Redshift z

[modest]

Yup, that sure is counter intuitive.

 

The article does say this though right after the sentence you quote: "However there are no objects in the Universe which have a fixed physical size and exist across a wide range of distances, so in practice this counter-intuitive behaviour is not observed."

 

If indeed this effect is not observed it is entirely based on an idea, i.e., it is expected by a theory.

 

Intuitively, then, the next sentence should read: 'Spatial curvature may either increase or decrease the angular-diameter distance, with a spherical geometry focusing light rays and making objects appear smaller, and a hyperbolic geometry having the opposite effect" (making objects appear larger).

 

I don't think the sentence should read like that. The wording in the paper is a bit odd there, but I think it should be understood closer to "not directly observed (because there are no objects of fixed size)" and certainly should not be understood as "not expected to be observed".

 

We should expect all objects to appear smaller in a spatially hyperbolic universe than they would otherwise appear in an Euclidean universe. This is easiest (I think) to see in the following diagram:

 

 

The observer is measuring an angle with the yellow lines. On all three manifolds the observer has measured out the same angle with the yellow lines—we'll say 5 degrees. The yellow lines make a 5º triangle. In the hyperbolic universe the white object is much smaller than that 5º. In the flat universe it is bigger and in the positively curved universe it is larger than the 5º.

 

Negative spatial curvature definitely works to make objects appear smaller in the sky. Expansion does the opposite and makes objects appear larger. Neither can be directly observed from a practical standpoint, because we would need to know the intrinsic size of the objects in order to compare them to the apparent size. The intrinsic size of galaxies, for example, can be estimated but it leaves a rather large error margin.

 

The best available data does show what we would expect in an expanding universe:

 

 

The error bars on the data are large, but it is good enough to show a general trend toward an increase in angular diameter with distance over the euclidean line. If our universe were static and spatially hyperbolic then we would expect the data to match a line that curves downward.

 

Observations of angular diameter therefore support expansion and wouldn't agree well with negative spatial curvature.

 

The luminosity distance, on the other hand (the distance objects appear to have based on their observed brightness) is observed empirically. This shows a strong reduction in the surface brightness of distant objects; redshift "reduces the overall luminosity of an object." That would seem to be consistent with hyperbolic geometry, where clocks would appear to tick more slowly with distance, and objects would be further away than expected in a Euclidean universe (i.e., they appear further than their true distance).

 

What we observe, in our universe, are objects which are closer than we would expect in a static euclidean universe when the metric is angular diameter distance and objects which are further than we would expect in a static euclidean universe when the metric is luminosity distance.

 

It looks like my ducks were lined up after all: Perhaps diagram A was the correct answer (meaning modest and quantumtopology would have been incorrect from the get-go, and coldcreation right).

 

 

Modest, what gives?

 

I think QT is right that the issue is between spatial curvature and spacetime curvature.

 

If angular diameters are not observed (as stated in your link) then what does the observational evidence show: would distances appear further or closer than they actually are? I think your answer will be that is depends on the model. But that means that observational bias is unavoidable, does it not? Everything hinges on the meaning of redshift z in a given model. Depending on its meaning (and depending on the sign of curvature) objects can be further or closer than the Euclidean (actual, proper, or real) distance.

 

Certainly the statement "distances appear further or closer than they actually are" would depend on the model and the measure of distance being used. How would we know how far objects really are? What we are doing is comparing two different measures of distance and comparing that ratio to what different models would predict.

 

It would be a mistake to think that supernova appear further than they really are. What happened was that supernova appeared further using luminosity distance than a previous assumption predicted.

 

The question is, if the universe is static and curved (assuming we don't know yet the sign of curvature), where redshift is due to the propagation of EMR along geodesics, then how can we know whether the curvature is hyperbolic of spherical, based on observations (if not by time dilation based on rise times of standard candles)?

 

Saying "static and curved" is problematic in a GR universe because any universe with matter in it that has curved spacetime will not be "static" in any sense of the word.

