why can't large-scale curvature alone include acceleration without Cosmological Const

[claycravens]

Why can't the acceleration of the expansion measured in type 1a surveys be a part of the geometry of the large-scale curvature of the universe without needing dark matter or a Cosmological Constant? When I think about the images of raisins in a cake or dots expanding over time on a page, the idea comes to mind that the expansion may be galaxies moving in curved space, just like local gravity but on a universe-scale and in the opposite direction, of course. If this were the case, you might expect an acceleration in the expansion with great distances due to the principle of equivalence.

Could the acceleration in the expansion be a natural part of the large-scale curvature geometry of the universe?

[Cougar]

Could the acceleration in the expansion be a natural part of the large-scale curvature geometry of the universe?

I'm no expert, but my answer would be no. As I understand it, the large-scale curvature of space in the universe is reflective of the gravitational potential of all the mass and energy within the universe. Recent independent observations are supportive of a very nearly flat overall curvature. But if the curvature is "less than flat", that is, if it is saddle-shaped, this just means there is not enough mass and energy to gravitationally halt the expansion. Such a curvature has no means to effect an acceleration on the expansion. An accelerating expansion must come from some as yet unknown "force," which by coincidence, is (so far) mathematically well described by Einstein's discarded cosmological constant.

[Thanatos]

I agree with Cougar, just taking a slightly different approach. If gravity and spacetime curvature are manifestations of the same underlying 'force', it makes sense to me they are indistinguishable. IOW, gravity and spacetime curvature are merely different ways of defining the same effect.

[Bob Angstrom]

Why can't the acceleration of the expansion measured in type 1a surveys be a part of the geometry of the large-scale curvature of the universe without needing dark matter or a Cosmological Constant? When I think about the images of raisins in a cake or dots expanding over time on a page, the idea comes to mind that the expansion may be galaxies moving in curved space, just like local gravity but on a universe-scale and in the opposite direction, of course. If this were the case, you might expect an acceleration in the expansion with great distances due to the principle of equivalence.

Could the acceleration in the expansion be a natural part of the large-scale curvature geometry of the universe?

Dark energy is the main problem that your view would eliminate or we could be looking at a cosmological constant.

"But if the principle of equivalence states we cannot discern gravity from accelerating, CONTRACTION then it also means that we cannot discern the Einstein-Perlmutter repulsive force (gravity’s opposite force between all the stars and galaxies), from an accelerating, EXPANDING universe."- Daniel Fitzpatrick

A major conundrum of the Big Bang theory is that the most distant galaxies that are moving away from the Earth with the greatest velocity are simultaneously moving towards us in curved spacetime. Angus Graham said something to that effect.

The following article explains how our use of special relativistic Doppler redshifts can lead to errors in measurement at extreme distances because they don’t consider the gravitational curved space-time geometry of general relativity. You can’t make a flat SR map match the large-scale geometry of curved space.

http://www.astronomycafe.net/cosm/expan.html

[claycravens]

Thanks for the replies and thoughts. The article Bob mentions and his notes are very interesting and a good read.

Since we know spacetime curvature makes things accelerate here based on experience, why wouldn't we EXPECT that celestial bodies would accelerate at greater distances in a saddle shaped large-scale curvature?

[Bjoern]

Since we know spacetime curvature makes things accelerate here based on experience, why wouldn't we EXPECT that celestial bodies would accelerate at greater distances in a saddle shaped large-scale curvature?

Sorry, but the two cases are in no way comparable for a variety of reasons. The geometry of spacetime is completely different in these two cases; in the first case, you have a spherically symmetric static spacetime, whereas in the second you have a homogeneous, isotropic, decidedly non-static spacetime. In the first case, there is a clearly defined center towards acceleration happens, in the second, there is no (clearly definable) center at all.

Additionally, you apparently have missed the fact that the acceleration of the expansion of the universe is happening *today*, whereas we see the distant galaxies as they were several billion years ago. Hence an acceleration of these galaxies obviously would have little to do with the observed acceleration today.

A further point is that if you look back even farther in time (i. e. to even more distant galaxies), you see that back then, there was *deceleration*, not acceleration.

Hope this helps.

[Coldcreation]

I'm no expert...

See the de Sitter effect.

Also, Einstein's cosmological term has nothing to do with dark energy, acceleration. The original cosmological constant was an equillibrium generating manifestation (the physical mechanism of which was unknown).

The new cosmological constant is not the original version on speed or crack cocaine, it is a grotesque (I could think of anything worse to say about it, but don't take it personally Cougar) fudge factor used in an attempt to salvage an outdated hypothesis: the standard canonical hot big bang model.

To answer the question asked in this thread: yes the deviation from linearity observed in the SNe Ia spectrum is due to general relativistic spacetime dilation (curvature). It is not evidence of an accelerated expansion: a far cry from it. In fact, it is evidence that the expansion is not real.

You see, a theory makes predictions, the theory is then tested against those predictions. If the predictions are not satisfied, then the theory is either modified or dumped. In this case, the theory (in this case not just any theory; the standard model) was modified, and the result is catastrophic. The modification, a gross one, certainly, leads to a universe that does not simply contain something strange, kooky and otherworldy, but is dominated by it (whatever IT is, no one knows).

No theory predicted the results of the SN survey, and no standard model should be subjected to this kind of unphysical abuse.

Edited to add: Look at...

http://antwrp.gsfc.nasa.gov/diamond_.../hub_1929.html

...Of which here is a well known quote:

The outstanding feature, however, is the possibility that the velocity-distance relation may represent the de Sitter effect, and hence that numerical data may be introduced into discussions of the general curvature of space. In the de Sitter cosmology, displacements of the spectra arise from two sources, an apparent slowing down of atomic vibrations and a general tendency of material particles to scatter. The latter involves an acceleration and hence introduces the element of time. The relative importance of these two effects should determine the form of the relation between distances and observed velocities; and in this connection it may be emphasized that the linear relation found in the present discussion is a first approximation representing a restricted range in distance.

From the Proceedings of the National Academy of Sciences
Volume 15 : March 15, 1929 : Number 3

A RELATION BETWEEN DISTANCE AND RADIAL VELOCITY
AMONG EXTRA-GALACTIC NEBULAE

By Edwin Hubble

Mount Wilson Observatory, Carnegie Institution of Washington
Communicated January 17, 1929

Note: 1929 is the supposed year Hubble discovered or proved the universe was expanding.


Don't loose your mittens.

Coldcreation

[Coldcreation]

See too in addition to 'de Sitter effect,' 'de Sitter redshift.'

[Bjoern]

See the de Sitter effect.

Also, Einstein's cosmological term has nothing to do with dark energy, acceleration. The original cosmological constant was an equillibrium generating manifestation (the physical mechanism of which was unknown).

The new cosmological constant is not the original version on speed or crack cocaine, it is a grotesque (I could think of anything worse to say about it, but don't take it personally Cougar) fudge factor

Quite wrong here. Both Einstein's cosmological term and the Lambda CDM model use exactly the same math. The only difference is in the value of one specific parameter - the cosmological constant. Einstein set this constant to the very specific value which would lead to equilibrium (well, in fact it wouldn't, since this situation is unstable against perturbations), for long decades it was assumed that the value is zero (for simplicity, and because there were no observations availabe showing otherwise), and some years ago we have discovered that it is non-zero, but different from Einstein's value.

So you want to claim that simply using another value for a parameter turns this parameter from being "an equilibrium generating manifestation" to "a grotesque fudge factor"? Doesn't sound very sensible.

To answer the question asked in this thread: yes the deviation from linearity observed in the SNe Ia spectrum is due to general relativistic spacetime dilation (curvature).

Feel free to come up with a quantitative description of the data obtained from that idea.

It is not evidence of an accelerated expansion: a far cry from it.
In fact, it is evidence that the expansion is not real.

You make no sense. Accelerated expansion explains the data, hence the data is evidence for accelerated expansion. It's that simple. Why do you think otherwise?

You see, a theory makes predictions, the theory is then tested against those predictions. If the predictions are not satisfied, then the theory is either modified or dumped. In this case, the theory (in this case not just any theory; the standard model) was modified, and the result is catastrophic. The modification, a gross one, certainly, leads to a universe that does not simply contain something strange, kooky and otherworldy, but is dominated by it (whatever IT is, no one knows).

Indeed, the universe is dominated by dark energy, and indeed, we so far don't know what that is. But why do you call that result "catastropic"?

Hint: the energy density of dark energy grows with time, hence obviously there has to come a time where it dominates! The time when it didn't dominate was in fact quite short (well, on a cosmological time scale): only a few billion years. So it's no big miracle (or "catastrophe") that it dominates today.

No theory predicted the results of the SN survey,

Well, models with a non-zero cosmological constant were used in cosmology already before the SN results (for example, in simulations of structure formation). But before the SN results, obviously no one knew the value of the cosmological constant - so how could anyone have predicted that?

