tag:blogger.com,1999:blog-22973357.post3634607792328530501..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Dark matter nightmare: What if we are just using the wrong equations?Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger210125tag:blogger.com,1999:blog-22973357.post-27181005156263559832020-01-10T11:01:55.239-05:002020-01-10T11:01:55.239-05:00This paper titled "Further evidence for a pop...This paper titled "Further evidence for a population of dark-matter-deficient dwarf galaxies" was published on 25 Nov. 2019, or 5 weeks after Sabine wrote this post. It's possible others have cited this paper upthread, but with 209 entries there were too many to examine. Googling this paper I haven't noticed any rebuttals, but could have overlooked them, without a more David Schroederhttps://www.blogger.com/profile/18048116250413347228noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20517260154303163962019-12-11T17:25:05.868-05:002019-12-11T17:25:05.868-05:00Seems strange that when we have a dwarf galaxy tha...Seems strange that when we have a dwarf galaxy that enables all the stars to be accounted for, there is no dark matter. In normal galaxies where we have at best poor estimates of the size number and distribution we find discrepancy with estimated radisl distribution of mass. Miles drakehttps://www.blogger.com/profile/04818665622491160354noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-65304800249759854132019-11-05T01:23:09.202-05:002019-11-05T01:23:09.202-05:00@drl I don't think you fully got what Dr Hoss...@drl I don't think you fully got what Dr Hossenfelder is arguing as a possibility (or maybe I am mistaken). That our assumption that dark matter is needed in our models is due to our models treating galaxies as smooth mass distributions, averaging the mass of all the stars. That maybe something more complicated... some emergent property of gravity... is what we are seeing. That such a Hontashttps://www.blogger.com/profile/10738914801980776396noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-76139748800097168902019-11-04T18:08:44.848-05:002019-11-04T18:08:44.848-05:00Beyond 200 comments, so this of mine may not be re...Beyond 200 comments, so this of mine may not be read by many ...<br /><br />From today's astro-ph: "<b>The Distribution of Ultra-Diffuse and Ultra-Compact Galaxies in the Frontier Fields</b>", Janssens+ (arXiv:1911.00011). From the abstract: "<i>We estimate the clusters host of order ∼200-1400 UDGs inside the virial radius (R200), consistent with the UDG abundance halo-mass JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5674509000197304572019-10-30T15:25:10.759-04:002019-10-30T15:25:10.759-04:00Thanks @bud rap.
By "Carrick & Coopersto...Thanks @bud rap.<br /><br />By "<i>Carrick & Cooperstock 2010 (2018)</i>" I think you mean Carrick & Cooperstock (2012), which is arxiv/1101.3224 (published in the January 2012 issue of Astrophysics and Space Science). Do you?<br /><br />"<i>It is the point of Cooperstock's work to show that that method is incorrect, and to offer a more realistic alternative.</i>" JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72422137628876276832019-10-30T14:43:20.938-04:002019-10-30T14:43:20.938-04:00The extent to which modern theoretical physics has...The extent to which modern theoretical physics has devolved into a futile exercise in defending failed models is on full display here. The failed model in this case is accurately summarized in the concluding comments of Carrick & Cooperstock 2010 (2018):<br /><br /><i>...there is an essential difference between the solar system dynamics and the galactic dynamics. In the case of the solar bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-71517136851099264782019-10-30T11:09:29.619-04:002019-10-30T11:09:29.619-04:00@Peter Erwin: Thanks for the comments.
