tag:blogger.com,1999:blog-22973357.post8368687479937448082..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Dark Matter – Or What?Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger71125tag:blogger.com,1999:blog-22973357.post-89005824414161205432019-02-26T13:28:38.791-05:002019-02-26T13:28:38.791-05:00Sabine,
If you cannot comprehend that no model ba...Sabine,<br /><br /><i>If you cannot comprehend that no model based on a differential equation ever explains its initial condition, I cannot help you.</i><br /><br />You seem unable to grasp that it is just that inadequacy of the standard model, that I am criticizing. Explaining to me that the model doesn't explain its original condition is like explaining to the Pope that he's a Catholic.bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-7673617826151004542019-02-25T02:22:37.275-05:002019-02-25T02:22:37.275-05:00Hi Sabine,
I find Bud Rap's comments to be co...Hi Sabine,<br /><br />I find Bud Rap's comments to be coherent and important. I won't say that I completely agree with them, but theoretical physics has really veered away from repeatable observable and predicting new facts...<br /><br />regards<br />MarcoMarco Parigihttps://www.blogger.com/profile/00702055111711651319noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-36055883802206328082019-02-24T13:46:09.336-05:002019-02-24T13:46:09.336-05:00bud rap,
I do not know why you continue to write ...bud rap,<br /><br />I do not know why you continue to write lengthy comments which do little more than display an appalling ignorance of not only cosmology, but astrophysics and even astronomy (I’m not as blunt as Sabine).<br /><br />“<i>significant empirical evidence against the existence of dark matter</i>” Huh? Perhaps I missed it, but you have not even hinted at any, have you?<br /><br />And JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-32572914527381314562019-02-24T13:13:48.263-05:002019-02-24T13:13:48.263-05:00bud rap,
Capital T commonly stands for temperatur...bud rap,<br /><br />Capital T commonly stands for temperature, not time. Believe that or not.<br /><br />No, I do not "feign" incomprehension, you indeed do not make sense. <br /><br />I have neither the time nor the patience to teach you cosmology. If you cannot comprehend that no model based on a differential equation ever explains its initial condition, I cannot help you.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-70260820247460065132019-02-24T12:14:22.781-05:002019-02-24T12:14:22.781-05:00...(continued)
5. Here you are correct, I oversta......(continued)<br /><br />5. Here you are correct, I overstated the case. Zwicky made a good faith effort to exam alternative explanations and a few other attempts have been made over the years. They have all failed. <br /><br />However, what has been overlooked is the straightforward GR consideration of gravitational redshifting applied to the expanding spherical wave fronts of light emitted by bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-7999820827714309642019-02-24T12:13:34.131-05:002019-02-24T12:13:34.131-05:00Sabine,
1) T=time, as always when referring to th...Sabine,<br /><br />1) T=time, as always when referring to the inexplicable original condition of LCDM. Surely, you know that. I have to assume you are trying to deflect the point about the incoherence of the standard model's original condition as being moot, since the official position now seems to be that the model provides no account for its origin. If that is what you're getting at, itbud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-16309540282223067202019-02-23T00:07:22.463-05:002019-02-23T00:07:22.463-05:00bud rap,
1) I don't know what 'T' is....bud rap,<br /><br />1) I don't know what 'T' is.<br /><br />2) It's an approximation and everyone knows that. (Except you, possibly.)<br /><br />3) So what?<br /><br />4) I have no idea what a "unified expansion" is supposed to be. <br /><br />5) Just wrong. There have been various attempts to explain the observations by other means, they just work very badly.<br /><br /Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-3186469856038088892019-02-22T15:50:13.442-05:002019-02-22T15:50:13.442-05:00Hi JeanTate,
That is the jist of it yes. A lot of...Hi JeanTate,<br /><br />That is the jist of it yes. A lot of those things have presumed formation mechanisms which cannot be “observed” in the way science intends repeatable observations.<br /><br />We certainly can observe snapshots of things we can surmise the properties of, like snapshots over decades of the Galactic centre, and say that those observations match what we believe a black hole Marco Parigihttps://www.blogger.com/profile/00702055111711651319noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5992904334839219282019-02-22T14:53:37.089-05:002019-02-22T14:53:37.089-05:00Sabine,