 

If we are assuming the universe is static and we're talking about spatial curvature then the method in this post will reveal the curvature.

 

 

Q

No. I disagree. For example it was found that the original Einstein universe, with or without lambda, was unstable.

 

Can you give me a reference on this, where it states that GR equations without lambda give an unstable universe? see my link

 

I agree with CC. While the introduction of Lambda was meant to create stability, it ultimately failed. As wiki says:

Moreover, it is unstable in the sense that any change in either the value of the cosmological constant, the matter density, or the spatial curvature will result in a universe that either expands and accelerates forever or re-collapses to a big crunch.

Static universe - Wikipedia, the free encyclopedia

And:

The limiting case for an expanding, positively curved universe is the loitering universe, which is shown by the curved green and red lines. Loitering universes reach a point with H = 0 and also zero acceleration, known as an Einstein solution (which lies at infinity on this graph because the critical density is zero). Along the green line the Einstein point is in the future, while it is in the past along the red line. At the Einstein point the repulsive negative pressure from the cosmological constant exactly balances the gravitational attraction of density:

 

rho_m = 2 rho_Lambda

 

This is a delicate and unstable balance.

If the density is slightly too high, the universe will collapse from the Einstein point, following the green line down to a big crunch at the Einstein-de Sitter point. If the density is too low, the expansion takes off and the universe follows the red line to the de Sitter point of total domination by the Cosmological constant.

Solving the Friedman Equation

 

Loitering universes are never stable.

 

~modest

[quantumtopology]

I agree with CC. While the introduction of Lambda was meant to create stability, it ultimately failed. As wiki says:

Static universe - Wikipedia, the free encyclopedia

And:

Solving the Friedman Equation

 

Loitering universes are never stable.

 

These links deal with Einstein universe. I am talking about the solution without lambda.

Once again you are missing my point. In the link I posted and that you know well, the solution Einstein tried at first and rejected because it had hyperbolic infinite space, it was equivalent to Minkowski spacetime, Minkowski spacetime cannot collapse or expand because it's empty and has no lambda, this last feature is what distinguishes it from de Sitter universe wich is empty but has lambda. We've gone thru this several times, you yourself have shown it to me several times in the de sitter effect thread.You are disagreeing with your own words:

 

Quoted from Modest, post 14, de sitter effect and cosmology history thread

"There should be three static solutions. For ease of readability let's use de Sitter's original shorthand:

 

Model A: Einstein's spherical universe with matter content and cosmological constant

Model B: De sitter's hyperbolic universe with no matter content and cosmological constant

Model C: Special relativistic Minkowski spacetime (eg the Milne model) with no matter content and no cosmological constant.

 

Models A and B arise from the modified field equations (with Lambda) and model C comes from the original field equations without Lambda. Both with and without the cosmological constant, these are the only three static solutions." end quote

 

Regards

[modest]

Minkowski spacetime cannot collapse or expand because it's empty

 

I didn't realize that was what you were talking about.

 

Yes, rho=0 is trivially static. Our universe has matter which rules out that possibility.

 

~modest

[quantumtopology]

The best available data does show what we would expect in an expanding universe:

 

 

The error bars on the data are large, but it is good enough to show a general trend toward an increase in angular diameter with distance over the euclidean line. If our universe were static and spatially hyperbolic then we would expect the data to match a line that curves downward.

 

Observations of angular diameter therefore support expansion and wouldn't agree well with negative spatial curvature.

 

Certainly that is not the best available data (it's from an article of 1998 based in very few observations)

Here is an update from 2010, I think is worth a look, not only deals with angular size (I still think this is not very reliable)but the Tolman test and a few other things.It's published in the International Journal of Modern Physics and it's full of technical details.

 

[1002.0525] Angular size test on the expansion of the Universe

 

 

Regards

 

Qtop

 

PS: CC, how is that explanation 2 going?

