The scientists, Stefano Finazzi, currently of the University of Trento in Povo-Trento, Italy; Stefano Liberati at SISSA, INFN in Trieste, Italy; and Lorenzo Sindoni from the Albert Einstein Institute in Golm, Germany, have published their study in a recent issue of *Physical Review Letters*.

The authors are far from the first who are dissatisfied with the cosmological constant. Previously, other scientists have suggested that the huge discrepancy between the observed and estimated values is due to the use of semi-classical effective field theory (EFT) calculations for estimating a quantity that can be computed only using a full quantum theory of gravity. Although no one can show what value a quantum theory of gravity would give without having such a theory, physicists have shown that EFT calculations fail at estimating similar values in analogue gravity models.

Here, the physicists consider an analogue gravity model in the form of a Bose-Einstein condensate (BEC), a group of atoms that behave as a single quantum system when cooled to temperatures near absolute zero. While a BEC may seem to have nothing in common with the expanding universe, the physicists showed in a previous paper that a BEC can be described by the same Poisson equation that describes nonrelativistic (Newtonian) gravity. This framework includes a term that is analogous to the cosmological constant; this term describes the part of a BEC’s ground-state energy that corresponds to the condensate’s quantum depletion.

Since BECs are accurately described by other (quantum) equations, the physicists decided to test how well EFT calculations could compute the BEC’s analogous cosmological constant term. They found that EFT calculations do not give the correct result. The finding confirms the earlier studies that showed that EFT calculations produce an incorrect result when used to compute the ground-state energy of other analogue gravity models.

“We have shown how conceptually subtle could be the computation of the cosmological constant, by considering an analogue gravity model,” Finazzi told *PhysOrg.com*. “This simple example shows that the knowledge of the microscopic structure of spacetime might be an essential guide for a correct interpretation of the nature of the cosmological constant, and hence for a correct estimate of it. We then reinterpret the large discrepancy between the naive computation and the observed value as a basic misunderstanding on this point. Interestingly, this reasoning might also be a guide to the selection of the correct quantum gravity theory.”

As the physicists explain, the BEC model described by Poisson equations is too simple to completely describe the complex features of the universe’s accelerating expansion. However, the failure of the EFT framework to describe BECs’ analogue cosmological constant supports the possibility that the EFT framework also fails at describing the cosmological constant.

The details have further implications. For one thing, the results suggest that there may be no a priori reason to describe the cosmological constant as vacuum energy. Instead, the cosmological constant may emerge from the underlying quantum theory of gravity describing spacetime. As the physicists explain, a quantum theory of gravity differs from various modified theories of gravity that have been proposed recently in that a quantum theory describes spacetime at the most fundamental level.

“In a modified gravity theory, one is just postulating a different gravitational dynamics that might show accelerated expansion also for a universe filled with standard matter (i.e., without the so-called dark energy component),” Liberati said. “We instead consider the case where a gravitational dynamics is emergent from a microscopic quantum theory, i.e., a theory describing the fundamental constituents, whatever they are, of our spacetime. From such a theory one would be able to derive a theory of gravity (general relativity or any form of modified gravity) in some appropriate limit (possibly similar in nature to the hydrodynamic limit of a gas of interacting atoms). Our point is that it is only throughout this derivation/emergence of the gravitational dynamics that in the end one can determine what is the gravitating ‘energy of the vacuum.’ We have proven this explicitly in our toy model where it is clearly shown that the use of the macroscopic constituents (and corresponding energy scales) of the emergent physics might lead to a completely wrong estimate.

“We can try to explain this issue with a simple analogy,” he said. “Water is made by molecules. At a microscopic level molecular dynamics is properly described by quantum mechanics. However, no one would use quantum mechanics to describe a flowing river, but rather one would use fluid mechanics laws. Of course, fluid dynamics must be compatible with quantum mechanics, i.e., it must be possible to derive it from the microscopic quantum theory of molecules. Finally, the choice of the most appropriate equations for the description of any phenomenon depends on the scale at which one observes the physical system. We hence can say that the microscopic quantum theory of gravity corresponds in the analogy to the quantum mechanics of molecules, a theory of gravity corresponds to fluid mechanics, and the evolution of the universe to the flow of the river.”

Continuing the analogy, Liberati adds that there might be a quantity in macroscopic fluid dynamics that cannot be calculated using macroscopic parameters alone. Instead, a microscopic model is necessary to calculate the correct value.

“We argue that, in the case of the calculation of the cosmological constant, this is exactly what happens: the reason of the ‘worst prediction of theoretical physics’ might ultimately be due to the attempt to compute a quantity that is sensitive to the microphysics only in terms of macroscopic quantities,” he said.

In the future, the physicists hope to further investigate how the BEC analogue model of gravity could possibly lead to the development of a quantum theory of gravity, since many proposed theories of gravity have features in common with the new model.

