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mmaayeh
2010-Aug-01, 10:52 AM
I was reading an article in Physorg.com regarding a cosmological model without a big bang. Basically, it states that time, space, length, and mass convert between each other and therefore you can have a universe without a big bang or dark energy (http://www.physorg.com/news199591806.html). What is the viability of such a model? Is it something that comes up from time to time and then not accepted eventually?

Cougar
2010-Aug-01, 11:55 AM
I was reading an article in Physorg.com regarding a cosmological model without a big bang. Basically, it states that time, space, length, and mass convert between each other and therefore you can have a universe without a big bang or dark energy (http://www.physorg.com/news199591806.html). What is the viability of such a model? Is it something that comes up from time to time and then not accepted eventually?

It's a variable speed of light/gravitational constant model. Surely this idea is not new. Maybe this author put some new twists on it. I just (attempted to) read Reinventing Gravity by John Moffat (http://en.wikipedia.org/wiki/John_Moffat_%28physicist%29), which makes many of the same claims using the same strategy. (It was one of the very few books that I absolutely could not finish. It seemed to me to be one handwave after another.)

These models may actually do what they claim, but the variability of these physical constants, on which the models are based, appear to be in gross conflict with repeated and various independent observations. Such conflict is not normally a good foundation for a proposed model.

Ken G
2010-Aug-01, 02:17 PM
What's more, it was impossible to tell from the flimsy article what the core of the idea really was. What characteristics did the driving equations have? How many free parameters were invoked? It's always easy to get a model that explains why A, B, C and D happened, I can come up with such a model right now: "A happened, and then "exchanging" A and B caused B to happen, and then "exchanging" B and C led to C, and "exchanging" C and D led to D." The trick is to do it in a unifying way, a way that lets you get out much more than you put in. If one is going to relax one of the most important unifying concepts in all of science, the constancy of the constants, then one had better have a huge simplification or unification coming in someplace else, or the net benefit is negative. That may be why the link cites only un-refereed publications.

forrest noble
2010-Aug-01, 04:12 PM
Maayeh,


Cosmological Models with No Big Bang, is this a valid model being considered?

Of course it is wise to have a general knowledge of alternative models. The BB may not be the last word on things. None of these "alternative models" presently could be considered mainstream though. Considering there are almost as many theories as there are theorists, most of these cosmological models are different versions of the BB model. Just because somebody gets more press than someone else and gets their model out there doesn't mean that model is more worthy of consideration than other alternatives "less advertised." All of us have limited time for such readings since most models developed by educated theorists are not simple to read or understand and require in-depth analysis. As perceived problems have arisen in the past with the standard model, more alternative/ competing theories have also risen to the surface to explain these perceived problem(s). Each person can decide for themselves concerning the possibilities of alternative models. Most however don't have the expertise for such evaluations so instead rely on the opinions of others. All must consider to what extent one should consider alternative models based upon what one's opinions are concerning perceived problems with the foundations of the basic BB model. As was indicated, generally no one can consider any theory that one cannot understand, if in fact the theory is generally self consistent, except by somebody else' opinion of it.

mmaayeh
2010-Aug-01, 06:35 PM
Thanks all, seems like for now I can see that this model needs serious peer review before being accepted as a potential alternative in the scientific community.

Sir Knots A Lot
2010-Aug-01, 10:37 PM
Here's the paper, complete with the field equations.

http://arxiv.org/ftp/arxiv/papers/1007/1007.1750.pdf

I'd like someone with some knowledge of GR to look this over.

I've been trying to develop a new kind of model for quantum mechanics of quark interactions and this cosmology suits it well due to it's natural dualities.

Ken G
2010-Aug-02, 02:33 AM
I think the paper is actually pretty interesting, the question is does it really deliver on its goals. The main idea of the paper is to let c be inversely proportional to the rate of change of the average density, with the idea that c would be infinite if the density weren't changing because in a universe where nothing changes (cosmologically speaking), there would be no cosmological concept of time. He then argues that if there's no cosmological concept of time, c should be infinite, because there should be no local sense of time either. That's a bit of a stretch, but it's not illogical. The only other thing of consequence he has to assume is that the gravitational constant G must vary in concert with how c varies to keep certain physically important conversion factors constant.

The general relativity in the paper is all completely standard, he's not changing that in any way. He is merely assuming a different parametrization of c and G, rather than letting them stay constant.

An important issue that I did not read carefully enough to judge, and I don't know if he really addressed it very completely, is whether the new model is consistent with all the other things we observe, like cosmic nucleosynthesis and the CMB-- normally considered pillars of the Big Bang. He is claiming the Big Bang didn't happen, so I think he's got a wee bit of a problem there.

An even worse problem may exist. He mentions in the paper that some authors have pointed out that monkeying with c and G is not really doing anything physical at all, since those parameters have dimensions. It is the dimensionless combinations that can be made from them that store all the physics, and he may be forcing those combinations to stay the same, that's not completely clear to me on a casual reading. The point about having dimensions is that you can get c to be a function of time by simply changing gradually from meters to feet, or some such thing-- it's not a physical difference. His defense against that is nonexistent-- he claims that his time has no beginning and no end, so is topologically different, but of course one can achieve that by simply converting the units of time in a continuous way that maps our familiar 13.7 billion years into an infinite amount of his coordinate time.

In short, I'm quite worried that all he has done is remap completely standard Friedmann-Walker cosmology into a new coordinate where the units of time and distance gradually vary. There may not actually be any new physics in the "model" at all-- so the problem isn't that anything is wrong, it's that all it does is put makeup on the standard solution for a compact universe. If so, his "model" would not have any observational consequences, and he would then have to misinterpreting what it predicts for the observations.

Sir Knots A Lot
2010-Aug-02, 01:53 PM
It seems to me that for this paper to be valid, and time to have no beginning and no end, there would have to exist a space-like dimension of time.

For the universe to be evolving in the manner described in this paper, there would have to be a process of white hole nucleosynthesis occuring at one end of the time-space where inflation and deceleration are occuring to counter balance the acceleration and compression of the black hole at the opposite end of time-space.

Does that seem like a logical extension?

Staticman
2010-Aug-02, 11:19 PM
An important issue that I did not read carefully enough to judge, and I don't know if he really addressed it very completely, is whether the new model is consistent with all the other things we observe, like cosmic nucleosynthesis and the CMB-- normally considered pillars of the Big Bang. He is claiming the Big Bang didn't happen, so I think he's got a wee bit of a problem there.


Not so much the nucleosynthesis of light elements that is easier to justify and in fact has been "explained" by many different models, but certainly if the paper lacks something is addressing the CMB observations, and the paper does not even mention it, which is a big flaw if their goal was to present a new model and be taken seriously


In short, I'm quite worried that all he has done is remap completely standard Friedmann-Walker cosmology into a new coordinate where the units of time and distance gradually vary. There may not actually be any new physics in the "model" at all-- so the problem isn't that anything is wrong, it's that all it does is put makeup on the standard solution for a compact universe. If so, his "model" would not have any observational consequences, and he would then have to misinterpreting what it predicts for the observations.
I agree, basically if one plays with constants one can get just about anything.




For the universe to be evolving in the manner described in this paper, there would have to be a process of white hole nucleosynthesis occuring at one end of the time-space where inflation and deceleration are occuring to counter balance the acceleration and compression of the black hole at the opposite end of time-space.

Does that seem like a logical extension?
From what I understood in this model there is no singularities, so probably it doesn't.

astromark
2010-Aug-03, 12:48 AM
It seems to me that for this paper to be valid, and time to have no beginning and no end, there would have to exist a space-like dimension of time.

For the universe to be evolving in the manner described in this paper, there would have to be a process of white hole nucleosynthesis occuring at one end of the time-space where inflation and deceleration are occuring to counter balance the acceleration and compression of the black hole at the opposite end of time-space.

