Origin of the Universe,,,,Bang or no Bang

[Pluto]

G'day From the land of ozzz

 

Freeztar said

 

I predict that the results from the JWST will strengthen the BBT, either by providing direct support or recommendations for revision, rather than abolish it.

 

We should take a poll of how JWST will or will not strengthen the BBT.

 

I vote that the evidence will be the last nail for the BBT.

 

If I'm wrong I will have to eat my hat.

[coldcreation]

The LCDM model is both a big bang model and a Friedmann universe. It uses the Friedmann metric.

 

The concordance model *is* an original Friedmann model. The only difference between the model then and the model now is the value of the parameters chosen for the model—in particular, a non-zero cosmological constant.

 

Remember the pre-1998 standard canonical hot big bang Friedmann models predictions:

 

(1) The favored possibility Ω = 1 describes the universe in which omega is precisely equal to one, the critical density. There is a one-to-one relation between the density of the cosmos and its spatial curvature, i.e., this model has a flat, Euclidean geometry (with zero curvature). The velocity of expansion tends to zero as its radius approaches infinity.

 

(2) Ω > 1: this model has a closed spherical geometry; it expands and collapses to infinite density in a finite time. There is enough gravitating mass to halt the expansion and reverse it, leading to a big crunch.

 

(3) The model with Ω < 1 has a hyperbolic geometry and expands for ever, tending to infinity with a finite velocity. The galaxies are undecelerated as there is not enough gravitating mass to stop expansion or to slow it down.

Non of the above predicted an accelerated expansion.

 

Compare SNe Ia data with the pre-1998 predictions:

 

Hubble Space Telescope Observations of Nine High-Redshift ESSENCE Supernovae See Figure 13 of the pdf file.

 

Notice the deviation from linearity. This deviation is the reason why the supposed "age" of the universe had to be revised down from 15 Gyr to 13.7 Gyr post-1998, why universal expansion had to be "accelerating" as opposed to pre-1998 standard model prediction of decceleration or coasting (recall, the latter was the favored Friedmann model, the so-called flat or critical model).

 

This deviation shown in Fig 13 is also the reason why 96% of the mass-energy of the universe is thought to consist of both nonbaryonic dark matter and an unknown form of energy (dark energy).

 

This curvature shown in Fig 13 of the above link is why the standard big bang model had to be replaced with the post-1998 Lambda-CDM model.

 

 

...set up repeateable experiments that attack the weakest point of the assumption...

 

Any assumption pertaining to cosmology can and should be attacked, especially those that remain speculative.

 

The problem, of course, is that NO direct experiments at all (let alone repeatable) can be devised, concocted, or set up in a laboratory that will validate or falsify inflation, cold dark matter or dark energy, even in principe.

 

 

 

...it is best to attack it where the proponents agree the idea is weakest...

 

The above phrase is equivalent to saying 'it is best not to attack it when proponents agree the idea is strongest.' Or simply, 'don't attack the strongest points,' which sound (unintentionally most likely) like an argumentum verbosium.

 

I am not persuaded by the volume of material that make the inflation, CDM and DE argument sound plausible. Though inflation, CDM and DE superficially appear to be well-researched, pinning down the actual physical properties of these (states, forces or whatever) is too laborious (in that there is no direct supporting empirical evidence) to let slide by unchallenged.

 

 

The proponents of BBT strongly assert, based on evidence and resolved predicitions, that oldness/flatness, horizon, 1a supernovas, are essentially dead

 

Interestingly enough, the opponents of BBT strongly assert, based on evidence and resolved predicitions, that oldness/flatness, horizon, 1a supernovas, are far from dead.

 

Inflation, from its inception, was generally accepted proof that the standard model was faltering, lurching from crisis to crisis.

 

Too, the oldness/flatness, horizon problem are thought to be resolved by the one-and-only inflation theory (you choose the version). Yet you write that inflation is one of the weakest points of the BBT.

 

 

 

Dark matter as a concept while not as solid as the above issues, has now been around long enough to have been indirectly observed in several different and independently observed phenomena ...

 

Euclid's Fifth Postulate was around for a couple thousand years, and Newton's theory of gravity for a couple hundred; that doesn't make them right.

 

 

Dark Energy, although silghtly newer and this having less time to amass such a catalogue of support,...Dark Energy has been around longer than we usually give credit. It dosn't hurt that the existing "hole" happened to nearly exactly match the "size" of the calculations required by observed data.

 

Same counter-argument as above.

 

The "hole" (96% of the mass energy density) was filled in with "stuff" that may not exist.

 

 

The implications of Dark Matter and Energy are disturbing not satisfying and I think it is fair to say that the vast majority of scientists wish it were not so and in the face of that denial *still* were forced to recognize how much they explain and how coherent a picture they complete.

 

The deductive argument is invalid because the conclusion doesn't follow from the premise in the manner described. No one should be "forced to recognize" something that may not exist at all. Accepting inflation, CDM and DE diverts attention away from the artifice in dispute rather than address them directly.

 

Recall when people were 'forced to recognize' the pre-Michelson–Morley-experiment aether.

