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Offline ukmicky

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dark matter
« on: 07/04/2007 16:11:32 »
Could dark matter come together to form a sun,and if not why not.

Over to you :)


 

Offline lightarrow

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dark matter
« Reply #1 on: 07/04/2007 17:50:42 »
Could dark matter come together to form a sun,and if not why not.
Over to you :)
Hello Michael!
If you tell me what dark matter is made of, I think I can dare to answer you. ;)
 

Offline ukmicky

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dark matter
« Reply #2 on: 07/04/2007 21:02:23 »
Cant do that I'm sorry to say, i know dark matter is  supposed to be formed out of some form of exotic particle.

I was just wondering whether a non baryonic sun was possible and if so would we be able to tell the difference
« Last Edit: 07/04/2007 21:22:19 by ukmicky »
 

Offline DoctorBeaver

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dark matter
« Reply #3 on: 07/04/2007 21:21:16 »
As far as I'm aware it is hypothesised that dark matter is only subject to the force of gravity not any of the other forces. Nuclear fusion, which causes the sun to burn, is the forming of heavier elements from lighter ones. That is not down to gravity. If dark matter is not subject to the forces that cause fusion, it cannot form a sun.

*waiting for George or Dave to correct me*
 

Offline ukmicky

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dark matter
« Reply #4 on: 07/04/2007 21:32:39 »
Hi doc
Like you i believe non baryonic matter only interacts with baryonic matter gravitationally but i'm unsure of how non baryonic matter interacts with non baryonic. Ive just read an earlier link by soul surfer where he says it does not clump together
http://www.thenakedscientists.com/forum/index.php?topic=7116.0

However why cant it clump together,what is it about exotic particles which prevents this.
« Last Edit: 07/04/2007 21:40:36 by ukmicky »
 

Offline DoctorBeaver

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dark matter
« Reply #5 on: 07/04/2007 22:03:42 »
However why cant it clump together,what is it about exotic particles which prevents this.

Halitosis  :D
 

Offline Soul Surfer

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dark matter
« Reply #6 on: 09/04/2007 10:56:43 »
For a star to form, the gas and dust has to cool down to a very low temperature and contract under gravity because if the molecules are moving faster than the escape velocity of the gravitiating object they will get away.  Remember that hydrogen molecules at room temeperature are moving too fast to be retained by the earth's atmosphere under the earth's gravity for any length of time.  This is why the earth does not have much molecular hydrogen unlike Jupiter and Saturn.

Think now about gas slowly collapsing to form a star.  As it collapses (losing gravitiational potential energy) the gas pressure rises and it heats up (adiabatic compression) Atoms can interact and loose energy by inelasic collisions where they radiate electromagnetic waves (heat)  whish can escape from the collapsing mass.  si the enegy can be got rid of to stop the gas getting too hot to be retained by the gravitiational field.  If it didnt do this a young star would get far too hot and "blow itself away" long before it formed a proper star.

Now dark matter cannot lose energy by radiating electromagnetic radiation it can only lose it by radiating gravitiational waves and this is vastly less efficient and takes almost infinitely longer.  So the real answer is that dark matter can and probably will evenually form small dense clumps but the universe is far far too young (many orders of magnitude)for this to have happened yet.
 

Offline DoctorBeaver

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dark matter
« Reply #7 on: 10/04/2007 08:19:06 »
*waiting for George or Dave to correct me*

Or Ian, of course!  :D
 

Offline socratus

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dark matter
« Reply #8 on: 10/04/2007 09:55:54 »
Cant do that I'm sorry to say, i know dark matter is  supposed to be formed out of some form of exotic particle.

