Facts against BB Theory

In article ,
jacob navia writes:
Arguing that "cold dark matter" explains anything is impossible since
nobody knows what dark matter *is* (physically, I mean) so anything
derived from an unknown "state of matter" is just wild speculation.

No. People can _assume_ specific properties and see what happens.
In particular, the usual assumption for cosmology is that CDM
consists of low-mass particles that interact only by gravity. With
that assumption, simulations show buildup of clusters and voids:
http://www.mpa-garching.mpg.de/galfo...go/millennium/
or
http://www.cfa.harvard.edu/news/2014-10
for some great videos.

These need to include additional physics _for the baryons_, but
that's physics for which we have direct evidence. The worry is that
both the non-baryonic and baryonic physics require some practical
approximations, and those approximations may be inaccurate. That's a
long way, though, from "wild speculation."

If I take your sentence at face value, voids were already existing at
the early universe what contradicts the BB cosmology of an homogeneous
universe.

No. There were very small fluctuations -- as measured in the CMB --
that grew over time. See the videos.

1: Voids are negative attractors since anything living in a void feels
the pull of other objects in the universe, repealing from the center of
the void.

Not if the surrounding material is symmetric.

2: Galaxies would therefore NOT enter the voids because of gravity and
they would stick together. This fact contradicts your affirmation that
"random motion of galaxies would fill the voids".

If you think that, I think you need to show your calculation.

--
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:

The voids are not created by evacuating galaxies. Galaxies are born at
the edges of large voids created by cold dark matter

Right.

The paper of Sutter et al doesn't give any explanation for the
appearence of voids. It just doesn't address the subject limiting itself
to void detection, establishing of the mask, and correlating the
observations to some models.

OK.

Those models are "lambda cold dark matter" models whatever that is.

These are models of structure formation which have been studied
extensively in the last 20 years or so. If you don't even know what
they are, your scepticism about modern cosmology cannot be very well
founded.

Arguing that "cold dark matter" explains anything is impossible since
nobody knows what dark matter *is* (physically, I mean) so anything
derived from an unknown "state of matter" is just wild speculation.

No. By definition, cold dark matter is matter which interacts only
gravitationally and is not moving relativistically. It doesn't matter
what it is composed of as far as structure formation goes.

If I take your sentence at face value, voids were already existing at
the early universe what contradicts the BB cosmology of an homogeneous
universe.

You are confusing things here. The universe is homogeneous on large
scales, not on small scales; if the latter were the case, we wouldn't be
here. Second, the field is structure FORMATION. Structures form by
growth from small initial perturbations (thus, the early universe is not
COMPLETELY homogeneous, but then no-one ever claimed that it was).
There is a HUGE literature on this. Thus, filamentary structures, and
the corresponding voids, develop with time, and galaxies form where
matter is dense (i.e. not in the voids).

1: Voids are negative attractors since anything living in a void feels
the pull of other objects in the universe, repealing from the center of
the void.

2: Galaxies would therefore NOT enter the voids because of gravity and
they would stick together. This fact contradicts your affirmation that
"random motion of galaxies would fill the voids".

The Earth attracts objects. But that doesn't mean that if I throw an
object up, that it won't move away from the Earth. Indeed, if I throw
it fast enough, it will escape forever.

Basically then, you just say:

This "dark matter" that nobody knows nothing about explains everything.

Great

You don't understand what voids are and how they are formed. You are
not familiar with basic cosmological literature of the past 20 years on
which the conclusions you attack are based. It is no wonder that
sarcastic answers like the last three quoted lines don't convince
anyone that modern cosmology is in a crisis.

On 5/24/2014 3:05 PM, Phillip Helbig---undress to reply wrote:
In , jacob navia
..
...
2: Galaxies would therefore NOT enter the voids because of gravity and
they would stick together. This fact contradicts your affirmation that
"random motion of galaxies would fill the voids".

The Earth attracts objects. But that doesn't mean that if I throw an
object up, that it won't move away from the Earth. Indeed, if I throw
it fast enough, it will escape forever.

Some planets hold their atmosphere, others have
too weak gravity fields to do so, so whether the
random motion of molecules will move them into
interplanetary space is a similar question as
whether the random motion of galaxies would fill
the voids.

It seems that these questions are (par excellence)
of the type the theory can answer in a quantitative
way! (A definitive prediction might perhaps even be
possible, if we can agree on what it means. :-) )

--
Jos

Le 24/05/2014 14:56, Steve Willner a écrit :

2: Galaxies would therefore NOT enter the voids because of gravity and
they would stick together. This fact contradicts your affirmation that
"random motion of galaxies would fill the voids".

If you think that, I think you need to show your calculation.


Can galaxies be compared to a rarefied *gas*?

Not really, galaxies tend to build filaments, something a gas doesn't.

A liquid?

Can gravity simulate surface tension by reasoning that the pull of the
other galaxies and matter tends to keep galaxies from straying away?

A condensing gas is maybe more appropiate?

Or are the voids pushing the galaxies and all matter away from them with
an unknown repulsive force?

Before I calculate something I have to get to a mental model that
justifies those calculations!

In general in physics, calculations are a consequence of a model of
reality and they do not prove anything, like in mathematics. Your asking
me to calculate if the galaxies would stay together or fill the voids
implies that you suppose that I have a mental model of galaxy movement
and cohesion forces, what is far from reality.

I do not know.

I wrote
Those models are "lambda cold dark matter" models whatever that is.

Phillip wrote:

These are models of structure formation which have been studied
extensively in the last 20 years or so. If you don't even know what
they are, your scepticism about modern cosmology cannot be very well
founded.

