2nd reply to this.

"there's no a priori reason to assume that existence should occur"

No, of course not! Nothing can come out of existence without a previous existing state.
It's for that reason one can safely conclude, that the Big Bang model can not be a model of the universe as a whole, cause it drops down to the need for such a "supernatural" cause (even if that part of the theoretical model is left out).
That is, one can safely conclude at least one of the premises of the Big Bang model aren't correct.
Uhm... let's see, what assumptions have been slipped into the cosmological model, that gave rise to the universe to either expand or contract (or to be stable, if one invents a cosmological constant) .... could it be the assumption that the universe consists of a finite amount of matter .....

Just gueswork here...!

heusdens -- see Tim Thompson's response to Van Flandern's similarly veined in this thread:

http://www.badastronomy.com/phpBB/vi...3021&forum=1&2

Orion -- I think it's about time you stopped trying to extrapolate from observations that you don't quite understand. I have no problem thinking creatively, but I'm not about to go fly in the face of confirmed observation.

The observations are clear: gravitational lensing has no effect on the redshift of the sources.

Not again that rethorical "You dont understand " What about measurements taken on deflected source?What is the validity of such measurements?Remember this is all that link talk about.
http://www.cfht.hawaii.edu/News/Lensing/#IC

Go to Figure 2
Deflection of light rays crossing the universe, emitted by distant galaxies

Figure 3
Image of the distant galaxies lensed by the dark matter of the universe

<font size=-1>[ This Message was edited by: Orion38 on 2002-11-26 22:10 ]</font>

heusdens wrote:
"I myself, didn't arrive at this conclusion by studying science, by looking at the cosmos, or by reading philosophic work.
I was ample going to school, when thinking about this one issue, so I guess I was not influenced or pre-biased in answering this question: why is there a world, instead of no world at all..."

Well, I politely recommend you do study some science, do look up at the cosmos, and do read some philosophy. You seem to have this idea that knowledge is biased, and that being biased about something is wrong. But actually, it's OK to be biased. For example: Being biased towards better understanding nature and the reality of processes observed in the real universe. Your criticism is drawn from the light of an inner mind, now be bold and look outward. Its also OK to admit that you could be wrong, and see what others (who study the universe directly,) think about these issues. It is actually fun to compare one's own ideas about the universe with what little is known about the real universe, and modify or discard one's concepts this way. This moves us towards wisdom. [img]/phpBB/images/smiles/icon_wink.gif[/img]


<font size=-1>[ This Message was edited by: Chip on 2002-11-27 04:46 ]</font>

Yeah.
But I think you didn't understood that this 'mind issue' I was talking about, was an issue I solved, and which I still conclude as the proper answer, when I was young. Since then I did study and observe and read, etc.
Further I think, no matter what you observe, or what you study, etc, every one's mind contains some preconceptions about what reality is like.
You can't realy say that physics and cosmology are totally independend and that scientists working in the field don't have conceptions about reality. It determines for instance of how willing one is to accept a certain interpretation of physical phenomena.
The issue and interpretation of quantum mechanics is such an issue for instance.

And let me further say that the current cosmological model, is the best fit model up to day and might even be some definite model fitting this 'space-time-matter' bubble we are in (although I think it is now a little bit too early to state that), but then our definition of 'universe' doesn't fit the cosmos, cause the universe was supposed to be a 'self-containment' which has existence of it's own without anything outside it.
So, the thing I had in my mind was, that the universe and material world as such, has the property that it exists uncaused and has no beginning or end, is always transforming and in motion, and is unlimited in extent. These two models can go together, as some theoretical outlines on this issue have showed.

What I was just stating that in my opinion it's too early and it's far beyond what we reasonably can conclude based on the data we have about the cosmos to speculate about this.

So, we just have to deal with this BB theory, as long as it holds, but still need to have an open mind on the possibility that restudying all the material and even the theories on which our interpretation reside, can show that BB theory (which assumes a limited amount of matter to be existent in the universe, and therefore needs an expanding model for the cosmos to be existent) is not the only model that fits the observations. It might turn out that as our observational horizon increases, and further observations and calculations about (dark)matter distributions, can give rise to an alternative model, which is based on an unlimited extent of matter,space and time.
We can not yet exclude these things.

<font size=-1>[ This Message was edited by: heusdens on 2002-11-27 08:49 ]</font>

I know the argument, but my reasoning goed from another viewpoint.

In first instance I try to conceive of a possible model for the universe as a WHOLE.

Not the BB theory can not be seen as a model of the universe as a WHOLE.

