Evidence that Dark Matter is real stuff

[J.C.MacSwell]

I think MacSwell didnt mean a component of a quark' date=' he meant that the nucleons can radiate via their quarks, which are charged.

 

even if overall the thing is neutral, if it has some part which is charged then it can radiate.

 

think that's what he meant, so no serious confusion hopefully[/quote']

 

That's correct. I meant that the quarks were components of the neutron. Is that not acceptable terminology?

[Martin]

That's correct. I meant that the quarks were components of the neutron. Is that not acceptable terminology?

 

it sure is acceptable to me!

 

tycho asked "what is a charged quark component?"

but you did not mean to suggest that quarks are built up from components.

neither you nor tycho made a mistake!

English sentences are often ambiguous.

 

Some linguist has counted several different things that the sentence

"Time flies like an arrow."

could mean.

 

I favor a "no-fault" approach to English semantics. It is a great language, a privilege to use, spelling is completely wacky and if you can be unambiguous at least half the time be happy.

 

BTW it is possible that, in fact, quarks are built up from components called "preons" (tho neither you nor tycho meant that!)

 

there is a feindish clever scheme by Sundance Bilson thompson that builds up quarks and electrons FROM THE SAME COMPONENT PARTS just arranged differently.

 

and these preons can themselves as different kinds of knots in space

 

Sundance rocks. Bascule had a post about some of Sundance work with Lee S.

[[Tycho?]]

I think MacSwell didnt mean a component of a quark' date=' he meant that the nucleons can radiate via their quarks, which are charged.

 

even if overall the thing is neutral, if it has some part which is charged then it can radiate.

 

think that's what he meant, so no serious confusion hopefully[/quote']

 

Okie doke. I didn't know neutrons could radiate their quarks either, but at least I dont have new vocabulary to learn as well.

[Martin]

'']Okie doke. I didn't know neutrons could radiate their quarks either, but at least I dont have new vocabulary to learn as well.

 

 

I seem to be having trouble with English. the neutrons don't radiate their quarks in the sense of "spitting them out" (ordinarily)

 

but they can interact with light because they have charged particles inside them

so they can absorb/radiate or anyway scatter light VIA the charged components inside them

 

even tho their total overall charge is zero

 

I am just acting as MacSwell's interpreter here

 

===========

must say that I personally do not have a very clear idea of what kind of stuff DM could be

 

it can't scatter light, or interact with light at all, of any wavelength (or correct me if I'm wrong) so it can't have electric charge, and none of its component parts can have electric charge----otherwise it would couple to the EM field.

 

it apparently is able to pass thru friggin walls. it interacts so little with usual normal baryons and leptons of regular matter that it cant even feel them

 

so a cloud of DM can pass thru a cloud of hydrogen without noticing, while two clouds of hydrogen doing otherwise the same collision will heat each other to millions of degrees temperature

[J.C.MacSwell]

I seem to be having trouble with English. the neutrons don't radiate their quarks in the sense of "spitting them out" (ordinarily)

 

but they can interact with light because they have charged particles inside them

so they can absorb/radiate or anyway scatter light VIA the charged components inside them

 

even tho their total overall charge is zero

 

I am just acting as MacSwell's interpreter here

 

===========

must say that I personally do not have a very clear idea of what kind of stuff DM could be

 

it can't scatter light' date=' or interact with light at all, of any wavelength (or correct me if I'm wrong) so it can't have electric charge, and none of its component parts can have electric charge----otherwise it would couple to the EM field.

 

it apparently is able to pass thru friggin walls. it interacts so little with usual normal baryons and leptons of regular matter that it cant even feel them

 

[b']so a cloud of DM can pass thru a cloud of hydrogen without noticing[/b], while two clouds of hydrogen doing otherwise the same collision will heat each other to millions of degrees temperature

 

As in a gravitation only effect, the weakest known force, or are there other possible effects they are looking for?

[Martin]

As in a gravitation only effect, the weakest known force, or are there other possible effects they are looking for?

 

I think you are asking by what effect can DM be seen

 

so far we just have evidence from its gravitation effect

 

there is a bunch of interactions called "weak force" that a DM particle might be involved in and so be revealed

 

I think if you look back in this thread you may find a post of Severian about this. He's probably the one to ask about weak interactions revealing a DM particle.

