LCDM and rotation of DM

On Friday, August 8, 2014 2:49:40 AM UTC-4, jacob navia wrote:

Besides, the geometry of that plane and the Milky Way plane (that is

also huge) are almost perpendicular (83 degrees). Is this a coincidence?

--------------------------------------------

One way to naturally generate such morphology
would be if the Milky Way Galaxy captured (or
interacted with, if one does not like the word
capture) a second galaxy whose mass was about
equal to the mass of the individual satellite
galaxies. The interaction between the MWG and
the 2nd galaxy led to the breakup of the latter,
whose remnants formed a planar distribution in
plane of the original capture orbit.

Simple, and no tooth fairies, new physics, or
ad hoc hypothetical articles/fields required.

RLO
It's a fractal world, old chum

Le 08/08/2014 22:41, Robert L. Oldershaw a ecrit :
On Friday, August 8, 2014 2:49:40 AM UTC-4, jacob navia wrote:

Besides, the geometry of that plane and the Milky Way plane (that is

also huge) are almost perpendicular (83 degrees). Is this a coincidence?

--------------------------------------------

One way to naturally generate such morphology
would be if the Milky Way Galaxy captured (or
interacted with, if one does not like the word
capture) a second galaxy whose mass was about
equal to the mass of the individual satellite
galaxies. The interaction between the MWG and
the 2nd galaxy led to the breakup of the latter,
whose remnants formed a planar distribution in
plane of the original capture orbit.

Simple, and no tooth fairies, new physics, or
ad hoc hypothetical articles/fields required.

RLO
It's a fractal world, old chum


Your answer is intriguing. What are you trying to say?

The morphology you refer to is the fact that the our galaxy and
Andromeda are perpendicular?

Or the fact that our galaxy and Andromeda have a huge flat disk around them?

Yes, a breakup of some huge galaxy could conveniently lead to satellite
galaxies in a plane, a big plane. So, we have thousands of galaxies that
have planes and all of them found a suitable partner to breakup.

What a coincidence really.

And you call this coincidence not a tooth fairy?

At least tooth fairies work: Always when she came my teeth falled and
she took them away.

Have you calculated the probability of all those hundreds of galaxies
measured already that find a suitable partner that breaks up and builds
a ring around them?

I am not advocating "new physics". It is just a matter of SCALE Mr
Oldershaw. I would postulate that for each scale there are different
forces that determine the morphology of things at that scale.

At the atomic scale (an atomic nucleus: 1.75x10-15 m) the strong force
is well... strong. But it has no effects at MY scale. (1.7 meters). I
can take nuclear force for granted, and other forces like gravity and
electro-magnetism are more relevant here.

Flies are smaller and other forces like cohesion forces are more
important and they can walk the walls upwards, what I can't do. Cohesion
forces aren't so relevant at my scale.

At solar system scales gravity is the main force. Morphology is
determined by gravity.

But at galactic scales?

WHAT DO WE KNOW?

What can we possibly know of forces so feeble and so long range that
only galaxies "feel" it?

Where time scales (for instance the rotation period of Andromeda's disk
at 150 Kpc) are in the order of 5 BILLION years?

All our cultural history has around 20 000 years only!!!

Yes, astronomy can give us (with time) explanations and maybe we can
figure out the galactic scale as we figured out the atomic scale.

But the forces at those scales are different. Gravity doesn't work, we
are just beginning to detect how big the Universe around us really is...

No human ever imagined that disk 1.3 million light years across. Until
we saw it, and then we discovered that MOST galaxies have a similar
structure.

What can be done now is what the explorers always do first:

Cartography.

Observe the surroundings and build a MAP at the next scale. The Universe
at large scales looks like foam. Let's see how that foam percolates in
the local group, the Virgo cluster, in detail.

Is this foam part of a gigantic drop in an ocean that goes on and on?

Maybe, and then, we will be able to glimpse the NEXT level. We can have,
as astronomy advances, more and more orders of magnitude.

But due to the fractal nature of being, there will be ALWAYS a next level!

A level of organization with forces MUCH more feeble and with a much
more longer range!

As with the infinetly small, there will be always something bigger than
the biggest structure you have detected. For all beings, since beings
are finite, and the Universe is not.

