tag:blogger.com,1999:blog-22973357.post1115956820445917981..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: How good is the evidence for Dark Energy?Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger154125tag:blogger.com,1999:blog-22973357.post-70429079224442755872020-07-20T12:58:17.820-04:002020-07-20T12:58:17.820-04:0020+ SDSS eBOSS preprints appeared in arXiv today. ...20+ SDSS eBOSS preprints appeared in arXiv today. The one which may be most relevant here (it's a tough call) is "The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological Implications from two Decades of Spectroscopic Surveys at the Apache Point observatory" (arXiv:2007.08991).<br /><br />A lot to take in; one sentence from the abstract is a good tease: &JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-57345594421204972832020-04-19T22:55:10.580-04:002020-04-19T22:55:10.580-04:00As I recall, Singal found the Solar System was mov...As I recall, Singal found the Solar System was moving at two different speeds in opposite directions, with both findings being in conflict with the CMB data.<br /><br />From his paper - Large peculiar motion of the solar system from the dipole anisotropy in sky brightness due to distant radio sources.<br />"Our results give a direction of the velocity vector in agreement with the Cosmic Bill Jameshttps://www.blogger.com/profile/14285507968714861216noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-6906874604464828332020-03-17T17:57:31.158-04:002020-03-17T17:57:31.158-04:00For what it's worth, I suspect that his take o...For what it's worth, I suspect that his take on the Hubble "tension" (at the end of the video) is probably correct. There, he's saying essentially that there is nothing mysterious going on, just sloppy work, but that has produced fewer headlines than the implication that "there is no evidence for dark energy" which some read into this work.<br />Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-61006851438631540212020-03-17T14:34:52.713-04:002020-03-17T14:34:52.713-04:00At about 40:15, in a parenthetical remark, he note...At about 40:15, in a parenthetical remark, he notes that the Hubble constant is not constant. In general, it is not constant in time, that is true, but he makes it sounds like it is some kind of misnomer or something. It is a constant like a is a constant in <i>y</i> = a<i>x</i> + b. That the Hubble constant can change in time is true, but the idea that this somehow means that the term "Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-82977614086566489932020-03-17T12:39:11.353-04:002020-03-17T12:39:11.353-04:00He dismisses some results as "inferences"...He dismisses some results as "inferences", which is correct. For example, the CMB together with measured Omega=0.3 implies Lambda via the sum rule. But at about 33:15 he discusses an experiment which will allegedly directly measure negative pressure. Nope, I don't think so, not in the way most people use the word "direct". Of course, almost all "measurements"Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-30680096830723961862020-03-17T11:17:59.138-04:002020-03-17T11:17:59.138-04:00"I'll see if I can find time to watch the...<i>"I'll see if I can find time to watch the video."</i><br /><br />OK, the corona virus is giving me some time. (The plague led to the <i>Principia</i>, so who knows what will come of the current pandemia.)<br /><br />Around 25:40, he makes it sound like no-one had suggested acceleration before the two supernova teams. The current concordance model, and the implied acceleration, Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-85015133788838673702020-03-17T11:12:33.682-04:002020-03-17T11:12:33.682-04:00No one is talking about "alternative theories...<i>No one is talking about "alternative theories".</i><br /><br />Starting around 31:00, he questions whether the sum rule is valid. Almost by definition, a model in which the sum rule is not valid is an alternative theory.<br />Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69678691254664757162020-03-10T17:33:00.898-04:002020-03-10T17:33:00.898-04:00April 2020, eh? Time travel has been invented! ;-)...April 2020, eh? Time travel has been invented! ;-)<br /><br />Taking a broad view, ideas like this have been explored for some time now (hundreds of papers), and are sorta/kinda discussed in the video. Opinions will differ, of course, but I think serious work on this general idea will continue for some time/years yet.JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8577038789729554962020-03-10T11:01:22.452-04:002020-03-10T11:01:22.452-04:00Or could it be we're all living in a bubble?
