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← Survey finds no hint of dark matter near Solar System

Survey finds no hint of dark matter near Solar System - Comments

Schrodinger's Cat's Avatar Comment 1 by Schrodinger's Cat

I'm not clear what they mean by dark matter in 'the space around the Solar System'. Given that dark matter supposedly does not interact other than gravitationally, why should one suppose that it is rotating along with the matter to the extent that there'd be any noticeable long term effect ?

Mon, 23 Apr 2012 16:12:13 UTC | #936725

Bumpy's Avatar Comment 2 by Bumpy

There's an excellent website run by a professional physicist I find very useful for keeping up with the latest from the frontiers of physics. There's also lots of careful explanations regarding firmly established theories and concepts.

I recomend it to those who worry that something gets lost in translation between the physicist and the news outlet desrcribing the findings and their implications. It's particulary good for getting the inside stories from the LHC.

There's an article about this story in which the author urges caution about the validity of the results and explains why it may not be much of an upheaval in any case.

Mon, 23 Apr 2012 17:05:00 UTC | #936739

Bumpy's Avatar Comment 3 by Bumpy

Comment 1 by Schrodinger's Cat :

I'm not clear what they mean by dark matter in 'the space around the Solar System'. Given that dark matter supposedly does not interact other than gravitationally, why should one suppose that it is rotating along with the matter to the extent that there'd be any noticeable long term effect ?

From the article discussing this on the website I mentioned above:

"Their approach is to study the gravitational effects of nearby matter, as reflected by the motions of a small sample of the stars that lie within a few thousand light years of the sun. [Sorry -- I still don't understand their method well enough to explain it to non-experts, but will fill in more details if and when I do.] . And they claim that the motions of those stars suggest that the only matter nearby is the ordinary matter we can see around us, with no dark matter in addition."

Hope that helps.

Mon, 23 Apr 2012 18:20:46 UTC | #936759

old-toy-boy's Avatar Comment 4 by old-toy-boy

Hooray! Never believed in the stuff, I reckon that the the powers that be have made a fundamental error in their observations. I also reckon that I know very little about astronomical physics and will soon have egg on my face.

(Just seen the video, is it just me or is the galaxy rotating the wrong way?)

Mon, 23 Apr 2012 21:42:00 UTC | #936813

DeepFritz's Avatar Comment 5 by DeepFritz

You see the thing about space is that it is black and the thing about Dark Matter is that it is black too. Bit like Grit...

Mon, 23 Apr 2012 23:31:15 UTC | #936846

Michael Gray's Avatar Comment 6 by Michael Gray

Is Dark Matter the new Ether?

Tue, 24 Apr 2012 03:53:02 UTC | #936900

prietenul's Avatar Comment 7 by prietenul

Oh no! Now there is a gap, and we know what some people will fill it with...

Tue, 24 Apr 2012 04:44:53 UTC | #936909

zombiewoof's Avatar Comment 8 by zombiewoof

Comment 4 by old-toy-boy :

Hooray! Never believed in the stuff, I reckon that the the powers that be have made a fundamental error in their observations. I also reckon that I know very little about astronomical physics and will soon have egg on my face.

(Just seen the video, is it just me or is the galaxy rotating the wrong way?)

I think it's the 'camera' that's moving, not the galaxy.

Tue, 24 Apr 2012 09:09:57 UTC | #936958

Schrodinger's Cat's Avatar Comment 9 by Schrodinger's Cat

Comment 3 by Bumpy

Hope that helps.

No, my point was that stuff that does not interact other than gravitationally should not be rotating with the galaxy. The matter in the galaxy rotates because of the angular momentum transferred in the collision of particles. This is precisely why dark matter supposedly exists in a spherical halo of material and not in a flat disk itself........and I'd imagine most dark matter particles in the galaxy to be in highly eliptical orbits around the center and not rotating along with the disk.

That being the case....my point was that the period of influence of the solar region on any area of dark matter...or vice versa....would be quite short. Much shorter than if the dark matter was going round with us.

Tue, 24 Apr 2012 09:25:35 UTC | #936961

Hariseldonsays's Avatar Comment 10 by Hariseldonsays

Many thanks to Bumpy for the the link.