Does that seem like a logical extension?

Not wishing to go down the ATM road... but. I understand things 'differently' As space time increases density so time must slow. As to why ?

The higher or nearer to velocity c. the slower time must be... from your perspective.

I think there's a general agreement with that. Well I think so., but have noticed a trend to argue whatever the point, to oblivion.

I am not interested in that attitude. But am thinking that. Time does not go back.
It might almost stop. but as c. is unobtainable. Its all a bit silly.

Also noting how easy it is to get so completely misunderstood... and to avoid that suggesting any 'new' idea. I am not.

Just attempting to relate that as your velocity gets near to c. Time will appear to have slowed.

and if it were possible to reach c. It would for all intentions have stopped.

The light does not experiance time. It is where ever it is, and going to in a instant.

I am interested if I can be understood. ? Mark. Watching the planets.

Sir Knots A Lot
2010-Aug-03, 01:30 AM
From what I understood in this model there is no singularities, so probably it doesn't.

Well, just because there isn't a singularity in the model doesn't eliminate the whole idea of black holes. It's just redefining what possibly occurs behind the event horizon.

Cougar
2010-Aug-03, 02:15 AM
...the nucleosynthesis of light elements... is easier to justify and in fact has been "explained" by many different models...
Tony Rothman (http://en.wikipedia.org/wiki/Tony_Rothman) reports:






"Actually, it is so difficult for a model to predict both the light isotope abundances and the cosmic microwave background that most alternative models have been of the big bang type."

"To keep helium below the 25% limit imposed by astronomers [observations] requires that the universe was highly isotropic at the time of element formation."

I expect the ~25% helium by mass is quite a constraint to any model. And if that doesn't do it, the observed 2 x 10-5 parts deuterium rather seals the deal, it would seem.

Sir Knots A Lot
2010-Aug-03, 02:59 AM
Tony Rothman (http://en.wikipedia.org/wiki/Tony_Rothman) reports:






"Actually, it is so difficult for a model to predict both the light isotope abundances and the cosmic microwave background that most alternative models have been of the big bang type."

"To keep helium below the 25% limit imposed by astronomers [observations] requires that the universe was highly isotropic at the time of element formation."

I expect the ~25% helium by mass is quite a constraint to any model. And if that doesn't do it, the observed 2 x 10-5 parts deuterium rather seals the deal, it would seem.

One issue that could be addressed by this paper in the notion of a space-like dimension of time is the CMB dipole anisotropy.

If the formation of galaxys begins with a white hole (non-singularity) that produces elliptical galaxies, and ends with a spiral galaxy being slowly absorbed by a black hole (non-singularity) there is a closed time-like curve being followed in the deceleration and acceleration. The meridians of a 3-sphere (the model that fits the equations of this paper) suggest the shape of this space-like dimension of time.

If we are indeed travelling along a CTC, could the dipole anisotropy in the CMB be evidence of this preferred galactic motion?

Nereid
2010-Aug-03, 02:34 PM
One issue that could be addressed by this paper in the notion of a space-like dimension of time is the CMB dipole anisotropy.

If the formation of galaxys begins with a white hole (non-singularity) that produces elliptical galaxies, and ends with a spiral galaxy being slowly absorbed by a black hole (non-singularity) there is a closed time-like curve being followed in the deceleration and acceleration. The meridians of a 3-sphere (the model that fits the equations of this paper) suggest the shape of this space-like dimension of time.

If we are indeed travelling along a CTC, could the dipole anisotropy in the CMB be evidence of this preferred galactic motion?
Could the dipole anisotropy in the CMB be evidence of this preferred galactic motion?

Highly unlikely, IMHO, if only because a mass distribution that would give rise to something very close to the observed CMB dipole has already been observed: it's the Great Attractor (to give it a shorthand), a particularly massive rich cluster of galaxies (or set of clusters, a supercluster).

Sir Knots A Lot
2010-Aug-03, 03:29 PM
Could the dipole anisotropy in the CMB be evidence of this preferred galactic motion?

Highly unlikely, IMHO, if only because a mass distribution that would give rise to something very close to the observed CMB dipole has already been observed: it's the Great Attractor (to give it a shorthand), a particularly massive rich cluster of galaxies (or set of clusters, a supercluster).

That would be fine, except that great attractor-like phenomenom seems to be predicted by Shu as a result of this time-like dimension of space. The 'great attractor' would be one of the end points already discussed where G is dominant over c2, as opposed to the opposite end of this time-like dimension of space where c2 is dominant over G.

Nereid
2010-Aug-03, 03:40 PM
That would be fine, except that great attractor-like phenomenom seems to be predicted by Shu as a result of this time-like dimension of space. The 'great attractor' would be one of the end points already discussed where G is dominant over c2, as opposed to the opposite end of this time-like dimension of space where c2 is dominant over G.
I'm not sure I follow - is Shu saying that there is not a distribution of mass - as determined by astronomical observations quite independent of those of the CMB - in/near a region of space called 'the Great Attractor' as a shorthand?

ETA: there is nothing in either the link in the OP nor Shu's arXiv preprint on the CMB dipole - is this your own interpretation, or do you have some other Shu paper?

Sir Knots A Lot
2010-Aug-03, 03:40 PM
Just out of curiousity, does the Big Bang provide an explanation for the great void in the CMB map?

http://www.nova.org/~sol/solcom/x-objects/void2com.jpg

Nereid
2010-Aug-03, 03:47 PM
Just out of curiousity, does the Big Bang provide an explanation for the great void in the CMB map?

http://www.nova.org/~sol/solcom/x-objects/void2com.jpg
Sure ... it is entirely consistent with the expected spectrum of fluctuations; one of the Seven-Year WMAP papers deals with this exact question (I forget which paper it is, maybe the 'anomalies' one).

Sir Knots A Lot
2010-Aug-03, 04:04 PM
I haven't read anything regarding theory that would produce such a void 1 billion light years across.

It's apparently void of all normal matter and dark matter as well.

Tensor
2010-Aug-03, 04:36 PM
I haven't read anything regarding theory that would produce such a void 1 billion light years across.

It's apparently void of all normal matter and dark matter as well.

Here (http://arxiv.org/pdf/1001.4758v1) is the paper Nereid is talking about. I believe the area you are talking about is their cold spot II, it is in section 3 of the paper. Observations have shown that the void isn't as empty as at first thought. They provide the papers showing that.

Staticman
2010-Aug-03, 04:51 PM
"Actually, it is so difficult for a model to predict both the light isotope abundances and the cosmic microwave background that most alternative models have been of the big bang type."


Right. He is talking here about predicting both, which is quite different than predicting just light elements abundance.


"To keep helium below the 25% limit imposed by astronomers [observations] requires that the universe was highly isotropic at the time of element formation."

Ok, Big Bang model is not the only isotropic model, is it?


I expect the ~25% helium by mass is quite a constraint to any model. And if that doesn't do it, the observed 2 x 10-5 parts deuterium rather seals the deal, it would seem.
Well, it is a constraint, can't argue with that. There are still models that are compatible with the Helium 25% limit, Hoyle and Burbidge(1998) for instance come to mind right now and others have been able to come up with similar models, models with universes infinite in time also usually justify HE/H ratios of about 0.24,
Of course I did not say anything about their validity as models, I just tried to say that the light elements abundance seemed to me not so striking for them not to mention in the paper (and after all the problems the BB model had in the 90's with the exact fitting with the observed quantities of light isotopes), as the CMB observations, given the great importance that they have gained since the WMAP data is being released. After all the CMB power spectrum is the "crown jewel" of the BB model.

But probably they should have mentioned both features.

Sir Knots A Lot
2010-Aug-03, 10:22 PM
If the Big Bang occurred everywhere at the same time (or in dhg64's left knee), why is there a frame of motion for the CMB?

