A better term for "dark matter"

On Jul 12, 10:31 am, Eric Flesch wrote:
On Thu, 12 Jul 12 06, Steve Willner wrote:
I'm mystified by the OP's suggestion that dark matter isn't matter.

On reflection, I've often mentioned a "gravitational scalar" which
seems to pervade the ISM, which gravitationally detaches stars from
eachother and so enables them to mingle ambiently within elliptical
galaxies and globular clusters. Also present in the IGM, allowing HI
to ooze away from galaxies like NGC 3628.

Now it occurs to me that "gravitational scalar" and "dark matter" are
not all that much different. Suppose "dark matter" subtends a
gravitational aura in places where it phantom-like inhabits. Much
like my gravitational scalar. You could see evidence for this in
close large bodies which are less bound to eachother than you might
expect from their masses. Hmm.

Congratulations, you have re-invented TeVeS.

Saying that dark matter is 'actually' some (tensor|{,pseudo}vector|
scalar) field doesn't really add anything to the discussion because
all you have done is pushed back the genesis of the problem back
another level.

On Fri, 13 Jul 12 08:49:40 GMT, Eric Gisse wrote:
On Jul 12, 10:31 am, Eric Flesch wrote:
Now it occurs to me that "gravitational scalar" and "dark matter" are
not all that much different. ...

Saying that dark matter is 'actually' some (tensor|{,pseudo}vector|
scalar) field doesn't really add anything to the discussion because
all you have done is pushed back the genesis of the problem back
another level.

It does add something because it shows e.g. that galaxies can't have
very extended haloes because "dark matter" raises the gravitational
background noise level. So the IGM is dark matter dominated,
gravitationally.

Mind you, I think "gravitational scalar" is a far better term than
"dark matter", but maybe "dark matter" isn't as bad a placeholder as I
was thinking.

"Eric Flesch" wrote in message
...
On Thu, 12 Jul 12 06, Steve Willner wrote:
I'm mystified by the OP's suggestion that dark matter isn't matter. ...
The non-baryonic dark matter (at least so far as we know now)
interacts gravitationally with both itself and with baryons in the same
way
as any other matter does. Its density varies with cosmic scale factor in
the same way as other matter (again so far as we know now) and not in
the same way as radiation. So why shouldn't we call it matter?

Your doubly-stated phrase "so far as we know now" is the succint
answer. Not enough evidence -- our observations are too beholden to
our limited instrumentation. All we have to deduce dark matter is
gravity, but gravity is not well understood, having never been united
into the concordance model. So we know there's extra gravity, but to
infer extra matter from that should stop when we find ourselves
chasing phantoms -- after all, it could be something else after all.


Could the "matter" (source of extra gravity) be "somewhere" else?

Gravity is "possibly" weak because some leaks into "other" dimensions.

Could not gravity be leaking into our 3 dimensions from matter "located" in
these other dimensions?

I realize this question might be better answered by the physicists working
on M-theory but this strikes me a relevant here-now.

On Sat, 14 Jul 12, David Staup wrote:
Could not gravity be leaking into our 3 dimensions from matter "located" in
these other dimensions?

I've certainly speculated thusly, but then we're back to the idea that
gravity comes only from matter. If it were as simple as that, then
gravity should have been successfully incorporated into the TOE.

Consider dimensions, they are space or time which seem like very
different things but are shown to be united as space-time. So could
not other dimensions be (apparently) very different again? I am
guessing that gravity may be a dimension, which is why it won't fit
into the TOE.

Anyway, all speculation in response to your "could ...". cheers

On Thursday, July 12, 2012 8:15:05 AM UTC+2, Steve Willner wrote:

Fluctuations in the cosmic microwave background also distinguish
between baryonic and non-baryonic dark matter. There's a cute
calculator tool at
http://lambda.gsfc.nasa.gov/toolbox/...n/cmb_plotter/

I can understand that there is a relation between baryonic and non-baryonic matter with the CMB power spectrum but not with dark matter because dark matter
is a concept related to human constraints i.e. the human eye and that has nothing to do with the physical processes which happened "around" the Big Bang.

When you goto: http://background.uchicago.edu/~whu/...e/summary.html
in the section "Damping Tail" the following parameters are introduced:
baryon density, matter density and dark baryons.
With baryon density they should mean all baryons in a region of space (visible and invisible). With matter density they should mean the total of all baryon and nonbaryon (or not use). The concept of dark baryons is IMO related to the CMB not relevant.

Nicolaas Vroom

In article , Nicolaas Vroom
writes:

On Thursday, July 12, 2012 8:15:05 AM UTC+2, Steve Willner wrote:

Fluctuations in the cosmic microwave background also distinguish
between baryonic and non-baryonic dark matter. There's a cute
calculator tool at
http://lambda.gsfc.nasa.gov/toolbox/...n/cmb_plotter/

I can understand that there is a relation between baryonic and
non-baryonic matter with the CMB power spectrum but not with dark matter
because dark matter is a concept related to human constraints i.e. the
human eye and that has nothing to do with the physical processes which
happened "around" the Big Bang.