“We believe that this model can help to change the way how people usually think about the cosmological constant,” Sindoni said. “In recent years, the idea that spacetime is a form of condensate is gaining momentum. Of course, to be able to get to theories as close as possible to general relativity, the microscopic models have to be considerably more complex than BECs. However, it can be conjectured that spacetime is the final outcome of a phase transition for a large number of suitable microscopic constituents, and that the determination of the resulting macroscopic dynamics might be essentially the same, at the conceptual level, of the determination of the dynamics of a BEC from the knowledge of effective molecular or atomic dynamics, near a phase transition. The translation of the language and ideas of BECs to quantum gravity models might be a key in the understanding of the physical content of the latter.”

Sindoni adds that the cosmological constant will provide a vital test of any proposed quantum theory of gravity.

“We think that the comparison of the observational value of the cosmological constant against its theoretical value, predicted by any theory of quantum gravity, can be a very good (if not the unique) test to validate such theories,” he said.

**Explore further:**
Physicists propose test for loop quantum gravity

**More information:**
Stefano Finazzi, et al. “Cosmological Constant: A Lesson from Bose-Einstein Condensates.” *PRL* 108, 071101 (2012). DOI: 10.1103/PhysRevLett.108.071101

## dtyarbrough

The rate of increase is density to create this illusion is a factor of 75 parts per 30,856,775,810,000,000,000 each second. That works out to 23652/308567758100000 per year. The density would have doubled over 13.04 billion years if this rate were not changing. The rate is however increasing as old stars are burning faster than new stars are forming. The rate of expansion appears to be increasing.

At the current rate, the sun will appear to be 0.712 miles farther away in 100 years.(twice its current distance in 13 billion years).

## dschlink

## hkreuz

So i'm assuming this is taking into account Edwin Hubble didn't exist.

## Mike_Massen

You havent heard of significant figures then or exponents ?

Where did those figures come from, can u show your working ?

Where does red shift place in your idea re those figures ?

What solar particles are you on about, other than protons (hydrogen) ?

What do you mean by "..more solar wind than is required.." - for what ?

At the beginning of the para you say there is no expansion then you say the expansion is increasing - can you explain this contradiction ?

Was the sun closer by ~0.712 miles 100 years ago ?

As the sun has no specific surface then how can one confirm aspects of your idea over such short comparative distances without knowing where the sun's center happens to be at the time ?

## TabulaMentis

## TabulaMentis

That statement is like frosting on a big juicy cake.

## Anda

No.

In the other hand there's no valid quantum gravity theory to date.

Waiting for you "water ripples"

## Kinedryl

The second perspective is used for observations of small object, which are always observed from outside. This perspective is therefore called extrinsic and it essentially corresponds the perspective of quantum mechanics. These perspectives cannot be mixed, they're separated with hundreds of extradimensions each other. Nevertheless it means, when you observe the water surface from intrinsic perspective, it appears like nondispersive environment, whereas from intrinsic perspective we are confronted with highly dispersive underwater.

## Noumenon

Where did they say they're turning away from 'Einstein Gravity'?

## Kinedryl

At the case of vacuum, which is behaving like extremely dense environment this ratio is more than one hundred orders of magnitude, which leads to so-called http://en.wikiped...strophe. This is how the deep difference in predictions of vacuum density calculated from quantum field and general relativity theories is called. The string theory uses a renormalization approach, so its prediction of cosmological constant differs from reality in forty orders of magnitude.

## TabulaMentis

## Kinedryl

It essentially means, if some artefact exists at the water surface, it MUST somehow exist at the cosmic space too. The opposite direction unfortunately doesn't work, because the Universe is way more complex, than the water surface. But the duality of observational perspectives and the values of cosmological constants and vacuum density can be deduced from the water surface analogy in quite trivial way. You needn't to bother with boson condensates and with river flow, as these parables just obscure the geometry of the water surface analogy

## Kinedryl

My suspicion is, the mainstream physics community avoids the using of all models, which would make the subject of their research more transparent for laymans. Many concepts of string theory or supersymmetry could be explained in much more straightforward way with it. But you can get these analogies only in close range of experts and they're generally considered a heretical.

Eduard Witten: "One thing I can tell you, though, is that most string theorists suspect that spacetime is a emergent phenomena in the language of condensed matter physics".

These guys know quite well about dense aether model. But they will not admit it.

## dtyarbrough

There is only the appearance of an increasing expansion. The numbers are based on the hubble constant of 75Km/sec expansion over a distance of 30,856,775,810,000,000,000 km. Red shift occurs when the light passes through various densities(I think).

## Kinedryl

This is suspicious claim and it sounds "crackpotish" for me. What the "fuel" is supposed to mean?

And this is unfortunately apparent BS already. The contemporary cosmology doesn't bother with solar wind at all, so it cannot face any excess of it. In addition, the speed in which light is losing its energy during travel trough vast areas of CMBR noise has nothing to do with intensity of solar wind at all. The intensity of solar wind has nothing to do with the speed of light dispersion (which propagates a way faster than the solar wind particles, BTW).

## Kinedryl

The similar result follows from general relativity, in which the space-time must be always curved - or it couldn't exist at all. After all, this is the original reason, for which Einstein adjusted his theory with arbitrary constant - and it has lead to Friedman models developed later.