 

 

I therefore repeat, if you wish to change minds and have any success at chipping away at as powerful an edifice as is the Standard Model, you must focus on what is widely agreed to be the weakest points - baryogenesis and inflation [...] These are the areas that are most speculative and likely will take longer to devise any useful experiments that have any hope of being definitive.

 

Baryogenesis, I agree, is a weak point. It seems to me nonbaryogenesis (the origin of CDM) would be even weaker. :)

 

Inflation is weak for sure (see below).

 

 

 

 

inflation itself remains on the fringes of science.

 

How so?

 

There is no way to experimentally distinguish between competing inflation models in the near or distant future. That is because there is no way to test inflation is a vacuum experiment. The false vacuum state, slow-rollover phase transition, are not producible or reproducible. For this reason, and others, inflation remains strictly hypothetical, speculative.

 

 

If you recall, we've discussed this before on a news release thread of the JWST. ;)

 

I predict that the results from the JWST will strengthen the BBT, either by providing direct support or recommendations for revision, rather than abolish it.

 

I remember. And I hope we can discuss this topic again soon. :shrug:

 

 

 

CC

[modest]

Remember the pre-1998 standard canonical hot big bang Friedmann models predictions:

 

(1) The favored possibility Ω = 1 describes the universe in which omega is precisely equal to one, the critical density. There is a one-to-one relation between the density of the cosmos and its spatial curvature, i.e., this model has a flat, Euclidean geometry (with zero curvature). The velocity of expansion tends to zero as its radius approaches infinity.

 

(2) Ω > 1: this model has a closed spherical geometry; it expands and collapses to infinite density in a finite time. There is enough gravitating mass to halt the expansion and reverse it, leading to a big crunch.

 

(3) The model with Ω < 1 has a hyperbolic geometry and expands for ever, tending to infinity with a finite velocity. The galaxies are undecelerated as there is not enough gravitating mass to stop expansion or to slow it down.

Non of the above predicted an accelerated expansion.

 

Sure they do, and I'm pretty sure we've already discussed this. Here is Carroll 1992. It would be a good read:

 

http://preposterousuniverse.com/writings/cpt92.pdf

 

It solves 5 friedmann "models" with different valued parameters,

 

 

which can have accelerated expansion,

 

 

This paper is from 1992, before the SN 1a findings. The concordance model is a Friedmann universe. It is an exact solution to General Relativity and it is a model of Big Bang theory.

 

The Freidmann equation can take this form:

[math]\frac{H^2}{H_0^2} = \Omega_R a^{-4} + \Omega_M a^{-3} + \Omega_k a^{-2} + \Omega_{\Lambda}[/math]

Making [math]\Omega_{\Lambda}[/math] non-zero doesn't make it NOT a Friedmann universe (and NOT big bang theory)... that wouldn't make sense.

 

~modest

[coldcreation]

Sure they do...

 

It solves 5 friedmann "models" with different valued parameters [...] which can have accelerated expansion,

 

This paper is from 1992, before the SN 1a findings. The concordance model is a Friedmann universe. It is an exact solution to General Relativity and it is a model of Big Bang theory. [...]

 

Making [math]\Omega_{\Lambda}[/math] non-zero doesn't make it NOT a Friedmann universe (and NOT big bang theory)... that wouldn't make sense.

 

~modest

 

Perhaps my point was missed. I reiterate:

 

 

The standard model, formerly known as the canonical hot big bang model (before the SNe Ia data began trickling in), which based on the Friedmann equations (with an FLRW metric) predicted three possible solutions, one of which was favored. The latter (with Ω = 1) predicted a flat universe. Flatness was needed in order to be compatible with inflation. Without flatness (i.e., without inflation) the problems inherent in the BBT could not be reconciled.

 

The two supernovae survey initially set out to measure the decceleration or expansion, the curvature of the cosmos (again, predicted to be Euclidean). It was thought that the SNe survey might pin-down the Hubble constant.

 

The favored Friedmann world-view assumed time to be linear and scale-invariant. The predicted evolutionary state in the look-back time is associated with the redshift z (given by the cosmic time scale) and assumed to be linear. To test the hypothesis, distant supernovae (SNe Ia) were used as standard candles. The detection rate of supernovae at large redshift, the radius of the supernovae shell or envelope, the assumed temperature flux and the SN luminosity, were expected to remain constant in time t.

 

Results of the SNe Ia data: The flatness hypothesis has not been confirmed observationally.

 

On the contrary, the results surprised everyone, except perhaps Carroll.

 

What was observed was curvature. (See Figure 13 of the above link).

 

The prediction did not pass the test of observation.

 

In denial, some of the theorists involved in the survey even suggest that the effect was caused by "tired light." :hihi:

 

 

The favored Friedmann model, consequently, had been drained of its interpretive validity. All that was left was to exhume Einstein's cosmological constant, with its false beauty, its magic, its false vacuousness, its anti-gravity, with its new stigma of over-repulsivness.

 

The revisionist attempts to rescue some validity in connection to the divide between unfolding observational evidence and the pre-1998 theoretical understanding of cosmology have relegated the new standard model (with its copious CDM and DE components) to the realm of artificial, to which—it is obvious—nature is rigorously opposed.