[coldcreation]

Certainly that is not the best available data (it's from an article of 1998 based in very few observations)

Here is an update from 2010, I think is worth a look, not only deals with angular size (I still think this is not very reliable)but the Tolman test and a few other things.It's published in the International Journal of Modern Physics and it's full of technical details.

 

[1002.0525] Angular size test on the expansion of the Universe

 

PS: CC, how is that explanation 2 going?

 

Hey Qtop, thanks for the link.

 

I enjoyed the conclusion:

 

It would be an irony of fate that, after all the complex solutions pursued by cosmologists for the last century, we had to come back to simple scenarios such as a Euclidean static Universe without expansion. None the less, we cannot at present defend any of these simple models apart from the standard one because this would require other analyses. The conclusion of this paper is just that the data on angular size vs. redshift present some conflict with the standard model, and that they are in accordance with a very simple phenomenological extrapolation of the Hubble relation that might ultimately be linked to a static model of the universe.

 

Though I haven't read the work yet, it is interesting that they arrive at a Euclidean static universe.

 

A perfect example to demonstrate the situation would be to imagine three sets of train tracks extending to infinity. One of them in a spherical universe with constant positive curvature, one in a Euclidean universe, and the other in a hyperbolic universe with constant negative curvature. What would you see? What would be the difference between the three images?

 

With regard to Explanation 2: It has certainly been more work and research than I had planned or expected. Instead of a simple post it is turning into a book.:soccerb: Last night, for example, I was working until 5 AM, on some illustrations (woke up at 8 AM).

 

For easy viewing I have separated the sections into an Abstract, Introduction, and other specified topics, with a Conclusion at the end. I will likely have to post it in several installments.

 

The result so far is consistent with expectations, i.e, I have found no evidence, yet, that disproves of falsifies the underlying hypothesis about redshift z and stability of the cosmos. The claim that a static universe is incompatible with general relativity would appear to be erroneous, surprisingly enough.

 

Another surprise, resulting from the investigation (not at all expected) is the compatibility with Newtonian theory (related not to redshift z, but global stability).

 

I have though left open the possibility that the global geometry of the universe could either be spherical or hyperbolic, pending a full-blown model and observational confirmation, if that the latter is not already available in the form of data.

 

Time-wise it looks like a few more days will be required.

 

 

 

PS. For what reason did you bring up the issue of Minkowski space (time) above? Why do you emphasize the distinction between 3-space and a four-dimensional continuum within the context of this thread?

 

 

Regards,

 

CC

[quantumtopology]

Hey Qtop, thanks for the link.

 

I enjoyed the conclusion:

Though I haven't read the work yet, it is interesting that they arrive at a Euclidean static universe. Despite my being a proponent for a non-Euclidean stationary universe, I arrive at the same conclusion (albeit perhaps for different reasons).

 

Hi, CC.

Let's see, they don't arrive at a Euclidean static solution, I'd rather think they use it as a simple model, since they are not specifically considering or focusing on a k=-1 space. I think they concentrate in the fact that the facts don't support an expanding scenario without introducing really strange assumptions about galactic evolution.

 

 

A perfect example to demonstrate the situation would be to imagine three sets of train tracks extending to infinity. One of them in a spherical universe with constant positive curvature, one in a Euclidean universe, and the other in a hyperbolic universe with constant negative curvature. What would you see? What would be the difference between the three images?

Obviously the track would remain parallel in the euclidean case and diverge or converge in the hyperbolic and spheric cases respectively.

With regard to Explanation 2: It has certainly been more work and research than I had planned or expected. Instead of a simple post it is turning into a book.:soccerb: Last night, for example, I was working until 5 AM, on some illustrations (woke up at 8 AM).

 

For easy viewing I have separated the sections into an Abstract, Introduction, and other specified topics, with a Conclusion at the end. I will likely have to post it in several installments.

