Results 1 to 5 of 5
Like Tree16Likes
  • 4 Post By not_Fritz_Argelander
  • 5 Post By Seeker725
  • 4 Post By not_Fritz_Argelander
  • 3 Post By not_Fritz_Argelander

Thread: it looks like MOND is falsified

  1. #1
    not_Fritz_Argelander's Avatar
    not_Fritz_Argelander is offline HYPER GIANT
    Points: 20,717, Level: 99
    Level completed: 44%, Points required for next Level: 283
    Overall activity: 45.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!750 Days+ Registered Achievement!First 1000 Experience Points
    Join Date
    Jul 2011
    Location
    US
    Posts
    2,506
    Points
    20,717
    Level
    99
    Thanks
    1,690
    Thanked 4,404x 1,924 Posts
    Downloads
    0
    Uploads
    0

    Default it looks like MOND is falsified



    here is an argument from the observed structure of the universe that appears to decisively falsify MOND and TeVeS in favor of General Relativity and dark matter.

    the last graph in the next link plots the per spectrum of matter (how it clusters) versus INVERSE distance. GR with no dark matter and MOND (snd TeVeS) with no dark matter are convincingly falsified while GE plus dark matter agrees nicely with the data.

    Why the Universe needs Dark Matter (and not MOND) in one graph – Starts With A Bang

    for those who want the scholarly preprint of the argument:
    http://arxiv.org/pdf/1112.1320v1.pdf

    so IMO MOND is dead.
    chas53, Bottle, Seeker725 and 1 others like this.

  2. The Following 5 Users Say Thank You to not_Fritz_Argelander For This Useful Post:

    Bottle (07-24-2014),chas53 (07-23-2014),KeithBC (07-24-2014),Seeker725 (07-24-2014),Solrian (07-24-2014)

  3. #2
    Seeker725's Avatar
    Seeker725 is offline Bright Giants
    Points: 5,103, Level: 48
    Level completed: 77%, Points required for next Level: 47
    Overall activity: 25.0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!50 Posts Achievement!First 1000 Experience Points365 Days+ Registered Achievement!
    Join Date
    Jan 2013
    Location
    Cincinnati Ohio US
    Posts
    352
    Points
    5,103
    Level
    48
    Thanks
    822
    Thanked 646x 291 Posts
    Downloads
    0
    Uploads
    0

    Default Re: it looks like MOND is falsified

    The article presents a very convincing argument. For a long time I had been hoping that MOND-like alterations to gravity would make dark matter...just go away.

    The ghost-like properties of DM just seem so contrived. The DM concept just doesn't "feel" natural.

    When faced with the choice between... 1. gravity is a little wrong and needs to be tweaked or 2. there is 5 times more stuff that you have no way of seeing pulling everything everywhere that passes though itself and ordinary matter interacting more or less only gravitationally and we don't know what it's made of or how it was made or where it comes from.

    Occam's razor says choose item 1. (when faced with equally competing theories that match observation, choose the simplest.) Unfortunately choice 1 no longer matches observation. Choice 2. still really really sucks.
    Ask me what I know and I won't say very much. Ask me what I think and you'll get an earful.
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.


    All the world's a hammer and I'm the only nail.
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.

  4. The Following 2 Users Say Thank You to Seeker725 For This Useful Post:

    chas53 (07-24-2014),not_Fritz_Argelander (07-24-2014)

  5. #3
    Solrian's Avatar
    Solrian is offline SUPER GIANT
    Points: 7,982, Level: 62
    Level completed: 44%, Points required for next Level: 168
    Overall activity: 42.0%
    Achievements:
    2 Posts Achievement5 Threads Achievement!20 Posts Achievement!50 Posts Achievement!200+ Posts Achievement!
    Join Date
    Mar 2014
    Location
    Over the Rainbow in Oregon
    Posts
    725
    Points
    7,982
    Level
    62
    Thanks
    997
    Thanked 613x 277 Posts
    Downloads
    0
    Uploads
    0

    Default Re: it looks like MOND is falsified

    Quote Originally Posted by not_Fritz_Argelander View Post
    here is an argument from the observed structure of the universe that appears to decisively falsify MOND and TeVeS in favor of General Relativity and dark matter.

    the last graph in the next link plots the per spectrum of matter (how it clusters) versus INVERSE distance. GR with no dark matter and MOND (snd TeVeS) with no dark matter are convincingly falsified while GE plus dark matter agrees nicely with the data.

    Why the Universe needs Dark Matter (and not MOND) in one graph – Starts With A Bang

    for those who want the scholarly preprint of the argument:
    http://arxiv.org/pdf/1112.1320v1.pdf

    so IMO MOND is dead.
    Thanks not_Fritz. That article is convincing.
    Solrian aka Jim

    "May All The Stars Shine Brightly In Your Life!"

  6. #4
    not_Fritz_Argelander's Avatar
    not_Fritz_Argelander is offline HYPER GIANT
    Points: 20,717, Level: 99
    Level completed: 44%, Points required for next Level: 283
    Overall activity: 45.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!750 Days+ Registered Achievement!First 1000 Experience Points
    Join Date
    Jul 2011
    Location
    US
    Posts
    2,506
    Points
    20,717
    Level
    99
    Thanks
    1,690
    Thanked 4,404x 1,924 Posts
    Downloads
    0
    Uploads
    0

    Default Re: it looks like MOND is falsified

    I can understand your pain but I cannot share it. It really is a matter of esthetics and Occam's razor actually cuts both ways. So in the spirit of simply sharing differences I'll reply to your points in detail below.

