but the Bullet Cluster is also an example of cherry picking for DM. The vast majority of clusters so far can be explained by either DM or DM-alternatives equally. Since you claim the 'vast majority' can be explained w/o DM, name two. I only know of one, and that non-DM explanation makes assumptions that I believe to have been invalidated in solar system scale tests. And making a case that DM describes the CMBR any better than any other theory is pointless. Considering I am yet to hear of a reasonable alternative that does so, I'm gonna disagree. I think most DM-alternative theories also lay claim to being able to explain the CMBR variations, just as much as DM lays claim to it. They lay claim but completely fail to deliver, like MOND. Really, it's a wash, many of the theories can explain the CMBR variations just as well as DM does. Like for example, in the following link, they are showing how TeVeS can explain the CMBR data pretty well too: The Third Peak in TeVeS "One can see, by inspection, that the scalar field plays the role usually ascribed to CDM of providing a driving term in the oscillations. "http://www.astro.umd.edu/~ssm/mond/CMB6.html "That said, it remains to be seen whether a tolerable fit to the WMAP data can be obtained. The authors showed plots at the conference that made it clear it was possible to obtain a third peak comparable to the data, but are still in the process of trying to fit the best cosmic parameters. There is no guarantee that this will work out. " How unconvincing. And of course DM completely falls apart in every case of dwarf galaxies, cannot begin to describe them, but the alternatives can. The current model of galaxy formation appears to fall apart. There's a difference. You mean like the current model of galaxy formation, involving Dark Matter? Even if what you said was 100% true, it still doesn't make DM wrong. It makes the model for formation wrong, which is somewhat different. Again - cherry picking. Grabbing the corner case and using it as represenative of the whole isn't a good idea. * snip Which if you think about it, then you're damning Dark Matter models implicitly. If you say we have no idea how dwarf galaxies and galaxies in general form, then that's a damnation of all Dark Matter models. All models, not just DM models. How is it damning of /all/ models? The DM alternatives seem to be able to explain the dwarf galaxy formations pretty well, it's only the DM models that fail. Again, cherry picking! The DM alternatives DO NOT WORK except in carefully chosen corner cases. [...] |
#4
|
|||
|
|||
Galaxy mix: No dark matter required
Stop wasting your time. Eric is convinced that DM is the true picture
of the universe and you cannot reason with that. I had once got him to admit that MOND does explain Galaxies very well although it does not work well at bigger scales. But then he explained it away as an artifact of DM. I don't understand how can anybody assume a matter to have zero degrees of freedom. If any equation with a single global free parameter can explain all galaxy rotation based on just the Baryonic Mass then how can DM be responsible for anything. -anand |
#5
|
|||
|
|||
Galaxy mix: No dark matter required
On Apr 6, 3:32*am, wrote:
Stop wasting your time. Eric is convinced that DM is the true picture of the universe and you cannot reason with that. Until there's a better explanation, I'll stick with the one I have. I had once got him to admit that MOND does explain Galaxies very well although it does not work well at bigger scales. Of course I admitted it. The success of MOND for modeling certain behaviors of certain galaxies is well documented. But then he explained it away as an artifact of DM. I don't understand how can anybody assume a matter to have zero degrees of freedom. If If you are going to whine, at least be right. DM has density and temperature as degrees of freedom. any equation with a single global free parameter can explain all galaxy rotation based on just the Baryonic Mass then how can DM be responsible for anything. Is that a complaint against DM...or MOND? -anand |
#6
|
|||
|
|||
Galaxy mix: No dark matter required
On Apr 7, 2:49*am, Eric Gisse wrote:
On Apr 6, 3:32*am, wrote: If you are going to whine, at least be right. DM has density and temperature as degrees of freedom. How do you observe the Density and Temperature at the Galaxy level. If it has temperature then it should be fairly easy to detect as any object with temperature higher than Absolute Zero will give of some radiation. That is why we call it the CDM model in that the DM is cold at Absolute Zero. There is no degree of freedom there. And it is always modeled to have a uniform density to give exactly the kind of observation that is predicted by MOND. Which really is having no freedom at all as the baryons are deciding where the DM will be through MOND. any equation with a single global free parameter can explain all galaxy rotation based on just the Baryonic Mass then how can DM be responsible for anything. Is that a complaint against DM...orMOND? It is a complaint against the thinking that DM can somehow give MOND phenomenology. It cannot period. For the record I am not against DM (cold or hot). Its just that MOND does not allow it at Galactic levels. I also don't think TeVeS is in any way a good theory it is just trying to put MOND phenomenology into a theory, which will not work. We will have to get a theory from the first principles. Recovering the MOND phenomenology at Galactic levels is an additional test. I am not saying that GR is wrong, it could be that we don't understand it very well. The LQG guys are trying to use GR at the quantum level. But the current form does not give MOND which is a fatal problem. Till we get a good enough theory, trying to answer any cosmological questions is meaning less. In essence, Cosmologists are just blundering in the dark, and wasting there time. I don't know why they don't do something constructive like trying to find a theory that does work, rather than wasting their time predicting the age of the universe without even knowing how mass moves. -anand |
#7
|
|||
|
|||
Galaxy mix: No dark matter required
On Apr 7, 2:49*am, Eric Gisse wrote:
On Apr 6, 3:32*am, wrote: If you are going to whine, at least be right. DM has density and temperature as degrees of freedom. How do you observe the Density and Temperature at the Galaxy level. If it has temperature then it should be fairly easy to detect as any object with temperature higher than Absolute Zero will give of some radiation. That is why we call it the CDM model in that the DM is cold at Absolute Zero. There is no degree of freedom there. And it is always modeled to have a uniform density to give exactly the kind of observation that is predicted by MOND. Which really is having no freedom at all as the baryons are deciding where the DM will be through MOND. any equation with a single global free parameter can explain all galaxy rotation based on just the Baryonic Mass then how can DM be responsible for anything. Is that a complaint against DM...orMOND? It is a complaint against the thinking that DM can somehow give MOND phenomenology. It cannot period. For the record I am not against DM (cold or hot). Its just that MOND does not allow it at Galactic levels. I also don't think TeVeS is in any way a good theory it is just trying to put MOND phenomenology into a theory, which will not work. We will have to get a theory from the first principles. Recovering the MOND phenomenology at Galactic levels is an additional test. I am not saying that GR is wrong, it could be that we don't understand it very well. The LQG guys are trying to use GR at the quantum level. But the current form does not give MOND which is a fatal problem. Till we get a good enough theory, trying to answer any cosmological questions is meaning less. In essence, Cosmologists are just blundering in the dark, and wasting there time. I don't know why they don't do something constructive like trying to find a theory that does work, rather than wasting their time predicting the age of the universe without even knowing how mass moves. -anand |
#8
|
|||
|
|||
Galaxy mix: No dark matter required
On Apr 7, 2:49*am, Eric Gisse wrote:
On Apr 6, 3:32*am, wrote: I had once got him to admit thatMONDdoes explain Galaxies very well although it does not work well at bigger scales. Of course I admitted it. The success ofMONDfor modeling certain behaviors of certain galaxies is well documented. So you don't agree that all known galaxy types are modelled well with MOND. Can I know an instance of types that have been proved to not work with MOND. Or even one which have not been attempted to be explained by MOND. I am sure it will be a good pointer for Dr. Stacy McGaugh. regards, -anand |
#9
|
|||
|
|||
Galaxy mix: No dark matter required
On Apr 7, 2:49*am, Eric Gisse wrote:
On Apr 6, 3:32*am, wrote: I had once got him to admit thatMONDdoes explain Galaxies very well although it does not work well at bigger scales. Of course I admitted it. The success ofMONDfor modeling certain behaviors of certain galaxies is well documented. So you don't agree that all known galaxy types are modelled well with MOND. Can I know an instance of types that have been proved to not work with MOND. Or even one which have not been attempted to be explained by MOND. I am sure it will be a good pointer for Dr. Stacy McGaugh. regards, -anand |
#10
|
|||
|
|||
Galaxy mix: No dark matter required
On Apr 6, 11:02*pm, wrote:
On Apr 7, 2:49*am, Eric Gisse wrote: On Apr 6, 3:32*am, wrote: If you are going to whine, at least be right. DM has density and temperature as degrees of freedom. How do you observe the Density and Temperature at the Galaxy level. Lensing to observe density, and density + gravitation to determine temperature. If it has temperature then it should be fairly easy to detect as any object with temperature higher than Absolute Zero will give of some radiation. That is why we call it the CDM model in that the DM is cold at Absolute Zero. There is no degree of freedom there. You think dark matter can radiate electromagnetically because.....? And it is always modeled to have a uniform density to give exactly the kind of observation that is predicted by MOND. Which really is having no freedom at all as the baryons are deciding where the DM will be through MOND. MOND no more decides anything than the Ballmer formula for the Hydrogen spectrum determines where the spectral lines will be. Curve fitting is not predictive, BULLET CLUSTER. any equation with a single global free parameter can explain all galaxy rotation based on just the Baryonic Mass then how can DM be responsible for anything. Is that a complaint against DM...orMOND? It is a complaint against the thinking that DM can somehow give *MOND phenomenology. It cannot period. That's personal conjecture on my part that has no validation. It might be worth demonstrating, though. For the record I am not against DM (cold or hot). Its just that MOND does not allow it at Galactic levels. MOND does not ALLOW? HA HA HA I also don't think TeVeS is in any way a good theory it is just trying to put MOND phenomenology into a theory, which will not work. How do you know? Have you tried? We will have to get a theory from the first principles. Recovering the MOND phenomenology at Galactic levels is an additional test. Why? MOND isn't an observation, its a curve fit to /other/ observations. I am not saying that GR is wrong, it could be that we don't understand it very well. The LQG guys are trying to use GR at the quantum level. But the current form does not give MOND which is a fatal problem. Even more fatal is the lack of testable predictions. Till we get a good enough theory, trying to answer any cosmological questions is meaning less. In essence, Cosmologists are just blundering in the dark, and wasting there time. I don't know why they don't do something constructive like trying to find a theory that does work, rather than wasting their time predicting the age of the universe without even knowing how mass moves. A handful of plane-on galactic cluster collisions plus the CMBR is rather compelling in my mind. Plus the individual lensing observations of galaxies not involved in collisions... -anand |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Galaxy mix: No dark matter required | john190209 | Amateur Astronomy | 1 | February 21st 09 02:49 AM |
Complete dark matter theory opens door to weight/energy potential(Dark matter is considered to be the top mystery in science today, solved,really.) And more finding on dark matter ebergy science from the 1930's. | [email protected] | Astronomy Misc | 0 | September 14th 08 03:03 AM |
Dark matter means ebergy (ebergy known since the 1930's to makeenergy from 'dark matter'). Dark matter is solved for the first time (100pages) | gb[_3_] | Astronomy Misc | 0 | August 5th 08 05:24 PM |
Galaxy Seen Colliding with Invisible Dark Matter Galaxy! | Double-A[_1_] | Misc | 0 | June 17th 07 12:56 PM |