Hmm... CC, I (and I think not only happens to me) have a hard time with long textbook-like posts, I'd suggest you to keep them short, outlining your central points as much as you can, and if there is need , we may enter in details afterwards.

I'm really glad you might be getting maerial for a book though. Keep it up!

The result so far is consistent with expectations, i.e, I have found no evidence, yet, that disproves of falsifies the claim that a static universe is not compatible with general relativity: Quite the contrary, surprisingly enough. Another surprise, resulting from the investigation (not at all expected) is the compatibility with Newtonian theory (related not to redshift z, but global stability).

You haven't told me but you think of the link I posted.

 

I have though left open the possibility that the global geometry of the universe could either be spherical or hyperbolic, pending a full-blown model and observational confirmation, if that the latter is not already available in the form of data.

Time-wise it looks like a few more days will be required.

 

Honestly, I find the question of the global shape of the universe or global geometry way beyond my capacity, and too much open for speculation.

 

PS. For what reason did you bring up the issue of Minkowski space (time) above? Why do you emphasize the distinction between 3-space and a four-dimensional continuum within the context of this thread?

 

I just think it's easier to separate the spacelike part of the manifold in order to treat the subject of cosmology, and also what you described about isometric gravity at infinity leads to Minkowski spacetime.

But the main reason is I never know when you talk about universes geometries if you are referring to 3D space or 4D spacetime, you might try to specify it onlater posts.

 

Regards

Qtop

[modest]

The best available data does show what we would expect in an expanding universe:

 

 

Certainly that is not the best available data (it's from an article of 1998 based in very few observations)

 

I can only assume that you're looking at the 18 data points and thinking that it corresponds to 18 observations. I know you have looked at the paper before:

 

The “angular size - redshift” relation for compact radio structures in quasars and radio galaxies

 

You might recall that the 18 data points are bins each containing 18-19 objects. The sample size is 330 you can see from fig. 4 and 5. The sample size in the paper you most recently linked, "Angular size test on the expansion of the Universe", is 393.

 

The 1998 data is VLBI and not out of date.

 

Here is an update from 2010...[1002.0525] Angular size test on the expansion of the Universe

 

It is not an update. The '98 paper is looking at compact radio sources and the 2010 paper at near-infrared galaxies. While they both give an angular size-redshift relationship they really are worlds apart. Because galaxies evolve and merge using them as a standard meter stick is problematic (we must assume we know how big they really were). Ultra compact radio sources have their own problems, but I would consider it the better method of looking at angular size-redshift, and certainly less open to interpretations and assumptions.

 

~modest

[quantumtopology]

I can only assume that you're looking at the 18 data points and thinking that it corresponds to 18 observations. I know you have looked at the paper before:

You might recall that the 18 data points are bins each containing 18-19 objects. The sample size is 330 you can see from fig. 4 and 5. The sample size in the paper you most recently linked, "Angular size test on the expansion of the Universe", is 393.

No need to assume that. Just assume I meant "based in vey fewer observations" as in 330 is less than 393. (english is not my first language)

 

The 1998 data is VLBI and not out of date.

VLBI? what's that?

 

 

Ultra compact radio sources have their own problems, but I would consider it the better method of looking at angular size-redshift, and certainly less open to interpretations and assumptions.

That is your opinion, not a fact. Others might opine otherwise.

From the paper:

"Comparison with angular size test for ultra-compact radio sources

Compact radio sources have been used by several authors to carry out the angular

size test because these sources were thought to be free of evolutionary effects. However,

the different results obtained with these sources has raised the suspicion that they may not be such good standard rods. Apparently, these rods are somewhat flexible. For example, Kellermann claimed that the angular size test for these sources fitted Einstein–de Sitter expectations very well, when Einstein–de Sitter was the fashionable model. Jackson & Dodgson claimed the opposite: that it was not compatible with Einstein–de Sitter, and that, given that m = 0.2, the best fit for the cosmological constant term was = −3.0; flat cosmological models were excluded with > 70% C.L. Jackson, in the era of the concordance model as the fashionable cosmology, again carried out the analysis of the same data used by Jackson & Dodgson, doing some new corrections due to selection effects and bias, and they get the best fit for m = 0.29, = 0.37, compatible within 1-with the concordance model. With further data, Jackson & Jannetta get the best