Forces have a RELEVANCE scale attached to them, measured in meters and
in seconds. An insect walking on water uses the viscosity and surface
tension of the liquid to walk. Those forces have no effect on us, we
have a different mass and size range. For insects they are much more
relevant.

Of course they HAVE an effect, we can measure them since they are not so
distant in orders of magnitude from the forces like gravity that we know
well.

So, the practical conclusion is that we can't extrapolate gravity into
galactic scales. New forces, with longer ranges appear, and shape the
morphology of the beings at that scale: galaxies, and maybe clusters.
But clusters could "feel" other forces, even feebler and more long range
than the galactic forces.

AND SO ON...

You said:

It's a fractal world, old chum

That implies new physics at every scale Mr Oldershaw. Each level in the
fractal is new. When you, for instance take

x -- x * x, that famous fractal of Mandelbrot, you see "replicas" of
the fractal at smaller scales. They have the overall shape of the main
figure. But when you look closer, they are not EXACT replicas!

Each level is *different*


[mod. note: non-ascii characters removed -- mjh]

On 8/8/2014 10:41 PM, Robert L. Oldershaw wrote:
On Friday, August 8, 2014 2:49:40 AM UTC-4, jacob navia wrote:

Besides, the geometry of that plane and the Milky Way plane
...
One way to naturally generate such morphology
would be if the Milky Way Galaxy captured (or
interacted with, if one does not like the word
capture) a second galaxy whose mass was about
equal to the mass of the individual satellite
galaxies. The interaction between the MWG and
the 2nd galaxy led to the breakup of the latter,
whose remnants formed a planar distribution in
plane of the original capture orbit.

Simple, and no tooth fairies, new physics, or
ad hoc hypothetical articles/fields required.

And no disagreement with LCDM! But that of course
was another thread, so to connect with the topic
he Would that scenario lead to a merged DM halo
with characteristic rotation properties? And would
the (merged) DM shape also reveal this history?

Probably DM will also end up in a flattened disk
so this might be detectable (even easier than to
detect the rotation of this DM, I'd expect!)

--
Jos

It's a unitary flow of worlds.

On Friday, August 15, 2014 6:56:22 AM UTC-4, jacob navia wrote:
So, the practical conclusion is that we can't extrapolate gravity into
galactic scales. New forces, with longer ranges appear, and shape the
morphology of the beings at that scale: galaxies, and maybe clusters.
But clusters could "feel" other forces, even feebler and more long range
than the galactic forces.

Are you aware that gravitational interactions
do not involve forces?

Are you aware that space and time measures on the
Galactic Scale differ by equivalent factors of about
10^17 from comparable S-T measures on the Stellar Scale?
Failure to these appreciate S-T scale differences has a
profoundly bad effect on one's reasoning.

[Mod. note: reformatted -- mjh]

Le 18/08/2014 14:13, Robert L. Oldershaw a écrit :
Are you aware that gravitational interactions
do not involve forces?

F = G * (m1*m2)/r^2

That doesn't count any more?

Excuse me but I sincerely do not understand what you say.

On Wednesday, August 20, 2014 9:44:09 AM UTC-4, jacob navia wrote:

F = G * (m1*m2)/r^2

That doesn't count any more?

-----------------------------------------

Well, that is a "Ptolemaic" approximation,
albeit one that gives very accurate and
quantitative answers for most, but not all,
tests. It is not how gravitation works.

Linearity, action-at-a-distance, gravitational
force, instantaneity -- all these are "Ptolemaic"
model-building fictions. The fact that this model
gave such good answers does not change that basic
fact, and is very instructive.

Since about 1915 we have had General Relativity
as a much more elegant, accurate and well-tested
theory of how gravitation actually works.

In article ,
Nicolaas Vroom writes:
One issue to explain galaxy rotation is the balance between baryonic
and non-baryonic matter.

Not much non-baryonic matter is needed to explain galaxy
rotation. The main evidence for non-baryonic matter consists of
cluster velocity dispersions and the CMB fluctuations.

The general argument is that if we cannot observe it (being visible)
than it should be non-baryonic.

Not really. About half of the baryons have been unaccounted for.
Recently there is evidence the "missing baryons" are in very hot
intra-cluster gas, but I don't know whether that's yet confirmed.