And can I ask a very fundamental question, which I think caused us to think that there was a necessity for a cosmological model to avoid expenasion or contraction of the universe as a whole.
It is concluded from the the theory of GR that the cosmos as a whole could not be stable, due to the overall attractive force of gravity throughout the universe.
That is of course obviously the case.

But when argued from a perspective in which the universe in infinitely large in size and in which matter is infinite in extent, I can't conclude that the universe would collapse on itself.

I showed this, by using a thought model of a 'initial orderered state' of the infinite universe, and disproof that this universe would collapse on itself.

See an elaboration of this model in my contribution to this thread:

http://www.badastronomy.com/phpBB/vi...021&forum=1&10

That is the point I was making, even if the overall force of gravity is attractive on all scales, in an truely INFINITE universe, a collapse would NOT occur.

<font size=-1>[ This Message was edited by: heusdens on 2002-11-27 10:46 ]</font>

No, heusdens. You are wrong that your assumption leads to such a universe. In a truly infinite universe you have a mathematical divergance problem in radial extent. There is also an observational problem because an infinite universe should have an infinite heirarchy of structure (which we do not see) unless it is expanding in inflationary periods and forming horizons in which case you have your big bang back. There's nothing that causes an infinite universe from either expanding or contracting, since it is infinite it couldn't care less about such trivial behavior.

What assumptions lead to what universe?

My logical reasonining was that a universe which was not infinite in extent and filled with matter, would either contract or expand, using the cosmological models.

An infinite universe doesn't have that property, and so that kind of universe is the only candidate for a self-contained universe.

Please explain this to me.

No, but that problem is trivial, cause we cannot see infinitely far.

An infinite universe with matter infinite in extent is the ONLY model that is self-contained.

A Big Bang model can at most model a part of the universe, but not the universe at a whole.

(I still use the universe as the totallity of everything that exists, so nothing outside it exists...that's a real problem for the Big bang model, cause it ultimaltely drops down to a state of the universe which can't have a predecessor)


Right!

That makes it for that reason the ONLY possible universe.

JS maybe you miss that post or you dont want to adress it.So again what is the validity of measurements taken from deflected sources.
"Deflection of light rays crossing the universe, emitted by distant galaxies"
That meant to me that all the measurement from distant galaxies and Quasars until today (including Redshift of course) are based on deflected sources.This is what that page tell to us,Indirectly.

<font size=-1>[ This Message was edited by: Orion38 on 2002-11-27 15:10 ]</font>

What about a universe that is closed in a higher dimension? (The usual example is the surface of the earth.) It's finite, but unbounded, and is self-contained.

Silas

I am sorry to inform you.... it will collapse because of the force of gravity acting on everything that constitutes such an universe ..... unless it is expanding!

But then this raises the question of what happened BEFORE this expanding took place, and what caused that expanding to occur??

That you cannot possible solve, not without cheating or tricks! (the cosmologist insist us on cheating cause EITHER the anwer can't be given, OR we have to assume something out of the ordinary, namely 'creation ex nihilo' OR it must be assumed the universe is not everything (which contradicts the very definition we use for universe, namely: Everything that exists)


So, I can tell you most convincingly, your universe is not self-contained, cause it doesn't exist.

We live in a universe though, and therefore it is self-contained, which means it must be an universe which is infinite in extent, and has no begin or end.


<font size=-1>[ This Message was edited by: heusdens on 2002-11-27 17:17 ]</font>

It works despite of the expanding universe Mr Princeton!

Now, Mr Princeton, you seemed at some time very sure of the Big Bang theory, and argued that since "I had something against the BB theory" I must be totally nuts.

Then I explained to you, on logic grounds and proper use of our definitions, why the BB theory can't be right.

All you can stumble now is that what we do is magic (which it is not of course), thereby clearly admitting that all the BB theory in fact does is "doing magic" and playing tricks on our minds, and assumes we are infants, who can't pinch through vacuum bubbles and that sort of things.

But you seem to have lost interest in the debate now, since you can't win the argument.

No Orion, I didn't miss your post. I think you need to think carefully about what you're saying.

You're saying that this is a new phenomenon. You're right, we haven't considered this phenomenon until very recently. The lensing of filamentary structures is indeed a "hot topic" right now.

It in no way does anything to redshifts. All it does is distort the image appearance (angular extent, mostly), intensity, and position in space. Those three things have nothing to do with redshift. So you see, there's nothing to worry about. Lensing is something that is facinating, but it doesn't provide a mechanism for redshifts -- even special new lensing due to filaments.

Intriguing, but no. What do you do about Obler's paradox again? Remeber, you can't have dust be the answer because we should see reradiation (to use a favorite Agora word).

