Comments on: MOND Laid to Rest? http://asymptotia.com/2006/08/21/mond-laid-to-rest/ Fri, 19 Mar 2010 08:56:40 +0000 http://wordpress.org/?v=2.7.1 hourly 1 By: Dark Puzzles - Asymptotia http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-72976 Dark Puzzles - Asymptotia Wed, 22 Aug 2007 16:06:59 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-72976 [...] This lovely composite image of Abell 520 that includes an inferred distribution of dark matter (blue) in a cluster of galaxies) illustrates a bit of a puzzle. It is not clear why the dark matter is separated out so much from the visible (including the hay red dust cloud). Learn more from the Astronomy Picture of the Day site (where this was posted on Monday*) here. You can learn more about the image credits there too. For a reminder of how people go about locating clusters of dark matter (even though it cannot be directly seen, and we don’t know what it is), see an earlier post here. For more on learning about dark matter by its interactions with clusters, see my earlier post on the Bullet cluster event. [...] [...] This lovely composite image of Abell 520 that includes an inferred distribution of dark matter (blue) in a cluster of galaxies) illustrates a bit of a puzzle. It is not clear why the dark matter is separated out so much from the visible (including the hay red dust cloud). Learn more from the Astronomy Picture of the Day site (where this was posted on Monday*) here. You can learn more about the image credits there too. For a reminder of how people go about locating clusters of dark matter (even though it cannot be directly seen, and we don’t know what it is), see an earlier post here. For more on learning about dark matter by its interactions with clusters, see my earlier post on the Bullet cluster event. [...]

]]> By: Further Information on Dark Energy - Asymptotia http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-4752 Further Information on Dark Energy - Asymptotia Thu, 16 Nov 2006 19:33:30 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-4752 [...] All very interesting, although I must say that I’m not really clear on the wisdom of NASA announcing things in this way. It is not quite “the boy who cried wolf”, since there was a wolf, but its a bit of a tame wolf really, and one we knew about already using the same wolf-identifying scenarios (i.e. this is not like the Bullet Cluster Dark Matter annoncement, which I think was indeed worth a bit of media excitement). We have to be careful about these things… what sort of press release would they orchestrate when there is something truly huge to announce? [...] [...] All very interesting, although I must say that I’m not really clear on the wisdom of NASA announcing things in this way. It is not quite “the boy who cried wolf”, since there was a wolf, but its a bit of a tame wolf really, and one we knew about already using the same wolf-identifying scenarios (i.e. this is not like the Bullet Cluster Dark Matter annoncement, which I think was indeed worth a bit of media excitement). We have to be careful about these things… what sort of press release would they orchestrate when there is something truly huge to announce? [...]

]]> By: Bullet Not Silver? - Asymptotia http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-912 Bullet Not Silver? - Asymptotia Thu, 07 Sep 2006 17:52:19 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-912 [...] I learned from New Scientist just now that various researchers working on modified gravity theories are casting doubt on the direct evidence of Dark Matter that was presented by Douglas Clowe and collaborators a few weeks ago. (The article is here.) Recall an earlier post on it, here. Some quotes: “One should not draw premature conclusions about the existence of dark matter without a careful analysis of alternative gravity theories,” writes John Moffat, of the University of Waterloo in Ontario, Canada [...] [...] I learned from New Scientist just now that various researchers working on modified gravity theories are casting doubt on the direct evidence of Dark Matter that was presented by Douglas Clowe and collaborators a few weeks ago. (The article is here.) Recall an earlier post on it, here. Some quotes: “One should not draw premature conclusions about the existence of dark matter without a careful analysis of alternative gravity theories,” writes John Moffat, of the University of Waterloo in Ontario, Canada [...]

]]> By: Spinach Blogging - Asymptotia http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-552 Spinach Blogging - Asymptotia Fri, 25 Aug 2006 02:33:28 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-552 [...] With that in mind, I’d like to offer some words about this week’s science coverage of the two big Astronomy/Astrophysics stories. I’ve heard the issue raised a number of times today (including by my colleague Sean over on CV) that it is somehow to be thought of as a bad thing that there’s more coverage in the press of the Pluto demotion than there is of the new results giving new direct evidence of Dark Matter. The former is supposed to be all about the politics of science while the latter is supposed to be covered more since it is a profound new result. [...] [...] With that in mind, I’d like to offer some words about this week’s science coverage of the two big Astronomy/Astrophysics stories. I’ve heard the issue raised a number of times today (including by my colleague Sean over on CV) that it is somehow to be thought of as a bad thing that there’s more coverage in the press of the Pluto demotion than there is of the new results giving new direct evidence of Dark Matter. The former is supposed to be all about the politics of science while the latter is supposed to be covered more since it is a profound new result. [...]