This argument can easily be wrong because a lot of mass in a galaxy can
be baryonic and invisible. Our Earth is one example.

Indeed. There are plenty of forms in which baryons are difficult or
impossible to observe, though observations over the years have
narrowed the possibilities.

The original idea was to explain the galaxy rotation strictly based on
what was visible. Including the observed size of the disc. As a consequence
there is a rather large discrepancy between the observed galaxy rotation
curve (based on speed/red shift) and the calculated curve based on visible
baryonic mass, which (assumed that that is all) is estimated too low.

Not only is the amount of visible matter insufficient, its
distribution is wrong. Rotation curves imply matter at larger radii
than the visible disk.

Historically, the first evidence for dark matter in any form was the
cluster velocity dispersions. Galaxy rotation curves came much later
and require a smaller dark matter fraction. Nowadays there is far
more evidence than either of these.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

In article ,
jacob navia writes:
To made a such thin disk MANY rotation periods are needed,

Why would you think that? Why couldn't the disk have collapsed along
the angular momentum axis in a free-fall time? (Of course angular
momentum prevents or at least delays collapse in the disk plane.)

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

In article , Steve Willner
writes:

In article ,
Nicolaas Vroom writes:
One issue to explain galaxy rotation is the balance between baryonic
and non-baryonic matter.

Not much non-baryonic matter is needed to explain galaxy
rotation. The main evidence for non-baryonic matter consists of
cluster velocity dispersions and the CMB fluctuations.

Right. And it was clusters which led to the first suggestion of dark
matter, by Fritz Zwicky.

Historically, the first evidence for dark matter in any form was the
cluster velocity dispersions. Galaxy rotation curves came much later
and require a smaller dark matter fraction. Nowadays there is far
more evidence than either of these.

Right.

Well, I suppose one could think of the planet Vulcan as dark matter,
postulated to explain the anomolous precession of the perihelion of
Mercury. But the correct solution, in this case, turned out to be
modified gravity. :-)

Op vrijdag 22 augustus 2014 18:56:27 UTC+2 schreef Steve Willner:
In article ,

Nicolaas Vroom writes:
One issue to explain galaxy rotation is the balance between baryonic
and non-baryonic matter.

Not much non-baryonic matter is needed to explain galaxy rotation.
Does that mean that only a small percentage of the total
mass of a galaxy is non-baryonic ?

The main evidence for non-baryonic matter consists of
cluster velocity dispersions and the CMB fluctuations.
The early history of dark-matter is explained in this
document: http://arxiv.org/pdf/astroph/9904251.pdf 1999.

What you need is an excel spreadsheet showing based on 2014
information for all the galaxies of the coma cluster what the
baryonic masses are of each and what the total is,
what the velocities are, what v2 is (sigma2 is)
and what the total mass is, using the viral theorem.
Comparing the the totals you get an idea bout what is missing.

The document shows a sigma value of 706 +- 267 km/sec2
which implies that the total mass has a large uncertainty range.

See also http://arxiv.org/pdf/1110.2649v1.pdf (2011)
which gives a very mixed picture.

The general argument is that if we cannot observe it (being visible)
than it should be non-baryonic.

Not really. About half of the baryons have been unaccounted for.
Recently there is evidence the "missing baryons" are in very hot
intra-cluster gas, but I don't know whether that's yet confirmed.

Which seems to indicate that the necessity for non-baryonic seems
to decrease.

Not only is the amount of visible matter insufficient, its
distribution is wrong. Rotation curves imply matter at larger radii
than the visible disk.

100% correct and seems to most logical explanation (part of).
This immediatly implies that there also could be much more baryonic
matter outside (but part of) the disk.

Historically, the first evidence for dark matter in any form was the
cluster velocity dispersions. Galaxy rotation curves came much later
and require a smaller dark matter fraction.
IMO, both, based on observations indicate a missing mass issue
which could be either baryonic or non-baryonic.

Nowadays there is far more evidence than either of these.
The CMB radiation fluctuations seem to indicate that roughly 20% of all
the mass in the present day is baryonic and 80% is non-baryonic.
The detailed reasoning how these numbers are derived is not
clear to me. Specific if this balance all ready existed immediate
after the BB and stayed constant there after untill present.

Nicolaas Vroom