fit for m = 0.25+0.04−0.03, = 0.97+0.09−0.13 (68% C.L.). It seems that the general trend

is to obtain the result expected from fashionable cosmologies on the date in which the test is carried out, and when incompatibilities appear, some selections effects, biases, small evolution effects are sought to try to make the results compatible. In my opinion, this is not a very objective way to do science,...."

 

Because galaxies evolve and merge using them as a standard meter stick is problematic (we must assume we know how big they really were)

That is discussed in the paper, and it looks that only the most extreme of evolutions would give you results compatible with an expanding universe.

[modest]

Just assume I meant "based in vey fewer observations" as in 330 is less than 393.

 

Yes, I clearly should have assumed 330 is far fewer than 393. Not sure what I was thinking ;)

 

VLBI? what's that?

 

VLBI observations from ~'98 make for good data.

 

That is your opinion, not a fact. Others might opine otherwise.

From the paper:

"Comparison with angular size test for ultra-compact radio sources

Compact radio sources have been used by several authors to carry out the angular

size test because these sources were thought to be free of evolutionary effects. However,

the different results obtained with these sources has raised the suspicion that they may not be such good standard rods. Apparently, these rods are somewhat flexible. For example, Kellermann claimed that the angular size test for these sources fitted Einstein–de Sitter expectations very well, when Einstein–de Sitter was the fashionable model. Jackson & Dodgson claimed the opposite: that it was not compatible with Einstein–de Sitter, and that, given that m = 0.2, the best fit for the cosmological constant term was = −3.0; flat cosmological models were excluded with > 70% C.L. Jackson, in the era of the concordance model as the fashionable cosmology, again carried out the analysis of the same data used by Jackson & Dodgson, doing some new corrections due to selection effects and bias, and they get the best fit for m = 0.29, = 0.37, compatible within 1-with the concordance model. With further data, Jackson & Jannetta get the best

fit for m = 0.25+0.04−0.03, = 0.97+0.09−0.13 (68% C.L.). It seems that the general trend

is to obtain the result expected from fashionable cosmologies on the date in which the test is carried out, and when incompatibilities appear, some selections effects, biases, small evolution effects are sought to try to make the results compatible. In my opinion, this is not a very objective way to do science,...."

 

Biased rubbish.

 

Jackson did consider Ω_M, Ω_Λ = .2, -3 the best fit which is reasonable considering the data he plots:

 

-source

 

The dark line seems to fit the data quite well. But, there was a problem with this data and when corrected it does indicate Ω_M, Ω_Λ = .2, 0.8 as a best fit. The problem is explained here:

 

Figure 5 shows the characteristic angular size versus redshift obtained by averaging over 16 redshift bins. As suggested by Gurvits (1993b), only the high-redshift part of this dependence should be used to fit theoretical curves for a standard rod in different cosmological models with experimental data. The reason for this limitation is the above-mentoined selection effect, that the low-redshift part of the sample (z < 0.5) and the high-redshift part (z > 0.5) contain sources of substantially different luminosity (up to three orders of magnitude; see Fig. 3). Furthermore...

Apparent milliarcsecond sizes of active galactic nuclei and the geometry of the universe

 

by L.I. Gurvits in 1994. 1994 is prior to the 1998 supernova standard candle observations which changed the favored cosmological model. It is just plain wrong then to claim these corrections due to selection effects were introduced as a means of fitting the favored cosmology. The author reveals their own bias in trying to twist the facts like that.

