tag:blogger.com,1999:blog-22973357.post2131424387676000750..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: New experiment cannot reproduce long-standing dark matter anomalySabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger80125tag:blogger.com,1999:blog-22973357.post-16606046525877333642019-05-15T04:58:37.354-04:002019-05-15T04:58:37.354-04:00by the way, rather than just plotting the multi-de...by the way, rather than just plotting the multi-decade average seasonal variation in the frequency of detected interaction events, what about a quick cross-check looking at variations between exceptionally dry and exceptionally wet years ? sure some must have occurred through the decades the experiment has been running.Lucahttps://www.blogger.com/profile/09075700300473999068noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-78952667224948093292019-05-15T04:38:49.236-04:002019-05-15T04:38:49.236-04:00Out of curiosity, has the possibility that seasona...Out of curiosity, has the possibility that seasonal variations in volume and/or distribution of the Gran Sasso mountain acquifers might in some way affect the frequency of detected "interaction events" ever been investigated? I mean, granted the exquisite sensitivity of the DAMA detectors, is that also just as exquisitely selective to definitely rule out the detection of other types of Lucahttps://www.blogger.com/profile/09075700300473999068noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-37295056975680803502018-12-23T23:32:47.015-05:002018-12-23T23:32:47.015-05:00@ David Schroeder:
But galaxies have great cloud...@ David Schroeder:<br /><br /><i> But galaxies have great clouds of hydrogen gas that are near absolute zero, so in principle could form Bose-Einstein condensates (BEC's).</i><br /><br />The coldest gas in galaxies has temperatures of about 10 K, which isn't exactly near the microkelvin levels required for BECs. (Also we see the same dark-matter-dominated dynamics in galaxies without any Peter Erwinhttps://www.blogger.com/profile/18415612458902079584noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-61652516211915374852018-12-23T07:18:31.311-05:002018-12-23T07:18:31.311-05:00Erratum, the name of the chief investigator of the...Erratum, the name of the chief investigator of the Cooper-pair mass anomaly is Janet Tate, not Jean Tate, as I mistakenly wrote above. She is now at Oregon State University.David Schroederhttps://www.blogger.com/profile/18048116250413347228noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34510703493336167512018-12-22T14:15:19.252-05:002018-12-22T14:15:19.252-05:00Just a flash-in-the-pan thought. Gravitomagnetism...Just a flash-in-the-pan thought. Gravitomagnetism (GM), which is incredibly feeble, would, at first blush, hardly be considered a factor in the anomalous rotation curves seen in galactic systems. From a quick Google search the idea of GM influencing galactic rotation curves seems to be limited to the GM field emanating from the massive black holes at the center of most disc galaxies. Even if David Schroederhttps://www.blogger.com/profile/18048116250413347228noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-45263903302625790072018-12-22T12:41:40.473-05:002018-12-22T12:41:40.473-05:00Jean Tate and Phillip Helbig, here's the paper...Jean Tate and Phillip Helbig, here's the paper on wide binaries that's mentioned by Marco Parigi above, which is linked on Mike McCulloch's site.<br /><br />https://arxiv.org/abs/1401.7063David Schroederhttps://www.blogger.com/profile/18048116250413347228noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-37137966593890484622018-12-21T19:28:36.499-05:002018-12-21T19:28:36.499-05:00As I mentioned, I am a former chemist, and as a ki...As I mentioned, I am a former chemist, and as a kid I read about the gas laws (PV=nRT) in a textbook. I was enthralled by the 'fact' that the outcome of so many experiments could be predicted (maybe to arbitrary accuracy - I didn't know) by such a simple formula. I didn't express this as mathematical beauty, but I guess that was what I felt. I still remember how let down I felt David Baileyhttps://www.blogger.com/profile/06172248428321078417noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34551004427373203462018-12-21T19:09:35.036-05:002018-12-21T19:09:35.036-05:00Problems with the "halo of dark matter"....Problems with the "halo of dark matter". I suggest to read this piece by Stacy McGaugh and then to drill down to specific peer reviewed papers he has written on the subject. I recommend a really broad view *before* drilling down to the specific maths that demonstrates how arbitrary the use of Dark Matter is in terms of Galactic Haloes. There's no point spending hours understanding Marco Parigihttps://www.blogger.com/profile/00702055111711651319noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44922815724564691522018-12-21T13:09:22.747-05:002018-12-21T13:09:22.747-05:00Phillip Helbig,