Also, I think it should be noted if this model is predicting a deceleration associated with a white hole, the edge of the event horizon would likely be the point of recombination, where light becomes transparent in space. In effect, the 'deceleration' model of a white hole sort of mirrors the inflationary modelling of the Big Bang.

So instead of the Big Bang being a onetime event, the emergence from the primodial atom, its a constantly occuring process somewhere in the Universe and the primodial atom never existed.

Nereid
2010-Aug-03, 10:29 PM
If the Big Bang occurred everywhere at the same time (or in dhg64's left knee), why is there a frame of motion for the CMB?

[...]
Do you know what 'co-moving time' (or a 'co-moving frame of reference')? If so, then you have your answer; if not, then Ned Wright's cosmology tutorial (http://www.astro.ucla.edu/~wright/cosmolog.htm) would be worth some of your time reading ...

Cougar
2010-Aug-04, 01:35 PM
[QUOTE=Sir Knots A Lot;1771718]Just out of curiousity, does the Big Bang provide an explanation for the great void in the CMB map?
http://www.nova.org/~sol/solcom/x-objects/void2com.jpg[/IMG]

The eraser tool in photoshop?

forrest noble
2010-Aug-06, 05:39 AM
Sir Knots A Lot,


Just out of curiousity, does the Big Bang provide an explanation for the great void in the CMB map?

BB theory does allow for as much heat variation as has been observed in the MWB. I think the problem is more in the size of this, being the largest of the known voids. If the MWB is a remnant of the era following the BB as theory asserts, such large "holes" in it are difficult to explain. Since this void in Boots is thought to be as big as you quoted, the temperatures within this volume have also been observed to be less than its surroundings. This defines the hole. But the problem seems to be that this volume also contains relatively few observable galaxies. If these observations are valid and hold up in time, further theoretical explanations may be needed. Much Fewer galaxies producing lower temperatures would seem to make sense, but maybe not if the MWB was caused by processes following the BB and not by the heat of galaxies as competing theories have asserted.

Nereid
2010-Aug-06, 09:25 AM
Sir Knots A Lot,



BB theory does allow for as much heat variation as has been observed in the MWB. I think the problem is more in the size of this and a view other voids. If the MWB is a remnant of the era following the BB as theory asserts, such large "holes" in it are difficult to explain. Since this void in Boots is thought to be as big as you quoted, the temperatures within this volume have also been observed to be less than its surroundings. This defines the hole. But the problem seems to be that this volume also contains relatively few observable galaxies. If these observations are valid and hold up in time, further theoretical explanations may be needed. Much Fewer galaxies producing lower temperatures would seem to make sense, but maybe not if the MWB was caused by processes following the BB and not by the heat of galaxies as competing theories have asserted.
Posts #18 and #20 in this thread already answered SKAL's question; the void isn't inconsistent with standard LCDM models, per the WMAP paper cited in post #20 (did you read that paper, fn?).

forrest noble
2010-Aug-06, 07:00 PM
Nereid,

Thanks for pointing out the link. I have now read the paper/link and think their argument has some validity concerning the possibility that such a void in the CMBR of that size, could exist by chance according to the standard model.

Regarding the void being coincidentally related to a sparsity of galaxies, which I think is the main point, their statements are hardly conclusive relating to what they consider possible evidence for the standard model. They said this (page 4, quoted snippits)


In theory, cold spots in the CMB can be produced by the integrated Sachs-Wolfe (ISW) effect as CMB photons traverse cosmic voids along the line of sight. If Cold Spot II (Boots) is due to a cosmic void, it would have profound implications because CDM does not produce voids of sufficient magnitude to explain it.
("Boots" added)

Mota et al. (2008) examined void formation in models where dark energy was allowed to cluster and concluded that voids of sufficient size to explain Cold Spot II were not readily produced.....
Cruz et al. (2006) reported that only 0.2% of their simulations had this type of feature.


These conclusions show that the the Boots void is difficult to explain as being separate from a large galactic void.


Since the original claims were only significant at the level, they can be plausibly biased by posterior data analysis choices: in this case, the angular scale and shape of the wavelet filter. Marginalizing over such choices will reduce statistical significance, but requires judgment in its execution. Had the anomaly been significant at the part per million level instead of a part per thousand (3 sigma significance), such marginalization would be moot: the feature (cold spot in Boots) would have been considered strong evidence for a possible failure of the model ( ΛCDM ).
(words in parenthesis and bold added)


Cruz et al. (2007a) suggested that the cold spot could be the signature of a topological defect in the form of a cosmic texture.

Here they are speculating concerning this void being a large possible anomaly in the "cosmic texture," which might explain away the problem.

Although there might be much to argue about in this and other related papers, in my opinion if theorists can generally prove beyond doubt, that this largest void in the microwave background is also not a general void of galaxies from our perspective, then the extent of the problem seems to be eliminated. If evidence in time proves to be to the contrary, however, I believe this will become a serious cosmological problem with the BB model.

forrest noble
2010-Aug-06, 09:13 PM
mmaayeh,


Cosmological Models with No Big Bang

Could they have validity?

To me the biggest problem facing the LCDM model and its BB variants, concerns observations of distant galaxies. The percentage of "old galaxies" and very large elliptical galaxies appears to be the same as the percentages of galaxies seen nearby. If these observations persist, at least the age of the universe according to the standard model, may need to be changed. Since such a change would be contrary to the expansion rate as presently indicated by a cosmological constant, further theoretical changes may also be needed.

If such observations persist over time, it would seemingly be difficult for explanations according to the standard model, to prevail. If, on the other hand, a cosmic dark ages were discovered in the future, then the standard model would gain additional supporting evidence that would be difficult to dispute.

http://esciencenews.com/articles/2010/05/12/ancient.galaxy.cluster.contains.modern.galaxies

http://curious.astro.cornell.edu/question.php?number=543

mmaayeh
2010-Aug-08, 10:54 AM
mmaayeh,



Could they have validity?

To me the biggest problem facing the LCDM model and its BB variants, concerns observations of distant galaxies. The percentage of "old galaxies" and very large elliptical galaxies appears to be the same as the percentages of galaxies seen nearby. If these observations persist, at least the age of the universe according to the standard model, may need to be changed. Since such a change would be contrary to the expansion rate as presently indicated by a cosmological constant, further theoretical changes may also be needed.

If such observations persist over time, it would seemingly be difficult for explanations according to the standard model, to prevail. If, on the other hand, a cosmic dark ages were discovered in the future, then the standard model would gain additional supporting evidence that would be difficult to dispute.

http://esciencenews.com/articles/2010/05/12/ancient.galaxy.cluster.contains.modern.galaxies

http://curious.astro.cornell.edu/question.php?number=543

Hi Forest Noble,

I am not sure I understand the concept. Why does the equal distribution of elliptical galaxies put into question the age of the universe and/or changes to the standard model?

nokton
2010-Aug-08, 04:44 PM
What's more, it was impossible to tell from the flimsy article what the core of the idea really was. What characteristics did the driving equations have? How many free parameters were invoked? It's always easy to get a model that explains why A, B, C and D happened, I can come up with such a model right now: "A happened, and then "exchanging" A and B caused B to happen, and then "exchanging" B and C led to C, and "exchanging" C and D led to D." The trick is to do it in a unifying way, a way that lets you get out much more than you put in. If one is going to relax one of the most important unifying concepts in all of science, the constancy of the constants, then one had better have a huge simplification or unification coming in someplace else, or the net benefit is negative. That may be why the link cites only un-refereed publications.

Ok Ken, let me have your thoughts on Petr Horavas new ideas on spacetime, ( causing much of a stir in the scientific community).
An idea that could come up with a unified theory that reconciles quantum mechanics and gravity.
And none of your double talk, no offence intended, just tell me you understand the above.
Nokton

forrest noble
2010-Aug-08, 07:47 PM
Hi also mmaayeh,

You live in Jordan, cool. The closest I came to Jordan was Egypt and Turkey.