Of course it is not well founded. I have no alternate theory, I am not a
professional astronomer and most of what I say is not well founded, as
you rightly said.

Of course, the fact that there is not a trace of dark matter after all
these years of search doesn't mean that there isn't "dark" matter
somewhere. Sure.

Actually dark matter is so dark, so really black and dark that
astronomers can't really tell me WHERE it is.

Some years ago it was in the intra-galactic space, now it is maybe in
the intra-cluster space...

In any case not in the solar system or is it? Is there "dark" matter
between the screen where my mail client is displayed and my eyes?

It interacts only gravitationally with matter, and it is completely
invisible otherwise. For a layman it is a hard pill to swallow.

No particle nor any physical stuff is associated with this "dark" matter
that arranges the equations so that they fit. Sudenly I have to believe
in this "matter" as an article of faith.

Yes, there are observations that point to a divergence between gravity
rules and rotation curves of galaxies. Yes, nobody knows what is behind.
But to propose an "unknown and invisible" state of matter that is not
associated with anything physical is kind of really new in physics.

I just can't believe it, sorry.

Yours sincerely

jacob

In article , jacob navia
writes:

In any case not in the solar system or is it? Is there "dark" matter
between the screen where my mail client is displayed and my eyes?

Maybe. It depends on what it is. There are 311 million or whatever
neutrinos per cubic metre, and dark matter interacts less than
neutrinos.

It interacts only gravitationally with matter, and it is completely
invisible otherwise. For a layman it is a hard pill to swallow.

Why? The alternative is that most of the universe just happens to be
detectable via our senses which evolved for completely different reasons
on Earth.

On Monday, May 26, 2014 3:09:26 AM UTC-4, jacob navia wrote:
I just can't believe it, sorry.

You might be interested in the work of K Maeda and H Sato. They
published papers concerning the growth of voids and the resulting
matter structures induced by their growth. They do not attribute
gravitational collapse to Dark Matter.

Brad

[Mod. note: quoted text trimmed, reformatted -- mjh]

On 5/21/14, 1:18 AM, Robert L. Oldershaw wrote:
I stand by my 1988 comment.

Your reference to Planck mass '10^-5 GRAMS'
of course is in context with h,G,c dimensional analysis:

Planck mass = h^(1/2)*G^(-1/2)*c^(1/2) = 2.18E-5 g
and the related
Planck length = h^(1/2)*G^(1/2) *c^(-3/2) = 1.61E-33 cm
Planck time = h^(1/2)*G^(1/2) *c^(-5/2) = 5.39E-44 sec

and Planck length/Planck time = c

This dimensional argument was done over 100 years ago
in the Max Planck era.
These extreme conditions probably will not be duplicated in the laboratory.

But dimensionally introduce the recent Hubble constant H value
not available in Max Planck's time
and the resulting mass,length and time values
are not so extreme
and may be interpreted in the context of observable nuclear reactions:

mass = h^(2/3)*(H/G)^(1/3) *c^(-1/3) = 1.09E-25 g
(a mass between the proton and electron)
length= h^(1/3)*(H/G)^(-1/3)*c^(-2/3) = 3.23E-13 cm
(the ~nuclear diameter)
time = h^(1/3)*(H/G)^(-1/3)*c^(-5/3) = 1.08E-23 sec
(~nuclear particle decay time such as for top quark)

and length/time = c (the same as Planck length/Planck time)

This h,G,c dimensionality including the Hubble constant (H)
may feed into your other 1988 comments.
Maybe there is a marriage between cosmology and particle physics.

Richard D Saam

[Mod. note: quoted text trimmed -- mjh]

Le 27/05/2014 09:36, Phillip Helbig---undress to reply a écrit :
In article , jacob navia
writes:

In any case not in the solar system or is it? Is there "dark" matter
between the screen where my mail client is displayed and my eyes?

Maybe. It depends on what it is. There are 311 million or whatever
neutrinos per cubic metre, and dark matter interacts less than
neutrinos.


Neutrinos are detectable. They interact in huge tanks of chlorine that
can detect them!

It interacts only gravitationally with matter, and it is completely
invisible otherwise. For a layman it is a hard pill to swallow.

Why? The alternative is that most of the universe just happens to be
detectable via our senses which evolved for completely different reasons
on Earth.


Please don't put in my mouth something I did not say. I do not try to
just use directly the five senses to detect gamma radiation from a star
or whatever!

We can build sophisticated detectors to TRANSLATE radiation forms
invisible to us into five senses input (mostly visual). An infra-red
camera traslates invisible infra-red into visible light that we can see.

This is OF COURSE OK. What I do not see in the "dark" matter theory is
any particle, wave or physical manifestation of that state of matter.

Nor any experiment that would attach that missing mass to SOMETHING!

In article ,
jacob navia wrote:
Yes, there are observations that point to a divergence between gravity
rules and rotation curves of galaxies. Yes, nobody knows what is behind.
But to propose an "unknown and invisible" state of matter that is not
associated with anything physical is kind of really new in physics.

I would suggest that you have this almost exactly backwards. We infer
by using standard lab/solar system physics that there is more matter
in these systems than is visible. If that is *not* true, then we have
to accept that the laws of physics that are well tested in the lab and
the solar system don't apply on the largest cosmological scales.
That's why most people are very reluctant to abandon the idea of dark
matter -- the alternative is to start making up new physics.

Martin
--
Martin Hardcastle
School of Physics, Astronomy and Mathematics, University of Hertfordshire, UK
Please replace the xxx.xxx.xxx in the header with herts.ac.uk to mail me