I didn'...@Peter Erwin: Thanks for the comments.<br /><br />I didn't comment on CT06 estimates of mass, nor your comments on an apparent discrepancy, in part because I didn't understand how CT06 addressed spiral galaxy bulges. Yes, per what's in CT06, there is an inconsistency; however, without something explicit on bulges ... To be clear, this is independent of any particular galaxy (yeah, Sb JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-62496444485512897482019-10-30T10:56:24.993-04:002019-10-30T10:56:24.993-04:00@weristdas: Who are "scientists"? Genera...@weristdas: Who are "scientists"? Generally, people who work in universities or research institutes, and who do research. They do not possess magical powers. The questions I asked can be answered by anybody, although at a minimum they require an understanding of the physics of refraction, and an ability to find information such as the density of the Moon's atmosphere.<br /><br />JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-50247545067282136392019-10-30T04:42:13.712-04:002019-10-30T04:42:13.712-04:00JeanTate2:48 PM, October 29, 2019
Questions which...JeanTate2:48 PM, October 29, 2019<br /><br />Questions which should be answered by scientists. That's the job of them, I thought.<br /><br />I'm only questioning why all people, especially scientists, are sure about a hypothetical effect, the "gravitational lensing", but nobody asks about the influence of the well-known effect, the light refraction.<br /><br />Modern physics weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-53259632097375106102019-10-29T20:30:53.718-04:002019-10-29T20:30:53.718-04:00The strangelet is another possibility for DM, thou...The strangelet is another possibility for DM, though I think that for various reasons is not high on the charts for DM. I will though generally leave this at that, Once these pages get to 200+ posts they are not convenient to work in.Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-42929429547779074252019-10-29T18:14:06.425-04:002019-10-29T18:14:06.425-04:00I think a better title would have been "What ...I think a better title would have been "What if we are just using the equations wrong".<br /><br />Since you are suggesting we have the right equations (from Einstein), but we don't have the appropriate mathematical methods to solve them for realistic models (i.e. very lumpy on the scales of star systems, galaxies and galactic clusters).<br /><br />Stephen C. Steelhttps://www.blogger.com/profile/02434440471033792376noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-37132638571000039102019-10-29T18:01:56.981-04:002019-10-29T18:01:56.981-04:00@ Jean Tate
1) I think it's a pity that dlr a...@ Jean Tate<br /><br /><i>1) I think it's a pity that dlr and bud rap cited the first paper (astro-ph/0507619) rather than the 2006 one (astro-ph/0610370, CT06). The 2006 paper is, IMNSHO, far better.</i><br /><br />Figure 3 of that version makes it <i>really</i> clear that their mass model doesn't resemble the baryon distribution of the Milky Way. That figure shows the mass distribution Peter Erwinhttps://www.blogger.com/profile/18415612458902079584noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81356567832285572072019-10-29T16:47:28.497-04:002019-10-29T16:47:28.497-04:00@drl, bud rap, Peter Erwin (PE), RGT: FWIW, I agre...@drl, bud rap, Peter Erwin (PE), RGT: FWIW, I agree with PE and RGT, the Fuchs&Phleps paper (arXiv:astro-ph/0604022, FP06) is pretty devastating, in terms of showing quite convincingly that what's presented in CT06 is <b>not</b> consistent with good observational data. <br /><br />CT06 address FP06 thusly:<br /><br />"<i>Even if one were to assume a logical basis for making their JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-14492718815129056042019-10-29T15:42:35.085-04:002019-10-29T15:42:35.085-04:00Oops! "5 ev" should be "5 keV"...Oops! "5 ev" should be "5 keV" :(JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-70242299133816700852019-10-29T15:00:10.731-04:002019-10-29T15:00:10.731-04:00@Lawrence Crowell: I like your square wave analogy...@Lawrence Crowell: I like your square wave analogy (toy? cartoon?)!<br /><br />"<i>Dark matter, where this term will stick for some time, could either be ...</i>": I think it's also important to keep in mind that DM may turn out to be heterogeneous: a little bit (in some places) dark baryonic matter (my fave is a bottom heavy IMF in regions of very low metallicity, microlensing JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34049180216220484882019-10-29T14:48:52.630-04:002019-10-29T14:48:52.630-04:00OK. Likely my last comment on this, here: what is ...OK. Likely my last comment on this, here: what is the density of the corona (it varies, with distance from the Sun's chromosphere)? How much refraction would you expect in a beam of "light" going through the corona? How does the expected refraction vary with wavelength, from radio (1.4 GHz, say) to x-ray (5 ev, say)?