## TabulaMentis

## Kinedryl

## Kinedryl

There are few less or more straightforward ways, how to understand this duality. In general, the hyperdimensional object becomes the more fuzzy, random and separated spatially, the lower number of dimensions we are using for its observation. We could say, we are observing it's noncompact lowdimensional slice of it.

## Kinedryl

## TabulaMentis

## Kinedryl

## Kinedryl

http://news.disco...19.html, but similar solutions have been provided before many years already. Because it's essentially invariant to the geometry of elements choosen, the same result provides the optimization of "entropy flow" for holographic projection by number of dimensions: http://arxiv.org/abs/1106.4548

## TabulaMentis

## jsdarkdestruction

## Kinedryl

String theory is too schematic. IMO the same result could be achieved in much easier way with finding of speed of energy spreading with common wave equations in gradually increasing number of dimensions. Why nobody checked how the wave equation behaves in higher dimensional space? We are missing the simplest numeric experiments in this directions.

## Torbjorn_Larsson_OM

@ KinedryL: "The cosmological constant controversy is easy to understand with water surface space-time analogy of AWT based on dense aether model."

We have known since the early 20th century that there is no aether. No go; and please do keep up!

## Cave_Man

Take a simple journey with me into conceptual space, try to imagine zero, the concept of it, try to imagine what zero really is. It's impossible to comprehend but we can say stuff like before the big bang or after the entire universe decays in a few quadrillion years etc etc. Some also equate zero with death and perfect stillness.

But since here we are in the universe which has stuff instead of nothing we start to progress conceptually, zero may be nothing but the funny part is that zero is a concept to us and therefore a thing. When examined it becomes a thing or ONE thing. Giving rise to the concept of one is interesting it sets up a more complex relationship of concepts ie zero and one.

Well now, if I take everything I have now, the concept of zero and the concept of one, well holy smokes that's two things. And as soon as you conceptualize two you now have three distinct concepts, zero, one and two.

## Cave_Man

I personally believe it is a big part of the meaning of the universe. In the same way we might draw interesting conclusions about the origins of consciousness or reality simply by studying other culture or employing hallucinogens.

Everything we do is adding another number to that chain of infinite quanta. Because if zero is "real" then every number you conceive of is really part of a system that is always exactly one higher than the current level.

## julianpenrod

That is given as a "conclusion" from the "discovery" that "supernovas five billion light years away are receding faster than they should be". Up to five billion light years away, galaxies are receding according to Hubble's Law, but, at five billion light years, galaxies are moving away at a faster Hubble Constant. But galaxies closer to us, galaxies viewed at less than five billion years ago, are moving at the lower Hubble Constant! But that means that expansion occurring in the recent past is less than that of galaxies five billion years ago! And that means that expansion is less than that at five billion years ago, and that means the universe is not speeding up!

## Callippo

## havasu

We cannot determine if the universe is expanding or accelerating until we properly account for "red" shifting of light frequencies due to bending. Shifting until the light changes from visible specturm to radio spectrum and gets confused as the echo of the Big Bang.

## bewertow

Reported for spamming.

Also, you are clearly an idiot. The wave equation is just a Sturm-Liouville hyperbolic PDE. It's behaviour is already well-understood in arbitrary dimensions.

## TabulaMentis

## jsdarkdestruction

substantial. sorry

## Silverhill

## Urgelt

*checks moon phase*

Yep, full moon.

## GuruShabu

The universe is NOT expanding, red-shift is NOT due to expansion but to photons loosing momentum due to encounters with electric charged particles, etc.

We need to stop pulling theories from our mind just because they are "beautiful"so they MUST be true...and last but not least: There was never a BigBang!

The universe is infinite.

Hopefully, the new space Webb Telescope will show that there are galaxies beyond 1e billion light-years that are complete, beautifully spirals, elliptical, whatever that could not have been formed before the BB.

## jsdarkdestruction

## Kinedryl

## Kinedryl

http://savethiste...pot.com/

http://www.spacen...wst.html

Anyway, we have enough of evidence, that the universe is way larger, than the Big Bang theory allows - despite the opinion of famous PO trolls, who cannot swallow new facts. http://www.techno...iv/26333

## bewertow

Wow, you're an idiot. Did you even read the article you cited? Everyone already knows that the universe is bigger than the observable universe.

This just places a lower limit on the size of the universe if it is positively curved.

Wow, so many people here who think they're experts in cosmology just from browsing the web. If you were actually interested in cosmology, you would care enough to read a basic introduction on the subject.

## Kinedryl

## bewertow

No. You have no idea what you are talking about. The universe is INFINITE in every possible scenario except when omega>1. Go ahead and solve the Friedmann equation for a flat universe with the current best estimates of energy densities for the different components and it will be obvious. You are an uneducated fool with no background in cosmology.

## Seeker2

Note Lorentz contraction, time dilation, and mass increase can be easily explained using a very simple quantum model of spacetime - hollow shells of energy carried on the surface, with propagation along this surface. A 2d cut of one of these quanta would be a circle with diameter ab, for instance. The propagation occurs on the circumference of the circle but the distance which the quantum travels would be the distance ab. Applied force (for example gravity) causes the circle to collapse so the distance ab becomes smaller. That is the distance which the quantum travels in the time it takes to propagate around the perimeter becomes smaller, but the distance around the perimeter remains constant. So the quantum appears to slow down.