 

Hawking’s 1999 remark with regards to the new cosmological repulsion is revelatory: “This led me to reconsider my theoretical prejudices. I now think it is very reasonable that there should be a cosmological constant.” (Astronomy, Oct. 1999 Vol. 27, 10, p. 44-51).

 

 

A force on the brink is recreated.

 

 

Hawking’s decision to restore, restage or rehabilitate the constant looked as if detrimental to his own interests. After all, for decades he had vilified lambda so unfairly: as a balancing force in conflict with the big bang, an error, or blunder, that never should have found its way into the field equations. But he had no choice. Now, physicists including Hawking seem thrilled at what they regard as a vindication, a renaissance of sorts, Einstein yet right again. Now lambda is retro but in.

 

Lambda (now synonymous with dark energy) has become one of the basic facts to be believed. Without revitalization, modern cosmology and its discourse is ineffective, and the entire faith feels suddenly futile. Now the cosmological constant has risen from the departed, and become the Firstfruit of those that slept.

 

The old constant has been sanitized for the public; the limitations, were stripped out. The way modern cosmology has hyped antigravity (DE) is not just a matter of intellectual curiosity. It is essential that the public recognize the implications because we are now being asked to accept a new principle that have nothing to do with any of the known forces of nature.

 

 

So again modest, and yes we've discussed this before (and will likely do so again), the standard model has changed, A little monkeying with physics has endowed the vacuum itself to create new space out of nothing at an accelerated (quasi-exponential) rate.

 

SNe Ia observational data are a signature of hyperbolic geometry, of spacetime curvature. For the alternative—that some innocent force had cross-contaminated the cosmos—would leave the investigation essentially where it has been from the start: Nowhere.

 

 

The situation is far from under control. Worse, it looks as if nature is playing whack-a-mole not just with the standard model, but with physics. Every time we bang the moles head down, another one springs up somewhere else.

 

 

 

A new era has begun.

 

 

 

 

 

CC

[modest]

Perhaps my point was missed. I reiterate:

 

Yes.. yes... I understand what you're saying. You see the three cases of spatial curvature corresponding to the ultimate fate of the universe (big crunch or heat death) as three Friedmann model predictions. In moving away from those three scenarios, you think cosmology as moved away from the "Freidmann models".

 

The thing is, any time you've ever seen spatial curvature compared to the scale factor in the way you envision, it came with the assumption that the cosmological constant was zero. This is an explicit assumption that comes along with that comparison. For example, Ned Wright's cosmology tour:

 

The figure above shows the three curvature cases plotted along side of the corresponding a(t)'s [scale factor as a function of time]. These a(t) curves assume that the cosmological constant is zero, which is not the current standard model. Ω > 1 still corresponds to a spherical shape, but could expand forever even though the density is greater than the critical density because of the repulsive gravitational effect of the cosmological constant.

 

Notice the explicit assumption that comes with this image “These a(t) curves assume that the cosmological constant is zero”. That assumption was just as true 20 years ago as it is now—we just didn’t hear it in layman literature as often. But, believe me, all of cosmology knew that was an assumption they were making all the way back to Einstein who I gave you a quote of saying exactly as much.

 

The Freidmann equations work just as well when the cosmological constant is not zero. There are more than 3 families of solutions as the picture above would imply. When the cosmological constant is not assumed to be zero and not factored out of the equation, we get these general possibilities:

Solutions of the Friedman Equation

 

 

The line Omega(Lambda) = 0 separates universes with negative and positive cosmological constant. Negative values mean that the universe always recollapse eventually: the expansion halts and reverses at a certain point.... After turnaround the collapse is a time-reversed version of the expansion (note that the Friedman equation specifies only H² and so doesn't fix the sign of expansion/collapse). These "Bang-crunch" universes with Omega(Lambda) < 0 form our first family of solutions.

 

The second family are the positive cosmological constant models bounded by the green and red lines. These represent universes which expand continuously from R = 0 to infinity. They start from the Einstein-de Sitter point and end at the de Sitter point, i.e a universe with zero matter density and critical density in the cosmological constant. This is because a positive cosmological constant will eventually dominate the total density as it does not fall at all as the universe expands

 

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)... This is a delicate and unstable balance.

 

The third family of Friedman solutions are the ones with positive cosmological constant, but which fall to the left of the green loitering line. For these, the repulsive term is not enough to prevent recollapse, so they expand from the Einstein-de Sitter point to a turnaround at infinity, and then recollapse back to a big crunch along the same track. This family is effectively continuous with the first family (negative cosmological constant) through the case with Lambda = 0. Thus all the tracks to the left of the green line expand from a big bang and recollapse to a big crunch.

 

The fourth family are those to the right of the red loitering line. In these universes the cosmological constant is so large that, projecting the universe back in time, the expansion turns around in the past; these are the bounce models, in which the universe collapses from infinity (contracting from the de Sitter point), bounces (both Omegas are infinite at the bounce as H = 0 here just as at turnaround in "bang-crunch" universes), and then re-expands, finishing in an expanding de Sitter phase.