Oops! You're wrong there. It's predicated on lambda-CDM (an expanding universe).

I argued you were totally nuts simply because you stated contradictions and advocated them as fact. I have always admitted that there may be some theory out there that would explain the universe better than the Big Bang, only you would have to explain everything the Big Bang explains just as well.

Ho ho! You think I'm going to admit to this, buster? First of all, you explained to me on logic based on a gut feeling you had why the BB theory can't be right. Secondly, you admitted it was a gut feeling, but kept saying it was somehow the must justified feeling in the world. Then I say, well, you're sounding very much like the pot calling the kettle black, trying to give you a little leeway to gracefully save face, but no, you decide that I am wavering.

Well, let me be frank: your idea is kind of a nice headtrip, but is based completely in your head and not in observations. You have proven yourself to be just uncranky enough to keep stringing us along before you start spouting more disinformation about your pet "theory", which isn't a "theory" at all since that would require scientific rigor, but rather is simply a headtrip. Well, I'm sorry, but I don't need to take your word for it in order to make a decent study of the universe. Let the informed reader make up her mind.

Suddenly you are a we?

No, all the Big Bang theory (and it truly is a theory in the Kuhn sense) does is work from observation to produce a consistent model of the universe as opposed to the INconsistent one you present, Mr. Heusdens.

Nope, an infinite universe can expand or contract EVERYWHERE and still be infinite. Infinity is strange that way. Multiply inifity by a scale factor and you still get infinity. Therefore you can't avoid expansion and contraction simply by stating the universe is infinite.

You have a problem describing your universe at infinity. You need all your fields to go to zero at infinity or you will end up with big big problems. This sets your "boundary" values (instead of initial conditions) to which your laws of physics have to conform. Now you are ready to build your model.

The problem is that you want a static model. This means you need to have some way of building a universe whose mass shells go to zero {indeed whose every force term and field in general go to zero) at infinity and start solving from there. The solution is problematic because you'll end up with a physical impossibility on the order of nonexistence (which you seem to hate) if your fields don't fall off in just the right way. What you'll find is that your universe will have many solutions (in fact, this exercise is done in some intro cosmology books) and some subset of these universes will look like Big Bangs. Now you're back to where you began with a Big Bang you wanted to get away from. Disturbing, ain't it?

That doesn't matter. We see an upper limit to structure size. Even if we can't see infinitely far (and why is it that we can't see infinitely far? The universe has been around long enough, hasn't it?) we should still see structures on ALL scales. Right now structure is only up to the supercluster (filamentary) scale which is below the current size of the universe that looks homogeneous and isotropic on the largest scales. This is an assumption (homogeneity and isotropy) that really leads to expansion and contraction of the universe. It's called the Cosmological Principle. If you don't have a homogeneous and isotropic universe, steady states are easy to come by. You just set up a dynamical equilibrium and bob's you're uncle. A finite amount of mass or an infinite amount of mass assumed doesn't matter, it's the Cosmological Principle that forces us into the regime of homogeneity and isotropy. Now, you might wish to attack this assumption, but we also have a lot of evidence for it on the largest scales (and the evidence just keeps getting better and better for it... especially with regards to the CMB).

As I showed, this statement is bogus.

Excellent admission and I actually think I agree. This is because we don't have a coherent quantum gravitational theory so therefore we don't have that part of the universe modelled yet!

No, you're getting confused with jargon and nomenclature. "Universe" can mean two things. To theorists it usually means what you describe it to be: "everything that exists". To an observer, universe actually means "observable universe". It's unfortunate that we aren't clear about this. I try to be as clear as I possibly can be when talking about these two different contexts, but "observable universe" is a clunky term so we usually get lazy. Bad excuse, for sure, and bad astronomy. From the context, though, you have to figure out whether they are talking about the observable universe or the theoreticians universe.

For example when they say, "the universe is 15 billion light years across"... they are talking about the OBSERVABLE universe and not the theoretical universe.

When they say, "this universe may have been spawned from another universe". They mean "The OBSERVABLE universe may have been spawned from something that is on a grander and unobservable scale".

It's a game, to some extent, and it's unfortunate we've confused you with nomenclature and jargon. On behalf of the astronomical community, I offer you my most sincere and humblest of apologies.

It need to be conditioned, of course.

Well, I would think that the matter need be distributed in such a way, that outside a shell of some (significantly large) diameter, all forces of gravity equal out (are zero) within the shell, in respect to all the matter outside the shell, at any point in space. Further on, one would assume all motion to be initially to be zero.
This ain't of course realistic initial conditions (the universe wouldn't have initial conditions), but just for simplicity to see if such a model could in principle work (being stable at the infinitely large scale, i.e. no overall contraction or expansion, except for the finite scales).