I was just wondering whether a non baryonic sun was possible and if so would we be able to tell the difference
========================================
...exotic particle............?
=======================
To solve some difficult problem the physicists
 create a simple abstract model.
Beginning from this simple model they learned
to solve practical and difficult tasks.
In that time it was the right way to solve that problem.
 Take, for example, the theory of “ideal gas “.
The " ideal gas " represents one theoretical model of gas
and the physicists say it does not exist in nature.
It was found, that properties of real gases are very close 
to “ideal gas”. The result “ very close “ was quite satisfied
for physicists. But from time of creation the theory of
" ideal gas " about 100 years have passed and the
quantum theory  was created. And from the quantum theory
 we know that to use the expression "very close" it is impossible.
Why?
Because very small (insignificant) changes in the microworld
is a cause of radical transformation in system.
We must be very cautious, using words
"very close …, almost equally”.
=========…
I offer to consider model "ideal gas" as real model of the vacuum.
Why?
Because the temperature of " ideal gas " is equal to -273 degrees.
And temperature of pure vacuum is the same.
Now it is considered that the Universe,
as an absolute frame of reference is  in a condition of  T = 2,7K
  (rests of relic radiation of the Big Bang ).
 But, the relic radiation is extended and in the future will change
and decrease down to Т=0К, isn’t it?
Now everyone knows, that absolute temperature T=0K
cannot be reached. But is it enough reason to think
that space T=0K doesn't exist?
If Columbus did not discover America,
there was not America, was it?
We have all theoretical and logical rights to investigate
the vacuum T=0K.
 ==========   
Einstein said,
"… we have not proven that the Aether does not exist, we
have merely proven that we do not need it (for computations)"
This is correct.
The vacuum does not have influence on the behaviour of particles.
Therefore we will say nothing about vacuum.
But...
What is it possible to say about particles in vacuum?
1.
The first question: “ Can they have volume?”
No.
Because according to  J. Charles law ( 1787),
when the temperature falls down on 1 degree
the volume decreases on 1/273. And when the
 temperature reaches -273 degree the volume
disappears. The physicists say, if the particle
 has completely lost its volume then:
a)
the substance, matter disappears
b)
the physical parameters of particles becomes infinite.
But such statement  contradicts the
"Law of conservation and transformation energy".
And then we must understand what the sense of the
"Law of conservation and transformation energy" is,
we should understand and accept that
when volume of the particles disappear
 they become  "indefinitely flat figures ".
What do "indefinitely flat figures " mean?
They mean, that we cannot reach Absolute Vacuum T=0K
and we also cannot reach density of the particle in the T=0K.
The “ Charles law” was confirmed by other physicists:
Gay-Lussac ( 1802), W. Nernst ( 1910), A. Einstein ( 1925) .
These "indefinitely flat figures " have the geometrical form
of a circle,  as from all flat figures  the circle has the most
optimal form:  C/D=pi= 3,14.
P.S.
We can see the same situation in quantum theory too,
when electron interacts with vacuum, its physical parameters
 become infinite. We see the “relay race” of misunderstanding
 in the physics, which goes from one  generation to another one,
only because at the beginning the " ideal gas " wasn’t understood.
2.
Let us take some area of Vacuum and mark it with letter R.
The number of particles in this area we will mark with letter N.
Then every particle of this area has gravity/ mass of rest: R/N= k.
3.
Classic physics asserts, that in a Vacuum T=0K the motion
 of particles stops, and the energy of Vacuum is equal to zero.
The quantum physics asserts, that in a Vacuum T=0K there is
 motion of particles, and the energy of Vacuum is not zero.
Therefore, let us take some energy area of Vacuum and
mark it with letter E.
The mass of this energy area of Vacuum we will
 mark with letter M.
Then every particle of this area has energy/mass of rest:
 E/M= c^2,  ( E=Mc^2,  M=Ec^2.)
4.
As these particles are in the state of rest condition
 their impulse is equal to zero ( h=0).
5.
Mathematical point.
In mathematics, such condition of the particles in Vacuum
 is characterized with the imaginary quantity : i^2 = -1.
============================== 
Now we have the whole bouquet of formulas to begin
to paint the picture of creating the Existence.
P.S.
The quantum physics approves that “virtual particles”
 exist in Vacuum
Astrophysics approve that “ latent mass, invisible
particles, dark matter ”  exist  in Vacuum.
Everything was created from them.
But nobody knows what they are.
Now maybe somebody will understand these
“virtual,  invisible, latent “particles.
=====================





 

Offline ukmicky

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dark matter
« Reply #9 on: 17/09/2007 22:55:45 »
 I found this quite interesting inrespect to my original question.


"Warm dark matter solves mystery of giant black holes"
http://space.newscientist.com/article/dn12646-warm-dark-matter-solves-mystery-of-giant-black-holes.html
 

Offline that mad man

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« Reply #10 on: 17/09/2007 23:41:17 »
No I don't think it could come together and form a sun.

The reason, I think that dark matter is in fact gravity waves that interact with matter and as such are like photons with no mass. Its invisible energy causes matter to have the effect of gravity, gives electrons their momentum. No dark matter = no mass = no gravity.

Well, that's what I think....cough!  :)

Bee
 

Offline Soul Surfer

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dark matter
« Reply #11 on: 17/09/2007 23:55:00 »
What you are saying does not make sense and considering the nature of your questions elsewhere on these pages I would advise you to do a lot more studying and learning before venturing to propose new ideas.
 

Offline Soul Surfer

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« Reply #12 on: 18/09/2007 00:09:08 »
To return to the topic.  The smallest structure that dark matter is likely form at this stage of the universe is a galaxy sized object and it has recently been suggested that some galaxies that appear to contain very little conventional matter have been found the. next possibility is a very large black hole because the bigger they are the easier they are to make and the less dense they have to be.  It may have been easier to form these dark matter black holes (which are indistinguishable from ordinary matter black holes early on in the evolution of our universe and these may have been the seeds for the galaxies.
 

Offline that mad man

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« Reply #13 on: 18/09/2007 01:35:48 »
What you are saying does not make sense and considering the nature of your questions elsewhere on these pages I would advise you to do a lot more studying and learning before venturing to propose new ideas.

I was giving my opinion as was asked and the idea of asking questions is to learn. I thought that this was the idea here or should I try wiki?  ;)

What I am saying may not make sense, notice the wink, but neither does dark matter, dark energy, black holes or what causes gravity.
They are unproven theories and none of the above has yet been detected or can be proven, trouble is some seem to take them as fact.


Bee
 

Offline Soul Surfer

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dark matter
« Reply #14 on: 18/09/2007 23:19:07 »
In the item that I was criticising you were not asking questions.  you were proposing a process whereby dark matter would not form "stars"  that was not physically correct or within the generally accepted tenets of current science.  This could be confusing to other people who may not understand that it is a "joke" put out by a fool and may put them on the wrong track and so it had to be countered.

Dark matter is clearly proved by many observations of galaxy rotation speeds.  and the motion of galaxies within clusters when analysed by the virial theorem.

Dark energy is a bit more dubious It only has the evidence of type 1a supernovae to support it and there are several potential areas for experimental or systematic error but there is a great deal of thinking on how it may be possible to create an independent measurement of precise expansion rates. 

The precise structure if blackholes or gravstars is a bit questionable but observations clearly show extremely massive extremely compact objects near the centres of a great many galaxies and there are several observations of extremely compact stellar mass objects that cannot be neutron stars.

In order to have a universe and life there must be some sort of physical properties of whatever constitutes the material and the space it occupies and the fact that material modifies the space it occupies to cause gravitation is a perfectly sensible sort of interaction. The peculiar thing about it is that matter causes such a tiny deformation of space time and gravity is so weak.

 

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dark matter
« Reply #14 on: 18/09/2007 23:19:07 »

 

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