h...Or could it be we're all living in a bubble?<br />https://www.sciencedirect.com/science/article/pii/S0370269320301076?via%3DihubThomas Sturmhttps://www.blogger.com/profile/02131614712384529253noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-49572857411741395122020-03-10T10:16:43.407-04:002020-03-10T10:16:43.407-04:00A big thank you Sabine, for this blogpost! :)
Sar...A big thank you Sabine, for this blogpost! :)<br /><br />Sarkar and his collaborators are, clearly, very smart and hard working. As are the members of the JLA collaboration, including those who got the Nobel gong.<br /><br />Cosmology is one of the fields you have dipped your toes into, albeit mostly from the theory side. If you have a continuing interest in experimental tests of cosmological JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-38723027828321719752020-03-08T18:32:11.547-04:002020-03-08T18:32:11.547-04:00This comment has been removed by the author.JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-31997211767739050712020-03-08T10:54:23.871-04:002020-03-08T10:54:23.871-04:00A few days ago, I wrote: "I have it on my TBD...A few days ago, I wrote: "<i>I have it on my TBD list to track down all the papers mentioned (at least those directly so)</i>"<br /><br />I'm going to have to take that back. And part of the reason why also points to why it's hard for outsiders - even those with good, relevant PhDs and a track record of good to excellent research - to quickly and easily come to grips with JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-60479625503884623762020-03-08T10:31:01.145-04:002020-03-08T10:31:01.145-04:00From the raw transcript (ctd. 11; I'm not goin...From the raw transcript (ctd. 11; I'm not going to even try to edit this):<br /><br />"<i>okay initially it was 3% now the claim is you can get to what almost 1% however even when the first Hubble parameter local Hubble constant measurement was done as a major project it was called the Hubble key project using the Hubble Space Telescope This was one of the flagship missions of the HubbleJeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56299004945559792482020-03-08T09:52:36.442-04:002020-03-08T09:52:36.442-04:00JimV 11:59 PM, March 07, 2020
"Well, there w...JimV 11:59 PM, March 07, 2020<br /><br />"Well, there were a huge number of players, so the odds of somebody winning were good, and I happened to be that one." The second explanation seems much more reasonable to me.<br /><br />The second one is the true reason. You only get regular winners in a national lottery if millions play regularly i.e. if the nation is thick. Which turns out to Steven Evanshttps://www.blogger.com/profile/13898046706669437332noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91013684193128510352020-03-08T05:55:10.903-04:002020-03-08T05:55:10.903-04:00Thank you JeanTate! and no, I wasn't aware of ...Thank you JeanTate! and no, I wasn't aware of these discussions, otherwise I wouldn't have posted my comments as they add exactly nothing to them. So I am a bit embarrassed now since "read before you write" (or "listen before you talk") is a motto I normally adhere to. I have only discovered Sabine's Blog long after finishing "Lost in Math", in fact, I Thomas Sturmhttps://www.blogger.com/profile/02131614712384529253noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-64321389009904212482020-03-08T04:41:10.025-04:002020-03-08T04:41:10.025-04:00I am afraid that the difference between energy and...I am afraid that the difference between energy and dark energy is compable with the difference between money and dark money.martenhttps://www.blogger.com/profile/02423871089614417690noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33247758021336536322020-03-07T23:59:40.095-05:002020-03-07T23:59:40.095-05:00"A big part of the problem seems to be that w..."A big part of the problem seems to be that we are stuck with the term "fine" tuning with its implication that a supreme being stirred up a universe and poured it out across the cosmos."--Steve Bullfox<br /><br />The more reasonable implication is that our universe is part of a multiverse, with a vast range of properties, so of course we find ourselves in the member of that JimVhttps://www.blogger.com/profile/10198704789965278981noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-82190604999255197812020-03-07T17:45:52.955-05:002020-03-07T17:45:52.955-05:00Don't forget dust!