## Kinedryl

## Seeker2

The area of the circle is reduced as the quantum is compressed, so the energy density (mass) of the quantum is increased. Finally if an infinite force is applied to the quantum its area goes to zero and its mass density goes to infinity. So in this model mass is the actual energy density of spacetime quanta. The spacetime quanta of matter take many different forms but its mass depends only on the density of these quanta.

## Kinedryl

## Seeker2

## Kinedryl

## Fleetfoot

Such interactions produce effects that are frequency dependent:

http://astronomy....0Measure

Cosmological redshift is independent of frequency. In 1985, Wolfe et al studied light from quasar PKS0458-02. The quasar itself is at z=2.29 but the light from it passes through a gas cloud at z=2.039. The Lyman alpha line and the 21cm line have the same redshift to within 0.03% even though the frequencies differ by a factor of over 172,000:

http://books.goog...;f=false

In addition, distant supernova light curves last longer because the distance between us and the source increases during the time we can watch them so expansion is proven beyond doubt. Deal with it.

## Kinedryl

## Seeker2

## Kinedryl

## Seeker2

## dtyarbrough

## Fleetfoot

There is no "dense aether model", a gaseous or liquid model cannot support transverse waves as I explained to you four days ago in this thread:

http://www.physor...um-.html

## Fleetfoot

That is because the posters here generally have limited knowledge of the current state of observational evidence. For example one poster has suggested that cosmological redshift might be due to particle interactions. He was obviously unaware of the use of that effect in measuring electron densities in the light path of pulsars and the widely known fact that cosmological redshift is frequency independent.

No purpose is served by people spending their time posting ideas that are not viable due to their ignorance of what we already know. For example, my posting the link to the measurements made by Wolfe et al. doesn't stop anyone thinking about the topic, but it does give them another data point that any workable theory must match.

## bewertow

You are so incredibly arrogant it's shocking. You don't even understand the Dunning-Kruger effect which you're referring to. The effect refers to the phenomenon where incompetent people (such as yourself) are too incompetent to realize why they are wrong.

I actually know what I'm talking about. I've taken courses in cosmology in astrophysics and I have personally solved the Friedmann equation more times than I can count.

I will repeat again since you can't grasp it. The observable universe is NOT the same as the size of the actual universe!

## Fleetfoot

"Bewertow" is correct, the "concordance model" which is the best fit to what we know is as close to flat as we can measure implying that it is either infinite or at least much bigger than the tiny patch we can observe. If anyone wants to learn a bit about the current models, this is probably the most cited tutorial around and reasonably accessible for anyone with some basic physics background:

http://www.astro....o_01.htm

For those who want to dispute the model, finding out what it says rather than tilting at windmills is probably a good idea too ;-)

## bewertow

Solve the Friedmann equation yourself if you don't believe me. Even if you consider a simplified two-component model (which is trivial to solve) then you can easily see what is going on.

If you can't even solve a simple ODE for yourself, then your opinions are clearly meaningless and irrelevant.

## Kinedryl

http://www.phys-a...dels.jpg

## bewertow

Oh really? So you took my advice and solved the Friedmann equation and proved it?

Oh right, I forgot, you are too incompetent to even solve a simple ODE!

I will repeat again since you are so incredibly stupid: THE ONLY CASE WHERE THE UNIVERSE IS FINITE IN SIZE IS FOR OMEGA>1. There is no arguing with this. This is literally the first or second chapter in any introductory cosmology book. Get your fat ass to the library and check out a book if you don't believe me.

## bewertow

You don't even understand the diagram you linked to.

The separation between galaxies is NOT the same as the size of the universe. The separation between galaxies is determined by the scale factor.

Seriously, you don't even understand the most basic principles of cosmology, astrophysics or GR.

## Kinedryl

## Fleetfoot

The word "open" means infinite.

Like cometary orbits, the "flat" and "hyperbolic" cases are infinite, only the "hypershpherical" case is finite. The volume of the universe is then like the surface of a sphere, finite but without a boundary.

Nope, he's teaching you cosmology 101.

## bewertow

I can't tell if you're just trolling, or if you are actually this incredibly stupid.

You keep linking to the same diagram. Scale factor is NOT the same as the size of the universe. I have been repeatedly telling you this over and over but you can't get it through your head.

The parameter which determines whether the universe is finite or infinite is the curvature constant. Hyperbolic and flat universes are ALWAYS INFINITE. We live in a flat, and therefore infinite universe.

Unlike you I actually have a degree in physics. I have studied cosmology. I know what I'm talking about.

## Fleetfoot

"Also remember that the o = 1 spacetime is infinite in extent so the conformal space-time diagram can go on far beyond our past lightcone, ..."

Prof. Wright's background:

http://www.astro....tro.html

## Fleetfoot

We can't be entirely sure of that though, inflation pushes curvature so close to flat that it could be just one side or the other and the difference would be immeasurable. Dark energy of course ensures there won't be a crunch either way so it's still uncertain if the universe is infinite or merely vastly larger than our small observable portion.