 

Solving the Friedman Equation

 

These were all well-known and well-described prior to the supernova standard candle tests. The concordance model *is* a Friedmann universe.

The model uses the FLRW metric, the Friedmann equations and the cosmological equations of state to describe the universe from right after the inflationary epoch to present and future.

 

Lambda-CDM model - Wikipedia, the free encyclopedia

 

I believe you've mistaken the assumption that [math]\Omega_\Lambda[/math] = 0 which was common in cosmology more than a decade ago with the necessity for that to be true with the model cosmology was using. There was no such necessity as the paper I linked from '92 shows.

 

~modest

[coldcreation]

The thing is, any time you've ever seen spatial curvature compared to the scale factor in the way you envision, it came with the assumption that the cosmological constant was zero. This is an explicit assumption that comes along with that comparison.

 

Notice the explicit assumption that comes with this image “These a(t) curves assume that the cosmological constant is zero”. That assumption was just as true 20 years ago as it is now—we just didn’t hear it in layman literature as often. But, believe me, all of cosmology knew that was an assumption they were making all the way back to Einstein who I gave you a quote of saying exactly as much.

 

When the cosmological constant is not assumed to be zero and not factored out of the equation, we get these general possibilities:

 

I believe you've mistaken the assumption that [math]\Omega_\Lambda[/math] = 0 which was common in cosmology more than a decade ago with the necessity for that to be true with the model cosmology was using. There was no such necessity as the paper I linked from '92 shows.

My bold.

 

 

Here is the problem:

 

Prior to L-CDM the standard model had taken for granted a zero value for lambda (i.e., it was accepted as true without proof and factored it out of the equation), based on assumptions made from the outset, not as a necessity.

 

Now, L-CDM (the new standard model) has taken for granted a nonzero value for lambda (i.e., it is accepted the existence of dark energy without direct evidence) based on an observed nonlinearity (e.g., see again Figure 13 above, along with WMAP data).

 

Indeed, cosmology has moved away from the pre-1998 Freidmann models (where lambda was assumed to be zero, i,e., irrelevant).

 

The error was (is) not in assuming lambda to be equal to zero, positive or negative. The error was (and still is) in the erection and specious assumption of validity of an entire edifice—not just any edifice either, but one that involves the entire history and fate of the cosmos—based on a foundation made of something so ethereal, speculative, as the existence or not of Einstein's cosmological constant—something about which nothing can be said with certainty, no one has any inkling of an idea as to what exactly, if anything, is operational.

 

The point should be made, it can easily be shown that the customary unambiguous conclusion of cosmological expansion is a direct consequence of two unverifiable assumptions: The Doppler-like redshift interpretation of astronomical spectra (change in the scale factor to the metric, with time) and the uniformity assumption (not to mention the unverifiable assumptions about the initial conditions that surround the big bang itself, t = 0, inflation, the matter-antimatter asymmetry, the contact, ignition and the blast-off, when and where the laws of physics are irrelevant).

 

And now, with the advent of a new standard model, L-CDM we have two more unverifiable assumptions: That the nonlinearity observed in the spectra and light curves of distant SNe Ia is a result of some superfluous form of cold dark matter and a form of elusive energy (dark force or vacuum energy). These are all assumed for priori reasons and cannot be tested empirically, even in principle.

 

Furthermore, there are overwhelming arguments showing that since its inception the standard model (with the FLRW metric in any form, i.e., with or without lambda) has not been able to mimic all the observations. The idea that the revival of lambda has alleviated the tribulations is nonsensical, since the tribulation created by such a faith-based 'force' is equally, if not more, damning (at least until some form of direct evidence emerges, which is likely never).

 

 

Since 1998 the entire nebulous picture of cosmology (and ultimately physics itself) has changed. With its new conception of stealthy energy assumed to dominate the universe, we are assured that the myriad of questions that surround the history of the cosmos are no longer amenable to a more meaningful discussion.

 

 

 

as·sump·tion (Source)

2. The act of taking possession or asserting a claim...

3. The act of taking for granted: assumption of a false theory.

4. Something taken for granted or accepted as true without proof; a supposition: a valid assumption.

 

7. Assumption

a. Christianity The taking up of the Virgin Mary into heaven in body and soul after her death.

 

 

You see modest (and anyone else who happens across this thread)' date=' with its dark matter and dark energy components cosmology has passed over from the realm of physical science to the domain of assumptions, speculation, of metaphysics.

 

 

 

[center']

“The assumption that seeing is believing makes us susceptible to visual deceptions”

(Kathleen Hall Jamieson)

 

 

"You must stick to your conviction, but be ready to abandon your assumptions"


(Denis Waitley)

 

 

“Assumption is the mother of the screw-up”

(Angelo Donghia)

 

 

 

CC[/center]

[modest]

The error was (is) not in assuming lambda to be equal to zero, positive or negative. The error was (and still is) in the erection and specious assumption of validity of an entire edifice—not just any edifice either, but one that involves the entire history and fate of the cosmos—based on a foundation made of something so ethereal, speculative, as the existence or not of Einstein's cosmological constant—something about which nothing can be said with certainty, no one has any inkling of an idea as to what exactly, if anything, is operational.