 

When Jackson's data admits Gurvits' concerns,

 

 

it is clear that Ω_M, Ω_Λ = .2, 0.8 is a very good fit, and from Jackson's 2005 paper (which is much more comprehensive than just cropping off part of the graph) it is clear that standard cosmology's Ω_M, Ω_Λ = .27, 0.73 fits even better.

 

In any case, that's all beside the point a little because this biased untruth:

It seems that the general trend is to obtain the result expected from fashionable cosmologies on the date in which the test is carried out, and when incompatibilities appear, some selections effects, biases, small evolution effects are sought to try to make the results compatible.

doesn't change the fact that compact radio sources are expected to have the least uncertainty due to the evolution of the source (see here) and the data would never (with or without selection effects) be considered to show angular size proportional to 1/z.

 

Like I've said before, I do not consider the data good enough to distinguish between like models, but it is good enough to clearly indicate expansion. It shows the opposite of what one would expect in a static and hyperbolic universe.

 

That is discussed in the paper, and it looks that only the most extreme of evolutions would give you results compatible with an expanding universe.

 

If one were to allege that angular size is proportional to 1/z without the size evolution of galaxies then any amount of size evolution would then be consistent with expansion. In other words, if one were to allege that the data falls on the [math]\theta \propto 1/z[/math] line when there is no size evolution of galaxies:

 

 

then any amount of size evolution would push the data above the Euclidean line consistent with expansion.

 

Observations (such as the the HDF) and galaxy evolution models force us to expect a strong size-evolution for galaxies.

 

http://iopscience.iop.org/0004-637X/650/1/18/pdf/62541.web.pdf

 

[astro-ph/0406562] Galaxy Size Evolution at High Redshift and Surface Brightness Selection Effects: Constraints from the Hubble Ultra Deep Field

 

~modest

[quantumtopology]

You are right, no doubt. None of your sources are biased but all of mine are. Expansion rules.

Now, let's convert CC.:)

 

 

P.S.I'm in a sarcastic mood today

[modest]

No take-backs

 

~modest :coffee_n_pc:

[quantumtopology]

Ok. Back to bussiness.

 

Modest, do you insist in calling rubbish everything that is not a direct proof of expansion? I presented data about near infrared galaxies and my comments about evolution were about this data, not about radio sources.

You recurr to dialectic tricks that are usually only used when people think is loosing in an argument.

If you reject the data from a reasoned and technically well done work by an astrophysicist with hundreds of papers published without giving any reason except that is rubbish the level of scientific discussion (no matter how low might have been to begin with) goes down the toilet.

[modest]

Modest, do you insist in calling rubbish everything that is not a direct proof of expansion?

 

I should hope not.

 

I presented data about near infrared galaxies and my comments about evolution were about this data, not about radio sources.

 

:confused:

 

You quoted this:

 

Comparison with angular size test for ultra-compact radio sources

Compact radio sources have been used by several authors to carry out the angular

size test because these sources were thought to be free of evolutionary effects. However,

the different results obtained with these sources has raised the suspicion that they may not be such good standard rods. Apparently, these rods are somewhat flexible. For example, Kellermann claimed that the angular size test for these sources fitted Einstein–de Sitter expectations very well, when Einstein–de Sitter was the fashionable model. Jackson & Dodgson claimed the opposite: that it was not compatible with Einstein–de Sitter, and that, given that m = 0.2, the best fit for the cosmological constant term was = −3.0; flat cosmological models were excluded with > 70% C.L. Jackson, in the era of the concordance model as the fashionable cosmology, again carried out the analysis of the same data used by Jackson & Dodgson, doing some new corrections due to selection effects and bias, and they get the best fit for m = 0.29, = 0.37, compatible within 1-with the concordance model. With further data, Jackson & Jannetta get the best

fit for m = 0.25+0.04−0.03, = 0.97+0.09−0.13 (68% C.L.). It seems that the general trend

is to obtain the result expected from fashionable cosmologies on the date in which the test is carried out, and when incompatibilities appear, some selections effects, biases, small evolution effects are sought to try to make the results compatible. In my opinion, this is not a very objective way to do science,....