]]> By: Sandground http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-500 Sandground Tue, 22 Aug 2006 19:08:02 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-500 pah, I'd much rather listen to James Binney on that. pah, I’d much rather listen to James Binney on that.

]]> By: Clifford http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-498 Clifford Tue, 22 Aug 2006 16:46:31 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-498 What you say is true. hence the... see my comment above. It is always hard -impossible maybe- to prove a negative. At this point I could start babbling about white swans and black swans..... etc... etc. But I've got to design an entire semester's course in the next few hours and so I'll just point to a <a href="http://en.wikipedia.org/wiki/Falsifiability" rel="nofollow"> convenient Wikipedia article</a>. Cheers, -cvj What you say is true. hence the… see my comment above.

It is always hard -impossible maybe- to prove a negative. At this point I could start babbling about white swans and black swans….. etc… etc. But I’ve got to design an entire semester’s course in the next few hours and so I’ll just point to a convenient Wikipedia article.

Cheers,

-cvj

]]> By: Sandground http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-497 Sandground Tue, 22 Aug 2006 16:00:41 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-497 Hey Clifford, I only mean to say that whatever would cause a 'MOND-like' modification to Poisson's equation may yet account for some/a little of the ~0.3 of dark matter, whereas the majority it seems comes from some kind of particle. As far as I can tell, this recent observation does not exclude the MOND thing as a dark matter candidate on scales of 10s of Megaparsecs. Indeed, as there never really has been a theory of MOND as such, it would be hard to say one way or the other what to expect! This scenario would obviously seem to stretch plausibility. However, if (big if!) the same physics that gave a low acceleration modification to Poisson's equation was the origin of the ~0.7 attributed to dark energy, then this is almost turned on its head; what was originally put forward as an empirical 'alternative' to dark matter may well be the signature of what is the dominant constituent of the universe which encroaches somewhat on the 0.3 hitherto attributed to dark matter but not dominantly. The MOND people make a big deal of the acceleration a_{0} being \sim c H_{0}. Hey Clifford,

I only mean to say that whatever would cause a ‘MOND-like’ modification to Poisson’s equation may yet account for some/a little of the ~0.3 of dark matter, whereas the majority it seems comes from some kind of particle. As far as I can tell, this recent observation does not exclude the MOND thing as a dark matter candidate on scales of 10s of Megaparsecs.
Indeed, as there never really has been a theory of MOND as such, it would be hard to say one way or the other what to expect!

This scenario would obviously seem to stretch plausibility. However, if (big if!) the same physics that gave a low acceleration modification to Poisson’s equation was the origin of the ~0.7 attributed to dark energy, then this is almost turned on its head; what was originally put forward as an empirical ‘alternative’ to dark matter may well be the signature of what is the dominant constituent of the universe which encroaches somewhat on the 0.3 hitherto attributed to dark matter but not dominantly. The MOND people make a big deal of the acceleration a_{0} being \sim c H_{0}.

]]> By: Clifford http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-493 Clifford Tue, 22 Aug 2006 14:11:23 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-493 That possibility exists..... hence the question mark in the title. And the use of the word "seems". Cheers, -cvj That possibility exists….. hence the question mark in the title. And the use of the word “seems”.

Cheers,

-cvj

]]> By: Elliot http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-492 Elliot Tue, 22 Aug 2006 13:59:48 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-492 Clifford, My point is that MOND "may" have some application to the Dark Energy issue. I am not advocating that as a solution, but this experiment only confirms Dark Matter. I just wanted to be cautious as to the implications of this experiment in general. Certainly it strongly implies that the MOND hypothesis for Dark Matter is greatly weakened. Elliot Clifford,

My point is that MOND “may” have some application to the Dark Energy issue. I am not advocating that as a solution, but this experiment only confirms Dark Matter. I just wanted to be cautious as to the implications of this experiment in general. Certainly it strongly implies that the MOND hypothesis for Dark Matter is greatly weakened.

Elliot

]]> By: Clifford http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-491 Clifford Tue, 22 Aug 2006 13:56:56 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-491 Sandground:- I don't understand what you mean....I simply said that what was an attempted non-dark-matter explanation of the dark matter problem is no longer viable. You need dark matter after all. I did not say that this meant that we now know what dark matter is. Cheers, -cvj Sandground:- I don’t understand what you mean….I simply said that what was an attempted non-dark-matter explanation of the dark matter problem is no longer viable. You need dark matter after all. I did not say that this meant that we now know what dark matter is.