    Quote Originally Posted by Seeker725 View Post
    The article presents a very convincing argument. For a long time I had been hoping that MOND-like alterations to gravity would make dark matter...just go away.

    The ghost-like properties of DM just seem so contrived. The DM concept just doesn't "feel" natural.
    The neutrino is no more ghost like in its properties than DM. In fact the earliest candidate for DM was neutrinos. It didn't work out though. But the history of the discovery of the neutrino gives courage that postulating a new kind of matter to be found in order to preserve laws of physics that are in some sense "beautiful" often pays off. Bohr wanted to give up conservation of energy to explain weak interaction decays. Pauli rightly asserted that conservation of energy was too beautiful to give up and postulated a missing hard to detect particle to save conservation of energy from Bohr.

    When faced with the choice between... 1. gravity is a little wrong and needs to be tweaked or 2. there is 5 times more stuff that you have no way of seeing pulling everything everywhere that passes though itself and ordinary matter interacting more or less only gravitationally and we don't know what it's made of or how it was made or where it comes from.
    There are a couple of things here. First MOND is a really ugly tweaking. The equations for MOND look really forced and artificial. Here is a discussion that I vehemently disagree with:

    The MOND pages

    IMO MOND is just a fudge without any conceptual motivation. Notice how the meaning of the modification of Newtonian dynamics is ambiguous: it can be interpreted either as a modification of the simplified Newton's second law (F=ma no longer holds) OR Poisson's equation for the Newtonian gravitational field is modified to be a particularly ugly equation.

    The Newtonian Poisson equation is beautiful. The MOND Poisson equation is repellently ugly. Dirac said:

    It seems that if one is working from the point of view of getting beauty in one's equations, and if one has really a sound insight, one is on a sure line of progress. If there is not complete agreement between the results of one's work and experiment, one should not allow oneself to be too discouraged, because the discrepancy may well be due to minor features that are not properly taken into account and that will get cleared up with further development of the theory.
    Your statement that dark matter alternative amounts to "there is 5 times more stuff that you have no way of seeing pulling everything everywhere that passes though itself and ordinary matter interacting more or less only gravitationally and we don't know what it's made of or how it was made or where it comes from" is unfair on several counts. The leading candidates interact both via gravitation and the weak interaction. It should also undergo "dark matter anti dark matter annihilation" so we should be seeing excess gamma rays from galactic halos (like those seen by Fermi). Plus supersymmetry provides a natural zoo of dark matter particles. Axions are another. Massive additional flavors of neutrino are another possibility. These additional forms of matter are all more natural than throwing away Poisson's equation.

    Occam's razor says choose item 1. (when faced with equally competing theories that match observation, choose the simplest.) Unfortunately choice 1 no longer matches observation. Choice 2. still really really sucks.
    I disagree about Ockham's razor. Choice 1 is profoundly more complicated and introduces a fudge factor into the Poisson equation. My gut tells me that HAS to be wrong. Also note that the anti dark matter folks complain that no one has seen dark matter in a lab. Well, to be fair, the MOND folks have not tested their modified Poisson equation in a lab EITHER. In fact it can be regarded as beyond our technology to test. So MOND is less testable than Dark Matter.

    Ockham is neutral. MOND is just gosh awful ugly and less testable (in a laboratory) than Dark Matter.
    chas53, Bottle, Seeker725 and 1 others like this.

  7. The Following 3 Users Say Thank You to not_Fritz_Argelander For This Useful Post:

    Bottle (07-24-2014),chas53 (07-24-2014),Seeker725 (07-24-2014)

  8. #5
    not_Fritz_Argelander's Avatar
    not_Fritz_Argelander is offline HYPER GIANT
    Points: 20,717, Level: 99
    Level completed: 44%, Points required for next Level: 283
    Overall activity: 45.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!750 Days+ Registered Achievement!First 1000 Experience Points
    Join Date
    Jul 2011
    Location
    US
    Posts
    2,506
    Points
    20,717
    Level
    99
    Thanks
    1,690
    Thanked 4,404x 1,924 Posts
    Downloads
    0
    Uploads
    0

    Default Re: it looks like MOND is falsified

    PS I have a Poisson equation afterthought......

    One of the beautiful things about physics is that there are parallel mathematical structures in the different fields. Consider Poisson's equation which in its normal non MOND form can be found here:

    Poisson's equation - Wikipedia, the free encyclopedia

    Note that the same cute little equation describes gravitational and electrostatic fields. Poisson's equation also models static temperature distributions and a whole wealth of problem areas.

    Poisson's equation (and the related Gauss's Law) has many consequences that are well attested and beautiful. The net zero interior acceleration due to a uniform spherical shell of mass or charge is a consequence. The effective shielding of conductors is another.

    It seems very artificial to modify Poisson's equation specially for gravitation and not for other fields.
    chas53, Seeker725 and Solrian like this.

  9. The Following 2 Users Say Thank You to not_Fritz_Argelander For This Useful Post:

    chas53 (07-24-2014),Seeker725 (07-24-2014)

 

 

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBulletin® Version 4.2.0
Powered by vBulletin®
All times are GMT. The time now is 01:29 PM.