The light from a supernova...Don't forget dust!<br /><br />The light from a supernova may pass through regions of the host galaxy a long way from the site of the BANG that are thick with dust ("thick" being understood appropriately). More than one region perhaps. The dust will dim the supernova (from our perspective), but how? Dust - of this kind - is not grey (more UV is absorbed than IR, for example); is the JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66867844340110164672020-03-07T17:35:54.242-05:002020-03-07T17:35:54.242-05:00I've started to go through Colin+ (2017) "...I've started to go through Colin+ (2017) "High-redshift radio galaxies and divergence from the CMB dipole", and find myself quite perplexed. I hope a knowledgable reader can help.<br /><br />Take these snippets (my bold):<br />"<i>The NVSS is a catalogue of radio <b>sources</b> at 1.4 GHz which ...</i>"<br />"<i>SUMSS contains 211,050 radio <b>sources</b> and ...</i>&JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56206725755822023272020-03-07T15:26:30.243-05:002020-03-07T15:26:30.243-05:00Imagine my dismay this am at reading that the issu...Imagine my dismay this am at reading that the issue of fine tuning has weaseled its way back into this blog. I nearly choked on my muffin and coffee squirted out my nose.<br /><br />A big part of the problem seems to be that we are stuck with the term "fine" tuning with its implication that a supreme being stirred up a universe and poured it out across the cosmos.<br /><br />After all,Steve Bullfoxhttps://www.blogger.com/profile/13990244011256349875noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87775599323160714122020-03-07T14:52:00.052-05:002020-03-07T14:52:00.052-05:00I suspect that just about every variable in a bina...I suspect that just about every variable in a binary system that leads to a 1a supernova has some influence on the luminosity of the final cataclysm, and contributes in some small way to the error bars. <br /><br />Somewhere in the various posts on this subject it was mentioned that the difference in magnitude that leads to the conclusion of an accelerating universe was only about .15 magnitude.Steve Bullfoxhttps://www.blogger.com/profile/13990244011256349875noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-46568251354304844652020-03-07T10:24:05.522-05:002020-03-07T10:24:05.522-05:00Thanks for your answer.
Using the Taylor series i...Thanks for your answer.<br /><br />Using the Taylor series is fine. <br />But if one expands f(x) = a0 + a1*x + a2*x^2 + … then the coefficients a0, a1, a2 , … do not depend on x.<br /><br />To check for directional dependence of the coefficients of the Taylor series is also a good idea.<br />But they shall still remain independent of the redshift z.<br /><br />Btw, it would be more generic (or Dimitrishttps://www.blogger.com/profile/10433911267529806559noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-88471878934024990422020-03-07T09:35:51.102-05:002020-03-07T09:35:51.102-05:00This comment is directly relevant to t marvell'...This comment is directly relevant to t marvell's above^1 and the "Reproducibility Crisis" blogpost (15 February, 2020).<br /><br />Modern astronomy, from ~1950 onward, has a largely unrecognized data validity problem, as I call it.<br /><br />To start, here are two quotes from Steven Evans' transcript^2<br /><br />"<i>We would be very happy to use the latest data if it is JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-55137374307028549232020-03-07T08:57:49.785-05:002020-03-07T08:57:49.785-05:00Arun7:36 AM, March 07, 2020
" for universes ...Arun7:36 AM, March 07, 2020<br /><br />" for universes with significantly different parameters,"<br />Which are not known to exist. He should re-package his paper as a sci-fi book.Steven Evanshttps://www.blogger.com/profile/13898046706669437332noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-6839112099364901482020-03-07T08:01:20.411-05:002020-03-07T08:01:20.411-05:00Thomas Sturm: have you had a chance to read Bee...Thomas Sturm: have you had a chance to read Bee's 30 November 2019 ("Dark energy might not exist after all") and 8 January, 2020 ("Update January 2020") blogposts? And all the hundreds of comments?<br /><br />Here's a comment from the latter which you might find particularly pertinent:<br /><br /><i>A review paper, by Ruiter, appeared on arXiv today (10 January 2019): JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.com