You fault a theory for not predicting something which it was simply not able to do - because the value for a crucial parameter was not known before, and was essentially determined by these observations which you claim should have been predicted! That makes little sense.

and no standard model should be subjected to this kind of unphysical abuse.

What is unphysical about doing observations which determine the value of a parameter in a theory?

[Coldcreation]

Originally Posted by Coldcreation
See the de Sitter effect.

Also, Einstein's cosmological term has nothing to do with dark energy, acceleration. The original cosmological constant was an equillibrium generating manifestation (the physical mechanism of which was unknown).

The new cosmological constant is not the original version on speed or crack cocaine, it is a grotesque (I could think of anything worse to say about it, but don't take it personally Cougar) fudge factor.

Quite wrong here. Both Einstein's cosmological term and the Lambda CDM model use exactly the same math. The only difference is in the value of one specific parameter - the cosmological constant. Einstein set this constant to the very specific value which would lead to equilibrium (well, in fact it wouldn't, since this situation is unstable against perturbations), for long decades it was assumed that the value is zero (for simplicity, and because there were no observations availabe showing otherwise), and some years ago we have discovered that it is non-zero, but different from Einstein's value.

So you want to claim that simply using another value for a parameter turns this parameter from being "an equilibrium generating manifestation" to "a grotesque fudge factor"? Doesn't sound very sensible.

For sure there is a zero value for lambda, only, there are no negative values, it is no parameter (yes it is being erroneously used as one, a grave error). There are no positive values.

The problem, both with respect to Einstein's and the new cosmological term, is that neither concept is backed by a physical definition that enlightens the mechanism behind lambda, for the simple reason that there is no such illumination for the mechanism behind the gravitational interaction. Only when light is shed on the latter will lambda take on its trus physical form. For now, dark matter means nothing, save the tweakable parameter to patch up a theory destined for the same place the cosmological constant was recently pulled.

The concept differences are enormous. One lambda was a stabilizing term, the other, the brute fury of Chi. The concept, the value and the physical definition make all the difference

Quote:

Originally Posted by Coldcreation
To answer the question asked in this thread: yes the deviation from linearity observed in the SNe Ia spectrum is due to general relativistic spacetime dilation (curvature). .

Feel free to come up with a quantitative description of the data obtained from that idea.

I will leave the adaptation of the math (to the data) to those more qualified to do the dirty work. I will negotiate the conceptual aspects. The math, by the way, has already been written. See the original de Sitter metric (1916-1918), his interpretation of GR to the "Kosmos."

Quote:

Originally Posted by Coldcreation
It is not evidence of an accelerated expansion: a far cry from it.
In fact, it is evidence that the expansion is not real.

You make no sense. Accelerated expansion explains the data, hence the data is evidence for accelerated expansion. It's that simple. Why do you think otherwise?

I understand all too well the train of thought leading to the idea of acceleration. The general relativistic curavture of the large-scale structure of spacetime explains the observations equally well (it is my contention that the GR approach is even more elegant) and without the artificial flavor of dark energy (something with which many sound quite compfortable, but it just isn't physics). It is that simple!

Originally Posted by Coldcreation
You see, a theory makes predictions, the theory is then tested against those predictions. If the predictions are not satisfied, then the theory is either modified or dumped. In this case, the theory (in this case not just any theory; the standard model) was modified, and the result is catastrophic. The modification, a gross one, certainly, leads to a universe that does not simply contain something strange, kooky and otherworldy, but is dominated by it (whatever IT is, no one knows).

Indeed, the universe is dominated by dark energy, and indeed, we so far don't know what that is. But why do you call that result "catastropic"?.

The first part of your question answers the second.

Hint: the energy density of dark energy grows with time, hence obviously there has to come a time where it dominates! The time when it didn't dominate was in fact quite short (well, on a cosmological time scale): only a few billion years. So it's no big miracle (or "catastrophe") that it dominates today.

What is growing with time, what dominates the universe?
Negative pressure, antigravity, a dark force? No one can answer these questions. Just as no one can explain what miraculous force could possibly cause the ocean to spread open to allow the passage of a chimerical convoy...

Originally Posted by Coldcreation
No theory predicted the results of the SN survey... .

Well, models with a non-zero cosmological constant were used in cosmology already before the SN results (for example, in simulations of structure formation). But before the SN results, obviously no one knew the value of the cosmological constant - so how could anyone have predicted that?

You fault a theory for not predicting something which it was simply not able to do - because the value for a crucial parameter was not known before, and was essentially determined by these observations which you claim should have been predicted! That makes little sense.

No theory predicted the results of the SN survey because most physicists had trashed lambda decades ago and did not care to see it return. Not because it was distastful, or because it was a fudge factor, but because if it returned then no one could exclude the possibility that it exactly balanced gravity, thus leading to stable, nonexpanding universe, as Einstein had originally suspected. This is exactly what I suspect today. Though the word "balance" used above is not entierly appropriate. The explanation may be beyond the scope of the present thread.

Quote:
Originally Posted by Coldcreation
and no standard model should be subjected to this kind of unphysical abuse.

What is unphysical about doing observations which determine the value of a parameter in a theory?

There is nothing physical to be said of dark energy. The observations are sound, it is the interpretation of those that is lacking, to say the least.

Regards

Coldcreation

[Bjoern]

A lot of assertions, with not even an attempt to back them up...

For sure there is a zero value for lambda,

How do you know?

only, there are no negative values,

Why not?

it is no parameter

Why not?

There are no positive values.

Why not?

The problem, both with respect to Einstein's and the new cosmological term, is that neither concept is backed by a physical definition that enlightens the mechanism behind lambda,

What does "physical definition" mean? And how would such a definition "enlighten the mechanism behind lambda"?

for the simple reason that there is no such illumination for the mechanism behind the gravitational interaction.

Hint: curvature of spacetime.

Only when light is shed on the latter will lambda take on its trus physical form.

And what is that supposed to mean?

For now, dark matter means nothing,

Ever heard of proposals like neutralinos?

Or do you confuse dark matter with dark energy here? If not, I don't see why you brought dark matter up in this connection.

save the tweakable parameter to patch up a theory destined for the same place the cosmological constant was recently pulled.

Both the cosmological constant and the density of dark matter are indeed "tweakable parameters" in the Big Bang Theory. So what? Where is the big problem with that? Do you claim that because we so far don't know what dakr energy and dark matter really are, we aren't allowed to use these parameters, or what?

The concept differences are enormous. One lambda was a stabilizing term, the other, the brute fury of Chi. The concept, the value and the physical definition make all the difference

Physics is about measurements which provide evidence for or refute a theory. Not about "concept differences". Just because one specific value of lambda leads to stabilization (and I already pointed out that in reality, this doesn't work actually), that doesn't imply in the least that all other values have to be treated in another way.

I will leave the adaptation of the math (to the data) to those more qualified to do the dirty work.

Well, so you admit that you haven't done the math on that so far, and apparently are not even able to do it. What was your basis then for claiming that this would work?

I will negotiate the conceptual aspects. The math, by the way, has already been written. See the original de Sitter metric (1916-1918), his interpretation of GR to the "Kosmos."

And what makes you think that de Sitter's model can explain the observed SN data? Just above you essentially admitted that you are unable to do the necessary math.

I understand all too well the train of thought leading to the idea of acceleration. The general relativistic curavture of the large-scale structure of spacetime explains the observations equally well (it is my contention that the GR approach is even more elegant) and without the artificial flavor of dark energy (something with which many sound quite compfortable, but it just isn't physics). It is that simple!

First, even if there would be an alternative explanation possible, that wouldn't negate the fact that the SN data is evidence for an accelerated expansion (hint: one observation can be evidence for several competing models at once). So you original claim that it is no evidence for an accelerated expansion is still wrong.

Second, here again you simply claim that "the general relativistic curvature" can also explain these observation, but again you don't bother to back up that claim. What about showing some math? Show us that this model can explain the data, quantitatively. Oh, wait - you have just admitted yourself that you can't do the math. A pity, isn't it?

Indeed, the universe is dominated by dark energy, and indeed, we so far don't know what that is. But why do you call that result "catastropic"?

The first part of your question answers the second.

Sorry, I still don't see why you call that "catastropic". We don't know what the stuff which dominates the universe is, right - but why do you call that a catastrophe?

What is growing with time, what dominates the universe?
Negative pressure, antigravity, a dark force? No one can answer these questions.

Wrong. Just like I said: the density of dark energy grows with time and dominates the universe. Why don't you simply read what I write instead of claiming that no one can answer this?

BTW: what is "a dark force" even supposed to mean?

Just as no one can explain what miraculous force could possibly cause the ocean to spread open to allow the passage of a chimerical convoy...

I have no idea what you are talking about here.

