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Quasar found 13 billion years away



 
 
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  #11  
Old June 28th 07, 08:08 AM posted to sci.astro.research
Richard Saam Richard Saam is offline
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Posts: 83
Default Quasar found 13 billion years away

Chalky wrote:
So, why wouldn't the thermal radiation from this known expanding cloud
of hot transparent gas, after the surface of last scattering, produce,
or, at least, contribute to, the observed CMB spectrum?

If something re-absorbs that thermal radiation, why does it not
simultaneously re-absorb the classically predicted CMBR, which we are
taught was only released at this surface of last scattering?


Possibly because most of the universe mass/energy at
1+z~1000, T~3000
was 'dark matter/energy' at temperature Td
in equilibrium ~T/Td with CMBR at that time
just as it is now ~T/Td at
1+z~1, T~3

Richard

[Mod. note: four generations of quoted articles snipped -- please do
this yourself -- mjh]
  #12  
Old June 28th 07, 08:10 AM posted to sci.astro.research
Chalky
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Posts: 219
Default Quasar found 13 billion years away

On Jun 27, 1:52 pm, "
wrote:
On 26 Jun, 10:35, Chalky wrote:
....

You have thus missed my real point, which is as follows:


Closer to us than the surface of last scattering, we should 'see'
successively closer shells of successively cooler gas, which should
emit thermal radiation, according to temperature. However, if the
temperature increases with redshift, and that radiation is, by
definition, redshifted by that redshift, all successive shells should
reinforce a black body 2.7K spectrum, when measured in the here and
now.


Rephrase it slightly - after correction for
the red shift, more distant neutral hydrogen
clouds, which were essentially in equilibrium
with the apparent temperature of the CMBR to
which they were exposed, should have higher
temperatures.

In fact that has been observed.


I agree, as does Jonathan Thornberg, apparently, in his posting
earlier.

However, I doubt that neutral hydrogen is the only thing which obeys
the basic rules of thermodynamics.

Phillip Helbig's quoted dark matter "bricks" would, I expect, be at
thermal equilibrium too.

Interesting, this term thermal equilibrium. It means the matter
(whatever it is) is emitting and absorbing thermal radiation in equal
measure.

Each lump of matter has the CMBR from the past, arriving from all
directions.
Each lump of matter must radiate as much as it absorbs, for thermal
equilibrium to be maintained.

So, is the theta and phi mapping of the CMBR a direct map of density
fluctuations at z=1069? That seems hardly likely once the above
described mechanism for maintaining thermal equilibrium in
intergalactic space therebetween, is taken into account.


Chalky.
  #13  
Old June 28th 07, 10:10 AM posted to sci.astro.research
Martin Hardcastle
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Posts: 63
Default Quasar found 13 billion years away

In article ,
Chalky wrote:
Closer to us than the surface of last scattering, we should 'see'
successively closer shells of successively cooler gas, which should
emit thermal radiation, according to temperature.


I don't really want to get involved in this argument, since I have to
moderate it, but here's a hint: since this 'cooler gas', after the
epoch of recombination, will be neutral atomic hydrogen, by what
emission process will it 'emit thermal radiation'? At what rest-frame
wavelength will the radiation appear? At what wavelength would we see
it now?

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
  #14  
Old June 28th 07, 10:18 AM posted to sci.astro.research
Chalky
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Posts: 219
Default Quasar found 13 billion years away

On Jun 28, 8:08 am, Richard Saam wrote:
Chalky wrote:
So, why wouldn't the thermal radiation from this known expanding cloud
of hot transparent gas, after the surface of last scattering, produce,
or, at least, contribute to, the observed CMB spectrum?


If something re-absorbs that thermal radiation, why does it not
simultaneously re-absorb the classically predicted CMBR, which we are
taught was only released at this surface of last scattering?


Possibly because most of the universe mass/energy at
1+z~1000, T~3000
was 'dark matter/energy' at temperature Td
in equilibrium ~T/Td with CMBR at that time
just as it is now ~T/Td at
1+z~1, T~3

Richard


Thermal equilibrium considerations (discussed in part with George
Dishman) would seem to confirm that the microwave intensity detected
now would be the same, either way, but that is not the point at
issue.

As far as I can tell, the intensity of that radiation released at ~
z=1069 has not been predicted to sufficient accuracy for any
confirmatory measurement, in the here and now, to form the basis for
justification of the concordance model. And this was certainly not the
method employed to derive the WMAP compatible concordance model in
practice.