There is a fundamental difference in philosophical terms between the two but pragmatically they are indistinguishable.

## Callippo

## Callippo

BTW It's just me and GuruShabu, who has been opposed here with opinion, the Universe is infinite. Now you're trying to convince us about the very same obstinately...;-)

## Seeker2

## Callippo

http://news.disco...119.html

and it will work for you. Be careful what you click, as it can save a lotta troubles for you.

## Fleetfoot

What you ask for is already on the diagram. The line marked "Omega=1 flat" is where WMAP etc. put us (though it should curve up to the right), and it is also the boundary between finite and infinite. Above or on that line, the universe is spatially infinite while below it space is finite but unbounded.

You don't appear to understand what the term "scale factor" means. It is a fractional change comparing distances between widely separated objects at different times. By convention, it has the value 1 at the present time. On its own it doesn't define the overall size. This is basic stuff, check any textbook on the subject.

## Kinedryl

## Fleetfoot

No. When Fred Hoyle coined the name "Big Bang model", he was talking of the expanding, finite age solution to the Friedmann Equations, they are one and the same.

Ignoring dark energy for a moment, the maths is simple. If the density of the universe was greater than a critical value, expansion would stop and reverse resulting in a "Big Crunch". That universe is also spatially of finite volume but unbounded, like the area of the surface of a sphere.

If the density is less than or equal to the critical value, the expansion would continue forever but would always be slowing like a bullet fired from the Earth at greater than escape velocity. That universe would be spatially infinite.

Observations say that the universe is probably flat:

http://map.gsfc.n...ape.html

## Messori

## Kinedryl

## Fleetfoot

Obviously, but if you learned a little about the subject before making wild statements, you wouldn't make so many errors.

For omega <= 1, the model says that spatial slices are and always have been of infinite extent.

The question is can you understand the difference between "age" and "spatial extent"?

## Kinedryl

Anyway, the whole formal model is pretty bothering for me, it just extrapolates the Universe formation with relativity (in pretty inconsistent way) - but it doesn't explain, what really happened with it, why it exploded, why it inflated, why it's expanding with accelerating speed. The contemporary cosmology is just a chain of formal regressions glued and fitted to observations. And because it lacks the sense, it remains ad-hoced.

## Fleetfoot

You need to think before posting, the curves in that plot all reach a scale factor of zero at a finite time in the past, that is the basic Big Bang model. What did you think it showed?

We live a long time after that event and the universe was opaque for the first 378 thousand years. In the absence of a QM model, extrapolating from what we can see is the best we can do.

## Callippo

## Fleetfoot

Zero scale factor times infinite extent doesn't give zero size, the product is undefined. That's the trouble with singularities.

To be more realistic, the Friedmann Equations are classical so they don't take account of QM effects. They can't tell us how that first event occurred or whether it resulted in a universe that is finite or infinite, only that it happened 13.7 billion years ago.

## Callippo

## Fleetfoot

No, the Friedmann Equations can be derived from the postulate that the universe is homogenous and isotropic (as shown by Robertson and Walker) so if they apply anywhere, they apply everywhere. Unfortunately there is no easy way to determine whether the universe is finite or infinite.

## Callippo

Here are another connections, which don't apply directly from the above Friedman model logic, but they're relevant to Big Bang model as well. For example, well known argument for finite Universe is Olber's paradox. It's believed, the light of distant objects are hidden with reionization epoch (dark ages), so they're unobservable. In Big Bang theory this epoch covers the particle horizon of Universe, thus placing strict limit for not only observable Universe size, but for the size of the whole Universe.

## Callippo

So, maybe it's easy determine whether the universe is finite or infinite, maybe not - but Big Bang theory rather clearly implies the finite size of Universe, which doesn't differ very much from observable Universe size. It can be ten times larger at best.

## Fleetfoot

On the contrary, for omega <= 1, that is the model that GR produces.

That is wrong again, Friedmann published the equations as a purely theoretical solution to GR in 1922.

http://en.wikiped...lativity

Hubble found the first Cepheid variable in the Andromeda Galaxy in 1923 proving that it wasn't just a gas cloud in our own galaxy as Shapley was arguing. Bear in mind the Great Debate was only 2 years before Friedmann published his solution.

http://apod.nasa....e20.html

## Fleetfoot

We can observe that epoch for "nearby" material, stuff from which light has taken nearly 13.7 billion years to reach us, but there is more stuff farther away that we can't see, and never will.

That's another common misconception. The HDF includes galaxies up to a redshift of 6 while. The distance between us and galaxies at a redshift of about 1 was increasing by about 1 light year per year. That's one reason why you cannot use a model with galaxies moving through space and redshift caused by Doppler shift, you have to use GR and the model of expanding space.

## Kinedryl

Whereas in steady state Universe model the galaxies don't move at all and the space-time doesn't expand. The light is propagating with increasing speed while dispersing itself. This is why the more distant galaxies appear relatively larger than these close ones, whereas in GR they should collapse with condensing space-time accordingly.