Why does the equal distribution of elliptical galaxies put into question the age of the universe and/or changes to the standard model?

Large elliptical galaxies at the centers of galaxy clusters are thought to be much older than the spiral galaxies which surround it. Based upon the present star dating of the Milky Way this galaxy is at least 12 billion years old. Recently they have seen a distant cluster of galaxies that appears to be very similar to close-by clusters. The distance is thought to be about 11 billion light years away/ old. In this cluster there are believed to be elliptical galaxies. This cluster could only be 2-3 billion years old according to the Big Bang model, which I think is close to impossible. In the BB scenario the percentage of young looking galaxies should increase as we look back in time. This is not what is being observed. Bottom line is that the BB model cannot withstand continued observations of this type without drastic changes to it. If they instead find the theoretical dark ages of the BB model, then the model will survive. If not, I believe, the model will be replaced by a model more consistent with observations if such a model exists.

Cougar
2010-Aug-08, 11:16 PM
To me the biggest problem facing the LCDM model and its BB variants, concerns observations of distant galaxies. The percentage of "old galaxies" and very large elliptical galaxies appears to be the same as the percentages of galaxies seen nearby.

You got a reference for that? The two links you gave don't say this, and neither mentions ellipticals.

Cougar
2010-Aug-08, 11:47 PM
Hmm. Funny I hadn't seen your most recent post....


Recently they have seen a distant cluster of galaxies that appears to be very similar to close-by clusters. The distance is thought to be about 11 billion light years away/ old.

The article says, "Analyzing the faint light from seven galaxies near the center the cluster, they found that the galaxies had an average redshift of 1.62. "This means that we are seeing it the way it looked 9.6 billion years ago."

This is a single remarkable cluster that had formed about 4 billion years after the beginning of the expansion. I'm not so sure that's even unlikely. 4 billion years is a fair amount of time, and clustering would have been a lot "easier" back then because everything would have been closer together (by ~160%, if I've theorized correctly).



In the BB scenario the percentage of young looking galaxies should increase as we look back in time. This is not what is being observed.

Please take another look at the Hubble Ultra Deep Field. (http://hubblesite.org/newscenter/archive/releases/2004/07/) That is exactly what is being observed.



...If not, I believe, the [BB] model will be replaced...

I'm not sure how we got off on this. The OP asked about the viability of a variable speed of light model, not any lack of viability of the big bang model.

tusenfem
2010-Aug-09, 07:35 AM
Ok Ken, let me have your thoughts on Petr Horavas new ideas on spacetime, ( causing much of a stir in the scientific community).
An idea that could come up with a unified theory that reconciles quantum mechanics and gravity.
And none of your double talk, no offence intended, just tell me you understand the above.
Nokton


Let's keep to the OP, please. If you want to discuss Horavas's work, do it in your own thread.
And although "no offence" written. you better stop making such comments, discuss the topic and not the poster. Next time you might get an infraction.

mmaayeh
2010-Aug-09, 05:14 PM
I appreciate everyone's feedback. All in all, it was helpful and gave me some things to think about and research.

So, if I think I understand the following:


That the no big bang model is yet to be empirically confirmed as to match many observations currently made. Except that transforming space to time and mass to length does away with dark matter & dark energy.
The main weakness is to reconcile with the CMB observations where if you do not have a big bang then, why is there a CMB. Therefore, this needs to be reconciled or will indicate or lead to the invalidation of this concept.


Does this seem fair or I missed something?

Ken G
2010-Aug-09, 06:24 PM
I think I would add one even more fundamental objection, which came up briefly above but I think is pretty telling. I suspect that this "no big bang theory", achieved by monkeying with c, is not actually a different theory at all. I suspect it is nothing but a different coordinate choice, a way to make tick marks in space and time such that the "speed of light" is varying, and the time coordinate can be extended back infinitely far, "pushing off the table" the Big Bang. But the "table" is just coordinates, like how you never get to the wall if you put a tick mark at the half way point each step. They claim they can get acceleration, and no big bang, just by changing the coordinates, but they keep the ratios between the physical parameters, which is what actually controls the physical phenomena, the same-- expressly to avoid changing the physical phenomena. If they don't change the phenomena, it's not a new theory at all, it's just an overinterpretation of a different coordinate system.

In other words, they are caught between a rock and a hard place-- if they don't change the phenomena, it's not a new theory (and it does not avoid a big bang nor a need for DM and DE), and if it does change the phenomena, then they have a whole lot of work to do to show that atoms still work, nucleosynthesis still explains H/He, they can understand the presence of a CMB, and so forth. Since none of that work is done in the paper, the claims are either unsupported, or else there really isn't any different physics there at all. I suspect the latter is the case.

mmaayeh
2010-Aug-09, 06:41 PM
I think I would add one even more fundamental objection, which came up briefly above but I think is pretty telling. I suspect that this "no big bang theory", achieved by monkeying with c, is not actually a different theory at all. I suspect it is nothing but a different coordinate choice, a way to make tick marks in space and time such that the "speed of light" is varying, and the time coordinate can be extended back infinitely far, "pushing off the table" the Big Bang. But the "table" is just coordinates, like how you never get to the wall if you put a tick mark at the half way point each step. They claim they can get acceleration, and no big bang, just by changing the coordinates, but they keep the ratios between the physical parameters, which is what actually controls the physical phenomena, the same-- expressly to avoid changing the physical phenomena. If they don't change the phenomena, it's not a new theory at all, it's just an overinterpretation of a different coordinate system.

In other words, they are caught between a rock and a hard place-- if they don't change the phenomena, it's not a new theory (and it does not avoid a big bang nor a need for DM and DE), and if it does change the phenomena, then they have a whole lot of work to do to show that atoms still work, nucleosynthesis still explains H/He, they can understand the presence of a CMB, and so forth. Since none of that work is done in the paper, the claims are either unsupported, or else there really isn't any different physics there at all. I suspect the latter is the case.

Thank you, that was a very good addition.

Staticman
2010-Aug-09, 09:57 PM
Please take another look at the Hubble Ultra Deep Field. (http://hubblesite.org/newscenter/archive/releases/2004/07/) That is exactly what is being observed.


Perhaps it's me but I can't find where in the link they mention that "the percentage of young looking galaxies should increase as we look back in time" is exactly what is being observed. Would you mind pointing us to the specific quote?

Thanks

Nereid
2010-Aug-09, 10:11 PM
Perhaps it's me but I can't find where in the link they mention that "the percentage of young looking galaxies should increase as we look back in time" is exactly what is being observed. Would you mind pointing us to the specific quote?

Thanks
Same evidence: join the Hubble Zoo (http://www.galaxyzoo.org/), one of the Zooinverse projects. You'll get to classify some of the several hundred thousand galaxies imaged by the Hubble in the AEGIS, GEMS, and GOODS projects (the various Hubble Deep Fields are really tiny in comparison to the sky estate covered by these). You'll very quickly learn that galaxies at higher redshifts than those which SDSS imaged (and which the zooites classified so assiduously in Galaxy Zoo 1) look very different indeed!

slang
2010-Aug-09, 10:47 PM
Since this void in Boots [...]

Boötes (http://en.wikipedia.org/wiki/Bootes), right? Pronounced (IIRC) as boh-oh-tess (o as in arrow), not as footwear.

forrest noble
2010-Aug-10, 12:22 AM
Slang,


Since this void in Boots [...

Boötes, right? Pronounced (IIRC) as boh-oh-tess (o as in arrow), not as footwear.

Right! I didn't really know how to pronounce it properly (and misspelled it too), thanks.