No theory predicted the results of the SN survey because most physicists had trashed lambda decades ago and did not care to see it return. Not because it was distastful, or because it was a fudge factor, but because if it returned then no one could exclude the possibility that it exactly balanced gravity, thus leading to stable, nonexpanding universe, as Einstein had originally suspected.

Wrong again.

First, as I have said already some times, such a universe would not actually be stable.

Second, it is absolutely ridiculous to claim that physicists "feared" using the cosmological constant because this might lead to a stable universe. There is precisely one value for which that would be the case, and infinitely many others. So why on earth should anyone fear that if one uses the constant again, precisely this one value would turn up again? This doesn't make any sense at all!

Third, I have already explained the real reason why it was assumed that the constant is zero: because that simplified the models, and because there was no observational evidence against that assumption. This is an absolutely sensible explanation consistent with the historical records. No need to come up with wild fantasies about fear of a stable universe...

There is nothing physical to be said of dark energy.

Please explain what you mean with "physical" resp. "unphysical".

The observations are sound, it is the interpretation of those that is lacking, to say the least.

Feel free to show that another interpretation (e. g. your favored de Sitter model) also matches the data. Simply claiming that the de Sitter model also would work (or even would work better) is not enough. Show that is can also explain the data!



Nevertheless:
a Merry Christmas to you, and all the other readers of this thread!

Bjoern

[brodix]

Coldcreation,

I tried running the basic idea through here a few weeks ago and didn't have much luck persuading anyone either.

My argument was that while we can take a god's eye view of another galaxy and say it's however many light-years across, if we were to actually shine a light across it, it would fall in the gravity well and we would relativistically say it has infinite radius. We don't have a god's eye view of the space in between galaxies and can only measure the light crossing it, which tells us that the space is expanding. The theory arising from this evidence is that the entire universe is expanding in absolute volume from an initial event, yet it's called relativistic expansion. Gravity relativistically contracts space and curves the path of light crossing it, so if this expansion is relativistic, it would seem the space not affected by gravity would be expanding due to lensing effects similar to gravity, although it wouldn't be curving light toward or away from any particular point. The result would cause the light waves crossing it to expand, creating the impression of a receding source. The more space it crosses, the greater the effect and the faster the source appears to be receding, so that eventually the source appears to be receding at the speed of light and this creates a horizon line. Because the expansion is integral to the relativistic effects of crossing expanding space, not an initial event, it declines at a rate requiring a cosmological constant to explain and thus, dark energy. It also causes light from all directions to be evenly red-shifted, creating the impression we are at the center of this expansion.

The question is what could cause this relativistic expansion of space? Obviously any material lensing would cause distortion that we do not detect.

Gravity causes mass to collapse until density ignites it and the energy radiates back out. As red-shift is a function of the light waves, could the interference from all the other light, of all other frequencies, crossing every point in space, be causing some wave interference, without directly interfering with the light particles. To the extent they would slow, it would an aftereffect of the wave action. Gravity collapses, radiation expands. Could the effect on space be similar.

[Coldcreation]

Coldcreation,

I tried running the basic idea through here a few weeks ago and didn't have much luck persuading anyone either.
.

I want to answer Bjoern's points and question's but first, the idea I am referring to has been around since the beginning of GR. Particularly since de Sitter interpreted the well knowm models based on it. Why de Sitter, why not Einstein's world model of the same epoch?

Because Einstein's world model was spherical. What is observed is a hyperbolic redshift-apparent magnitude relation. The furthur our observations take us the more this becomes noticable.

Thought the idea has been around for about 90 years, the telescopes available have not been able to show the difference between the two models (change in the scale factor to the metric and a GR based curvature approach, the de Sitter solution). In fact only since the late 1990s has it become possible to see the deviation from linearity. The Doppler approach, historically and practically was an easier method to solving the redshift problem, and as Hubble wrote was chosen for convenience.

The history of the problem is well documented.

I don't feel the need to reiterate it all here. It will suffice for anyone to look up the de Sitter effect or the de Sitter redshift in a search engine for a general discussion. The preferrable place to do research is of course a physics library.

The question is what could cause this relativistic expansion of space? Obviously any material lensing would cause distortion that we do not detect..

The idea is that there is a relativistic effect that simulates a Doppler shift, and that appears to be an acceleration at large distance due to the hyoperbolic metric of the manifold. There is no relativistic or (more acurately) Newtonian expansion.

snip...As red-shift is a function of the light waves, could the interference from all the other light, of all other frequencies, crossing every point in space, be causing some wave interference, without directly interfering with the light particles. To the extent they would slow, it would an aftereffect of the wave action. Gravity collapses, radiation expands. Could the effect on space be similar.

Large-scale curvature of the spacetime continuum (as viewed from the perspective of any observer) is the only other phenomenon that could cause the observed redshift z across the 19 octaves of the spectrum.

The beauty of this interpretation is that it requires no new physics (no dark energy). It is entirely based on the original Einstein-de Sitter brainstorm of 1916-1918, both of which were satatic solutions to the field equations.

The apparent instability associated with either model is easily done away with when the physical mechanism of lambda and spacetime curvature (gravity) are understood.

Merrrrrry Xmaaaaas Ho Ho HO

[Coldcreation]

A lot of assertions, with not even an attempt to back them up...Bjoern

I will have to come back to the first questions you pose later, deleted above, on the value of lambda etc.

I am not defendung an ATM idea here, and this is not my thread. All I say is that, in answer to the question posted in the title of this thread, there is a solution to the query. It was first produced by de Sitter with his hyperbolic metric. It can easily be made to fit the data, just as it was easy to use lambda (dark energy, whatever that is) as a parameter (along with several other parameters, vis, dark matter) for the data to fit a new standard expanding model. The new standard expanding model, unlike it's prior Friedmann incarnation, pre-1998, is interpreted as acceleration, erroneously.

Hint: curvature of spacetime.Bjoern

Curvature is not a mechanism.

Ever heard of proposals like neutralinos?Bjoern

Have you ever seen one? If they dominate the universe, wouldn't you expect to find one locally. Local physics is global physics. Unless your saying that the laws of nature, physics, are not the same everywhere. That in any case is not my contention.

I have a feeling we'll be waiting a long time before dark energy (e.g., neutralinos) or nonbaryonic dark matter is discovered: forever.

Or do you confuse dark matter with dark energy here? If not, I don't see why you brought dark matter up in this connection.Bjoern

Yup, It was meant dark energy.
Note though that I did mention DM above. That's simply because it is anopther parameter, with DE, used to make observations fit, grossely, I might add.

Both the cosmological constant and the density of dark matter are indeed "tweakable parameters" in the Big Bang Theory. So what? Where is the big problem with that? Do you claim that because we so far don't know what dakr energy and dark matter really are, we aren't allowed to use these parameters, or what?Bjoern

By "dakr energy" I assume you meen dark energy. "Dakr" sounds more like a rally that starts in Paris and finishes in Senegal. (smile).

I think predictions should be made, and those predictions should be stuck to.
The problem emerges when an endless set (or even three) of parameter are continually used to make a theory work, and especially so when no one has any incling of an idea what the physicality of the parameters are (DE, DM, quintessence, vacuum energy with a minus sign, whatever).

Physics is about measurements which provide evidence for or refute a theory. Not about "concept differences". Just because one specific value of lambda leads to stabilization (and I already pointed out that in reality, this doesn't work actually), that doesn't imply in the least that all other values have to be treated in another way.Bjoern

Exactly, that's why when the 1998 evidence surfaced refuting the Friedmann models, the standard theory should have been abandoned rather than modified. Ironically it was modified using a relic ressurection of general relativity, all too often bashed as a Einstein's greatest blunder.

Well, so you admit that you haven't done the math on that so far, and apparently are not even able to do it. What was your basis then for claiming that this would work?Bjoern

I'll be back for the rest...

[Bjoern]

Coldcreation,
My argument was that while we can take a god's eye view of another galaxy and say it's however many light-years across, if we were to actually shine a light across it, it would fall in the gravity well and we would relativistically say it has infinite radius.

Sorry, I don't understand how you arrive at the conclusion of infinite radius.

We don't have a god's eye view of the space in between galaxies and can only measure the light crossing it, which tells us that the space is expanding. The theory arising from this evidence is that the entire universe is expanding in absolute volume from an initial event, yet it's called relativistic expansion.

I'm not entirely sure what exactly you mean with "absolute volume" and "relativistic expansion". Please explain.

Gravity relativistically contracts space

No, it (usually) doesn't. Where did you get that from?

and curves the path of light crossing it, so if this expansion is relativistic, it would seem the space not affected by gravity would be expanding due to lensing effects similar to gravity,

Again, I don't see how you arrive at that conclusion, sorry. What are "lensing effects similar to gravity" supposed to mean, and how could they cause space expanding? What a (gravitational) lens does is well understood; expanding space does not belong to its properties.

although it wouldn't be curving light toward or away from any particular point. The result would cause the light waves crossing it to expand, creating the impression of a receding source. The more space it crosses, the greater the effect and the faster the source appears to be receding, so that eventually the source appears to be receding at the speed of light and this creates a horizon line. Because the expansion is integral to the relativistic effects of crossing expanding space, not an initial event, it declines at a rate requiring a cosmological constant to explain and thus, dark energy.