 

But, you believe strongly in the cosmological constant :naughty:

 

I am, by the way, a fervent believer in Einstein's cosmological term. I believe that its value is not just close to zero, but is precisely zero.

 

-post

 

I believe the cosmological constant arises naturally from the derivation of general relativity and its existence is strengthened by quantum field theory. I'm simply saying we should not arbitrarily assume it is equal to zero which used to be common practice in cosmology. We need to measure cosmic parameters to know its value,

 

The postulate of general relativity requires the introduction of the [cosmological constant] into the field equations. It will be our factual knowledge of the composition of the starry heavens, of the apparent motions of the stars, and of the state of spectral lines as a function of conditions far from us that will allow us empirically to answer the question whether the [cosmological constant] equals zero or not. Conviction is a good mainspring, but a bad judge!

 

-

source

 

I also believe (and I can support) that the Friedman metric tells us how a homogeneous and isotropic universe with (or without) a cosmological constant would evolve if that universe is subject to the rules of general relativity.

 

~modest

[coldcreation]

I think it is fair to say that all of cosmology now depends on the existence of cold dark matter and dark energy. Since without both (or either) of these hypothetical, speculative entities, force, or states, the standard model, and thus the big bang theory fails (i.e., is in disagreement with observations).

 

For this reason, the discussion on the validity of the BBT (the topic of this thread) has come to be centered on lambda.

 

 

But, you believe strongly in the cosmological constant.

 

I do believe strongly in the cosmological constant (and yes with a zero value). But what I believe or not is not relevant right now. For it is the L-CDM model, with its interpretation of lambda that on trial. Unfortunately, without convincing evidence the case is too weak to decide on a verdict either way.

 

Something else will have to be used to test the validity of the BBT. That something, as mentioned previously, will be the determining factor: the age of stars and galaxies located near the so-called dark age boundary or transition (during the latter stages of reionization, from z = 8 → 6), where it is predicted by the standard model that all material objects (proto-stellar populations, proto-galaxies) have begun to form, and so are young, morphologically immature, metal-poor. If the standard model is accurate these should be found in large numbers by next-generation programs (i.e., JWST).

 

 

 

Our view of extragalactic astronomy has grown so much in the last decade that it is fair to say that almost every year there is enough new information to hold a full symposium on recent results. The discovery of stellar populations in grown-up galaxies at higher and higher redshifts' date=' approaching z ~ 10, constitutes an extraordinary achievement of observational astronomy and detector technology, and poses formidable challenges for theories and models of galaxy formation, evolution, merging and clustering. Very large samples of galaxies have been observed photometrically (several million galaxies) and spectroscopically (of the order of a million galaxies), and comparing the properties of the stars in these galaxies with our knowledge of how stellar populations evolve has enabled new constraints on the ages and stellar masses of these galaxies. [...']

 

Some of these questions are:

 

• Are star formation processes seen in local dwarf and resolved galaxies typical in giant galaxies?
   
  
• What determines the galaxy mass threshold for star formation quenching to be effective? Is this threshold the same in galaxy clusters as in the field? Are giant ellipticals formed monolithically, by merger events, or both? What is the final answer?
   
  
• Are there chemical abundance patterns that can decide in favor or against one of these scenarios?
   
  
• How can we reliably model the UV emission from early-type galaxies (EHB stars, or recent star formation, or PNN)?
   
  
• How crucial is the inclusion of binary stars in population synthesis models?
   
  
• Does dark matter play any role in the evolution of stellar populations? Do stars in galaxies with more dark matter evolve identically to stars in galaxies with less or no dark matter?
   
  
• How universal is the IMF? Is it the same in all extragalactic globular clusters studied so far? Does it depend on the strength of the merger events that trigger cluster formation?
   
  
• In what direction should stellar evolution go to provide tools needed to understand the chemical abundance patterns observed in stellar populations. Do we need evolutionary tracks computed for different enhancement ratios for different families of chemical elements? Are there enough observations to constrain different enhancement processes proposed for different elements?
   
  
• Can we explore population III stellar populations using current models? 2013 will see the launch of JWST, 2015 the arrival of the first ELT's and we need to be able to investigate stars with zero metal content at the reionization epoch.
  

Source

 

 

I believe the cosmological constant arises naturally from the derivation of general relativity and its existence is strengthened by quantum field theory.

 

I too believe the cosmological constant arises naturally from the derivation of general relativity. Though, the past and current interpretation of its properties leaves something to be desired.

 

 

 

I'm simply saying we should not arbitrarily assume it is equal to zero which used to be common practice in cosmology.

 

We need to measure cosmic parameters to know its value

 

True, again. But first it has to be known what exactly should be measured. I am not convinced that measuring redshift and light curves is the way to determine the value of lambda. I guess that depends on the model. Certainly, within the bounds of the actual standard model that is the way to go. That just may turn out to be a false premise (promise).

 

 

 

I also believe (and I can support) that the Friedman metric tells us how a homogeneous and isotropic universe with (or without) a cosmological constant would evolve if that universe is subject to the rules of general relativity.

