Hello Demetris!

I am a fan of Occam's Rasor. And not because I was a barber, but I remarked so far that nature loves it simple. Nature is complicated enough to accept other complications artifficially introduced from outside.

Time is not a kind of spatial coordinate. Time is different. It is not a simplification of the model to consider time a kind of spatial coordinate.

Now on the Big Bang. Assume that a big neighborhood of us is the result of an explosion. Then we have two possibilities: (1) that there is a local, although huge, phenomenon, and (2) that this explosion was the beginning of the Universe. Is the hypothesis that the Universe has something like a begin a simplification of the problem? No. It makes all much more complicated. So I think that the Big Bang is a local phenomenon. For us a huge one and almost a total one, but for the infinite universe, just local.

Now about space expansion. Is it logic to introduce the notion of comoving speed to define the speed of expansion, while speed relatively to the space (won by proper acceleration) must remain less than c? No. It is again this kind of artificial complication.

Is a bounded Universe plausible? Does this model somehow simplify the model? No. It is much more rational to consider it infinite in both time and space.

So possibly all that we know about the universe is just something very local.

As we are in some area with more matter, surrounded by large volumes without matter, the new created matter accelerates to fill (or at least to touch) vaste empty spaces "outside" this area. Probably matter appears in regions which are just too empty, following some simple law, in order to establish some kind of equilibrium. Probably there was no explosion and there is no limit speed. Probably the universe looked always more or less as it looks now, suggesting an expansion, and will always look so.

Of course, I wrote here only speculations. But all the existing hypotheses and theories are also speculations.

I am also pragmatic so I accept any other model, including the Big Bang, so far it is able to produce verifiable predictions. But all models accumulate in time too many layers of artificial complexity from outside, so from time to time must be shaved with Occam's Rasor.

Hello Demetris!

I am a fan of Occam's Rasor. And not because I was a barber, but I remarked so far that nature loves it simple. Nature is complicated enough to accept other complications artifficially introduced from outside.

Time is not a kind of spatial coordinate. Time is different. It is not a simplification of the model to consider time a kind of spatial coordinate.

Now on the Big Bang. Assume that a big neighborhood of us is the result of an explosion. Then we have two possibilities: (1) that there is a local, although huge, phenomenon, and (2) that this explosion was the beginning of the Universe. Is the hypothesis that the Universe has something like a begin a simplification of the problem? No. It makes all much more complicated. So I think that the Big Bang is a local phenomenon. For us a huge one and almost a total one, but for the infinite universe, just local.

Now about space expansion. Is it logic to introduce the notion of comoving speed to define the speed of expansion, while speed relatively to the space (won by proper acceleration) must remain less than c? No. It is again this kind of artificial complication.

Is a bounded Universe plausible? Does this model somehow simplify the model? No. It is much more rational to consider it infinite in both time and space.

So possibly all that we know about the universe is just something very local.

As we are in some area with more matter, surrounded by large volumes without matter, the new created matter accelerates to fill (or at least to touch) vaste empty spaces "outside" this area. Probably matter appears in regions which are just too empty, following some simple law, in order to establish some kind of equilibrium. Probably there was no explosion and there is no limit speed. Probably the universe looked always more or less as it looks now, suggesting an expansion, and will always look so.

Of course, I wrote here only speculations. But all the existing hypotheses and theories are also speculations.

I am also pragmatic so I accept any other model, including the Big Bang, so far it is able to produce verifiable predictions. But all models accumulate in time too many layers of artificial complexity from outside, so from time to time must be shaved with Occam's Rasor.

Dear Demetris,

Do you want to put the last nail on the coffin of the so-called standard model of cosmology?

Article A Cosmological Model with Variable Constants (Functions of t...

Dear Mihai,

Since the problem is too complicated, not by itself but from our large set of (convenient) hypotheses, I think that we have to clear it step by step.

Thus I focused on the implicit role of time:

• it is supposed to be the 4th coordinate in a 4D 'spacetime'
• while all other spatial ones must depend on it

It is like to arbitrarily have chosen the z-axis for example to have a primitive role and then take Vx=dx/dz and Vy=dy/dz as the first derived entities.

Under such a non proper for coordinates it is easy to explain so many paradoxes occurring in our 'beloved' and broadly accepted theories.

For example:

• what is radial velocity Vr?

Answer:

• Vr=lim(Δr/Δt)=dr/dt with r=sqrt(x(t)2+y(t)2+z(t)2) in Cartesian CS

But it is supposed that (x,y,z,ict), thus (x,y,z,t) too, are the equivalent coordinates of 'spacetime' and cannot be distinguished each one from another.