How do you get from "the expansion is integral to..." to "it [requires] a cosmological constant"???

And: What about showing the math behind all that verbiage?

[Bjoern]

The apparent instability associated with either model is easily done away with when the physical mechanism of lambda and spacetime curvature (gravity) are understood.

And you know this how, precisely?

[Bjoern]

I am not defendung an ATM idea here, and this is not my thread. All I say is that, in answer to the question posted in the title of this thread, there is a solution to the query. It was first produced by de Sitter with his hyperbolic metric. It can easily be made to fit the data, ...

You keep claiming that - but you have not shown this so far.

Curvature is not a mechanism.

Why not? What exactly would you accept as a "mechanism"?

Have you ever seen one? [neutralino]

No. Hint: that's why I said "proposal".

If they dominate the universe, wouldn't you expect to find one locally.

Hint: that's why (well, among other reasons) they are building the LHC.

I have a feeling we'll be waiting a long time before dark energy (e.g., neutralinos) or nonbaryonic dark matter is discovered: forever.

Neutralinos are a possible candidate for dark matter, not for dark energy! Thanks for confirming my suspicion that you confuse dark energy and dark matter.

And: what's your basis for that feeling?

Note though that I did mention DM above. That's simply because it is anopther parameter, with DE, used to make observations fit, grossely, I might add.

So you ignore the fact that there are multiple lines of evidence pointing to the existence of dark matter?


[QUOTE=Coldcreation;891065]
I think predictions should be made, and those predictions should be stuck to.

But how could one make sensible predictions with a theory as long as the basic parameters are not all known? That was the case with the Big Bang Theory prior to ca. 1998. The SN data brought the first possibility to get an idea of the value of the parameter Lambda, and the WMAP data have refined the measurements of most cosmological parameters since then.

The problem emerges when an endless set (or even three) of parameter are continually used to make a theory work,

Sorry, I don't see a big problem with using three parameters - as long as the values of these parameters are kept essentially fixed (within the errors of measurement). And exactly that has happened with the Big Bang theory: since we have been able to measure Lambda, Omega_DarkMatter etc. accurately, the values for these parameters have essentially stayed constant.

Essentially you are whining that the values used for these parameters when we were not yet able to measure them accurately differ from the values used today, when we are able to measure them accurately. And simultaneously, you are ignoring that the data we have obtained in the latter time from multiple lines of evidence are consistent with each other.

and especially so when no one has any incling of an idea what the physicality of the parameters are (DE, DM, quintessence, vacuum energy with a minus sign, whatever).

Please explain what "physicality" means.

Exactly, that's why when the 1998 evidence surfaced refuting the Friedmann models, the standard theory should have been abandoned rather than modified. Ironically it was modified using a relic ressurection of general relativity, all too often bashed as a Einstein's greatest blunder.

I have already set the record straight and explained what actually happened: it was realized from new, more sensitive measurements that a parameter of the theory which was for simplicity by most (but not all!) assumed to be zero isn't really zero. That you keep ignoring the sensible, real explanation is telling.

[Bjoern]

All I say is that, in answer to the question posted in the title of this thread, there is a solution to the query. It was first produced by de Sitter with his hyperbolic metric.

I think that we should have a common ground for discussing, so it would be helpful if you could describe what model by de Sitter you are talking about, specifically. Please give both the metric and the energy-momentum-tensor.

The reason for asking you to do this is that what I know about de Sitter's model strongly contradicts several of your claims about that model. Hence either you are talking about a different model, or you don't really understand his model. I'd like to clear this up first.

[Coldcreation]

I think that we should have a common ground for discussing, so it would be helpful if you could describe what model by de Sitter you are talking about, specifically. Please give both the metric and the energy-momentum-tensor.

The reason for asking you to do this is that what I know about de Sitter's model strongly contradicts several of your claims about that model. Hence either you are talking about a different model, or you don't really understand his model. I'd like to clear this up first.

I will start a new thread for this discussion. My claims go beyond the scope implicit here, and too, go beyond the hyperbolic static de Sitter manifold.
I have aleady expounded quite extensively on these and other related topics here in this forum, the text of which is easily accessible, though not comletely. See the SNe Ia thread and my own threads.

[Coldcreation]

And you know this how, precisely?

Well, a very good question indeed.
The answer to it is the subject of a thread, about to begin, that will attempt to specify exactly what is the mechanism that lurks behind the gravitational interaction, and thus, opens the door to the understanding of what lambda really is. One without the other is unthinkable. One that over-powers or dominates the other is equally unthinkable.

The answer really is very simple. Perhaps it is the simplicity that has masked the properties.

[Coldcreation]

You keep claiming that - but you have not shown this so far.

I have not shown quantitatively how the de Sitter model fits the observations. Correct. I have only explained conceptually that there is an alternative approach to the mainstream (new physics) view, it is based on mainstream physics (Einstein's) and that it needs to be explored further. It has been discounted on insufficient grounds and needs to be reviewed by those qualified to do so. (This is certainly not the best place to go into detail. Until that happens, the scientific community runs the risk of falling prey to illusion (one of Einstein's expressions): believing that the universe is accelerating when it is not, inventing a new form of hypothetical energy when there is no such thing, and speculating that some unknown type of matter exists that contains no electron, protons or neutrons.

Why not? What exactly would you accept as a "mechanism"?

The mechanism responsible for the gravitational interaction should explain why spacetime is distorted (curved) in the presence of massive bodies, energy and pressure, what causes the acceleration of a test particle in a gravity field and why a freely-falling body feels no force or acceleration (the Euclidean conection). Also, why there is an equivalence between inertia and gravity, etc. It does not suffice to say gravity is curvature, though it was indeed great insight to have come to that conclusion.

It follows that the correct explanation for the mechanism not only elucidates what is lambda, but also open the way to unification (gravity with the other forces, albeit not in the way expected by the mainstream, at high energy densities and at short distances (e.g., the Plank scale)).

No. Hint: that's why I said "proposal".

Yes, yes, I know. My point was clear. There is no proof so far.

Hint: that's why (well, among other reasons) they are building the LHC.

Let's hope the LHC reaches the energies required to test the new standard model.

Neutralinos are a possible candidate for dark matter, not for dark energy! Thanks for confirming my suspicion that you confuse dark energy and dark matter.

That was a low blow. Somewhere I wrote dark matter by accident. It should have been written dark energy. My mistake. Thanks for pointing it out. No, granted, they are not the same. There is however a common denominator between the two. Both DE and nonbaryonic dark matter (NBDM) are new physics (not physics yet).

And: what's your basis for that feeling?

My feeling is that DE and NBDM are both human inventions, products of pure imagination, to explain phenomena that are clearly not understood (e.g., the deviation from linearity interpreted as an accelerated expansion, to name one). And so, in my opinion, because they don't exist in nature, ie, outside the human psyche, the discovery of DE and NBDM remains futile, ad infinitium.


[QUOTE=Bjoern;891072] So you ignore the fact that there are multiple lines of evidence pointing to the existence of dark matter?

Absolutely not. Those observations leading to the belief of DE and NBDM (rotational curves, light curves, acceleration of expansion, etc.) are interpreted in a different way; one that requires no such thing.

I think predictions should be made, and those predictions should be stuck to.

But how could one make sensible predictions with a theory as long as the basic parameters are not all known? That was the case with the Big Bang Theory prior to ca. 1998. The SN data brought the first possibility to get an idea of the value of the parameter Lambda, and the WMAP data have refined the measurements of most cosmological parameters since then.

I understand your viewpoint, but with all due respect, I disagree with your premise.

Sensible predictions were made prior to 1998 that ended up in conflict with what was (and is) observed in the real world. (The search for the deceleration parameter turned into crude awakening.)

WMAP was a last ditch effort designed to save some form of inflation; a theory, too base on new physics, which predicted a flat universe (without the flatness a host of problems intrinsic to the BB remained intact).

The problem was that the 1998 data contradicted inflation. The universe was no longer flat. That was shown in the redshift at high z, and the light curves of distant SN Ia. A flat universe would have shown a smooth, linear, redshift-apparent magnitude relation in accord with the Hubble law, or very nearly so. Recall, that is what was predicted.

At worse, omega (roughly, the mass-energy density parameter) would have been sufficient to cause a deceleration (a closed model). But something else emerged, something unpredicted that would change the standard model forever...

Sorry, I don't see a big problem with using three parameters - as long as the values of these parameters are kept essentially fixed (within the errors of measurement). And exactly that has happened with the Big Bang theory: since we have been able to measure Lambda, Omega_DarkMatter etc. accurately, the values for these parameters have essentially stayed constant.