It might be of relevance to establish whether the more subtle effect
hinted at by my current musings, was encompassed within that more
subtle analysis, or not.

Chalky
  #15  
Old June 28th 07, 10:54 AM posted to sci.astro.research
Chalky
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Posts: 219
Default Quasar found 13 billion years away

On Jun 28, 10:10 am, Martin Hardcastle
wrote:
In article ,

Chalky wrote:
Closer to us than the surface of last scattering, we should 'see'
successively closer shells of successively cooler gas, which should
emit thermal radiation, according to temperature.


I don't really want to get involved in this argument, since I have to
moderate it, but here's a hint: since this 'cooler gas', after the
epoch of recombination, will be neutral atomic hydrogen,


Actually, if the concordance model is correct, it is mostly dark
matter.

by what
emission process will it 'emit thermal radiation'?


Since the term "dark", as applied to both energy and matter, is as
much a reflection of our lack of contemporary understanding as
anything else, the answer to this question must necessarily be
speculative.

However, if dark matter does not obey the rules of thermodynamics, by
emitting thermal radiation, the term "cold dark matter" would be an
oxymoron (given initial conditions).

At what rest-frame
wavelength will the radiation appear?


What do you mean by rest frame? The possibilities are infinite.

At what wavelength would we see
it now?


From thermodynamic and logic considerations, black body spectrum. (You

can't get any darker than black).

From observation, this is centred around a 2.7K black body emission

peak.

Chalky.
  #16  
Old June 28th 07, 11:41 AM posted to sci.astro.research
Martin Hardcastle
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Posts: 63
Default Quasar found 13 billion years away

In article ,
Chalky wrote:
On Jun 28, 10:10 am, Martin Hardcastle
wrote:
In article ,

Chalky wrote:
Closer to us than the surface of last scattering, we should 'see'
successively closer shells of successively cooler gas, which should
emit thermal radiation, according to temperature.


I don't really want to get involved in this argument, since I have to
moderate it, but here's a hint: since this 'cooler gas', after the
epoch of recombination, will be neutral atomic hydrogen,


Actually, if the concordance model is correct, it is mostly dark
matter.


We're talking about the material that might radiate, or affect
radiation. That's normal baryonic matter, mostly neutral hydrogen.
Non-baryonic dark matter does not directly interact with radiation,
practically by definition.

However, if dark matter does not obey the rules of thermodynamics, by
emitting thermal radiation, the term "cold dark matter" would be an
oxymoron (given initial conditions).


There's no 'rule of thermodynamics' that says that material --
baryonic or non-baryonic -- has to radiate or interact with radiation.
`cold dark matter' vs `hot dark matter' refers to the energy of the
(putative) dark matter particles.

At what rest-frame
wavelength will the radiation appear?


What do you mean by rest frame? The possibilities are infinite.


`rest frame' is used by physicists to mean `a frame in which the body
under discussion is at rest'.

From thermodynamic and logic considerations, black body spectrum. (You

can't get any darker than black).


A black-body spectrum is produced only if radiation is in thermal
equilibrium with matter. (There's a common misconception, which can
sometimes even persist past undergraduate level, that `thermal
radiation' = `black-body radiation' but that's not so.) Since being in
thermal equilibrium with radiation requires the material to be
optically thick, it's not true of baryonic matter after the epoch of
recombination and it's essentially never true of dark matter. So,
given this, what contribution would you expect the baryonic matter
post-recombination to make to the observed background radiation?
Again, you should try to think about the process by which this matter
might radiate.

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
  #17  
Old July 2nd 07, 07:33 PM posted to sci.astro.research
[email protected]
external usenet poster
 
Posts: 96
Default Quasar found 13 billion years away

On 28 Jun, 08:10, Chalky wrote:
On Jun 27, 1:52 pm, "
wrote:
On 26 Jun, 10:35, Chalky wrote:
....


You have thus missed my real point, which is as follows:


Closer to us than the surface of last scattering, we should 'see'
successively closer shells of successively cooler gas, which should
emit thermal radiation, according to temperature. However, if the
temperature increases with redshift, and that radiation is, by
definition, redshifted by that redshift, all successive shells should
reinforce a black body 2.7K spectrum, when measured in the here and
now.


Rephrase it slightly - after correction for
the red shift, more distant neutral hydrogen
clouds, which were essentially in equilibrium
with the apparent temperature of the CMBR to
which they were exposed, should have higher
temperatures.


In fact that has been observed.


I agree, as does Jonathan Thornberg, apparently, in his posting
earlier.


OK, so I think that answers your question above.