So, starting from the very first steps, we have ill defined everything.

Thus, why should we trust next steps?

Dear Guolinag,thank you for sending me such a glorious task!

Frankly, I don't think that situation is so easy.

Recently I had been to a presentation (seminar) about so called "Geometrodynamics" and related "alternative" gravity theories. I asked the above question and speaker seemed not to understand it. The answer was just "...it comes from the equations".

So, the current status in modern Cosmology (but not only there) is next:

• Give us a mathematically complicated model that will take long for everyone to understand the very basics
• Adapt the model by a limitation process (or by naive curve fitting methods) in order to a mimic the reality
• Publish your results at a respective Journal
• Promote it like a kind of religion
• You are done!

Yes, but paradoxes increase geometrically in time...and nothing predicted can be unambiguously been found!

See https://www.researchgate.net/publication/241311635_The_universe_in_perspective

Jan Boeyen's has addressed just this question. See also his book http://www.springer.com/us/book/9789048138272

Article The universe in perspective

Dear Christian,

I copy from your arXiv 1409.5338v5

"...1. Existence happens in time. The “time” that it

meant here does not have to be identical to the

time that an observer would measure using a clock,

but we assume that there is a monotonic functional relationship ...

According to the axioms there exist one (or

a set of) constant function(s) H(ψ1, ψ2, . . . ψk) = const,

where ψ is a list of variables. Hence we may write (with

the presumption H = const...

"

So:

Dear Hugh,

I copy from arXiv:

"...It is noted at the outset [1] (p.339):

′′that the use of a distinguished time-coordinate marks the abandonment

of a completely covariant treatment of the cosmological

problem. This is the price one has to pay to simplify the cosmological

models and to describe physical reality in convenient

mathematical terms′′

So simple and we run away to do complex tensor computations?

I'd like a deeper justification fort an equation like (1) that argues to describe the universe...

Dear Christian, thank you for interesting contribution.

However my question is strictly cosmological and cannot be mixed by quantum mechanics concepts, since the metric -which is start point- is merely a general relativity one.

If you can give an explanation for why should we trust for universe(s) such a naive approach (that divides 'spacetime' in a convenient 3+1 way), then your answer is highly welcome!

(Who knows, probably people outside the frame of relativity could be more intuitive...)

Whether the basic foundations are valid or not doesn’t preclude a model from being wrong. Validity can be judge on several grounds, one of which being mathematical validity. The problem with the current model is that it was built upon incomplete knowledge. At the time, it was simply impossible to test all aspects relative to observation; some variables were just fine-tuned with respect to fitting others. Here lies the central problem in modern cosmology; we are making ad hoc adjustments to old models in order to fit new data. This is not science, but the continuation of a broken ideology.

For example, the first problem was redshift versus luminosity distance, which required dark energy for accelerated expansion. Then we had the problem of there being too many galaxies with respect to big bang cosmology, which requires various ad hoc models of evolution. Then we find that distant galaxies are too small to be consistent with LCDM, but again it is assumed that some type of exotic evolution is occurring. These are just a small fraction of the overall anomalies, as nearly every aspect of the theory is plagued by them. Why does it matter if LCDM can fit a limited amount of observations if those observations all have anomalies?

This is the central issue, Occam’s razor. You can get any theory to match observations with enough ad hoc modifications or tunable variables. This is all that LCDM has become after decades of more detailed observations, a failed fine-tuned model. Unfortunately, the field is compartmentalized into specific topics and the vast majority of scientists are simply unaware of the significant problems underlying big bang cosmology. They work on hypothetical scenarios that fit their model to limited observations rather than using all observations to derive the simplest, best fitting theory.

If you let observations dictate the proper model, then it becomes clear that the accelerated expansion is an illusion due to gravitational lensing (to >3.5 sigma). In other words, a cosmological-scale gravitational potential (which we are distant from the center of) is deflecting local geodesics towards it's center; where local objects are accelerating into. This provides the illusion of nearly spherical accelerated expansion (the resulting asymmetry has been observed in other publications).

http://adsabs.harvard.edu/abs/2014AstRv...9c...4P

Article Evidence of a Global Gravitational Potential

Cosmology is still in development. We don't agree on what comprises the basic foundations. Our opinions change over time.

FLRW makes an obvious mistake and continues in error long after the mistake is discovered. Radiation is ignored usually in FLRW, and added to gravity if considered at all. To be correct radiation counteracts gravity and must be subtracted from it in field equations. A correction can be found in expression of electromagnetic stress energy tensors, but is not well expressed elsewhere.