That does not sound very concsiencious to me. The best would be no parameter at all. I realize that is not possible, especially with regard to the mass-energy density. But the DE and DM are not the type of parameters I would consider most desirable for a model considered the standard.

Essentially you are whining that the values used for these parameters when we were not yet able to measure them accurately differ from the values used today, when we are able to measure them accurately. And simultaneously, you are ignoring that the data we have obtained in the latter time from multiple lines of evidence are consistent with each other.

Another blow below the belt, followed by awkward triviality. You are arguing (why whining?) about acurately measuring parameters, yet, have no idea (neither does anyone else) of what it is being measuring. That sounds like a joke to me. It's funny but it not science. It is devoid of all physicality. Do I understand that you're saying it's ok, fine. Does not science have to live up to a certain standard; one preferably that vacates speculation about specuous forces?

Please explain what "physicality" means.

Simply, there is nothing physical about it. No known physics is capable of describing its properties. There are no natural laws that shed any light on anything remotely similar. By definition (thus the "dark") there is no way even in principle to observe or detect DE directly. It remains therefore outside the physical world. But because there is no outside of the universe (this is my opinion of course), one can only conclude that DE and most forms of DM (of the nonbaryonic variety) are pure chimera.

Originally Posted by Coldcreation
Exactly, that's why when the 1998 evidence surfaced refuting the Friedmann models, the standard theory should have been abandoned rather than modified. Ironically it was modified using a relic ressurection of general relativity, all too often bashed as a Einstein's greatest blunder.

I have already set the record straight and explained what actually happened: it was realized from new, more sensitive measurements that a parameter of the theory which was for simplicity by most (but not all!) assumed to be zero isn't really zero. That you keep ignoring the sensible, real explanation is telling.

No record has been set straight. The real history of lambda is much more elaborate, complex, than what we've exposed here. Again, you assume something is not zero but cannot explain using physics what you are measuring to be nonzero. That sounds like a fudge factor if ever there was one.

Coldcreation

[Bjoern]

I have not shown quantitatively how the de Sitter model fits the observations. Correct. I have only explained conceptually that there is an alternative approach to the mainstream (new physics) view, it is based on mainstream physics (Einstein's) and that it needs to be explored further.

You have done more than that: you have claimed, repeatedly, that this alternative approach can explain the data as least as well as the mainstream model. So far, you haven't backed up that claim. And I keep calling you on that.

speculating that some unknown type of matter exists that contains no electron, protons or neutrons.

We already know from particle physics that such stuff exists resp. should exist - so where is the big problem?

The mechanism responsible for the gravitational interaction should explain why spacetime is distorted (curved) in the presence of massive bodies, energy and pressure,

You are right that GR does not explain the why of that.

what causes the acceleration of a test particle is a gravity field and why a freely-falling body feels no force or acceleration (the Euclidean conection).

In contrast, that is explained by GR.

It does not suffice to say gravity is curvature, though it was indeed great insight to have come to that conclusion.

Why do you think you are in a position to judge what is sufficient and what isn't?

Let's hope the LHC reaches the energies required to test the new standard model.

All theoretical predictions say that the "new" particles should be in the energy range available to LHC. Hence if LHC finds nothing, particle physicists have to go back to the drawing boards and come up with some entirely new ideas.

My feeling is that DE and NBDM are both human inventions, products of pure imagination, to explain phenomena that are clearly not understood (e.g., the deviation from linearity interpreted as an accelerated expansion ,to name one). And so, because they don't exist in nature, outside the human psyche, the discovery of DE and NBDM remains futile, ad infinitium.

I asked you what the basis for that feeling is. You didn't answer my question - you merely repeated that you have such a feeling.

So you ignore the fact that there are multiple lines of evidence pointing to the existence of dark matter?

Absolutely not. Those observations leading to the belief of DE and NBDM (rotational curves, light curves, acceleration of expansion, etc.) are interpreted in a different way; one that requires no such thing.

Please elaborate. Exactly how does your different interpretation work? Be quantitative, please!

I understand your viewpoint, but with all due respect, I disagree with your premise.

Sensible predictions were made prior to 1998 that ended up in conflict with what was (and is) observed in the real world. (The search for the deceleration parameter turned into crude awakening.)

You totally ignore my argument - that prior to 1998, there simply were no measurements available which were sensitive enough to detect a non-zero lambda.

WMAP was a last ditch effort (a sham) designed to save some form of inflation;

Pardon??? What on earth are you talking about??? You call the most succesful, most sensitive probe ever used in cosmology a "sham"???

The problem was that the 1998 data contradicted inflation. The universe was no longer flat. That was shown in the redshift at high z, and the light curves of distant SN Ia. A flat universe would have shown a smooth, linear, redshift-apparent magnitude relation in accordance with the Hubble law, or very nearly so. Recall, that is what was predicted.

That was predicted only if one insisted that lambda = 0! Hence the observations obviously showed that lambda is not zero!

At worse, omega (roughly, the mass-energy density parameter) would have been sufficient to cause a deceleration (a closed model). But something else emerged, something unpredicted that would change the standard model forever...

Models with a cosmological constant were used in cosmology already before 1998 (not often, but they were there), as I already pointed out. So calling this result "unpredicted" is an attempt to rewrite history. True, practically no one really expected this result - but not because this somehow contradicts the basic theory, but only because everyone was used to the simplifying assumption of setting lambda to zero!

That does not sound very concsiencious to me. The best would be no parameter at all. I realize that is not possible, especially with regard to the mass-energy density. But the DE and DM are not essential parameters, once a world model in adopted that represents the real world; however subjective that is.

How do you know that they are not essential, that they do not represent the real world?

Another blow below the belt, followed by trivial nonsense.

You really have strange ideas of both what constitutes a "blow below the belt" and "trivial nonsense".

You are arguing (whining?) about acurately measuring parameters, of something, yet have no idea of what it is you are measuring.

The value of lambda, a free parameter in the theory. That no one is sure how one has to interpret the meaning of lambda doesn't in the least imply that we can't measure it.

That sounds like a joke to me. It's funny but it not science. It is devoid of all physicality.

Evasion of the actual argument noted.

Simply, there is nothing physical about it. No known physics is capable of describing it. No properties of it (DE).

Depends on how exactly you define "known physics". E. g. one model for DE, quintessence, uses a scalar field. The physics of scalar fields has been known for decades and is very well understoof.

There are no natural laws that shed any light on anything remotely similar.

For quintessence, wrong again. E. g. the Higgs field has many similarities.

By definition (thus the "dark") there is no way even in principle to observe or detect DE directly. It remains therefore outside the physical world.

Non sequitur. Simply because one can not detect something directly, this does not mean that this thing is "outside the physical world". Ever heard of indirect detections? Hint: most things in modern physics today can only be detected indirectly. Take e. g. quarks and gluons.

No record has been set straight. The real history of lambda is much more elaborate, complex, than what we've exposed here.

Obviously, yes. But my account is a lot closer to the truth than yours.

Again, you assume something is not zero but cannot explain using physics what you are measuring to be nonzero. That sounds like a fudge factor if ever there was one.

Again: Lambda is simply a free parameter in the theory. That we can't explain its meaning so far does not in the least imply that it is simply a dreamt-up fudge factor which we aren't allowed to use or aren't able to measure.

[Coldcreation]

You have done more than that: you have claimed, repeatedly, that this alternative approach can explain the data as least as well as the mainstream model. So far, you haven't backed up that claim. And I keep calling you on that.

I will not get quantitative here and now. I will save that for a thread signed Coldcreation, so it pops up in a search engine with the name Coldcreation.

You are right that GR does not explain the why of that.

That takes nothing away from Her Einstein's general postulate of relativity, of course. But finding solutions for the the mechanism behind the gravitational interaction is indeed extremely important. One of the reasons there is no unified field theory is because of this unknown.

Why do you think you are in a position to judge what is sufficient and what isn't?

The problem of gravity is a very interesting one. My feeling simply echos Feynman's. There are fundamental aspect of gravity that remain elusive, notably how it works, what causes it. My position will become clear, also in a Coldcreation thread. Sorry to keep you hanging on that, but I will say that without a full, comprehensive understanding of the workings of gravity, the unification of natures forces, the dicrepancy between QM and GR, will not find a solution.


A

ll theoretical predictions say that the "new" particles should be in the energy range available to LHC. Hence if LHC finds nothing, particle physicists have to go back to the drawing boards and come up with some entirely new ideas.

Which new particles would those be. The candidate for dark matter: neutralino?

I asked you what the basis for that feeling is. You didn't answer my question - you merely repeated that you have such a feeling.

Good question. It's like asking why do I think god does not exist. You know I have no proof, just indirect evidence that points in a more physical direction (that's why its a good question). Likewise, I know you have no proof, so we could spin ad infinitium on whether DE exists of not.