However, I doubt that neutral hydrogen is the only thing which obeys
the basic rules of thermodynamics.

Phillip Helbig's quoted dark matter "bricks" would, I expect, be at
thermal equilibrium too.

Interesting, this term thermal equilibrium. It means the matter
(whatever it is) is emitting and absorbing thermal radiation in equal
measure.


Yes, that relates to another of your posts too.

Each lump of matter has the CMBR from the past, arriving from all
directions.
Each lump of matter must radiate as much as it absorbs, for thermal
equilibrium to be maintained.

So, is the theta and phi mapping of the CMBR a direct map of density
fluctuations at z=1069? That seems hardly likely once the above
described mechanism for maintaining thermal equilibrium in
intergalactic space therebetween, is taken into account.


What we see is specific nebulae in front of
the microwave background but of course it takes
some care to remove such foreground features and
there is always going to be some contamination.
The question is to what degree foreground artefacts
pollute the measurement.

George
  #18  
Old July 6th 07, 09:33 AM posted to sci.astro.research
Chalky
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Posts: 219
Default Quasar found 13 billion years away

On Jun 28, 8:08 am, Richard Saam wrote:
Chalky wrote:
So, why wouldn't the thermal radiation from this known expanding cloud
of hot transparent gas, after the surface of last scattering, produce,
or, at least, contribute to, the observed CMB spectrum?


If something re-absorbs that thermal radiation, why does it not
simultaneously re-absorb the classically predicted CMBR, which we are
taught was only released at this surface of last scattering?


Possibly because most of the universe mass/energy at
1+z~1000, T~3000
was 'dark matter/energy' at temperature Td
in equilibrium ~T/Td with CMBR at that time
just as it is now ~T/Td at
1+z~1, T~3


Interesting point. So the CMB would have precisely the same
temperature now, no matter when it originated.

C.
  #19  
Old July 6th 07, 09:34 AM posted to sci.astro.research
Chalky
external usenet poster
 
Posts: 219
Default One final point on CMBR

On Jun 28, 8:08 am, Richard Saam wrote:
Chalky wrote:
So, why wouldn't the thermal radiation from this known expanding cloud
of hot transparent gas, after the surface of last scattering, produce,
or, at least, contribute to, the observed CMB spectrum?


If something re-absorbs that thermal radiation, why does it not
simultaneously re-absorb the classically predicted CMBR, which we are
taught was only released at this surface of last scattering?


Possibly because most of the universe mass/energy at
1+z~1000, T~3000
was 'dark matter/energy' at temperature Td
in equilibrium ~T/Td with CMBR at that time
just as it is now ~T/Td at
1+z~1, T~3


One final point on this subject:

George Dishman pointed out some time ago that all radio telescopes
radiate heat to the night sky, until thermal equilibrium is reached.

Many respondents, including George, have pointed out that any
efficient radiator is also an equally efficient absorber, at the same
wavelength.

Ergo, a microwave dish capable of detecting black body radiation at
2.7 K, is also a 2.7 K black body radiator, whose own radiation is in
thermal equilibrium with its own matter.

Therefore, we cannot say with any certainty where, and, more
importantly, when, the observed CMB came from.
  #20  
Old July 6th 07, 04:42 PM posted to sci.astro.research
Phillip Helbig---remove CLOTHES to reply
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Posts: 198
Default One final point on CMBR

In article , Chalky
writes:

One final point on this subject:

^^^^^
???

George Dishman pointed out some time ago that all radio telescopes
radiate heat to the night sky, until thermal equilibrium is reached.


Everything radiates heat to everything, until thermal equilibrium is
reached (in which case it still radiates, but absorbs just as much).

Ergo, a microwave dish capable of detecting black body radiation at
2.7 K, is also a 2.7 K black body radiator, whose own radiation is in
thermal equilibrium with its own matter.


The conclusion doesn't follow from the premises. Assume I have
something which is COLDER than the surroundings. It can absorb heat,
but is not in thermal equilibrium.

Therefore, we cannot say with any certainty where, and, more
importantly, when, the observed CMB came from.


Are you seriously suggesting this?

There are four interesting things about the CMB. First, there is a
strong dipole, which is consistent with our motion relative to the bulk
of the unuiverse. Second, when the dipole is removed, one is left with
a very exact black-body spectrum. Third, the signal is the same from
every direction. Fourth, at a very low level, there are inhomogeneities
consistent with theoretical predictions. Any alternative model would
have to explain ALL four points without any ad-hoc hypotheses.
 




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