My Bad :silenced:

forrest noble
2010-Aug-10, 01:27 AM
RE: distant galaxy clusters

Cougar, Yours is a good example. Here was the 11 Ga observation that I was referring to, and the other relating to very distant, old looking galaxies.

http://www.sciencedaily.com/releases/2010/05/100510131505.htm
http://news.softpedia.com/news/Fartherst-Galaxy-Cluster-Discovered-11-4-Billion-Light-Years-Away-82157.shtml

your quote:

I'm not sure how we got off on this. The OP asked about the viability of a variable speed of light model, not any lack of viability of the big bang model.

I was answering these questions by mmaayeh, which was based on a previous statement of mine which followed from the OP questions.


Cosmological Models with No Big Bang.................What is the viability of such a model?


Why does the equal distribution of elliptical galaxies put into question the age of the universe and/or changes to the standard model?

mmaayeh
2010-Aug-10, 10:47 AM
RE: distant galaxy clusters

Cougar, Yours is a good example. Here was the 11 Ga observation that I was referring to, and the other relating to very distant, old looking galaxies.

http://www.sciencedaily.com/releases/2010/05/100510131505.htm
http://news.softpedia.com/news/Fartherst-Galaxy-Cluster-Discovered-11-4-Billion-Light-Years-Away-82157.shtml

your quote:


I was answering these questions by mmaayeh, which was based on a previous statement of mine which followed from the OP questions.

Yes, the article from the sciencedaily.com indicates:

The group of roughly 60 galaxies, called CLG J02182-05102, is nearly 10 billion years old -- born just 4 billion years after the Big Bang. However, it's not the size nor the age of the cluster that amazes the team of researchers led by Dr. Casey Papovich, an assistant professor in the Texas A&M Department of Physics and Astronomy and member of the George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy. Rather, it's the surprisingly modern appearance of CLG J02182-05102 that has them baffled -- a huge, red collection of galaxies typical of only present-day galaxies.

So, could gravitational interactions due to a smaller universe force these galaxies to evolve quicker then now, say? This would still require a big bang and it would maintain the current age of the universe, no? Also, how much of a significance does the existence of Alpha-Lyman blobs found, where I believe galactic clusters and super clusters formed from? If these can be spotted then, does this mean the age of the universe is what has been observed 13.7 billion years? Can you help clarify?

Staticman
2010-Aug-10, 11:57 AM
Same evidence: join the Hubble Zoo (http://www.galaxyzoo.org/), one of the Zooinverse projects. You'll get to classify some of the several hundred thousand galaxies imaged by the Hubble in the AEGIS, GEMS, and GOODS projects (the various Hubble Deep Fields are really tiny in comparison to the sky estate covered by these). You'll very quickly learn that galaxies at higher redshifts than those which SDSS imaged (and which the zooites classified so assiduously in Galaxy Zoo 1) look very different indeed!

Thanks, Nereid, great site.
So you are saying that galaxies at hig redshifts are very different than those nearer in the SDSS. In what ways do they differ mainly? Does the percentage of young galaxies actually increase then? can you cite references where they quantify this?

Regards

Nereid
2010-Aug-10, 12:57 PM
RE: distant galaxy clusters

Cougar, Yours is a good example. Here was the 11 Ga observation that I was referring to, and the other relating to very distant, old looking galaxies.

http://www.sciencedaily.com/releases/2010/05/100510131505.htm
http://news.softpedia.com/news/Fartherst-Galaxy-Cluster-Discovered-11-4-Billion-Light-Years-Away-82157.shtml

[...]
I really, really wish long-time BAUTians would not use popsci sources in answering questions in this Q&A section, unless accompanied by reference to the related, published papers (if any), and a para or two explaining the shortcomings of the popsci source! :mad:

I'll later dig up those papers, and write some words on why these sorts of reports are, in this context, misleading.

While I do not know what the redshifts of the objects referred to are (deriving an age from a redshift is model dependent, and the model used is not specified), this recent preprint may well be relevant: A Massive Molecular Gas Reservoir in the z=5.3 Submillimeter Galaxy AzTEC-3 (http://arxiv.org/abs/1008.0389). Here we see a distant galaxy, located in a protocluster, with a great deal of gas, undergoing very rapid star formation, which could continue for ~30 Myr.

Quote from the last sentence of the preprint:

The discovery of a massive, metal-enriched gas reservoir in a SMG at the heart of a large z=5.3 protocluster considerably enhances our understanding of early massive galaxy formation, pushing back to a cosmic epoch where the Universe was less than 1/12 of its present age.

Nereid
2010-Aug-10, 01:01 PM
Thanks, Nereid, great site.
So you are saying that galaxies at hig redshifts are very different than those nearer in the SDSS.
Broadly speaking, yes.


In what ways do they differ mainly?
There are fewer ellipticals (and other early-type galaxies); many, many more irregulars; such spirals as there often look quite different (very clumpy); mergers and collisions seem far more common; ...


Does the percentage of young galaxies actually increase then?
Dramatically.


can you cite references where they quantify this?
Well, the Hubble Zoo team has not even hinted that they have enough data yet to start writing a paper (so, please, keep on classifying), but there have been some other papers (I'll post some links later).

Nereid
2010-Aug-10, 01:35 PM
RE: distant galaxy clusters

Cougar, Yours is a good example. Here was the 11 Ga observation that I was referring to, and the other relating to very distant, old looking galaxies.

http://news.softpedia.com/news/Farth...ay-82157.shtml

[...]
The relevant paper seems to be A Candidate Brightest Proto-Cluster Galaxy at z = 3.03 (http://arxiv.org/abs/0803.3808) (link is to the preprint abstract; it was later published in ApJ Letters); here is the abstract:

We report the discovery of a very bright (m_R = 22.2) Lyman break galaxy at z = 3.03 that appears to be a massive system in a late stage of merging. Deep imaging reveals multiple peaks in the brightness profile with angular separations of ~0.''8 (~25 h^-1 kpc comoving). In addition, high signal-to-noise ratio rest-frame UV spectroscopy shows evidence for ~5 components based on stellar photospheric and ISM absorption lines with a velocity dispersion of sigma ~460 km s^-1 for the three strongest components. Both the dynamics and high luminosity, as well as our analysis of a LCDM numerical simulation, suggest a very massive system with halo mass M ~ 10^13 M_solar. The simulation finds that all halos at z = 3 of this mass contain sub-halos in agreement with the properties of these observed components and that such systems typically evolve into M ~ 10^14 M_solar halos in groups and clusters by z = 0. This discovery provides a rare opportunity to study the properties and individual components of z ~ 3 systems that are likely to be the progenitors to brightest cluster galaxies.

Now compare this with fn's first comment, presumably based on the SP article (at least in part):

Large elliptical galaxies at the centers of galaxy clusters are thought to be much older than the spiral galaxies which surround it. Based upon the present star dating of the Milky Way this galaxy is at least 12 billion years old. Recently they have seen a distant cluster of galaxies that appears to be very similar to close-by clusters. The distance is thought to be about 11 billion light years away/ old. In this cluster there are believed to be elliptical galaxies. This cluster could only be 2-3 billion years old according to the Big Bang model, which I think is close to impossible.

Pretty clear that this is rather dramatically differs from what's in Cooke et al.'s actual paper!

Note, too, the SP article's first sentence: "LBG-2377 is a galaxy proto-cluster located 11.4 billion light years away from Earth - the most distant galaxies ever observed": regulars here know that this is pure nonsense. Perhaps even worse is the image that accompanies this SP article - it's of the Antennae galaxies, not LBG-2377.

Pretty good evidence in support of a conclusion that SP is not a reliable source.