 

Yes again. But general relativity is so general that it has to be determined with accuracy to what extent nature is subject to that kind of generality. In other words, there may be limits, thresholds, critical points, minima and maxima that affect the extent to which natural phenomena (that involve spacetime and material objects) respond to stress, condensation, curvature, high energy, low energy and so on.

 

For example Einstein himself wrote in the context of singularities:

’One may…not assume the validity of the equations for very high density of field and matter [...] in the mathematical sense’

(Einstein, from Pais, A. 1982, ‘Subtle is the Lord…’ The Science and the Life of Albert Einstein).

 

Right now it is assumed the validity of the equations for very high density of field and matter. Nature may not be 'aware' of these generalities. :confused:

 

I think it is essential, as you may recall, that resolution of the problem will come once the physical mechanism of gravity has been identified. That was the goal of the discussion now located here: Physical Mechanism of Gravity - The Spatiotemporal Ground-State. Perhaps I should research engine the topic to see if there's anything new to add there. I don't think the goal of pin-pointing the mechanism is beyond reach (though it has shown to be hitherto elusive). I think we were getting somewhere: Just how close remains to be seen (empirically of course).

 

 

Incidentally, the case of Redshift z as a potential geometrical phenomenon (as opposed to a changing scale factor to the metric) has not been closed yet either...

 

 

 

CC

[Pluto]

G'day from the land of ozzzz

 

I have had 2 friends reading both coldcreation and modest. They love the discussion.

 

In my opinion coldcreation has hit the nail on the head.

 

As for star formation and calculating the age of stars. That is practicularly impossible. Since stars are being formed as we speak and rejuvinated as we speak. How can anybody calaculate the age of stars and make it a reference to the age of the universe.

 

The age could be related to the phase or stage of the star.

 

This link is quite interesting and I would like to share it. This does not mean I agree with it.

 

[0812.2187] Star-forming cores embedded in a massive cold clump: Fragmentation, collapse and energetic outflows

Star-forming cores embedded in a massive cold clump: Fragmentation, collapse and energetic outflows

 

Authors: Martin Hennemann, Stephan M. Birkmann, Oliver Krause, Dietrich Lemke, Yaroslav Pavlyuchenkov, Surhud More, Thomas Henning (MPIA Heidelberg, Germany)

(Submitted on 11 Dec 2008)

 

Abstract: The fate of massive cold clumps, their internal structure and collapse need to be characterised to understand the initial conditions for the formation of high-mass stars, stellar systems, and the origin of associations and clusters. We explore the onset of star formation in the 75 M_sun SMM1 clump in the region ISOSS J18364-0221 using infrared and (sub-)millimetre observations including interferometry. This contracting clump has fragmented into two compact cores SMM1 North and South of 0.05 pc radius, having masses of 15 and 10 M_sun, and luminosities of 20 and 180 L_sun. SMM1 South harbours a source traced at 24 and 70um, drives an energetic molecular outflow, and appears supersonically turbulent at the core centre. SMM1 North has no infrared counterparts and shows lower levels of turbulence, but also drives an outflow. Both outflows appear collimated and parsec-scale near-infrared features probably trace the outflow-powering jets. We derived mass outflow rates of at least 4E-5 M_sun/yr and outflow timescales of less than 1E4 yr. Our HCN(1-0) modelling for SMM1 South yielded an infall velocity of 0.14 km/s and an estimated mass infall rate of 3E-5 M_sun/yr. Both cores may harbour seeds of intermediate- or high-mass stars. We compare the derived core properties with recent simulations of massive core collapse. They are consistent with the very early stages dominated by accretion luminosity.

[modest]

I think it is fair to say that all of cosmology now depends on the existence of cold dark matter and dark energy. Since without both (or either) of these hypothetical, speculative entities, force, or states, the standard model, and thus the big bang theory fails (i.e., is in disagreement with observations).

 

In fact, general relativity fails to agree with observation unless there is more cosmic mass density than is readily visible and a vacuum energy density.

 

For this reason, the discussion on the validity of the BBT (the topic of this thread) has come to be centered on lambda.

 

I think you're putting the cart before the horse. Hoyle's steady state universe requires a cosmological constant significant enough to prevent a big bang in the past ([math]\Omega_\Lambda \geq 1[/math]). Big bang theory cannot have a cosmological constant that large as there would have been no big bang. But, it's not big bang theory itself that demands a cosmological constant. Observations that are consistent with big bang theory such as cosmic microwave background anisotropies and supernova redshift/brightness demand it.

 

For it is the L-CDM model, with its interpretation of lambda that on trial. Unfortunately, without convincing evidence the case is too weak to decide on a verdict either way... I too believe the cosmological constant arises naturally from the derivation of general relativity. Though, the past and current interpretation of its properties leaves something to be desired.

 

Lambda-CDM does not interpret Lambda. FLRW is an exact solution to general relativity. GR is far more demanding that you say here:

 

Yes again. But general relativity is so general that it has to be determined with accuracy to what extent nature is subject to that kind of generality. In other words, there may be limits, thresholds, critical points, minima and maxima that affect the extent to which natural phenomena (that involve spacetime and material objects) respond to stress, condensation, curvature, high energy, low energy and so on.