Can you cite a summary paper (or ...Phillip Helbig,<br /><br />Can you cite a summary paper (or two) on “MOND phenomenology ...” (sorry can’t copy/paste the rest), other than galaxy-scale things? Especially those “not obvious with CDM”? To clarify one thing: I am aware of some of “MOND phenomenology”, other than galaxy rotation curves, but no unexpected successes at scales greater than ~100 kpc.<br /><br />My question to Marco was JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-83480356540214780852018-12-21T12:37:20.457-05:002018-12-21T12:37:20.457-05:00Re the wide binary: can you cite a reference pleas...<i>Re the wide binary: can you cite a reference please? I don’t think I’ve read anything on this.</i><br /><br />I recently discussed this with someone who knows more about it than I do. If I understood correctly, it is an interesting test of MOND, because MOND makes a clear prediction here, while any CDM explanation would look very contrived. But I don't think that there are any Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1628094726533031352018-12-21T12:31:28.821-05:002018-12-21T12:31:28.821-05:00"MOND (and even its relativistic extensions) ...<i>"MOND (and even its relativistic extensions) is bad to totally dead, except as an fitting formula for galaxy rotation curves"</i><br /><br />Whatever the arguments for and against MOND and LambdaCDM, to claim that "MOND is just rotation curves" displays an ignorance of the literature.<br /><br />Whatever one thinks of MOND from a theoretical point of view, there can be no Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74079492323380868462018-12-21T10:06:54.469-05:002018-12-21T10:06:54.469-05:00Marco Parigi,
Thanks for your post, I think I now...Marco Parigi,<br /><br />Thanks for your post, I think I now have a better understanding of your perspective.<br /><br />Clearly, we view astrophysics differently, and - it seems to me - have very different approaches when it comes to evaluating observational results. Out of curiosity, wrt CDM, could you sketch an observational program that you think could advance our understanding of the JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-57930065213588506572018-12-20T17:17:15.677-05:002018-12-20T17:17:15.677-05:00JeanTate says: How about the formation and evoluti...JeanTate says: <i>How about the formation and evolution of galaxy clusters and giant filaments? AFAIK, not much work has been done, from a MOND-like perspective. CDM does very well....<br /><br />Finally, the CMB...<br /><br /> Viewed this way, CDM is good to very good ... <br /><br />Because, despite many scientists’ wishes, galaxies are very complex, messy systems,...<br /></i><br /><br /><br /Marco Parigihttps://www.blogger.com/profile/00702055111711651319noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-39723556439111993862018-12-20T13:35:41.171-05:002018-12-20T13:35:41.171-05:00Very nice, well-written post, Peter Erwin! :)
To ...Very nice, well-written post, Peter Erwin! :)<br /><br />To see just how messy/difficult it is to derive a galaxy rotation curve from data on stars alone, check out arXiv.1810.09466, “The Circular Velocity Curve of the Milky Way from 5 kpc to 25 kpc”.<br /><br />Also of note is that, with GAIA, there are papers on the rotation curves of some nearby galaxies, based in part on proper motions of JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72686769911634286202018-12-20T12:28:27.702-05:002018-12-20T12:28:27.702-05:00@ Marco,
Let me see if I can explain what's g...@ Marco,<br /><br />Let me see if I can explain what's going on with galactic and cluster kinematics and dynamics, and hopefully alleviate some of your confusion.<br /><br />No one measures galaxy rotation curves using individual stars. In most cases -- including the classic work by Vera Rubin and collaborators -- the measurements are Doppler shifts for *gas clouds*: either ionized clouds Peter Erwinhttps://www.blogger.com/profile/18415612458902079584noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-38292756137936953732018-12-20T10:34:11.446-05:002018-12-20T10:34:11.446-05:00Erratum: Is not much good if it is inconsistent wi...Erratum: <i>Is not much good if it is inconsistent with all relevant results</i> -> “is not much good unless it is consistent with all relevant results”JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91754365470956679082018-12-20T09:41:55.142-05:002018-12-20T09:41:55.142-05:00Marco Parigi,
I’ll turn the contrast up to beyond...Marco Parigi,<br /><br />I’ll turn the contrast up to beyond Spinal Tap’s 11.<br /><br />Is a relatistic MOND extension compatible with lung cancer oncogenesis? Is CDM? Silly question, right? But why is it silly?<br /><br />How about with the Permian-Triassic Great Extinction? Still silly, but perhaps there might be some indirect connection.<br /><br />The Orion Molecular Cloud Complex? No longerJeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-19795962870352616972018-12-20T09:09:28.526-05:002018-12-20T09:09:28.526-05:00David Bailey:
Allow me, please, to try to describ...David Bailey:<br /><br />Allow me, please, to try to describe how I see things, especially “MOND” vs CDM”.<br /><br />First, if we’re having a discussion about physics, particularly about fundamental physics, then MOND was DOA the day Milgrom’s paper was published in 1983. Why? Because even he knew (and likely said, I’ll see if I can find what he said on this), as he developed MOND, that it is JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-85572458955154666302018-12-19T17:07:04.488-05:002018-12-19T17:07:04.488-05:00Peter Erwin says Only in the Milky Way is it possi... Peter Erwin says <i>Only in the Milky Way is it possible to see individual stars moving across the sky (proper motion); everything else is based on Doppler shift measurements</i><br /><br />Only in and near our local group can we resolve individual stars for their Doppler Shift. We can calibrate doppler shift with proper motion and be quite certain of the relationship between star's velocityMarco Parigihttps://www.blogger.com/profile/00702055111711651319noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-38439336926375504842018-12-19T15:42:10.237-05:002018-12-19T15:42:10.237-05:00"whether galaxy rotation relations extend to ... <i>"whether galaxy rotation relations extend to similar laws in clusters" -- proponents of MOND all agree that MOND doesn't work on scales of galaxy groups and clusters:</i><br /><br />I will go back to the issue of burden of proof. Dark Matter does not *explain* Galactic rotation relations. In fact, the galactic rotation relations mean that dark matter is in precisely the right Marco Parigihttps://www.blogger.com/profile/00702055111711651319noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-7266677884895328702018-12-19T14:42:49.864-05:002018-12-19T14:42:49.864-05:00@Peter Erwin: I recall in the comment section of ...@Peter Erwin: I recall in the comment section of an earlier post here, (can't remember which post), it was mentioned that angular kinetic energy would be conserved in a Mondian interpretation of the anomalously high rotation rates of the outer stars of a galactic system, without a Dark Matter halo. That, naturally, puzzled me as I automatically assumed that extra kinetic energy can't David Schroederhttps://www.blogger.com/profile/18048116250413347228noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-90980757894226432112018-12-19T12:19:12.279-05:002018-12-19T12:19:12.279-05:00Jean Tate wrote
"Th logical fallacy is in th...Jean Tate wrote<br /><br />"Th logical fallacy is in the last sentence/paragraph, where you present a choice between two things, as an either/or. Even if one restricts oneself to just two, there are four logical possibilities, “both” and “neither” being the two you did not, apparently, consider."<br /><br />I would argue that suggesting DM plus modified gravity would fail on the groundsDavid Baileyhttps://www.blogger.com/profile/06172248428321078417noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-76515562652289157682018-12-19T11:19:37.963-05:002018-12-19T11:19:37.963-05:00@Marco Parigi: I echo what Peter Erwin wrote; what...@Marco Parigi: I echo what Peter Erwin wrote; what you wrote seems to reflect several misunderstandings of the relevant astrophysics. And cosmology. You also seem to misunderstand the scope of MOND; it is universal, so it is entirely reasonable to ask how well it can explain the CMB observations.JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-54604960624928346092018-12-19T11:00:16.719-05:002018-12-19T11:00:16.719-05:00@David Bailey: please re-read what I wrote. Th log...@David Bailey: please re-read what I wrote. Th logical fallacy is in the last sentence/paragraph, where you present a choice between two things, as an either/or. Even if one restricts oneself to just two, there are four logical possibilities, “both” and “neither” being the two you did not, apparently, consider.JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-3752996723330689152018-12-19T09:19:27.957-05:002018-12-19T09:19:27.957-05:00@ Yves:
The discussion was about the amount of gas...@ Yves:<br />The discussion was about the amount of gas in galaxy disks (e.g., whether there's more mass in the form of gas within a spiral arm than there is in the form of stars). Since the stellar disk of the Milky Way extends to roughly 15 or 20 kpc in radius, that's the scale of the problem.<br /><br />The paper you referenced is about gas in a very extended halo, mostly outside the Peter Erwinhttps://www.blogger.com/profile/18415612458902079584noreply@blogger.com