When you goto: http://background.uchicago.edu/~whu/...e/summary.html
in the section "Damping Tail" the following parameters are introduced:
baryon density, matter density and dark baryons.
With baryon density they should mean all baryons in a region of space
(visible and invisible). With matter density they should mean the total
of all baryon and nonbaryon (or not use). The concept of dark baryons is
IMO related to the CMB not relevant.

This is true as far as it goes. However, we know from non-CMB sources
what the amounts of total matter, total baryonic matter and non-dark
matter are, so we can figure out how much dark matter there must be.

On Tue, 17 Jul 12, Phillip Helbig---undress to reply wrote:
we know from non-CMB sources what the amounts of total matter,
total baryonic matter and non-dark matter are, so we can figure
out how much dark matter there must be.

Reminscent of thermodynamics, where "entropy" is calculated as the
residue of the temperature & enthalpy, etc. -- but the entropy is
actually only the gap between calculation and measurement, dressed up
in a fancy word. Took me 20 years to realize that that emperor
(thermodynamics) has no clothes either.

This is further remiscent of the excluded middle in mathematics, which
is used by the rationalists to "prove" useless things like Cantorian
infinities, and which constructivists avoid -- they say you need to
construct something for it to be real, and not use gaps. Yes, I'm a
constructivist, it's a very sane worldview..

On Wednesday, July 18, 2012 11:08:28 AM UTC-5, Eric Flesch wrote:

[...]
Reminscent of thermodynamics, where "entropy" is calculated as the
residue of the temperature & enthalpy, etc. -- but the entropy is
actually only the gap between calculation and measurement, dressed up
in a fancy word. Took me 20 years to realize that that emperor
(thermodynamics) has no clothes either.

Huh?

Entropy is simply a calculation of the number of states a system can have.

How does that translate to 'residue of temperature' and such? To say nothing of being the 'gap between calculation and measurement' ?

[...]

In article ,
Nicolaas Vroom writes:
I can understand that there is a relation between baryonic and
non-baryonic matter with the CMB power spectrum but not with dark
matter because dark matter is a concept related to human
constraints

Yes, that's correct: all cosmological tests "care" only about
baryonic and non-baryonic matter (and other constituents, of course,
such as dark energy and neutrinos).

The historical situation has been that very little of the baryonic
matter was directly detected, and of course none of the non-baryonic
matter has been. The term "baryonic dark matter" therefore meant all
the baryonic matter not associated with stars and stellar remnants.
Matter that is associated with stars and known forms of stellar
remnants is called "luminous matter," even though not all of it is
actually detectable. With these definitions, "baryonic dark matter"
is almost but not quite synonymous with "baryonic matter," and
sometimes people will use one when they mean the other.

Recent evidence suggests that much of the baryonic matter is in the
form of very hot (10^6 K) gas associated with galaxy clusters. To
the extent this matter is detected by X-ray emission, it is no longer
"dark," but it may take some time for the terminology to catch up.

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

On Friday, July 20, 2012 8:29:06 AM UTC+2, Steve Willner wrote:
Yes, that's correct: all cosmological tests "care" only
about baryonic and non-baryonic matter (and other constituents,
of course, such as dark energy and neutrinos).

How difficult terminology is becomes clear when you study Time
Magazine of 23July 2012, which reads: "Take dark matter. Galaxies are
large enough and spin fast enough that by rights they ought to fly
apart. The fact that they don't means the gravity from some unseen
form of matter is holding them together. And in order to exert so much
pull, it would have to be an awful lot of that matter--fully 80% of
the universe. Most physicists believe that the invisible stuff is made
of a particle of some kind. If that particle has mass, it's
interacting with the Higgs. Find the Higgs responsible and you may
pull back the curtain on what the dark particles are."

IMO this text is misleading because different orders of scale are
compared. IMO a more appropiate text with the word "dark matter" is:
Take the missing matter problem. The measured speed of a galaxy as a
function of distance is called the galaxy rotation curve (grv) In
order to calculate this curve (using Newton's Law) you can follow two
roads: (1) by starting from a distribution of matter in bulge and disk
from what is observed (2) by starting from a theoretical distribution
of matter. The object of this second calculation is that calculated
grv resembles what is observed. The two amounts of matter do not
match. The difference between the two is called the missing matter
problem. The issue is what is this missing matter. The most obvious
solution is baryonic matter in objects of all sizes. Including
blackholes, stars, brown stars, planets, asteroids and gasses. Only
when all the baryonic matter is included nonbaryonic matter can be
considered. At the scale of the Universe a similar problem exists. The
amount of nonbaryonic matter involded at that scale can be different.
If the LHC finds any new nonbaryonic particle it does not mean that
missing matter problem is solved.

Nicolaas Vroom
http://users.telenet.be/nicvroom/