 

This is not true. There is no leeway with GR or FLRW. The Friedmann equation describes what will happen given a certain mass/radiation density/pressure and cosmological constant. Observations will either agree or not. The physical mechanism for the cosmological constant (or its interpretation) is incidental. It will act the way GR demands it act. There's no tweaking that. All you can do is set its value and solve.

 

Something else will have to be used to test the validity of the BBT. That something, as mentioned previously, will be the determining factor: the age of stars and galaxies located near the so-called dark age boundary or transition (during the latter stages of reionization, from z = 8 → 6), where it is predicted by the standard model that all material objects (proto-stellar populations, proto-galaxies) have begun to form, and so are young, morphologically immature, metal-poor. If the standard model is accurate these should be found in large numbers by next-generation programs (i.e., JWST).

 

I think JWST will be a good test for modern cosmology

 

LCDM has passed every test we've thrown at it, and its up to cosmology to do more to try and break it. Well see...

 

~modest

[Pluto]

G'day from the land of ozzzz

 

 

Modest said:

 

LCDM has passed every test we've thrown at it, and its up to cosmology to do more to try and break it. Well see...

 

What test did it pass?

[freeztar]

What test did it pass?

 

Start at the beginning of this thread, and read it through. It's not fair to ask someone to repeat information that has already been given many times through in this very thread.

[coldcreation]

In fact, general relativity fails to agree with observation unless there is more cosmic mass density than is readily visible and a vacuum energy density.

 

Actually, general relativity has passed every test tossed in its direction (except for those related to gravitational waves). It seems that GR is not to blame for the standard model mishaps. Galactic rotational curves being largely flat (e.g.) does not make GR wrong, nor does it mean CDM is responsible.

 

Finally, the notion of vacuum energy—whether it exists or not, what it is, its value—depends on how the model is set up to deal with observations.

 

 

 

...But, it's not big bang theory itself that demands a cosmological constant. Observations that are consistent with big bang theory such as cosmic microwave background anisotropies and supernova redshift/brightness demand it.

 

In fact, the pre-1998 BBT failed to agree with observation, that is why cold dark matter and dark vacuum energy had to be added to the mix.

 

So it is indeed the big bang theory itself that demands CDM and DE.

 

Observations don't demand anything, theories do.

 

The BBT had also failed to predict the CMB anisotropies. That is why DE had to be exhumed and CDM had to be implemented. It is no coincidence that L-CDM and CMBR are consistent.

 

 

The physical mechanism for the cosmological constant (or its interpretation) is incidental. It will act the way GR demands it act. There's no tweaking that. All you can do is set its value and solve.

 

Au contraire, GR does not demand that lambda act in a particular way.

 

Incidentally, it was the standard model that required parameter tweaking. Without parameter tweaking (and there are six to tweak) BBT was in gross noncompliance with observations.

 

Incidental, the physical mechanism for the cosmological constant may be. But maybe not.

 

 

“Justice is incidental to law and order.”

(J. Edgar Hoover)

 

 

LCDM has passed every test we've thrown at it, and its up to cosmology to do more to try and break it.

 

However, ΛCDM is a model. Cosmologists anticipate that all of these assumptions will not be borne out exactly, after more is learned about the applicable fundamental physics. In particular, cosmic inflation predicts spatial curvature at the level of 10−4 to 10−5. It would also be surprising if the temperature of dark matter were absolute zero. Moreover, ΛCDM says nothing about the fundamental physical origin of dark matter, dark energy and the nearly scale-invariant spectrum of primordial curvature perturbations: in that sense, it is merely a useful parameterization of ignorance.

 

Source

 

My bold.

 

 

CC

[Pluto]

G'day From the land of ozzzzzz

 

Freeztar said:

 

Quote:

Originally Posted by Pluto

What test did it pass?

 

Start at the beginning of this thread, and read it through. It's not fair to ask someone to repeat information that has already been given many times through in this very thread.

 

Yes I know what Modest wrote and yet new readers need to be reminded of the so called evidence.

 

What I'm saying is:

 

What evidence is there that cannot be disputed and not be related to another model, totally supporting the BBT.

 

=================================

 

On a topic on origins of jets, that I started to discuss before.

 

This paper is quite interesting.

 

[0710.1326] Magnetar Driven Bubbles and the Origin of Collimated Outflows from GRBs

Magnetar Driven Bubbles and the Origin of Collimated Outflows from GRBs

 

Authors: N. Bucciantini (1), E. Quataert (1), J. Arons (1), B.D. Metzger (1), Todd A. Thompson (2) ((1)Astronomy Department, UC Berkeley, (2)Department of Astrophysical Sciences, Princeton)

(Submitted on 5 Oct 2007)

 