<br /><br />If refraction is expected everywhere, what is its JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-75521692044443614072019-10-29T11:55:10.370-04:002019-10-29T11:55:10.370-04:00The "International Skeptics Forum" seems...The "International Skeptics Forum" seems to me to be not of interest.<br /><br />I have had a look on it.weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20438129412444713612019-10-29T09:37:19.422-04:002019-10-29T09:37:19.422-04:00@weristdas: Sorry, the International Skeptics Foru...@weristdas: Sorry, the International Skeptics Forum, in the Science, Mathematics, Medicine, and Technology section.<br /><br />I find refraction by the Sun's corona interesting, and am happy to discuss it. Just not here, in Comments on a particular blogpost in Bee's blog ...JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-19827117760860355022019-10-29T06:31:35.534-04:002019-10-29T06:31:35.534-04:00JeanTate5:01 PM, October 28, 2019
I can't ima...JeanTate5:01 PM, October 28, 2019<br /><br />I can't imagine that the light refraction effect of the sun corona is "faaaar" too small to detect because the effect increases as closer the light passes the sun and therefore the dense of the media increases. So there are areas where the effect has to be strong, yes, "verrrry" strong.<br /><br />Unfortunately I have no clue weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-21629081762112376522019-10-28T17:01:08.176-04:002019-10-28T17:01:08.176-04:00@weristdas: At one level, your questions are easil...@weristdas: At one level, your questions are easily answered (the effect is faaaar too small to detect); at another level, they are good questions and deserve good answers. Unfortunately, the comments in this blog are a very poor venue for such. I have created a thread in the ISF, Science section, <i>Excellent discussion of unusual alternative to Dark Matter</i>, where I'd like to walk JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59913148366832337612019-10-28T16:56:23.618-04:002019-10-28T16:56:23.618-04:00This is @ everyone who's commented on the Coop...This is @ everyone who's commented on the Cooperstock idea ...<br /><br />1) I think it's a pity that dlr and bud rap cited the first paper (astro-ph/0507619) rather than the 2006 one (astro-ph/0610370, CT06). The 2006 paper is, IMNSHO, <i>far</i> better.<br /><br />2) I echo Peter Erwin (Kent 1987?!?) but go further: why choose only three of the 16 galaxies? There may be a good reason, JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-88494440964183728482019-10-28T02:39:05.122-04:002019-10-28T02:39:05.122-04:00RGT and Peter Erwin,
Both of your criticisms seem...RGT and Peter Erwin,<br /><br />Both of your criticisms seem deliberately misleading. C&T are not attempting to model galactic disk(s). They are using GR to model galactic rotation curves using an idealized <i>"uniformly rotating fluid without pressure and symmetric about its axis of rotation"</i> with a <i>continuous distribution</i>. Nothing in the original or subsequent papers bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-83906829837177189622019-10-27T13:09:44.745-04:002019-10-27T13:09:44.745-04:00Peter Erwin,
The RAR, which is basically a reform...Peter Erwin,<br /><br /><i>The RAR, which is basically a reformulation of MOND...</i><br /><br />You are misinformed about the RAR; it is an empirical relationship:<br /><br />https://arxiv.org/abs/1609.05917<br />bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-28886974344424320602019-10-26T12:36:23.002-04:002019-10-26T12:36:23.002-04:00@ bud rap
What is interesting about this, is that...@ bud rap<br /><br /><i>What is interesting about this, is that the C&T approach seems to mimic observations such as the Radial Acceleration Relation wherein the "missing matter", if any, tracks the baryonic distribution. I believe that is the case here, isn't it?</i><br /><br />No, it isn't. The RAR, which is basically a reformulation of MOND, is about <i>starting with the Peter Erwinhttps://www.blogger.com/profile/18415612458902079584noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-11175416138742422232019-10-26T12:07:07.626-04:002019-10-26T12:07:07.626-04:00bud rap,
You dismiss the F&P paper as "d...bud rap,<br /><br />You dismiss the F&P paper as "disingenuous nonsense" and not a "substantive critique"of C&T. <br />It is true that the C&T model accurately predicts RAR under certain conditions - but the authors fail to consider whether the model has any relevance to other observed factors. This was picked up by F&P and they demonstrated, conclusively, RGThttps://www.blogger.com/profile/07140943290963588247noreply@blogger.com