Nereid
2010-Aug-10, 02:36 PM
RE: distant galaxy clusters

Cougar, Yours is a good example. Here was the 11 Ga observation that I was referring to, and the other relating to very distant, old looking galaxies.

http://www.sciencedaily.com/releases/2010/05/100510131505.htm
[...]
The source paper seems to be A Spitzer-Selected Galaxy Cluster at z=1.62 (http://arxiv.org/abs/1002.3158) (link is to arXiv abstract; the paper itself is - or soon will be - published in ApJ); here's the abstract:

We report the discovery of a galaxy cluster at z=1.62 located in the Spitzer Wide-Area Infrared Extragalactic survey XMM-LSS field. This structure was selected solely as an overdensity of galaxies with red Spitzer/IRAC colors, satisfying [3.6]-[4.5] > -0.1 AB mag. Photometric redshifts derived from Subaru XMM Deep Survey (BViz-bands), UKIRT Infrared Deep Survey-Ultra-Deep Survey (UKIDSS-UDS, JK-bands), and from the Spitzer Public UDS survey (3.6-8.0 micron) show that this cluster corresponds to a surface density of galaxies at z ~ 1.6 that is more than 20 sigma above the mean at this redshift. We obtained optical spectroscopic observations of galaxies in the cluster region using IMACS on the Magellan telescope. We measured redshifts for seven galaxies in the range z=1.62-1.63 within 2.8 arcmin (<1.4 Mpc) of the astrometric center of the cluster. A posteriori analysis of the XMM data in this field reveal a weak (4 sigma) detection in the [0.5-2 keV] band compatible with the expected thermal emission from such a cluster. The color-magnitude diagram of the galaxies in this cluster shows a prominent red-sequence, dominated by a population of red galaxies with (z-J) > 1.7 mag. The photometric redshift probability distributions for the red galaxies are strongly peaked at z=1.62, coincident with the spectroscopically confirmed galaxies. The rest-frame (U-B) color and scatter of galaxies on the red-sequence are consistent with a mean luminosity-weighted age of 1.2 +/- 0.1 Gyr, yielding a formation redshift z_f = 2.35 +/- 0.10, and corresponding to the last significant star-formation period in these galaxies.

While the abstract is, seemingly, quite different to what fn originally wrote (quoted in my last post), the Discussion section of the paper bears some resemblance to that comment (sans the personal opinions, which I think were totally uncalled for). However, Papovich et al. are far more tentative than fn, and the lead-in to the Discussion section concludes like this: "With our full sample, we will compare the properties of ClG J0218.3-0510 against other overdensities of galaxies at this redshift to determine how the galaxies in this object compare to other co–eval (proto–)clusters and to field galaxies."

Note that, once again, the popsci article begins with what regulars know to be nonsense: "Using NASA's Spitzer Space Telescope, a Texas A&M University-led team of astronomers has uncovered what may be the earliest, most distant cluster of galaxies ever detected"; what Papovich et al. actually said is "Although other candidates for high–redshift galaxy (proto–)clusters at z > 1.5 have been reported (e.g., Miley et al. 2004; Brodwin et al. 2007; McCarthy et al. 2007; Zirm et al. 2008; Eisenhardt et al. 2008; Andreon et al. 2009; Kurk et al. 2009; Chiaberge et al. 2010), this is the highest redshift, spectroscopically–confirmed cluster with a strong, well–defined red sequence"! Note too that SD got even the name of the object wrong!! :surprised (The acronym is ClG - capital C, lower case l, capital G - which stands for Cluster of Galaxies).

Some of Papovich et al.'s work was subsequently confirmed by Tanaka et al. The spectroscopically confirmed X-ray cluster at z=1.62 with a possible companion in the Subaru/XMM-Newton deep field (http://fr.arxiv.org/abs/1004.3606) (link is to arXiv abstract; the paper has been accepted, but is not yet published); here is the abstract:

We report on a confirmed galaxy cluster at z=1.62. We discovered two concentrations of galaxies at z~1.6 in the Subaru/XMM-Newton deep field based on deep multi-band photometric data. We made a near-IR spectroscopic follow-up observation of them and confirmed several massive galaxies at z=1.62. One of the two is associated with an extended X-ray emission at 4.5 sigma on a scale of 0'.5, which is typical of high-z clusters. The X-ray detection suggests that it is a gravitationally bound system. The other one shows a hint of an X-ray signal, but only at 1.5 sigma, and we obtained only one secure redshift at z=1.62. We are not yet sure if this is a collapsed system. The possible twins exhibit a clear red sequence at K<22 and seem to host relatively few number of faint red galaxies. Massive red galaxies are likely old galaxies -- they have colors consistent with the formation redshift of z_f=3 and a spectral fit of the brightest confirmed member yields an age of 1.8_{-0.2}^{+0.1} Gyr with a mass of 2.5_{-0.1}^{+0.2} x 10^11 M_solar. Our results show that it is feasible to detect clusters at z>1.5 in X-rays and also to perform detailed analysis of galaxies in them with the existing near-IR facilities on large telescopes.

Note that this directly contradicts fn's opinion ("This cluster could only be 2-3 billion years old according to the Big Bang model, which I think is close to impossible"):

"Massive red galaxies are likely old galaxies - they have colors consistent with the formation redshift of z_f=3 and a spectral fit of the brightest confirmed member yields an age of 1.8_{-0.2}^{+0.1} Gyr".

forrest noble
2010-Aug-10, 03:43 PM
Neried,

I agree there is a difference of opinion concerning what's being observed concerning distant galaxies. I don't think we are going to have to wait too long however since continuously more distant galaxies are being discovered and we will have years to analyze those distant galaxies already discovered to make maybe better conclusions concerning their ages and constituents. Here are some funny related quotes:

“It is the theory that decides what can be observed"
“If the facts don't fit the theory, change the facts.” Albert Einstein

“Our knowledge can only be finite, while our ignorance must necessarily be infinite.” Karl Popper"

“How empty is theory in the presence of fact” Mark Twain

“Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve” Karl Popper

forrest noble
2010-Aug-10, 04:33 PM
mmaayeh,


So, could gravitational interactions due to a smaller universe force these galaxies to evolve quicker then now, say?

According to the BB model the universe was much smaller in the times of those distant galaxies now being observed. Realize that the universe according to this model has expanded many fold since that era so accordingly the theory asserts that expansion has prevailed over gravity. According to the BB model there will need to be an explanation why some galaxy clusters appear to be old already in these supposedly early times, your conjecture may be one of the ideas considered.

If these observations persist and no acceptable explanations for the largest oldest appearing galaxies is realized then theory may have to change.


This would still require a big bang and it would maintain the current age of the universe, no?

I think one should realize that observation trumps theory. But theory interprets observations, not the reverse. Eventually observation wins out so it is presently just a matter of conjecture if present theory can survive without change which I think will always be the case regardless of the theory.


Also, how much of a significance does the existence of Alpha-Lyman blobs found, where I believe galactic clusters and super clusters formed from?

Alpha-Lyman blobs evolving into galaxies or clusters is one of the popular hypothesis being considered. Another possibility is that these objects are so distant that our observations may be distorted and these objects are instead different than what they presently appear to be. Since local, young newly forming galaxies have been found, there seemingly could be Alpha-Lyman type blobs a little bit closer to study than those presently observed. Only the most distant have been observed so far, to my knowledge.


If these can be spotted then, does this mean the age of the universe is what has been observed 13.7 billion years? Can you help clarify?

The 13.7 billion year age of the universe is directly calculated from what is presently believed to have been the average expansion rate of the universe since its inception. If this rate is changed by theorists based upon contradictory observations, not only the theoretical age of the universe could change, but the theory itself could change or be replaced -- which could always happen no matter what theory we are talking about. No theory is sacrosanct.

Cougar
2010-Aug-10, 04:36 PM
"Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve" -- Karl Popper

Popper just seems to be popping off with this one, with which I thoroughly disagree. Observations constrain theories. A theory may never be "the last word," but some theories get very constrained, which indeed removes other speculative possibilities.

Cougar
2010-Aug-10, 04:51 PM
Perhaps it's me but I can't find where in the link they mention that "the percentage of young looking galaxies should increase as we look back in time"...