Abstract: We model the interaction between the wind from a newly formed rapidly rotating magnetar and the surrounding progenitor. In the first few seconds after core collapse the magnetar inflates a bubble of plasma and magnetic fields behind the supernova shock, which expands asymmetrically because of the pinching effect of the toroidal magnetic field, as in PWNe, even if the host star is spherically symmetric. The degree of asymmetry depends on the ratio of the magnetic energy to the total energy in the bubble. We assume that the wind by newly formed magnetars inflating these bubbles is more magnetized than for PWNe. We show that for a magnetic to total power supplied by the central magnetar $sim 0.1$ the bubble expands relatively spherically while for values greater than 0.3, most of the pressure in the bubble is exerted close to the rotation axis, driving a collimated outflow out through the host star. This can account for the collimation inferred from observations of long-duration gamma-ray bursts (GRBs). Given that the wind magnetization increases in time, we thus suggest that the magnetar-driven bubble initially expands relatively spherically (enhancing the energy of the associated supernova) while at late times it becomes progressivelymore collimated (producing the GRB). Similar processes may operate in more modestly rotating neutron stars to produce asymmetric supernovae and lower energy transients such as X-ray flashes.

[modest]

Actually, general relativity has passed every test tossed in its direction (except for those related to gravitational waves). It seems that GR is not to blame for the standard model mishaps. Galactic rotational curves being largely flat (e.g.) does not make GR wrong, nor does it mean CDM is responsible.

 

In fact, galactic rotation curves leave 2 possibilities:

1. GR is wrong
   
2. there is unaccounted-for mass
   

The only way to make galactic rotation curves agree with General Relativity is to add mass because GR itself cannot be tweaked—it cannot be adjusted. This is something you often disagree with for one reason or another, but it isn't open to interpretation. GR is exactly demanding.

 

Furthermore, the predictions of general relativity are fixed; the theory contains no adjustable constants so nothing can be changed. Thus every test of the theory is either a potentially deadly test or a possible probe for new physics. Although it is remarkable that this theory, born 90 years ago out of almost pure thought, has managed to survive every test, the possibility of finding a discrepancy will continue to drive experiments for years to come.

 

The Confrontation between General Relativity and Experiment (section 7: conclusions)

 

General Relativity is composed of non-linear partial differential equations that are extremely difficult to solve for any real-world situation. It is, however, possible to find *exact* solutions to GR:

 

The Einstein field equations are nonlinear and very difficult to solve. Einstein used approximation methods in working out initial predictions of the theory. But as early as 1916, the astrophysicist Karl Schwarzschild found the first non-trivial exact solution to the Einstein field equations, the so-called Schwarzschild metric.

 

-

General relativity

 

The Schwarzschild metric is an exact solution to GR. It gives exact answers in the setting of a non-rotating spherically symmetric mass. It is, therefore, useful when considering something like a planet or a solar system. There are other such exact solutions and the FLRW metric is one such non-trivial, exact solution.

 

The best-known exact solutions, and also those most interesting from a physics point of view, are the Schwarzschild solution, the Reissner-Nordström solution and the Kerr metric, each corresponding to a certain type of black hole in an otherwise empty universe,[41] and the Friedmann-Lemaître-Robertson-Walker and de Sitter universes, each describing an expanding cosmos.

 

-

General relativity

 

From a physics standpoint, this has a lot of meaning. The same theory that predicts gravitational effects in our solar system to extraordinary precision also predicts the behavior of the FLRW metric (i.e. a Friedmann universe). Any observation of a homogeneous, isotropic universe that obeys the physics of General Relativity *must* agree with the FLRW metric or General Relativity is proven wrong by example. There is no leeway on this.

 

Our cosmic observations do indeed agree with the FLRW metric if the makeup of the universe is currently 74% vacuum energy density and 26% mass density as a ratio to the critical density. Either this is not the makeup of our universe, the universe is not homogeneous and isotropic, or FLRW and by extension GR are wrong.

 

The only Leeway FLRW affords is setting the values (the Omegas) which is the same as declaring what our universe is made of. That's it. You seem to be confusing the setting, measuring, and changing of these parameters with a change to the underlying physics. Notice:

 

Ned Wright's Javascript Cosmology Calculator

 

You can set Omega-M and Omega-Vac and get a prediction at a chosen redshift. Pre-1998 cosmology can be solved on this calculator as well as the current Lambda-CDM model, because they use *exactly* the same physics.

 

~modest

[Pluto]

G'day from the land of ozzzzzzz

 

I have some friends reading some of the comments.

 

They have asked me to ask Modest, can you explain the above, sounds great, but! what does it mean, how does it explain the workings of the parts within the universe?

[modest]

G'day from the land of ozzzzzzz

 

I have some friends reading some of the comments.

 

They have asked me to ask Modest, can you explain the above, sounds great, but! what does it mean, how does it explain the workings of the parts within the universe?

 

Your friends are welcome to join.

 

CC and I are discussing the concordance model which also goes by the name Lambda-CDM or ΛCDM. You/they can read about it here:

Lambda-CDM model - Wikipedia, the free encyclopedia

 

how does it explain the workings of the parts within the universe?

 

The concordance model is a model of the universe. It explains (with specific answers) why a galaxy at some certain distance will have a given brightness, redshift, angular size, etc. It's a model of the universe's past and future based on the physics of General Relativity.

 

What specific workings or parts of the universe are you/they considering?

 

~modest