If you have a model with one free paramet...Sabine,<br /><br /><i>If you have a model with one free parameter, you measure that parameter and that makes the model predictive.</i><br /><br />LCDM has six free and six fixed parameters. The fact that the model can be tweaked to agree with observations on the basis of those parameters is irrelevant to the question of whether those model specific parameters correspond to anything in physical (bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-13176823434727357862019-02-22T12:14:50.135-05:002019-02-22T12:14:50.135-05:00bud rap,
"The free parameterization of a mod...bud rap,<br /><br /><i>"The free parameterization of a model is not good scientific methodology..."</i><br /><br />That's just wrong. If you have a model with one free parameter, you measure that parameter and that makes the model predictive. That's standard scientific procedure.<br /><br /><i>"despite the fact that it is now common practice in the scientific establishment.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-47126852542575488542019-02-22T12:06:17.914-05:002019-02-22T12:06:17.914-05:00Sabine,
The observations document that there is s...Sabine,<br /><br /><i>The observations document that there is something we cannot explain with the current theories. Dark matter is a parametrically explanation. That is standard procedure in science and it is good scientific methodology.</i><br /><br />I agree with everything you say there - except the last clause. The ability to freely parameterize a model essentially renders it unfalsifiable. bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56606137233152090232019-02-22T10:11:37.319-05:002019-02-22T10:11:37.319-05:00Maro,
Thanks for the clarification.
It seems tha...Maro,<br /><br />Thanks for the clarification.<br /><br />It seems that , by your criteria, most of astrophysics, and much of astronomy, cannot be science ... no black holes, no neutron stars, no white dwarfs, no surface of last scattering, and perhaps even no gravitational wave radiation.JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33507399789724952022019-02-22T03:17:03.502-05:002019-02-22T03:17:03.502-05:00This comment has been removed by the author.Yehonatan Knollhttps://www.blogger.com/profile/09680318989713357978noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-40939202871989396412019-02-21T20:05:07.386-05:002019-02-21T20:05:07.386-05:00I believe that I do understand the relevant astron...I believe that I do understand the relevant astronomical observations. <br /><br />Science is strictly about the observable and repeatable. Models can certainly be observed and made to fit what we believe are the results of Galaxy Mergers. However, we do not observe galaxy mergers. We do observe star and gas velocities. We do not observe the Big Bang in progress. We do observe the CMB. We do not Marco Parigihttps://www.blogger.com/profile/00702055111711651319noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-46821343300200432052019-02-21T13:30:35.365-05:002019-02-21T13:30:35.365-05:00bud rap,
I have refrained from commenting on your...bud rap,<br /><br />I have refrained from commenting on your comments, so far, but your last contains one misunderstanding/misrepresentation too far: “<i>They provide model-based, inferential evidence only.</i>”<br /><br />What, may I be so bold as to ask, do you think astronomy is, other than exactly what you state?<br />JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2522121099152565102019-02-21T13:11:46.902-05:002019-02-21T13:11:46.902-05:00bud rap,
You claim "theorists now mainly stu...bud rap,<br /><br />You claim "theorists now mainly study mathematical models" quoting an article about Nima Arkani-Hamed. I am pointing out that you are blaming me for what someone else has said in an interview.<br /><br /><i>"What you list are empirical observations from which you infer via the standard model the existence of dark matter."</i><br /><br />The observations Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72850197826823085452019-02-21T13:05:33.440-05:002019-02-21T13:05:33.440-05:00Sabine,