Please elaborate. Exactly how does your different interpretation work? Be quantitative, please!

This will be the principle topic of the Coldcreation thread once I can get the short pdf online. My intension is not to highjack this thread. If you'de like we can take a break fro this one, until the CC thread emerges.

You totally ignore my argument - that prior to 1998, there simply were no measurements available which were sensitive enough to detect a non-zero lambda.

Actually there were plenty of deviations from linearity, dating from the original Hubble-Humason charts all the way leading up to the SNe Ia Hubble Telescope data. There has never been proof of the linear redshift z-apparent or absolute magnitute relation, not to mention quasars, the physics of which may or may not be well understood. Quasars fit like a shotgun blast.

There was sufficient sensitivity to make predictions. It turns out, though, that with higher definition at high-z those predictions failed.

Prediction are made, then tested, not the other way around, as you well know, I assume. Before the 1998 observations predictions were made within a margine (depending on parameters). The results were not anywhere near the predictions. No more time to elaborate.

Pardon??? What on earth are you talking about??? You call the most succesful, most sensitive probe ever used in cosmology a "sham"???

The word sham was a little harsh perhaps. I was in the process of editing my post when you wrote yours. That world is not in the original post anymore. I had used it though with the intention of highlighting (shockingly) the paradox that the CMB is being used as if it were a guide, a map, of the early cosmos, a redshifted vestige, relic, fossil. I disagree with that interpretation. There is no proof it has been redshifted from a higher thermal spectrum. It is a local radiation....

To use it then for topological finding purposes is an outrage, from my perspective. There is no way, from the anistropy, or from anything else related to the CMBR, to determine the metric properties of the spacetime continuum (whether it is flat of hyperbolic or spherical, linear, open or closed).

That was predicted only if one insisted that lambda = 0! Hence the observations obviously showed that lambda is not zero!

As I said above. There is no way to test curvature with the CMB. Inflation and its false vacuum flatten the universe for very specific reasons, today, those reasons feel kind of old, passé.

Models with a cosmological constant were used in cosmology already before 1998 (not often, but they were there), as I already pointed out. So calling this result "unpredicted" is an attempt to rewrite history. True, practically no one really expected this result - but not because this somehow contradicts the basic theory, but only because everyone was used to the simplifying assumption of setting lambda to zero!

Friedmann and everyone that followed had the option at hand to adjust lambda above, below or at zero. That is what lead to the three Friedmann models (open, closed and flat). The open model got close, but still a wopping 20-25% off the mark. Conceptually, it was much further off the mark.

Do you know why a fourth model was not predicted, one that would resemble the open-ended accelerated expansion?

Hint: It was not because the telescopic sensitivity was not available or sufficient throughout the 20th century.

It was because nobody then wanted to indroduce an ad hoc force, exotic energy, DE, a fifth force of nature that would blow away gavity, and more so with increasing distance. To be honest, it is still extremely distastful.

You really have strange ideas of both what constitutes a "blow below the belt" and "trivial nonsense".

I was also changing that in my post when you wrote your, No offence. (smile)

It was not nonsense. I replaced that with awkward triviality. Awkward because the data we have obtained since from multiple lines of evidence are not consistent with each other, contrary from what you claim. See eg, the CMB argument above.

The value of lambda, a free parameter in the theory. That no one is sure how one has to interpret the meaning of lambda doesn't in the least imply that we can't measure it.

It would be far more sound from the perspective of physics to know what you are measuring. I could sell uncut unicorn horn by the gram if someone is willing to buy it.

Depends on how exactly you define "known physics". E. g. one model for DE, quintessence, uses a scalar field. The physics of scalar fields has been known for decades and is very well understoof.

Good call.

For quintessence, wrong again. E. g. the Higgs field has many similarities.

I was under the impression (I might be wrong as I have not checked lately) that the hypothetical Higgs field and the Higgs particle(s) have not been observed. Correct me If I'm wrong.

Non sequitur. Simply because one can not detect something directly, this does not mean that this thing is "outside the physical world". Ever heard of indirect detections? Hint: most things in modern physics today can only be detected indirectly. Take e. g. quarks and gluons.

I was writing about dark energy only, nothing else. I was in a hurry too. So my post was cut short. Tell me though, which of the other items in physics cannot be directly detected in principle?

My intention was to include (had there been more time) that dark energy, unlike real energy, heat, entropy, or anything else in physics (or thermodynamics), and particularly unlike gravity (or any other 'force'), dark energy will always remain elusive. Every other property or constituent of the universe is available locally to at least test, experience or observe, in principle, indirectly or directly. DE is an exception, and therefore if on a scale of 0 to 10, where 0 is do not believe in DE, and 10 is do believe absolutely, my choice is 0. There is no doubt.

Obviously, yes. But my account is a lot closer to the truth than yours.

I could think of a fun analogy but I won't go there

Again: Lambda is simply a free parameter in the theory. That we can't explain its meaning so far does not in the least imply that it is simply a dreamt-up fudge factor which we aren't allowed to use or aren't able to measure.

There we disagree.

It is fun to post in an ATM section. I feel like an atheist in a theology forum, where the big bang is god and inflation is its prophet.

Edited to add:

Don't fight the chill.

Coldcreation

[Bjoern]

I will not get quantitative here and now. I will save that for a thread signed Coldcreation, so it pops up in a search engine with the name Coldcreation.

I'm waiting.

But finding solutions for the the mechanism behind the gravitational interaction is indeed extremely important.

We seem to have different understandings about what constitutes a "mechanism behind the gravitational interaction". I still think that "curvature of spacetime" is such a mechanism - although GR does not explain why spacetime does curve in the presence of energy (and pressure).

One of the reasons there is no unified field theory is because of this unknown.

And you know this how, precisely? See new thread, right?

The problem of gravity is a very interesting one. My feeling simply echos Feynman's. There are fundamental aspect of gravity that remain elusive, notably how it works, what causes it.

I've read quite a lot by Feynman, but it would be news to me that he was in any way not satisfaid with GR's description of gravity (well, beside the obvious failures to quantize it).

Which new particles would those be. The candidate for dark matter: neutralino?

The neutralino is the most probable candidate. Another proposal is e. g. the axion. Another particle which should show up at the LHC, but which has nothing to do with dark matter, is the (or at least one) Higgs boson.

You argue that dark matter is an unessential, made-up parameter, but don't even know what particle physics has to say about its existence?

Good question. It's like asking why do I think god does not exist. You know I have no proof, just indirect evidence that points in a more physical direction (that's why its a good question). Likewise, I know you have no proof, so we could spin ad infinitium on whether DE exists of not.

False analogy, I'd say. There is no evidence, not even indirect, that a god exists. OTOH, there is indirect evidence that dark energy exists. Hence you must have a reason why you regard that evidence as insufficient. Judging from what you said so far, that reason is that you think that all the available evidence could also be explained in another way, right? Well, if yes, then I probably have to wait for your new thread, where you will explain all that.

BTW, please don't forget to include both the metric and the stress-energy-tensor of your model in that new thread.

This will be the principle topic of the Coldcreation thread once I can get the short pdf online. My intension is not to highjack this thread. If you'de like we can take a break fro this one, until the CC thread emerges.

Agreed. This will be my last post to this thread. If you want to answer anything in it, please do it in the new thread you want to open.

I had used it though with the intention of highlighting (shockingly) the paradox that the CMB is being used as if it were a guide, a map, of the early cosmos, a redshifted vestige, relic, fossil. I disagree with that interpretation. There is no proof it has been redshifted from a higher thermal spectrum. It is a local radiation....

I don't understand why you call this a "paradox". What is inherently contradictory about that interpretation?

There are plenty of arguments against the CMBR being local (the dipole showing that the rest system of the CMBR is moving with respect to our solar system, our galaxy, our local group etc.; the SZ effect; the integrated Sachs-Wolfe-effect; measurements of the CMBR temperature in distant galaxies; development of present-day large-scale structure out of the initial fluctuations etc. - that's just what I can think of in the moment) . You have been posting to this forum for quite a while, so I suspect you have already seen then? If yes, you apparently again think that all these pieces of evidence can also be explained in another way? New thread, right?

To use it then for topological finding purposes is an outrage, from my perspective. There is no way, from the anistropy, or from anything else related to the CMBR, to determine the metric properties of the spacetime continuum (whether it is flat of hyperbolic or spherical, linear, open or closed).

First, you appear to confuse topology with the metric here. Second, the WMAP papers explain in detail how these properties were determined. Obviously, this only works if the CMBR is a "remnant" from the BB, and not local. But as mentioned above - there are plenty of good arguments for that...

Friedmann and everyone that followed had the option at hand to adjust lambda above, below or at zero. That is what lead to the three Friedmann models (open, closed and flat).

Did you just make a typo here, or do you really not understand the difference between the two parameters Lambda and Omega? It is the second which determines if the universe is open, closed or flat, not the first!