Cheers,

-cvj

]]> By: Dissonant http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-490 Dissonant Tue, 22 Aug 2006 13:20:42 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-490 Discussion <a href="http://cosmocoffee.info/viewtopic.php?t=650" rel="nofollow">here</a>. Note the reference to <a href="http://arxiv.org/abs/astro-ph/0606216" rel="nofollow">astro-ph/0606216</a>, which actually seems to put the foundation of this "direct proof" in question. Discussion here. Note the reference to astro-ph/0606216, which actually seems to put the foundation of this “direct proof” in question.

]]> By: Sandground http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-489 Sandground Tue, 22 Aug 2006 13:08:57 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-489 Perhaps not clifford but your words would seem to imply a certainty that what gave 'MOND' wasn't what gave dark energy! MOND is dead, after all. Perhaps not clifford but your words would seem to imply a certainty that what gave ‘MOND’ wasn’t what gave dark energy! MOND is dead, after all.

]]> By: Clifford http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-485 Clifford Tue, 22 Aug 2006 03:51:05 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-485 "We still have that little issue of Dark Energy which is still outstanding." Hi.. nowhere in the post does it say that this issue is not outstanding.... I'm confused by what you're getting at. -cvj “We still have that little issue of Dark Energy which is still outstanding.”

Hi.. nowhere in the post does it say that this issue is not outstanding…. I’m confused by what you’re getting at.

-cvj

]]> By: Elliot http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-484 Elliot Tue, 22 Aug 2006 02:17:59 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-484 Clifford, With all due respect. MOND is not dead per se. We still have that little issue of Dark Energy which is still outstanding. I am not saying this is "good news" for MOND but I don't think it is completely clear that the the casket is closed, nailed shut, and being lowered into the grave. It's a very exciting time for cosmology and cosmologists. Elliot Clifford,

With all due respect. MOND is not dead per se. We still have that little issue of Dark Energy which is still outstanding. I am not saying this is “good news” for MOND but I don’t think it is completely clear that the the casket is closed, nailed shut, and being lowered into the grave.

It’s a very exciting time for cosmology and cosmologists.

Elliot

]]> By: Science and Reason http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-481 Science and Reason Mon, 21 Aug 2006 23:35:29 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-481 <strong>NASA finds direct proof of dark matter...</strong> Heedless of the skeptics, evidence for dark matter just keeps piling up. Here is the latest, just released today, and it is a lot less indirect than previous evidence.... NASA finds direct proof of dark matter…

Heedless of the skeptics, evidence for dark matter just keeps piling up. Here is the latest, just released today, and it is a lot less indirect than previous evidence….

]]> By: Life on the Lattice http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-479 Life on the Lattice Mon, 21 Aug 2006 22:05:00 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-479 <strong>Singing Vikings...</strong> On the physics front, everything is now abuzz with news that the Chandra X-ray observatory has made the most direct observation of dark matter so far. Read more about it [...]... Singing Vikings…

On the physics front, everything is now abuzz with news that the Chandra X-ray observatory has made the most direct observation of dark matter so far. Read more about it [...]…

]]> By: Plato http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-477 Plato Mon, 21 Aug 2006 21:22:56 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-477 So much for Mond then.:) So, can we continue to assume "<a href="http://eskesthai.blogspot.com/2006/08/gravitational-wave-detectors-are-best.html" rel="nofollow">sound in analogy</a>" as to the thinking of gravitational wave detection and possible(?) relations to the "bulk perspective." I mean it is important to try to grasp this from a layman standpoint so the ideas here do not seem so "mathematically abstract: in regards to bulk considerations. If there are so many things wrong with what I am saying then we should correct it while you can, since Wayne Hu and LISA are running with it. So much for Mond then.:)

So, can we continue to assume “sound in analogy” as to the thinking of gravitational wave detection and possible(?) relations to the “bulk perspective.”

I mean it is important to try to grasp this from a layman standpoint so the ideas here do not seem so “mathematically abstract: in regards to bulk considerations.

If there are so many things wrong with what I am saying then we should correct it while you can, since Wayne Hu and LISA are running with it.

]]> By: Sandground http://asymptotia.com/2006/08/21/mond-laid-to-rest/comment-page-1/#comment-476 Sandground Mon, 21 Aug 2006 19:45:33 +0000 http://asymptotia.com/2006/08/21/mond-laid-to-rest/#comment-476 yeah, nice one... see astro-ph/0212293 . This has been known for a long time to those MOND advocates. MOND is not a theory, it's an algorithm. They continue only because, to their minds, this algorithm works and keeps on working on smaller scales. yeah, nice one…

see astro-ph/0212293 . This has been known for a long time to those MOND advocates. MOND is not a theory, it’s an algorithm. They continue only because, to their minds, this algorithm works and keeps on working on smaller scales.

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