 

and then there's Wikipedia and the arxiv search tool

 

BTW MacSwell, just now thinking of Dark Matter ("things invisible to see") reminded me of this lovely old Donne song

 

http://www.pjbsware.demon.co.uk/DonneS1.htm

 

maybe you know it.

[J.C.MacSwell]

I think you are asking by what effect can DM be seen

 

so far we just have evidence from its gravitation effect

 

there is a bunch of interactions called "weak force" that a DM particle might be involved in and so be revealed

 

I think if you look back in this thread you may find a post of Severian about this. He's probably the one to ask about weak interactions revealing a DM particle.

 

and then there's Wikipedia and the arxiv search tool

 

BTW MacSwell' date=' just now thinking of Dark Matter ("things invisible to see") reminded me of this lovely old Donne song

 

http://www.pjbsware.demon.co.uk/DonneS1.htm

 

maybe you know it.[/quote']

 

Thanks Martin. I was not clear again. I was thinking of an effect we could "see" from Earth to detect it where theory "needs it". I guess if we detect something on Earth, via collider or something, that could strengthen the case for it or argument for it. I will have to check the Wiki and other links. My main interest was in the possibility of it not being "needed", though that sounds unlikely with current measurements and thinking.

[Martin]

... My main interest was in the possibility of it not being "needed", though that sounds unlikely with current measurements and thinking.

 

there still is the possibility that a DM particle is NOT needed.

everybody's hunch is that a particle is needed and everybody's expectation is that one will be found (maybe thru accelerator or highenergy astrophysics somehow)

 

but us old experienced guys know that human hunch and expectation are not stable! pendulums can swing:D

 

check out "Can MOND take a bullet?" (are you one of those who called my attention to this article, several people have)

 

Look at the pictures which are Figure 7 on page 7

THEY GOT DOUBLECENTERED LENSING TO HAPPEN within a TeVeS MOND context!

 

They got something from TeVes that looks like the Bullet Cluster lensing maps. that undermines the whole point of the CHANDRA press release which was that no way can any form of MOND get that kind of doublecenter lensing

 

http://arxiv.org/abs/astro-ph/0606216

Can MOND take a bullet? Analytical comparisons of three versions of MOND beyond spherical symmetry

Garry W. Angus, Benoit Famaey, HongSheng Zhao

14 pages, 9 figures, accepted for publication in MNRAS

 

"A proper test of Modified Newtonian Dynamics (MOND) in systems of non-trivial geometries depends on modelling subtle differences in several versions of its postulated theories. This is especially important for lensing and dynamics of barely virialised galaxy clusters with typical gravity of scale [itex]\sim a_0 \sim 1\AA{\rm s}^{-2}[/itex]. The original MOND formula, the classical single field modification of the Poisson equation, and the multi-field general relativistic theory of Bekenstein (TeVeS) all lead to different predictions as we stray from spherical symmetry. In this paper, we study a class of analytical MONDian models for a system with a semi-Hernquist baryonic profile. After presenting the analytical distribution function of the baryons in spherical limits, we develop orbits and gravitational lensing of the models in non-spherical geometries. In particular, we can generate a multi-centred baryonic system with a weak lensing signal resembling that of the merging galaxy cluster 1E 0657-56 with a bullet-like light distribution. We finally present analytical scale-free highly non-spherical models to show the subtle differences between the single field classical MOND theory and the multi-field TeVeS theory."

 

so tell all your friends that boffins say MOND is dead but don't believe it yourself, because these academic pendulums do sometimes swing back.

 

Personally I see matter beginning to appear as a QUANTUM GRAVITY EFFECT ("You are made of spacetime" article in 12 August New Scientist)

and so for me it is no difference whether it is called a new "particle" which is just one kind of quantum gravity effect or whether it is portrayed as a TeVeS-like quantum gravity effect that is displaceable from the center of baryonic mass.

Bascule flagged the New Scientist article free version

 

http://www.scienceforums.net/forums/showthread.php?t=22548

 

http://www.newscientist.com/article/mg19125645.800.html