I am not sure if such conditions would make it stable for all eternity...(i would think though that if no expanding or contraction occurs for the universe as a whole, it would never occur thereafter, but this can be wrong).

But from your explenation, I did figure out I oversimplified it, and I would need to reconsider it.

The boundary condition would be the universe to be stable i.e. not being in a state of overall collapse or expansion, but on every finite scale this could for sure and does for sure happen.

Yes, it's an intruiging question, and far further reaching as I at first instance thought it would.

How could a universe look locally a big bang, and not having that feature as an overall feature, and in that model, what happened before this big bang state?

Would this have any possibility of having realy happened (it would strip of the singularity part)?

I think the assumption that in a universe filled with matter in any part of space, makes it reasonable to assume that light could not travel infinitely far.
Are structures like the Great Wall conceived of as a supercluster?

Well, let's use soapfoam as an example, it can have smaller bubbles, groups of smaller bubbles, and all sizes of larger bubbles.
The largest structure though is the universe itself, and although that will be an observable limit, it may turn out it is not the highest structure.

It is different as what I initially thought it could be like, which you showed to be incorrect. It invalidates part or most of my statement, that is my assumption that this expanding spacetime bubble could be infinite in extent for space, time and matter, could be regarded from this argument as incorrect (and probably as well for other reasons, like the light element abundances, etc.)

In another way, it can still be correct.
We don't know if the 'universe' (the inflating, expanding bubble, our 4D spacetime frame we inhabit) is finite or infinite, and if it is self-contained (exists without external cause).
It could turnout that the universe as a whole (a self-contained universe) is definately infinite, and with no begin or end. I could not think that could be otherwise.

I think you mean here, that we need a coherent theory there to explain what happened in the very first instant.
And also, we don't know if the expanding that occurs, is a feature of all of the universe, or only the observable universe, since it follows from your examples, the expanding might occur only locally (i.e. at least to the amount of space that contains the observable universe) etc.
But I was not aiming at this.
I was aiming at the position that a big bang asks for the explenation as to why it happened, what caused it (and part of that answer can be in quantum gravity aspects) but it could also mean that a 'higherorder' world needs to exist.

Well, there must be even (at least) a third concept to define what we are talking about.
Apart from the observable universe, and the surrounding (non-observable) universe, the expanding spacetime bubble we inhabit, might be part of a higherorder world. And THAT world, could be also part of an even higher world.

We need a word or definition for the highest order world (it might theoretically be, there is no highest order, the degree could be infinite). That world by definition would be self-contained and everything that exists.

My statement about an infinite universe, without begin or end, as the only possible 'model' (it is not a real model however), can still be valid, even when at the level of this universe (the expanding spacetime bubble) there might be a definitive begin and it might be finite in extent. But that feature would just indicate in my view, that it is not selfcontained, and therefore a higherorder world must exist, etc.

But these kind of things are not very conceivable, since we only conceive this 1st order universe (and can see a small part of it), and can only postulate theoretical assumptions about a possible higherorder world (like the brane worlds).
So, it's a bit theoretical.

** note **
Perhaps the notion/concept of eternal inflation, in which inflation process spawns other inflation processes, is an unending proces, without begin or end, is a better description for this.


<font size=-1>[ This Message was edited by: heusdens on 2002-11-29 15:36 ]</font>

JS Princeton:

On 11/24/02 you wrote (as part of a lengthy post):

I just caught up to your post a minute ago, and, as a slight joke, would like to offer the notion that both objects orbit each other, but the center of the combined orbits lies very near the center of the more massive body. For instance, Earth orbits the Sun, but the Sun also orbits the Earth with the center of the combined orbits lying practically at or very, very near the center of the Sun. Of course, it is just silly on my part, but I found it interesting when I read it sometime ago. And, of course, it does not help that I have forgotten where I read it. Typical...

ljbrs [img]/phpBB/images/smiles/icon_biggrin.gif[/img] [img]/phpBB/images/smiles/icon_wink.gif[/img] [img]/phpBB/images/smiles/icon_cry.gif[/img]

__________________
"There is in the universe neither center nor circumference." Giordano Bruno Born 1548. Torched 1600.

ljbrs--- you are right, of course, it's just that for more massive bodies the center of mass tends to be closer to their center of mass.

heusdens --

Thanks for toning down the rhetoric in your last post. There are still a few conceptual errors that, IMHO, stem mostly from you being uncomfortable with the marriage between theory and observation. You have a problem with theories that talk about unobservable mechanisms that don't look like things we see in our universe. This is understandable because we like to think we as humans have a good grasp on the way the universe is and that it shouldn't look really weird "elsewhere".