When correctly expressed radiation pressure accounts for acceleration of galaxy clusters by slight excess over gravity in deep space.

New reports say acceleration is faster than previously thought. So I don't see how we could debate the merits of basic foundations in cosmology.

Dear Demetris: FLRW says mathematically  that the Universe is homogeneous and isotropic and obviously GR, otherway you do not have any support to define proper time the way RW derived their metric. The homogeneity and isotropy can be checked back roughly to the first 500 thousand years with Microwave Sky Background Radiation, where you find the structures the Universe have had at that particular age. That is so precise that allows to define the best standard of rest for astronomical distances, widely accepted by the community. We are also confidently sure that the Universe is flat or might have a too mild negative curvature. So if RW is to be put under suspects, the departing point is from the structure of MWBR to ealier times up to the BB.

The existence of a cosmic time, that is, that space-time and the evolution of the Universe can be separated in succesive 3-D spatial slices, can only be an hipothesis. but is now supported by observations at different redshifts, where/when the Universe is seen younger (Hubble deep field legacy),  less dense and evolving (QSOs era, younger galaxies, etc).

So, by now it seems to me that  RW metric is simple and very useful  as a framework to study the Universe. It also include the possibility of the cosmological cte, because it is in the Einstein equations from 1916. My guess, that could totally wrong, is that drastic changes would'nt appear in RW metric, unless thinks like entanglement, could have afected the first instants of the Universe.

You can have a steady state system that has acceleration in it. For example, a water fountain has portions that are converging, diverging, accelerating and decelerating. However, the water fountain itself is in a relatively steady state.

There are several observations that provide direction for cosmological foundations.

If we are left with Doppler and gravitational redshift as the only reasonable explanations, then the resulting models are relatively limited. If we also agree that Earth does not hold a special location in the universe, then it would not make sense to place us at the center of a cosmological gravitational potential. However, if we place ourselves distant from the center of such potential, then it is possible to produce the illusion of accelerated expansion. There wouldn’t actually be expansion, but instead a distorted projection of the universe where distant objects are gravitationally accelerating towards a central point.

Several observations support this view:

In fact, the only way to differentiate between this possibility and LCDM are through observations currently producing significant anomalies. As space telescopes get better the anomalies will only increase. For example, we are currently missing a large portion of galaxies in infrared bands due to their angular size and redshift distribution. Instead of having to explain away 10-20x of too many galaxies in only the B-band (due to a tighter/lower redshift distribution), theorist will have a much greater difficulty with creating consistency for expanding metrics.

Our largest view of local universe is the so called Laniakea Supercluster visualization.

An interesting observation is that all our local galaxies are moving towards 'The Great Attractor.

Probably if our observations increase, then we should be able to answer the question:

• Is universe really expanding or is it just another local phenomenon?

http://cdn3.vox-cdn.com/uploads/chorus_asset/file/680698/great_attractor.0.png

https://en.wikipedia.org/wiki/Laniakea_Supercluster

https://www.youtube.com/watch?v=rENyyRwxpHo

Dear colleagues: I have copied below the abstract of the paper whre Launakea is defined (Nature, Spt 2014) I did not find any critic to the cosmic flow in this paper. On the contrary, the "local" flow leading to Laudakea was discovery by patterns arising from the differences between the whole set of velocities and the mean cosmic flow! That is to say, a second order effect. Even the fountain effect mentioned by Michael is descrbed as a "local effect" (understanding by local the size of Laudakea) by the Brend Tully and co-authors. Must I remember that Tully is one of the discoverer of the Tully-Fischer effect? So useful in standard cosmology? Should they have discovered something contradicting the standard cosmology, certainly they would have mention it in the paper and would be the issue to challenge a Nobel price!

Otherway, you are clearly able to challenge, or reinterprete that result.

Maybe you look more carefully the point rised in this paper?!

To me, the discussion is closed.

*********

ABSTRACT

"Galaxies congregate in clusters and along filaments, and are missing from large regions referred to as voids. These structures are seen in maps derived from spectroscopic surveys1, 2 that reveal networks of structure that are interconnected with no clear boundaries. Extended regions with a high concentration of galaxies are called ‘superclusters’, although this term is not precise. There is, however, another way to analyse the structure. If the distance to each galaxy from Earth is directly measured, then the peculiar velocity can be derived from the subtraction of the mean cosmic expansion, the product of distance times the Hubble constant, from observed velocity. The peculiar velocity is the line-of-sight departure from the cosmic expansion and arises from gravitational perturbations; a map of peculiar velocities can be translated into a map of the distribution of matter3. Here we report a map of structure made using a catalogue of peculiar velocities. We find locations where peculiar velocity flows diverge, as water does at watershed divides, and we trace the surface of divergent points that surrounds us. Within the volume enclosed by this surface, the motions of galaxies are inward after removal of the mean cosmic expansion and long range flows. We define a supercluster to be the volume within such a surface, and so we are defining the extent of our home supercluster, which we call Laniakea."