First, please stop blaming me for some ar...Sabine,<br /><br /><i>First, please stop blaming me for some article about Nima Arkani-Hamed.</i><br /><br />I honestly don't know what you mean by that. I cited the article in support of my argument. Why would you think I am blaming you for an article somebody else wrote? Could the German word for blame have some connotation that does not translate in this context?<br /><br /><i>I have bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72971830345709864862019-02-21T08:47:02.346-05:002019-02-21T08:47:02.346-05:00Sabine,
Wow, this is a lot messier than I realize...Sabine,<br /><br />Wow, this is a lot messier than I realized from looking only at your slides. While my poor quick reading of those slides left me with the impression that you advocate the straightforward 2016 Berezhiani and Khoury particle-based boson condensate interpretation of DM, I'm assuming from your comments above that you really still prefer your own 2017 covariant modification of Terry Bollingerhttps://www.blogger.com/profile/03915136249111338024noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87690400126567169742019-02-21T00:21:57.761-05:002019-02-21T00:21:57.761-05:00bud rap,
First, please stop blaming me for some a...bud rap,<br /><br />First, please stop blaming me for some article about Nima Arkani-Hamed.<br /><br />Second, your statement <br /><br /><i>"You may consider the absence of empirical evidence for the existence of dark matter..."</i><br /><br />Is wrong. I have listed empirical evidence for the existence of dark matter in my slides.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66847792383062751442019-02-20T23:59:42.090-05:002019-02-20T23:59:42.090-05:00Sabine,
I understand full well that you and those...Sabine,<br /><br />I understand full well that you and those who share your mathematical point of view consider the failure, of a model's free parameters to actually appear in physical reality, an irrelevancy. That <b>is</b> the prevailing paradigm throughout the theoretical sciences of the academy. My argument is: <b>that</b> approach has crippled theoretical physics and delivered it to a bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-28749489367253427862019-02-20T11:20:55.381-05:002019-02-20T11:20:55.381-05:00Marco,
It seems that you do not really understand...Marco,<br /><br />It seems that you do not really understand the relevant astronomical observations.<br /><br />Yes, for galaxies, there certainly is a degree of arbitrariness (“wiggle room”), but for the CMB, and galaxy clusters?<br /><br />Re galaxies: what’s often not discussed, or even mentioned, is “selection bias”. Galaxies are very complex systems, arguably more so than large mammals, and JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-7825915562076461822019-02-20T08:04:50.317-05:002019-02-20T08:04:50.317-05:00Fascinating, thanks! I will read more deeply into ...Fascinating, thanks! I will read more deeply into this.Terry Bollingerhttps://www.blogger.com/profile/03915136249111338024noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-79395408353238108232019-02-20T01:19:02.747-05:002019-02-20T01:19:02.747-05:00Terry,
In a sense I believe that's what Verli...Terry,<br /><br />In a sense I believe that's what Verlinde is trying. Alas, I don't see how this would work, at least not at present.<br /><br />Let me also say that as a pragmatist, it doesn't seem to me a useful idea to pursue. The reason is that the type of theory we can test with observations would be an effective theory regardless and you wouldn't be able to draw the Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-472927897191885852019-02-20T01:14:17.953-05:002019-02-20T01:14:17.953-05:00bud rap,
"The point is that physical reality...bud rap,<br /><br /><i>"The point is that physical reality should carry more weight than a model and when your model diverges significantly from reality (cf. 95% of the model's 'universe' is invisible in physical reality), it is highly likely that it is the model that is at fault and not physical reality."</i><br /><br />Whether it's "visible" or not is Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33258245652061202632019-02-19T23:07:16.594-05:002019-02-19T23:07:16.594-05:00Your two-phase theory is intriguing, especially in...Your two-phase theory is intriguing, especially in how it captures some of the strangely predictive aspects of MOND without resorting to point-blank modification of GR.<br /><br />If space and gravity are emergent from and thus dependent on matter, it would seem plausible that space might also subtlety share certain aspects of some of the particles of matter, e.g. of spin-1 vector bosons.<br /><Terry Bollingerhttps://www.blogger.com/profile/03915136249111338024noreply@blogger.com