## Fleetfoot

Of course it's relevant, you were claiming we couldn't see older objects if expansion between us exceeded the speed of light and that's simply not true. You have so many misconceptions about the model that your objections don't even make sense.

Nope, the density determines curvature and whether it is open or closed but not the size.

Reionisation ended around z=6 (Gunn Peterson trough). The first stars are estimated at around z=65. We can see the CMBR at z=1089. Try again.

## CardacianNeverid

Indeed. I don't know which notion boggles the mind more - that the universe is infinite or that it has a finite limit.

## Benni

If we are to have in the Universe an average density of matter which differs from zero, however small may be that difference, then the Universe cannot be quasi-Euclidean. On the contrary, the results of calculation indicate that if matter be distributed uniformy, the Universe would necessarily be spherical (or elliptical). Since in reality the detailed distribution of matter is not uniform, the real universe will deviate in individual parts from the spherical, but it will be necessarily finite. In fact the theory supplies us with a simple connection between the space-expanse of the universe & the average density of matter in it.

Albert Einstein:Relativity-Section 30

Written: 1916 (revised edition 1924)

Part III: Considerations on the Universe as a Whole

"The Structure of Space According to the General Theory of Relativity"

## Fleetfoot

This is from the WMAP site but it is a standard result you will find in most textbooks:

"The density of the universe also determines its geometry. If the density of the universe exceeds the critical density, then the geometry of space is closed and positively curved like the surface of a sphere. .. If the density of the universe is less than the critical density, then the geometry of space is open (infinite), and negatively curved like the surface of a saddle. If the density of the universe exactly equals the critical density, then the geometry of the universe is flat like a sheet of paper, and infinite in extent.

We now know that the universe is flat with only a 0.5% margin of error. This suggests that the Universe is infinite in extent; however, since the Universe has a finite age, we can only observe a finite volume of the Universe."

## Fleetfoot

The link wouldn't fit into the character limit, it is:

http://map.gsfc.n...ape.html

## Seeker2

Not according to my posts which were censored yesterday.

## Seeker2

## Callippo

## Benni

## Callippo

http://arxiv.org/abs/1101.5476

Everything else is a speculation, which doesn't follow from L-CDM model, but some other private cosmology, which is inconsistent with it.

## Callippo

"The velocity-distance relation is linear, the distribution of the nebula is uniform, there is no evidence of expansion, no trace of curvature, no restriction of the time scale and we find ourselves in the presence.... If redshifts are velocity shifts which measure the rate of expansion, the expanding models are definitely inconsistent with the observations that have been made, i.e. expanding models are a forced interpretation of the observational results. If the redshifts are a Doppler shift, then observations as they stand lead to the anomaly of a closed universe, curiously small and dense, and, it may be added, suspiciously young. On the other hand, if redshifts are not Doppler effects, these anomalies disappear and the region observed appears as a small, homogeneous, but insignificant portion of a universe extended indefinitely both in space and time."

## daywalk3r

Well, it's all nice that you point out the errors of others, try to teach them proper physics, and free them from their (obvious) "misconceptions"..

But do you ever try to fully comprehend what you write yourself?

For starters - many of your arguments were about a model which is based on GR. But regardless of that, you managed to butcher one of the most fundamental tenets of relativity just within the above quoted single sentence..

cont..

## daywalk3r

The tenet being, that SPACE and TIME are ONE entity.

There is no such thing as space without time (and vice-versa), up to a point where one could even say that space is an emergent property of time.

My point being, that you simply can NOT suggest infinite space WITHOUT infinite time to support it (as you did in the above quoted sentence).

The fact that you can divide and multiply zeroes/infinites on paper does not imply that it has any ressemblance to reality whatsoever.

Maybe I am being too picky here and you just used slightly wrong words to make youself clear..

Seeing as you are baseing it on Omega, perhaps "no limit" (from intrinsic perspective) would have been more fitting than "infinite extent" in this case?

cont..

## daywalk3r

I explain..

[Omega > 1] - would basicaly represent a black hole from the INSIDE perspective. Being seemingly infinitesimaly large when observed from the inside (due to full 4pi curvature), but seemingly infinitesimaly small when observed from the outside (being bellow the SS radius).

[Omega = 1] - could be called "Schwarzshild unity" in the BH slang :-)

[Omega < 1] - is where my brain refuses to cooperate, but suggests that we are part of an (ever faster) expanding "explosion", as is depicted by the BB model.

So yes, for [Omega > 1], from the "inside" perspective, you can move towards the "edge" but never be able to reach it, giving an impression of infinite freedom (eg. infinite extent), but this is just an illusion, as essentially you would be "moving in circles" at some point.

This is not the same as "infinite extent", as is clearly demonstrated by the "outside" perspective.

And as I don't want to play the semantics violin, I omitt the rest of my response.. x-D

Howgh.

## Callippo

## Callippo

## CardacianNeverid

On this point you are 100% correct. You bring delusion and confusion into every thread you post in, so is it any wonder?

## Kinedryl

But because it threatens the social status and employment of many people involved into development of contemporary cosmology and formal education, it's just me who is accused from doing of confusion at the very end. Of course, the enhancing of the fact, the contemporary theories are logically inconsistent may appear like attempt for confusion of readers - but is it really the problem of mine?