This site looks interesting, albeit only after an initial read.

HSS

Tue, 24 Apr 2012 17:36:46 UTC | #937051

Functional Atheist's Avatar Comment 11 by Functional Atheist

If there really are a fourth, fifth, or more physical dimensions, as suggested by String Theory, maybe the dark matter exists there, and is only detectable to us because of gravitational interactions with the matter in the familiar three physical dimensions.

Perhaps gravity's weakness in our familiar physical dimensions is linked to its relationship with dark matter in extra-dimensional space. Or maybe dark energy also exists in the extra-dimensional space, and is a kind of anti-gravity, attenuating gravity's power to such an extent that the expansion of the universe is accelerating.

I'm no physicist, just a blue-sky bullshitter who would welcome someone explaining to me why my suppositions are baloney.

Wed, 25 Apr 2012 22:09:00 UTC | #937349

mmurray's Avatar Comment 12 by mmurray

Comment 11 by Functional Atheist :

If there really are a fourth, fifth, or more physical dimensions, as suggested by String Theory, maybe the dark matter exists there, and is only detectable to us because of gravitational interactions with the matter in the familiar three physical dimensions.

Perhaps gravity's weakness in our familiar physical dimensions is linked to its relationship with dark matter in extra-dimensional space. Or maybe dark energy also exists in the extra-dimensional space, and is a kind of anti-gravity, attenuating gravity's power to such an extent that the expansion of the universe is accelerating.

I'm no physicist, just a blue-sky bullshitter who would welcome someone explaining to me why my suppositions are baloney.

But they were looking for dark matter by checking for its gravitational effects.

In their survey, Christian Moni Bidin of the University of Concepcion in Chile and his colleagues used the European Southern Observatory’s 2.2-metre telescope in La Silla and three other telescopes to weigh, in effect, an extended volume of space centred around the Sun. Although this area cannot be measured directly, the total mass within the volume can be inferred by its influence on the motions of stars that are passing through.

So even if you are right they should have seen it.

Michael

Wed, 25 Apr 2012 23:07:17 UTC | #937361

Roedy's Avatar Comment 13 by Roedy

I asked an astronomer about half a dozen things that dark matter might be and how we know that is not it.

I was happy to discover they had considered each of my alternatives, and oddly there were champions for various alternatives. For now it seems to be a really knotty puzzle, just the thing to keep an astronomer extremely happy.

My hunch is the solution is Newton's inverse square law for gravity being just an approximation. The astronomer thought that would be a long shot. It is something so familiar, intuitively obvious and solid, it is hard for people to question, so I thought it might have been overlooked.

It might depend on distance in a subtly different way, or gravitational fields might add in a slightly non-linear way.

I think of Einstein looking at all the "conflicting" evidence. Something presumed to be invariant just had to give no matter how strongly the intuition rebelled.

I eagerly await any more clues to this mystery.

Thu, 26 Apr 2012 17:30:43 UTC | #937514

mmurray's Avatar Comment 14 by mmurray

Comment 13 by Roedy :

I eagerly await any more clues to this mystery.

It seems like that wasn't the last word.

http://telescoper.wordpress.com/2012/05/23/dark-matter-dearth-evaded/

Michael

Fri, 25 May 2012 11:05:39 UTC | #943457

Bumpy's Avatar Comment 15 by Bumpy

Nobody will read this comment since this thread is long dead. But the website I mentioned earlier (Comment 2) has a follow up article on this story. It seems that the audacious claims made about the paucity of dark matter near our solar system's region of space are illfounded - as in literally founded on false assumptions.

Of course, the unaudacious claim that the audacious claim is probably incorrect won't make the headlines.

Fri, 25 May 2012 13:02:32 UTC | #943471

mmurray's Avatar Comment 16 by mmurray

Comment 15 by Bumpy :

Nobody will read this comment since this thread is long dead.

That doesn't follow. Depends how you read this site. I always look at the Recent Posts list on the front page so even an old thread will pop up there if you post on it. Thanks for the link.

Michael

Fri, 25 May 2012 13:18:33 UTC | #943475