Oh, I meant for the image itself to demonstrate that. There are a few larger, "normal looking" galaxies in the foreground, but there are many, many small, irregular-shaped, even "tadpole-shaped" galaxies (http://iopscience.iop.org/0004-637X/639/2/724) in the far distance. There were apparently lots of small galaxy interactions going on in the early universe, building up larger galaxies and ellipticals.

forrest noble
2010-Aug-10, 04:58 PM
Cougar,


Popper just seems to be popping off with this one, with which I thoroughly disagree. Observations constrain theories. A theory may never be "the last word," but some theories get very constrained, which indeed removes other speculative possibilities.

Sounds good to me. My idea was that all possibilities should never be totally out of mind.

Here is another "funny" related quote:

“You should never bet against anything in science at odds of more than about 10-12 to 1”. -- Ernest Rutherford

Staticman
2010-Aug-10, 05:16 PM
Broadly speaking, yes.


There are fewer ellipticals (and other early-type galaxies); many, many more irregulars; such spirals as there often look quite different (very clumpy); mergers and collisions seem far more common; ...


Dramatically.


And I guess you discard the possibilty that this may be due (at least in part) to a bias in the sample of distant galaxies that we are able to see , like being able to see the most luminous sources("collisions seem far more common") rather than the faint or other types of selection bias (model dependent, etc). I,m deducing that you discard these possibilities based on your apparently definite assertions and the fact that you must know a lot about these things. But since I am new to the astrophysics field, these are questions that pop up, probably due to my ignorance.

Nereid
2010-Aug-10, 05:25 PM
And I guess you discard the possibilty that this may be due (at least in part) to a bias in the sample of distant galaxies that we are able to see , like being able to see the most luminous sources("collisions seem far more common") rather than the faint or other types of selection bias (model dependent, etc). I,m deducing that you discard these possibilities based on your apparently definite assertions and the fact that you must know a lot about these things. But since I am new to the astrophysics field, these are questions that pop up, probably due to my ignorance.
These kinds of selection effects - and many more besides - are well-known to astronomers (and have been for well over a century).

Sometimes they are hard to even quantify, much less account for; in this case the results are pretty robust, out to at least z ~1 (that's what surveys are carefully designed to do).

Staticman
2010-Aug-10, 05:32 PM
Oh, I meant for the image itself to demonstrate that. There are a few larger, "normal looking" galaxies in the foreground, but there are many, many small, irregular-shaped, even "tadpole-shaped" galaxies (http://iopscience.iop.org/0004-637X/639/2/724) in the far distance. There were apparently lots of small galaxy interactions going on in the early universe, building up larger galaxies and ellipticals.

Ah, Ok, you meant judging by the picture. I guess my eyes are not trained enough to draw conclusions from a photograph, one question though, are all the luminous sources visible in the picture from approximately the same distance wrt us? If not, it would appear to me a bit hard to tell small galaxies from more distant ones, but since I'm no astronomer perhaps this question is just nonsense.

Regards

Nereid
2010-Aug-10, 05:33 PM
Neried,

I agree there is a difference of opinion concerning what's being observed concerning distant galaxies. I don't think we are going to have to wait too long however since continuously more distant galaxies are being discovered and we will have years to analyze those distant galaxies already discovered to make maybe better conclusions concerning their ages and constituents.
The point is that BAUT's Q&A section is not the place to be posting one's personal opinions - we need to stick to the actual science.

Further, one of the things we - long-time BAUTians - should be doing is providing better answers than the often flawed ones found in popsci articles.

And, FWIW, I strongly disagree with your opinions; AFAIK, the amazingly rapid increase in detailed observations of high-z objects has, overwhelmingly, provided support for LCDM cosmological models.

Perhaps the biggest unknown, today, in extragalactic astrophysics is galaxy formation and evolution; it'll take years, perhaps decades, for this sub-field to begin to reach its first good conclusions ...


Here are some funny related quotes:

“It is the theory that decides what can be observed"
“If the facts don't fit the theory, change the facts.” Albert Einstein

“Our knowledge can only be finite, while our ignorance must necessarily be infinite.” Karl Popper"

“How empty is theory in the presence of fact” Mark Twain

“Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve” Karl Popper
All nice, but surely not relevant in threads in the Q&A section?

Staticman
2010-Aug-10, 05:49 PM
Sometimes they are hard to even quantify, much less account for; in this case the results are pretty robust, out to at least z ~1 (that's what surveys are carefully designed to do).

What results? the Hubble zoo? the deep field images? can you provide me with a link to some of these surveys? The quotes of papers you provided in post 48 (about the old galaxy cluster at z=1.62) are relevant in any way?

Thanks for answering lots of questions

Thanks

Nereid
2010-Aug-10, 05:57 PM
What results? the Hubble zoo? the deep field images? can you provide me with a link to some of these surveys?
I'm working on it; please be patient.


The quotes of papers you provided in post 48 (about the old galaxy cluster at z=1.62) are relevant in any way?
Only indirectly.

forrest noble
2010-Aug-10, 06:21 PM
Nereid,


The point is that BAUT's Q&A section is not the place to be posting one's personal opinions

I'm not talking about my personal opinions, I'm talking about a difference of theoretical opinion. To put it a different way, theorists and observationalists sometimes differ concerning what is being observed.

Nereid
2010-Aug-10, 07:36 PM
Nereid,



I'm no talking about my personal opinions, I'm talking about a difference of theoretical opinion.
"This cluster could only be 2-3 billion years old according to the Big Bang model, which I think is close to impossible" - seems like a personal opinion to me.


To put it a different way, theorists/ observationalists differ concerning what is being observed.
They do? Can you provide any evidence of this, with specific reference to published papers (not popsci articles)?

Nereid
2010-Aug-10, 09:54 PM
Nereid,

Concerning theorists / observationalists differences of opinions

They do? Can you provide any evidence of this, with specific reference to published papers (not popsci articles)?

A solution to this disagreement between observations and theory is to ... All material on this site has been created and updated between 1997-2010. ...

What is the source of this quote?



http://www.google.com/#hl=en&q=obser...31cdd35a4d476d

Looks like a google search; not exactly what I was looking for.



http://www.pnas.org/content/95/1/22.full

This is dated 1998!!!

Rather a lot has happened in extragalactic astrophysics in the ensuring 12 years ...

forrest noble
2010-Aug-10, 10:05 PM
Just showing that differences of theory exist; and observation does not always match theory.


What does this mean in terms of cosmological theories? Analytic theories allow the relationships of luminosity, temperature, size and mass to be determined ......................
and the properties of clusters can be used to place strong limits on cosmological theories of structure formation and evolution.


Most theories of how the Universe evolved make a prediction for the mass function of galaxy clusters. However, the mass function is only poorly determined by observations. This is especially true at high redshifts........


A solution to this disagreement between observations and theory is to invoke an epoch of 'pre-heating' in the clusters history..........

http://imagine.gsfc.nasa.gov/docs/features/topics/clusters_group/evolution.html

Cougar
2010-Aug-10, 10:09 PM
...are all the luminous sources visible in the picture from approximately the same distance wrt us?

Of course not. We're looking out into 3-dimensional space


If not, it would appear to me a bit hard to tell small galaxies from more distant ones, but since I'm no astronomer perhaps this question is just nonsense.

Well, I'm not saying that after a brief look at the HUDF one is able to conclude numerous profound facts about early structure formation in the universe. But just in general, one might easily get at least a qualitative sense of galactic evolution. If one takes the time to analyze the HUDF, you might end up with something like:


GALAXY MERGERS AT z >1 IN THE HUDF:
EVIDENCE FOR A PEAK IN THE MAJOR MERGER RATE OF MASSIVE GALAXIES. [pdf] (http://iopscience.iop.org/0004-637X/678/2/751/pdf/0004-637X_678_2_751.pdf)

astromark
2010-Aug-10, 10:53 PM
By analysis of the information available. Conclusions have been arrived at.