## Benni

@Darwalk

I appreciate your posts. The biggest problem I see with the geometry of the universe that infers "infinite parameters" is "information loss". This is the conundrum Hawking got caught up in & which Einstein avoided with his stand on a "closed & spherical" universe.

To me, a universe that has an infinite parameter, such as the "flat" or "saddle" universe, is a "leaky universe", subject to "information loss" (ie:energy). I'd like to get an opinion from one of the two of you why "information" (energy, photons) is not lost in a universe with an unbounded parameter such as the "saddle" or "flat".

## CardacianNeverid

Delusional.

Delusional.

Yep, scientists are only in it for the money and social status! Delusional - the reality is quite the opposite.

Yes. Absolutely. And pick single handle already!

## Kinedryl

## Fleetfoot

BEC has been observed many time but mostly in alkaline earths:

http://en.wikiped...Isotopes

Hardly. Try putting these together:

http://www.physor...rse.html

http://www.electr...time.htm

http://www.esa.in...x_0.html

## Fleetfoot

You understand that omega=1 corresponds to flat. The main contributions to omega are:

dark energy 0.72

dark matter 0.23

IGM plasma 0.04

visible matter 0.01

http://www.univer...ventory/

The total is 1.00 to the WMAP accuracy so the universe is very close to flat. The dark energy part is what causes expansion to accelerate, if it was all matter expansion would still be slowing.

The important words there are "a lower limit", the finite speed of light only defines what is observable, an infinite universe is a standard prediction of the LCDM model.

## Fleetfoot

Interesting question. My immediate reaction would be that that photons are only moving around within the universe, not being lost so I can't see any mechanism for a "leak". Redshift seems to lose energy but energy is frame-dependent so it is no worse than the Doppler effect. The whole subject is however much more complex. This is the physics FAQ article on the question which says more than I could:

http://math.ucr.e..._gr.html

## Fleetfoot

Close, he only got the infinite age part wrong. Compare that with what I said a few posts back:

## Fleetfoot

Emergence is a more complex question but certainly they are interchangeable to a degree. However, that doesn't mean both must be infinite, only that wherever you have space you also have time. Have a look at the grahic below the Mercator Projection near the bottom of Ned Wright's tutorial here:

I'm using what is standard terminology in the subject. This paper may be of interest, compare figure 2 with Ned Wright's graphic:

http://arxiv.org/.../0102010

## Fleetfoot

The diagram on the right here may perhaps help:

http://en.wikiped...Universe

The top image of a sphere shows a closed universe with the big bang at the bottom and the big crunch at the top. A horizontal slice is a circle representing the volume of the universe at that epoch. You can think of a small patch near the "equator" as a Minkowski spacetime diagram.

The other two are for flat and negative curvature and both are infinite in extent.

## Fleetfoot

http://www.astro....o_03.htm

## Fleetfoot

Note at the bottom of page 507 it states that the paper adapted a formula previously derived by Tolman. It is now known as the "Tolman Test". Note also that in item 3 just above the footnotes it is mentioned that Eddington had cautioned that there was an assumption that all galaxies had the same brightness.

This article gives a summary of more modern results:

http://en.wikiped...ess_test

## Moebius

## Fleetfoot

If inflation happened as is currently thought, it finished around 10^-32s.

Nucleogenesis happened when the universe was a few seconds to a few minutes old.

The light we see as the CMBR was emitted from the hot plasma when it was around 378,000 years old after which the universe was filled with little more than thin, cool hydrogen/helium gas mix.

The first stars couldn't form until it was 30 million to 130 million years old (depending on details of simulations).

## YawningDog

## PS3

## Fleetfoot

If by "stretch" you mean the Hubble expansion then no, that would cause expansion in two directions (towards the mass and along the orbit) but contraction in the direction perpendicular to the plane of our orbit. There also seems to be no evidence of rotation though it is difficult to be sure.

## Benni

## Benni

...If after a GRB at z=10 is detected we, in my opinion, are looking at a universe having formed longer than 13.7 billion years ago. Then if we start seeing them at z=11, then 12, then 13, cosmology will go into a new metamorphisis.

The "new metamorphisis" will support Einstein's concept of a "spherical universe", & detract from the "flat universe" concept because the boundary of the universe at increased redshift beyond z=10 must shift, this allows for smaller curvature over a longer distance before the full cicumference of Einstein's sphere is realized.

I look upon the "flat" or "saddle" universe with great suspicion due to the "infinity" parameter of each. Any infinity parameter strongly hints at "loss of information", hence Einstein's conclusion of a spherically closed Universe in order that energy be conserved.

So far, no one has ever come up against Einstein & won, not even Einstein, he did it once & lost, the biggest blunder of his career.

## Fleetfoot

GRBs are thought to be from black holes, not stars.

You need to look up "Pop III" stars. They were the first to form so there was nothing beyond Helium in them. H and He radiate poorly so their mass was much higher, maybe 300 times our Sun so they had lifetimes of less than 10 million years. The heavier elements weren't produced slowly but in the supernova at the end of its life, in just a few seconds perhaps.