Do you know why a fourth model was not predicted, one that would resemble the open-ended accelerated expansion?

As I already mentioned: such a model was indeed used in some cosmological calculations. However, I don't know if it was ever applied to predicting SN data before 1998.

Hint: It was not because the telescopic sensitivity was not available or sufficient throughout the 20th century.

It was because nobody then wanted to indroduce an ad hoc force, exotic energy, DE, a fifth force of nature that would blow away gavity, and more so with increasing distance.

sigh If nobody wanted to introduce this - why was it then used in several models even before 1998??? You keep ignoring this!

Awkward because the data we have obtained since from multiple lines of evidence are not consistent with each other, contrary from what you claim. See eg, the CMB argument above.

In the CMB argument above, you didn't mention any inconsistencies in the data. So, what are you talking about here?

Oh, and what about this paper?
http://lambda.gsfc.nasa.gov/product/...parameters.pdf
In this paper, they compare the WMAP results (first year - but the third year results aren't that different) with data from several other sources - and find agreement (consistency!).

(1) Where exactly do you disagree with the findings of this paper? Where exactly do you see an inconsistency here?

(2) If the CMBR is local - how could it have been possible that parameter values consistent with other observations were determined from it?

It would be far more sound from the perspective of physics to know what you are measuring.

Well, yes, that would be "more sound". But so what? Again: Not knowing what exactly the parameter means does not in the least imply that we aren't allowed to measure it, or that it is simply a fudge factor.

Nevertheless, we have an interpretation of Lambda: it essentially gives the energy density of the vacuum (where "vacuum" refers to a spacetime without matter, both ordinary and dark, and radiation). Didn't you know that?

I could sell uncut unicorn horn by the gram if someone is willing to buy it.

What has that to do with measuring the value of a parameter in a theory?

I was under the impression (I might be wrong as I have not checked lately) that the hypothetical Higgs field and the Higgs particle(s) have not been observed. Correct me If I'm wrong.

Yes, they have not yet been observed. So what? Nevertheless, I'd call that "known physics".

If you prefer other particles which already have been observed: e. g. some mesons are also described with scalar fields. I simply didn't bring these up first because they are not fundamental particles, and their description is somewhat messy. But scalar fields are there nevertheless.

I was writing about dark energy only, nothing else. I was in a hurry too. So my post was cut short. Tell me though, which of the other items in physics cannot be directly detected in principle?

I already gave two examples above: quarks and gluons. You could e. g. add the wave function of QM.

And if you don't restrict this to "not directly detectable in principle" (I don't see any reason why we couldn't be able some time in the future to detect dark energy directly), you could also add black holes, the cores of stars and planets etc.

Additionally, this all depends on what constitutes direct detection and what not. One could argue that essentially nothing is "directly" detected in physics.

My intention was to include (had there been more time) that dark energy, unlike real energy, heat, entropy, or anything else in physics (or thermodynamics), and particularly unlike gravity (or any other 'force'), dark energy will always remain elusive. Every other property or constituent of the universe is available locally to at least test, experience or observe, in principle, indirectly or directly. DE is an exception, and therefore if on a scale of 0 to 10, where 0 is do not believe in DE, and 10 is do believe absolutely, my choice is 0. There is no doubt.

I don't understand this argument. First, there is, as already pointed out, indirect evidence (so your claim that dark energy can not even indirectly be observed is wrong). Second, there is no reason why dark energy should always be "elusive" to direct tests.

And, BTW, this is not about "believe", it's about following the evidence.

It is fun to post in an ATM section. I feel like an atheist in a theology forum, where the big bang is god and inflation is its prophet.

I have never seen a theologist bringing up quantitative evidence for the existence of a god, so the analogy fails quite badly.

[Bjoern]

I will start a new thread for this discussion. My claims go beyond the scope implicit here, and too, go beyond the hyperbolic static de Sitter manifold.
I have aleady expounded quite extensively on these and other related topics here in this forum, the text of which is easily accessible, though not comletely. See the SNe Ia thread and my own threads.

I have looked a bit at the thread "Coldcreation Cosmology: the Ultimate Theory". Unfortunately, I did not find anything quantitative there (well, the thread is quite big - perhaps I missed that).

I'll be specific in what I'd like to see when you start the new thread you promised: please tell us (1) what metric your model uses (please provide an equation, don't simply say "I use the de Sitter model" or something like that); (2) what energy-momentum-tensor you use (same here) (3) what other parameters and/or assumptions your model uses, if any (4) how you derive mathematically from these basic building blocks that the universe is static, but nevertheless a redshift is seen which increases with increasing distance.

Please be specific and quantitative. Do no simply post lots of verbiage (no insult intended) as in the thread mentioned above. Show how your assertions follow mathematically from the premises of your model.

I'd also like to see a quote by de Sitter where he says that his model is static, or a reference to the relevant paper. But that is not as important as the analysis described above.

Thanks in advance.

[brodix]

Sorry, I don't understand how you arrive at the conclusion of infinite radius.

This is not complicated. We can look at a galaxy through a telescope and say it's a 100,000 light years in diameter, but if we were to actually try to shine a beam of light across it and stand there waiting with the stop watch, it would never arrive, having fallen into the black hole at the center. Therefore the time it takes a real beam of light to cross it is much longer then 100,000 years.

We don't have that bird's eye view of the space in between galaxies, we can only measure the light crossing them.

I'm not entirely sure what exactly you mean with "absolute volume" and "relativistic expansion". Please explain.

Current BBT proposes the universe is expanding from a smaller size in real/absolute volume. My point is that while gravity draws mass and any reference points together, it uses a flat framework/Euclian space against which to measure it. In other words, we know the path of a beam of light is curved, because we are comparing it to an abstract flat line, otherwise we wouldn't know it to be curved. If there is an opposite effect, the redshift of light would be due to the lensing effect, opposite that which curves light, not actual increasing volume of the universe.(I explain this further down the post.)

No, it (usually) doesn't. Where did you get that from?

It draws everything into a gravitational vortex, thus curving the path of any light passing in the vicinity of the gravitational source.

Again, I don't see how you arrive at that conclusion, sorry. What are "lensing effects similar to gravity" supposed to mean, and how could they cause space expanding? What a (gravitational) lens does is well understood; expanding space does not belong to its properties.

Mass condenses until it ignites and radiates the energy back out. Having a particular location, it "lenses," ie. curves the path of light passing by it. Now if radiation has the opposite effect, it isn't condensing to a point, so there is no object which light beams are being curved toward, or away from. Rather then drawing everything to a point, it is pushing everything apart, so the effect would be of the distance between the source and reception of light being increased. Obviously it wouldn't affect mass, as the gravitational properties would neutralize this effect, so only light/radiation is affected.

How do you get from "the expansion is integral to..." to "it [requires] a cosmological constant"???

The cosmological constant was a variable to balance gravity. Since what I'm describing would be a convective cycle of expanding radiation, cooling down and condensing out as mass, until it reached the density at which it ignites and is radiated back out, these two effects are like two sides of the same coin. They are always going to balance.

Black holes are the eye of the storm and recent studies have shown very little mass is actually falling into them. While the cosmic background radiation would be the dew point, above which radiation condenses out as the most elemental components of mass, at the string level. Obviously the gap between photons and hydrogen is rather broad, but the sea of activity in between is just starting to be investigated.

And: What about showing the math behind all that verbiage?

Math is logical shorthand. Somewhere along the line, it has to be thought out in long hand first.

[Bjoern]

This is not complicated. We can look at a galaxy through a telescope and say it's a 100,000 light years in diameter, but if we were to actually try to shine a beam of light across it and stand there waiting with the stop watch, it would never arrive, having fallen into the black hole at the center. Therefore the time it takes a real beam of light to cross it is much longer then 100,000 years.

But the black hole has a diameter which is so small in comparison to the whole galaxy that if you shine a beam of light "across" it, there is an almost 100% probability that you will miss that black hole, and the beam will continue to the other side (perhaps a bit deflected, but not much). True, the beam of light wouldn't go through the exact center then - but nevertheless, this would give you a very accurate diameter for the galaxy.

Current BBT proposes the universe is expanding from a smaller size in real/absolute volume.

That would only be right for a closed universe, with a finite volume. But the evidence points to a flat (or open) universe, with infinite volume.

My point is that while gravity draws mass and any reference points together, it uses a flat framework/Euclian space against which to measure it. In other words, we know the path of a beam of light is curved, because we are comparing it to an abstract flat line, otherwise we wouldn't know it to be curved.

Right - but I don't see any connection to the following...

If there is an opposite effect, the redshift of light would be due to the lensing effect, opposite that which curves light, not actual increasing volume of the universe.(I explain this further down the post.)

Good, since I cannot follow you here at all.

It draws everything into a gravitational vortex, thus curving the path of any light passing in the vicinity of the gravitational source.