So, let me make things more clear.

Laniakea cluster and the work on it gave us some new results:

• almost 50% of galaxies go away from us while the other 50% come toward us
• there exist a strong local attractor

The above two facts are enough to make us think that:

• our cosmological observations are poor and not even locally completed
• there exists the possibility that our observed expansion is a local issue

PS The CMB radiation is another story, I prefer to study direct observation only at this question.

Demitrus,

Your question is valid! The foundations of cosmology are not valid. See https://www.researchgate.net/publication/241311635_The_universe_in_perspective and the other works by Jan Boeyens. Unfortunately he passed on August 2015 so no longer accessible to discuss. But you'll see by his track record that he was a top scientist. Nobel Prize worthy work he's done, in my view.  Big bang theory is not a scientific theory - it's a creation myth. 

Article The universe in perspective

From the arxiv.org version oft article, see link, we copy:

"During a second half rotation of the scene there is a display of the peculiar velocity vectors that are fundamental to the current analysis. Peculiar motions toward us are in blue and those away are in red. The density of measurements is dense within 7500 km s−1 = 100 Mpc and falls off quickly beyond that distance."

Video has a better visualization.

But, why almost 50% of galaxies seem to come towards us?

Isn't it a violation of the global expansion?

https://arxiv.org/ftp/arxiv/papers/1409/1409.0880.pdf

Let’s consider a scenario where the local space developed from a dense region of turbulent, x-ray emitting gas. Over time, the gas begins to expand and cool resulting in a Hubble-like expansion. When allowing this bulk flow of expanding gas to accelerate into a cosmological-scale gravitational potential, the resulting predictions match observations quite well.

The local asymmetry in SNIa redshift versus luminosity distance for example occurs due to the gravitational potential itself. On small scales such potential can be viewed as a tilted plane with one direction contributing redshift and the other blueshift. However, the Hubble flow dominates locally because the measured slope of the potential is relatively small; it’s effects do not become noticeable until around 0.10z. When you take the average motion into consideration, half of the galaxies will have peculiar redshift and the other half with peculiar blueshift. The same goes for CMB power asymmetry. Large-scale gravitational lensing blurs the imprint of the CMB on foreground objects such as cluster medium. The direction with less gravitational lensing produces a sharper image, while the other is blurred; i.e. power asymmetry.

Perhaps one of the reasons these problems have not been so obvious is due to our orientation in the Milky Way. Gravitational lensing itself converts CMB E-modes into B-modes, and the resulting dipole pattern is the hallmark of the CMB originating from the center of a cosmological potential. According to WMAP large-scale B-modes (only spatial mapping available), the direction with least lensing is slightly northwest of galactic center. The galactic center is heavily obscured so we see an incomplete picture of this asymmetry, but it has definitely been observed in various forms. See my publication for a more detailed explanation, but several major tests for this include galaxy counts, angular size of various objects, ect. and these all fit a static metric.

So, Michael, do you support the 50%-50% claim or not?

Local anisotropies (50%-50%) have been observed by dozens of authors, most supporting a dipole with redshift increasing faster in directions toward the galactic center. There are also other large bulk-flows depending on what’s being measured. For example, if you measure the bulk flow of hot x-ray emitting gas, you will find what is known as the ‘dark flow’. Such feature is expected in water fountain-like universes, i.e. it’s the ‘fountain’ portion of the system that newly formed galaxies and clusters originate from. Logically, we would need to see the tail end of this for full consistency in such model, the only model left when considering classical origins of redshift.