 

It is talking about the evolution of compact radio sources. That is what I was responding to.

 

You recurr to dialectic tricks that are usually only used when people think is loosing in an argument.

 

:confused: :confused:

 

I gave a dated source showing that the selection effects in question were not a response to the changing favored cosmological model. That's not a trick.

 

If you reject the data from a reasoned and technically well done work by an astrophysicist with hundreds of papers published without giving any reason except that is rubbish the level of scientific discussion (no matter how low might have been to begin with) goes down the toilet. :(

 

I think you'll find me rather more open minded and willing to discuss alternative cosmologies than most.

 

This paper:

[1002.0525] Angular size test on the expansion of the Universe

from 2010 introduces nothing new.

 

That the angular size of galaxies is approximately proportional to 1/z has been known for some time. I think you were saying that the 1998 paper was out of date and that the 2010 paper is an update which shows something different. But, that is really not the case. Both say the same on this point. From the 2010 paper:

their average angular size for a given luminosity is approximately proportional to z

⁻¹

Angular Size Test on the Expansion of the Universe

and the 1998 paper:

The observed [math]\theta[/math] − z relation for double radio sources appears to follow a simple 1/z law even at high redshift

The “angular size - redshift” relation for compact radio structures in quasars and radio galaxies

I would, of course, agree with this, but it is only by ignoring the size evolution of galaxies that this would imply a static and Euclidean space—and, a static and Euclidean space hardly leaves room for redshift to be caused by hyperbolic space.

 

Trying to find consistent evidence to support a static universe can be frustrating, but I would submit that this is not my fault as much as it is the nature of the evidence itself.

 

~modest

[quantumtopology]

I think you'll find me rather more open minded and willing to discuss alternative cosmologies than most.

I have acknowledged this earlier. but that doesn't mean you are allowed to make rude remarks unnecesarily.

 

Trying to find consistent evidence to support a static universe can be frustrating, but I would submit that this is not my fault as much as it is the nature of the evidence itself.

 

And I have said several times before that Angular size-redshift is not a good way to support any model(and I'm not the only one that thinks this way), you kept bringing it up and I fell in the trap bringing myself that paper, but I explicitly warned that I still didn't find Angular size reliable and that the article also alluded to other tests such as the tolman test.

That is why I say you must have thought your position was weakening, I consider you more clever than sticking to the gurvits paper figure on and on to defend expansion.

 

Regards

Qtop

[quantumtopology]

Reading the Corredoira paper I see mentioned the Time dilation test, wich I didn't know previously and that he seems to find to be a valid test.

 

The Time dilation test of expansion with supernovae Ia lightcurves is supposed to validate expansion (well I haven't heard it mentioned in the last few years so maybe my criticism of it has already been discerned), but I see a problem with this test in that any mechanism that produces a redshift of the spectrum is gonna cause the time dilation effect too, for example gravitational redshift wich is static in space gives you the dilation. That can be seen too in that a redshift implies also a lower frequency on the receiver side of the electromagnetic wave and therefore a higher frequency of the source and that means (as the wave itself doesn't change unless one admits energy loss of the photon and thus interaction and scattering wich is not found) there is time dilation.

So provided one found a mechanism of redshifting in a static universe(that is the tough part) one would also have time dilation in the lightcurves.

Therefore the time dilation test proves redshifting, not expansion, and redshift is what we use to say there is expansion, that should invalidate the test to prove expansion.If you find a flaw in this reasoning, by all means point me to it.

 

Regards

Qtop

[modest]

I have acknowledged this earlier. but that doesn't mean you are allowed to make rude remarks unnecesarily.

 

I find nothing rude about calling Corredoira's remarks rubbish. The important thing is that I showed why the remark's implication was mistaken.