## Fleetfoot

Most textbooks say the first stars formed around z=25 which is 132 million years. Recent simulations which note that since dark matter doesn't interact with light therefore doesn't feel radiation pressure allow it to collapse earlier and put the first stars at z=65 which is 32 million years.

WMAP suggests reionisation wasn't a sudden event but gradual, starting around z=25 but possibly higher. JWST is designed to investigate out to z=15 or more.

We can already see the CMBR from z=1090 and age 378,000 years so finding anything later than that can only raise questions about our star formation theories, not the big bang.

## Fleetfoot

Exactly, and infinite extent is what his models predict for a flat universe, to go against that you need to discard GR.

Energy isn't necessarily conserved in any of the models but it's a complex question. Dark energy conserves energy because it acts as a negative pressure in gravitational terms.

However, what you should consider is that for the flat universe, the negative gravitational potential energy exactly balances the positive energy of matter, radiation etc. so the total is zero. The Hamiltonian of a closed universe is also zero so energy is conserved either way. That approach doesn't help us decide.

## Benni

@Fleet: Great points. I guess I don't have the scale for redshift properly scaled for distance, it appears to be logarithmic formula from the numbers you've given me.

I'm curious, how'd you like the point I made about Einstein going up against Einstein & losing. My point being that whatever issue in science Einstein leans most heavily toward, is where the rest of us ought to be....

## Fleetfoot

Unfortunately it's a complex integral. The easy way is to use an applet like this one:

http://www.astro....alc.html

I tend not to respond to such points, authority doesn't count for much because the data on which opinions are based is always moving forward. The equations of his theory are all that matters, so far they have never failed (in the range where they are applicable) so we have no reason to discard them. Einstein was wrong about QM and no human is infallible.

## Callippo

## Kinedryl

http://upload.wik...ated.jpg

And this is real result.

http://www.hitach...fig2.gif

It looks the same, but it's not the same: the paths of individual electrons are still observable. QM just cannot predict them.

## Fleetfoot

I was referring to Einstein's often quoted "God doesn't play dice with the world.". The article you quote is not relevant to that but instead refers to non-locality. AFAIK, the outcome of specific trials is still random in QM and can only be predicted statistically.

Regarding non-locality, Einstein's argument is stated mathematically in Bell's inequalities and the experiment by Aspect, repeated by many others for various particle types, showed that Bell's Inequality is violated in reality as predicted by QM. Einstein might have been able to win the argument, but he would subsequently have been proven to be wrong.

## Fleetfoot

You can't see paths in either picture, all you see is where the particles were detected by the (photo-)multiplier plate.

## Kinedryl

## Fleetfoot

Yes, those are the points where the particles hit. You can't see what path they took to get there (in fact there is no unique path, the pattern is deterined by both slits). In the first picture, there are simply a lot more dots so the image doesn't resolve them.

Exactly, QM predicts only the statistics, the place where the next dot will appear is random, to be determined by a throw of the dice in Einstein's phrase and contrary to his belief.

## Kinedryl

## Fleetfoot

OK, you see the same if you use a bright light and do the experiment for real.

I think you cited the wrong article, that one is about a triple slit experiment which only tested statistics, not paths.

Bottom line though is still that if you look at your original second image, there are only points of detection, no paths to those points. I have no idea what you think you are seeing.

## Kinedryl

It seems, you're right - the citation of experiment which I had on mind is here

## Iourii Gribov

## Fleetfoot

Even though it is simulated, your upper picture would be typical for any double slit using a bright source, either light or electrons. Similarly, the lower image could also be the same experiment run with dim light or a low current of electrons. That's why I used the generic term "particles", you can't tell what was used.

That story is what I thought you meant. I don't see it's relevance to what we were discussing.

## PS3

## Fleetfoot

There's a readable description here:

http://scienceblo..._obs.php

"They haven't done anything to prove orthodox quantum mechanics wrong, though I can predict with confidence that there will be at least one media report about this that is so badly written that it implies that they did. In reality, though, their measurements are completely in accord with ordinary quantum theory. ... I confidently predict that there will be no shortage of crazy people trying to claim this as conclusive proof for their particular favorite interpretation of quantum theory."

I still can't see a connection to the discussion of the cosmological redshift or even to my statement that I don't give much credence to authoritative opinion, it is only the equations that matter.

## Fleetfoot

I should have said that what they did was find the mean momentum of a large number of photons at different locations and use that to map the average of many "trajectories" in the way that iron filings map the flux lines of a magnet.

## PS3

I was thinking of the quantum eraser,but maybe I read it wrong?

## Fleetfoot

I think so. I don't have access to the full paper but the reviews don't mention using entaglement at all and there is no attempt to measure individual trajectories, just the average of a very large number. It only confirms QM's prediction of the overall statistics.

## Fleetfoot

If you think of a map of the galaxies, that map is currently expanding by about 1% every 200 million years everywhere. No matter how far away from here you looked, you would see the same overall picture. An explosion suggests a region in space filled with matter expanding into a void which is incorrect.

Absolutely.