SNIa

http://arxiv.org/abs/1109.0941

http://phys.org/news/2011-09-evidence-spacetime-cosmological-principle.html

http://lanl.arxiv.org/abs/0809.4041

http://archive.cosmosmagazine.com/news/is-universe-expanding-asymmetrically/

http://www2.uwaterloo.ca/profiles/research_profiles/profile-archive.php?id=81

Dark flow

http://arxiv.org/abs/1411.4180

http://www.nasa.gov/centers/goddard/news/releases/2010/10-023.html

http://www.nasa.gov/centers/goddard/pdf/276175main_ApJ_inpress.pdf

Various observations of galaxies do support the idea that they recently formed from dense, hot gas. Such environment prohibits the formation of asymmetric galaxies and massive stars (blue), resulting in early-type galaxies. Furthermore, we see that environments containing abundant x-ray emitting gas are dominated by early-type galaxies, while the outskirts or field is dominated by late-types. This implies that the evolution of galaxies is driven primarily by properties of the gas. What we observe in local early-type galaxies that are displaced from hot gas are higher angular spin, cooler interstellar medium and the formation of disk or small spiral arms. We directly observe all stages of galactic evolution but refuse to accept the simplest explanation due to reliance on LCDM.

      "A comparison of early-type galaxies in cluster environments

      versus the field however provides deeper insight. Field ETGs for

      example are nearly six times more likely to contain detectable

      amounts of neutral hydrogen in comparison to those in clusters

      (Oosterloo et al. 2010) (148). Nearly half of the ETGs with detectable

      HI have or are developing a rotating disk of neutral hydrogen

      (Oosterloo et al. 2010) (148), which is consistent with

      earlier observations of rotating x-ray disk and small spiral arms

      in elliptical galaxies (Vader et al. 1991; Statler et al. 2002; Young

      2002) (191; 179; 209). Early-type galaxies can further be classified

      as either fast rotors or slow rotors (Cappellari et al. 2011)

      (22). The fraction of slow rotors is observed to increase towards

      cluster centers, where fast rotors are typically lenticular galaxies

     (Cappellari et al. 2011) (22). This demonstrates that E galaxies

     are typically rotating slower in comparison to S0. A recent

     study of three rich galaxy clusters has further cast doubts on the

     purely passive evolution paradigm,..."

                                    - Evidence of a global gravitational potential

http://adsabs.harvard.edu/abs/2014AstRv...9c...4P

As a computer scientist working primarily in the area of machine intelligence, my perspective on the issue of space and time is a bit different. Biological intelligence requires a certain level of "fish in the water" perspective to allow us to function quickly and efficiently in a dangerous environment. That built-in imperative also makes it surprisingly tricky to perceive issues fundamental to rapid response as anything other than "fundamental" or just "givens." What that means in practical terms is that it’s very hard for us to perceive space and time as nothing more than complicated mathematical relationships, and very easy to perceive them as smooth, simple, “easy” givens that do not really need much explanation at all. The idea that isotropic, 3+1 spacetime with near-infinite volume and almost infinitely fine granularity is very much an example of this effect. To a machine intelligence not so closely wedded to navigating and accepting this complicated structure as a given, its level of complexity comes over as remarkably arbitrary and deeply in need of further exploration.

Adding quantum characteristics to this suite – that is, recognizing that just from known data the details of that 3+1 structure start to break down in the most peculiar ways at certain scales – adds further to the range of structure involved. As humans we like to partition such added difficulties off into smaller packages, which again undermines the process of determining the deeper real sources of all of this complexity. After all, just as Newtonian physics unraveled only after folks insisted on pulling harder and more seriously at the annoying dangling threads at the edge of an otherwise beautiful tapestry, the oddly expanded perspective that quantum gives on both space and time likely is telling us all sorts of important messages about the seemingly independent nature of space and time at the level of galaxies and galaxy clusters. Some are trying, sure, but we are so not there yet.

The point is simply this: The experimentally determined structure and properties of spacetime are remarkably complex, and not even remotely intuitive when analyzed by an unbiased (read “not embedded on a daily basis within them”) cognitive observer trying to understand physics. So just from a cognitive analysis perspective, I do not see how any truly deep explanation of how the universe works will be possible until someone comes up with a plausible, experimentally meaningful, highly reductionist theory that shows how the fully integrated package of relativistic and quantum spacetime properties and behaviors emerge from some smaller, much simpler set of logical principles. Such a theory would, for example, easily and with clarity explain why we observe three isotropic spatial dimensions.

(Note: By "reductionist theory" I mean something akin to Dirac's matrix work that uncovered antimatter. The opposite or "anti-reductionist" approach is nicely captured by string theory, which is a set of work that a lot of us in computer science would characterize mostly as a multi-decade exercise in experimentally unverifiable high-level programming.  In true fish-in-the-water style, that laborious suite of notation expansion building starts by accepting concepts such as "vibrations" and "strings" as givens. While they feel “simple” to us fish, such concepts imply as givens the complexities not just of space and time, but even of the atom-mediated binding and cohesion of condensed matter.)