This was about your assertion that gravity "contracts space".

(1) What you describe here has nothing to do with "contracting space".

(2) What you describe here is only true for a Schwartzschild-like metric. I thought we were talking about the universe as a whole? (Robertson-Walker metric!)

Mass condenses until it ignites and radiates the energy back out. Having a particular location, it "lenses," ie. curves the path of light passing by it. Now if radiation has the opposite effect, it isn't condensing to a point, so there is no object which light beams are being curved toward, or away from. Rather then drawing everything to a point, it is pushing everything apart, so the effect would be of the distance between the source and reception of light being increased. Obviously it wouldn't affect mass, as the gravitational properties would neutralize this effect, so only light/radiation is affected.

But we already know from GR that radiation has no such effect (well, there is radiation pressure, but I don't think you mean that). If you doubt the validity of GR, please provide evidence against it.

The cosmological constant was a variable to balance gravity.

Yes, that was its original purpose. But even Einstein himself knew already that this isn't the only thing which it can do.

Since what I'm describing would be a convective cycle of expanding radiation, cooling down and condensing out as mass,

Radiation "cooling done" and then "condensing out as mass"? What on earth are you talking about? Do you have any evidence that this is possible?

until it reached the density at which it ignites and is radiated back out, these two effects are like two sides of the same coin. They are always going to balance.

Why should they?

Additionally, I still don't understand what this has to do with your original assertion (quoting from an earlier post):

Because the expansion is integral to the relativistic effects of crossing expanding space, not an initial event, it declines at a rate requiring a cosmological constant to explain and thus, dark energy.

This still looks like complete world salad to me, and I see no connection to what you wrote here.

Black holes are the eye of the storm and recent studies have shown very little mass is actually falling into them.

Please give references to these studies. Which black holes were studied, specifically? E. g. the black holes in active galaxies are very active (duh).

While the cosmic background radiation would be the dew point, above which radiation condenses out as the most elemental components of mass, at the string level.

More word salad. What does it mean to call the CMBR the "dew point"? What does it mean to be "above" the CMBR? What are "the most elemental components of mass"? What does "at the string level" mean?

Obviously the gap between photons and hydrogen is rather broad, but the sea of activity in between is just starting to be investigated.

What investigations are you talking about, specifically?

And why jump from photons directly to hydrogen? Why not first "condense" to electrons or some other simple particle like that?

Math is logical shorthand. Somewhere along the line, it has to be thought out in long hand first.

As long as you don't have math (and hence can't make quantitative descriptions and predictions), you are not doing physics - you are merely making up stories.

[Nereid]

[snip]

As long as you don't have math (and hence can't make quantitative descriptions and predictions), you are not doing physics - you are merely making up stories.

I'd like to use that as my sig - do I have your permission, Bjoern?

(and a (very) belated welcome to BAUT! )

[Bjoern]

I'd like to use that as my sig - do I have your permission, Bjoern?

Feel free to use it.

(and a (very) belated welcome to BAUT! )

[/QUOTE]

Thanks. And I wouldn't say just four days is that late...

[Coldcreation]

We seem to have different understandings about what constitutes a "mechanism behind the gravitational interaction". I still think that "curvature of spacetime" is such a mechanism - although GR does not explain why spacetime does curve in the presence of energy (and pressure).

I've read quite a lot by Feynman, but it would be news to me that he was in any way not satisfaid with GR's description of gravity (well, beside the obvious failures to quantize it)..

See for example, and read a sample below:

Feynman, P.R., 1994, Six Easy Pieces, pp. 107-110

"All we have done is to describe how the earth moves around the sun, but we have not said what makes it go. Newton made no hypothesis about this: he was satisfied to find what it did without getting into the machinery of it. No one has since given any machinery."

In short, we use math to describe the nature of gravity (or curved spacetime) without knowing what mechanism is operating.

This, despite what you may think, is a huge problem, and it's resolution will lead to great insight into the workings of nature on a much broader base than just gravitationally.

The neutralino is the most probable candidate. Another proposal is e. g. the axion. Another particle which should show up at the LHC, but which has nothing to do with dark matter, is the (or at least one) Higgs boson.

You argue that dark matter is an unessential, made-up parameter, but don't even know what particle physics has to say about its existence?.

I am pragmatic. Anything that is nonbaryonic (i.e., dark matter used to fill the gap between theory and observation, some supposed 25% of the mass-density of the universe), I will have to see to believe, and then some. Sorry.

snip... there is indirect evidence that dark energy exists. Hence you must have a reason why you regard that evidence as insufficient. Judging from what you said so far, that reason is that you think that all the available evidence could also be explained in another way, right?....snip.....

The problem boils down to which conceptual interpretation of the data does one believe. (Assuming the math fits the divergent interpretations.)

Agreed. This will be my last post to this thread. If you want to answer anything in it, please do it in the new thread you want to open..

I noticed you continued posting, and I could not let stand as a final word the remarks you left here without a promt response on my part.

I don't understand why you call this a "paradox". What is inherently contradictory about that interpretation?

There are plenty of arguments against the CMBR being local (the dipole showing that the rest system of the CMBR is moving with respect to our solar system, our galaxy, our local group etc.; the SZ effect; the integrated Sachs-Wolfe-effect; measurements of the CMBR temperature in distant galaxies; development of present-day large-scale structure out of the initial fluctuations etc. - that's just what I can think of in the moment) . You have been posting to this forum for quite a while, so I suspect you have already seen then? If yes, you apparently again think that all these pieces of evidence can also be explained in another way? New thread, right?.

When I use the word local it is meant out to distance compatible with the Local Group. Of course there is a viable alternative.

snip...`Obviously, this only works if the CMBR is a "remnant" from the BB, and not local. But as mentioned above - there are plenty of good arguments for that... .

See above...

Did you just make a typo here, or do you really not understand the difference between the two parameters Lambda and Omega? It is the second which determines if the universe is open, closed or flat, not the first!.

Perhaps it was a lack of rigor, or an abundance of fine Spanish wine, or both. I do know the difference, thanks. (Do I detect another low blow?). It is lambda that is supposedly blowing apart the universe. Omega is simply too small to stop it.

As I already mentioned: such a model was indeed used in some cosmological calculations. However, I don't know if it was ever applied to predicting SN data before 1998..

It was not, as far as I know.

sigh If nobody wanted to introduce this - why was it then used in several models even before 1998??? You keep ignoring this!.

For convenience. But too, because there were already signs__observations could not determine, due to the lack of sensitivity as you rightly pointed out above, what the deceleration parameter was or should have been__that showed something was amiss, obviously.

Well, yes, that would be "more sound". But so what? Again: Not knowing what exactly the parameter means does not in the least imply that we aren't allowed to measure it, or that it is simply a fudge factor.

No, I don't by that. Now you are showing a lack of rigor.

Nevertheless, we have an interpretation of Lambda: it essentially gives the energy density of the vacuum (where "vacuum" refers to a spacetime without matter, both ordinary and dark, and radiation). Didn't you know that?.

Did know that.

Did you that lambda has to be cut down by 120 orders of magnitude with humongous precision in order to account for the missing two-thirds of the critical density by just the right value? That fine-tunning problem is the worst failure in the history of science.

Did you know that extrapolating back in time the situation is far worse (I'll spare readers the gory details). That is the extent to which cosmologists are prepared to go in pursuit of a subjective interpretation that separates them from Einstein, coupled with the stress that lay on the intellect as transformers of appearance, rather than acknowledge the real greatest blunder.

The self-repulsive ogre is growing fast and out of control. And it's so ugly it repels itself.

Did you know too that the energy associated with the vacuum (call it what you please, lambda, quintessence, Casimir force, ZPE, ground-state energy) is less than a millielectron-volt?

Yes, they have not yet been observed. So what? Nevertheless, I'd call that "known physics"...

More, pardon the expression, lack of rigor.

If you prefer other particles which already have been observed: e. g. some mesons are also described with scalar fields. I simply didn't bring these up first because they are not fundamental particles, and their description is somewhat messy. But scalar fields are there nevertheless..

ok, sounds good (messy). I'll adopt a wait and see approach. Let's see what pops into existance at the hadron collider.

And if you don't restrict this to "not directly detectable in principle" (I don't see any reason why we couldn't be able some time in the future to detect dark energy directly), you could also add black holes, the cores of stars and planets etc.

Additionally, this all depends on what constitutes direct detection and what not. One could argue that essentially nothing is "directly" detected in physics..

Please show (quantitatively if you wish) how in principle dark energy, of the kind believed to dominates the universe, can be directly detected, now or in the future. Indirect lines of evidence are all too often left open to divergent interpretations. Please do so in a way that would rule out other interpretations of what is happening.

And, BTW, this is not about "believe", it's about following the evidence.

.

I've used the word beleif (believe) appropriately above.

Coldcreation