Nothing I have read here changes that., or are those notions of theory being challenged.

It does not work. Its ATM stuff which I find hard to understand.

How can a Universe which is expanding ever faster not have been at some point past not have been a single point source.

That IS the only explanation that fits the information available... Where is this wrong ?

We have called it the big bang... We do not like that much but it fits the scene imagined.

Not withstanding that if a time line is traced back... but as the density of mater exceeds the state of mater

as we understand it and the rules of physics go out the window and time itself slows to a crawl...

from a observer in the frame of reference...

as there is no start point achievable at that point in time space when a single point is reached time would have stopped...

and if time has stopped then no progress past that moment can ever be possible... or that moment can never be reached.

and if that is what you are attempting to say why did we get so lost.. ?

I do hope you can find the understanding required to follow this rant... and I welcome further comment. @39deg South Mark.

Staticman
2010-Aug-10, 11:00 PM
Well, I'm not saying that after a brief look at the HUDF one is able to conclude numerous profound facts about early structure formation in the universe. But just in general, one might easily get at least a qualitative sense of galactic evolution.


Yes, but probably one might get a wrong impression just as easily, even easier if one has some strong prejudice about how galactic evolution should look like. Probably that is why there is little consensus among observationists.



If one takes the time to analyze the HUDF, you might end up with something like:


GALAXY MERGERS AT z >1 IN THE HUDF:
EVIDENCE FOR A PEAK IN THE MAJOR MERGER RATE OF MASSIVE GALAXIES. [pdf] (http://iopscience.iop.org/0004-637X/678/2/751/pdf/0004-637X_678_2_751.pdf)

Would you mind explaining what a peak in merger rate at such a relatively low redshift means?

It is acknowledged in the paper that "our observed merger rate dramatically differs from what is found by numerous authors" and therefore seems to be a not very representative interpretation of current data about galactic evolution.

Nereid
2010-Aug-11, 12:01 AM
Galaxy morphology evolution, a selection of recent papers (links are to arXiv preprints):

How was the Hubble sequence 6 Gyrs ago? (http://arxiv.org/abs/0906.2805)

Galaxy morphology in the LambdaCDM cosmology (http://arxiv.org/abs/0806.4189) - a 'theoretical model' paper

The Hubble sequence: just a vestige of merger events? (http://arxiv.org/abs/0903.3962)

Tracing Galaxy Assembly: Tadpole Galaxies in the Hubble Ultra Deep Field (http://arxiv.org/abs/astro-ph/0511423)

The Assembly of Diversity in the Morphologies and Stellar Populations of High-Redshift Galaxies (http://arxiv.org/abs/astro-ph/0501088)

Galaxy Morphologies in the Hubble Ultra Deep Field: Dominance of Linear Structures at the Detection Limit (http://arxiv.org/abs/astro-ph/0508216)

The Morphological Demographics of galaxies in the ACS Hubble Ultra Deep Parallel Fields (http://arxiv.org/abs/astro-ph/0509759)

Morphology of Spitzer 24um-Detected Galaxies in the UDF: the Links between the Star Formation and Galaxy Morphology (http://arxiv.org/abs/astro-ph/0603453)

The Hubble Ultra Deep Field (http://arxiv.org/abs/astro-ph/0607632) - snippet: "Visual inspection of the images shows few if any galaxies at redshifts greater than ~4 that resemble present-day spiral or elliptical galaxies. The image reinforces the conclusion from the original Hubble Deep Field that galaxies evolved strongly during the first few billion years in the infancy of the universe."

Rapid formation of exponential disks and bulges at high redshift from the dynamical evolution of clump cluster and chain galaxies (http://arxiv.org/abs/0708.0306) - another 'theoretical model' paper

The Structures of Distant Galaxies I: Galaxy Structures and the Merger Rate to z~3 in the Hubble Ultra-Deep Field (http://arxiv.org/abs/0711.2333)

The Structures of Distant Galaxies - II: Diverse Galaxy Structures and Local Environments at z = 4-6; Implications for Early Galaxy Assembly (http://arxiv.org/abs/0904.4250)

The Structures of Distant Galaxies - III: The Merger History of over 20,000 Massive Galaxies at z < 1.2 (http://arxiv.org/abs/0812.3237)

The Structures of Distant Galaxies - IV: A New Empirical Measurement of the Time-Scale for Galaxy Mergers - Implications for the Merger History (http://arxiv.org/abs/0906.4704)

I estimate that there are over a thousand good, recent, relevant papers published on this topic within extragalactic astronomy and astrophysics; to say that it's a 'hot research topic' would be an understatement.

Cougar
2010-Aug-11, 12:39 AM
Would you mind explaining what a peak in merger rate at such a relatively low redshift means?

Here, by "relatively low redshift," these authors mean to say that "the peak in our merger number density is consistent with the peak in the cosmic star formation rate density at 1<z<1.5." Using standard constants, that's between 4.3 and 6 billion years after the big bang.


It is acknowledged in the paper that "our observed merger rate dramatically differs from what is found by numerous authors" and therefore seems to be a not very representative interpretation of current data about galactic evolution.

On the other hand, the paper states:






For low to moderate redshifts (z<1), there have been numerous
measurements of the galaxy pair fraction. While many
studies disagree on the precise values of the pair fraction, they
generally agree that the fraction rises from ~2% at z= around 0 to
~15% at z= about 1, as a power law in (1+z). Where our observations
overlap with previous work, we find a merger fraction of
15% +/- 5% at z= about 1,which is in good agreement with published
values (e.g., Le Fe`vre et al. 2000; Lin et al. 2004; Kartaltepe et al.
2007).

Note that the authors' observed merger rate that "dramatically differs" from other authors is only where z>1. But then...






At higher redshift (z>1), there are no other studies of merging
using the pair fraction, due to the difficulty in acquiring sufficiently
deep redshift data sets.

So the other "numerous authors" were using different methods to estimate this apparently elusive progression.

Why is the prevalence of galaxy mergers important?






Since galaxy merging has been linked to numerous astrophysical processes, including star formation and the fueling of supermassive black holes (SMBHs), which trigger active galactic nuclei (AGNs), the merger history of galaxies is critical for a complete understanding of galaxy evolution.

Staticman
2010-Aug-11, 11:20 AM
Thanks Nereid and Cougar

JAXAi
2010-Dec-31, 04:35 PM
This may sound really like a dumb question, but one thing after reading this paper made me ask was this (and realize I can read none of the math in the paper...way over my head):

If I am getting this right one of the things that this theory states is that light`s constant is not constant in this model. Not 186,000 Kmps? To quote the introduction of the article:
i The speed of light and the gravitational “constant” are not constant, but vary
with the evolution of the universe

Not I may be reading this way wrong (and forgive me if I am) but does this mean it is possible that the light from distant stars is getting here (relatively) faster than if calculated at 186,000 Kmps? Does this also open up the door of travelling to the stars (while never actually faster than light, as you can not do that) but at a faster rate than currently measured? In other words we say that Gliese 581 is 20.2 light years from here, but that is assuming that c is constant. Which according to this it may not be.

I lay this question out to the wolves to be shredded I imagine, but I had to ask.

tommac
2010-Dec-31, 05:01 PM
arent there equally crazy assumptions in the mainstream theories? In fact even for mainstream dont we back into the science?




These models may actually do what they claim, but the variability of these physical constants, on which the models are based, appear to be in gross conflict with repeated and various independent observations. Such conflict is not normally a good foundation for a proposed model.

Grey
2011-Jan-01, 05:50 PM
arent there equally crazy assumptions in the mainstream theories? In fact even for mainstream dont we back into the science?I don't think so. What "crazy" assumptions are you thinking of? What do you mean by "back into the science"?