 

And I have said several times before that Angular size-redshift is not a good way to support any model(and I'm not the only one that thinks this way), you kept bringing it up and I fell in the trap bringing myself that paper, but I explicitly warned that I still didn't find Angular size reliable and that the article also alluded to other tests such as the tolman test.

That is why I say you must have thought your position was weakening, I consider you more clever than sticking to the gurvits paper figure on and on to defend expansion

 

I found it necessary to correct this:

 

The article does say this though right after the sentence you quote: "However there are no objects in the Universe which have a fixed physical size and exist across a wide range of distances, so

in practice

this counter-intuitive behaviour is

not observed

."

 

If indeed this effect is not observed it is entirely based on an idea, i.e., it is expected by a theory.

 

Intuitively, then, the next sentence should read: 'Spatial curvature may either increase or decrease the angular-diameter distance, with a spherical geometry focusing light rays and making objects appear

smaller

, and a hyperbolic geometry having the opposite effect" (making objects appear

larger

).

 

because one would never expect spherical geometry to make objects of a fixed size appear smaller and hyperbolic geometry make them larger.

 

Likewise, to correct this:

 

The best available data does show what we would expect in an expanding universe:

 

 

...Certainly that is not the best available data (it's from an article of 1998 based in very few observations)...

 

simply because the 2010 paper is not an update of the 1998 paper (they are based on different types of observations) and the 1998 paper is not based on "very few" observations. You can criticize me for focusing on these subjects, but I would feel negligent if I did not correct something that I believed was mistaken.

 

Also, I'm not disagreeing in order to "defined expansion". I'm disagreeing because I read something that appeared wrong to me.

 

but I explicitly warned that I still didn't find Angular size reliable and that the article also alluded to other tests such as the tolman test.

 

You can't divorce the two. The Tolman test is a combination of angular diameter distance and luminosity distance. In other words, surface brightness is a function of how bright and how large an object at a certain distance will appear. In terms of redshift, the Tolman relationship should be D_L = D_A(1+z)².

 

Reading the Corredoira paper I see mentioned the Time dilation test, wich I didn't know previously and that he seems to find to be a valid test.

 

The Time dilation test of expansion with supernovae Ia lightcurves is supposed to validate expansion (well I haven't heard it mentioned in the last few years so maybe my criticism of it has already been discerned)

 

I would say that time dilation is consistent with expansion and inconsistent with certain other causes of redshift. It is a test of expansion in the sense that if supernova light curves were found to be the same length as our rest frame then expansion would be falsified.

 

but I see a problem with this test in that any mechanism that produces a redshift of the spectrum is gonna cause the time dilation effect too, for example gravitational redshift wich is static in space gives you the dilation.

 

I agree that gravitational time dilation will cause redshift, but I would have issue with calling that space 'static' in the sense that things are not drawn away from the observer. My reasons are outlined in post 537.

 

Time dilation is considered a falsification of tired-light-type causes of redshift.

 

The tired light model does not predict the observed time dilation of high redshift supernova light curves.

Errors in Tired Light Cosmology

 

~modest

[quantumtopology]

I find nothing rude about calling Corredoira's remarks rubbish.

OK, I take it as a relaxation of the minimum of politeness requirable in a friendly conversation. Hope you don't complain about my adjectives in future.

 

I agree that gravitational time dilation will cause redshift, but I would have issue with calling that space 'static' in the sense that things are not drawn away from the observer. My reasons are outlined in post 537.

Are you arguing that the earth is receding from the GPS satelites that have to account for gravity time dilation to accurately work? I think everybody would call the earth static in this context.

 

Time dilation is considered a falsification of tired-light-type causes of redshift.

That is a strawman. I explicitly left out of my reasonin tired light mechanisms.

 

All the references I read like Leibundgut et al. 1996 talk about time dilation test as a way to prove expansion, if you have some more recent reference that says the Time dilation test refers only to falsification of tired light please show it.

 

Ultimately you haven't addressed what I asked, where is the flaw in my argument?