This isn't the first time in science people were upset by nonphysical theories that explained observations. For example, FIELD theories seemed very non-physical to certain scientists. Fields seemed to be "non-entities", "not real". There were people who found field theories suspect because you couldn't touch or feel a field and it seemed to spookily act without regards for the way "logic" would have things act.

There is one more error: you still think that an infinite universe cannot be "in motion" as it were, other than locally. Actually, an infinite universe can be globally "in motion". The entire universe could be expanding or contracting. If it were infinite there is no problem. Multiplying infinity by a number gives you infinity. Therefore you can expand and contract over the entire scale and still be "self-consistent". In other words, your boundary condition of "no motion" is unsupportable.

One more point with the hierarchy of scales. You can't simply say that the observable universe itself is the highest scaled structures after superclusters (by the way, the Great Wall is a supercluster). This is because the universe is so much larger.

Think of the bubble analogy. You have a bath full of bubbles. Some are big and some are small. Now consider a bath that is full of bubbles that are all smaller than a given size. You might say that the "bath itself" is the largest sized bubble. This would seem to make sense, except there are no intermediate bubbles. There are no bubbles that are half the size of the bath. There are no bubbles bigger than the size of your fingernail when you look at a fifth of the bath. Where are those medium-sized and large sized bubbles? The Big Bang says they didn't have the seeds to form. The universe "froze out" its structure early on, and once it inflated up to a larger scale, that set the largest scaled structure in the universe. There could easily be larger scale structure (I can conceive of larger bubbles) but I don't see them. Why is this? Why does structure suddenly stop, or make a quantum leap from superclusters to the observable universe? It just doesn't make sense if I have an infinite universe that is around for an infinite amount of time that I could have such an inhomogeneous hierarchy of structure. I should have clusters of superclusters (but I don't) I should have weavings of filaments (but I don't). All I have is a foam that looks from the large scale as being "smooth over everything".

This is another reason to discount an infinite universe idea.

Your explenation was an "eye-opener" on seeing where I got my model wrong. I had not looked at it that way, and so I must drop that possibility all together, I think. I can see now it was an absurd idea.
But happily one is not too old to learn from one's mistakes.....

My argument came however from a different perspective. My main critics I had on Big Bang theory, were in the domain of the "ugly nature" of the Big Bang singularity, which makes us guess and wonder as to what happens at t=0. The model I had seen before about/around this issue was the Instanton theory (Hawking/Turok) which in my perspective did not realy lift the problem. I had read some on Inflation theory, but this was then part of the Big Bang scenario, and in fact did not remove the "ugly nature" of the Big Bang theory.

A universe can be unlimited (spacially and materially) and eternal in more then one way.

I had not looked in this before, but an improved inflation scenario (called "chaotic inflation"), developed by Andrei Linde in my mind most closely reflects this idea, and removes the pitfalls of the Big Bang.

This is a model of eternal self-reproducing inflation, so it would not need a begin or end, it could go on forever.
In this model, Big Bang theory becomes part of Inflation theory, and not the other way around.

Here's a link to a lecture of Andrei Linde on this form of Inflation and a text concerning the theory itself.

Lecture Andrei Linde on "Inflation and String Cosmology"

Article Andrei Linde : "The Self-Reproducing Inflationary Universe"

Although physics and philosophy are different terrains, they do have some interrelation, esp. in cosmology, for instance in the issue of models with a definite beginning, or one that has no begin.

For philosophical reasons, I do prefer a model that does not require a begin. I think Nature has no beginning.

<font size=-1>[ This Message was edited by: heusdens on 2002-11-29 22:27 ]</font>

JS Princeton --

And by the way I am very thankfull for your excellent explenation, and showing me where I was wrong in the infinite universe model.

The model of Andrei Linde shows however that Nature at a different level can supply a form of infinity and eternity in the form of self-reproducing.

I was not looking for "self-consistency" but I instead used the term "self-contained".

As a matter of fact I don't think of the material world to be self-consistent, I would not know if that term could possible apply to the real world.

The boundary condition of "no motion" is absurd of course. All I was looking for is a boundary condition in which there wouldn't be a total collapse or inverse thing happening in an infinite and never ending universe, that would lead to an irreversible situation.
As to that, I don't "oppose" a Big Bang, at least as a local event, if the conditions under which the universe underwent a Big bang, can be dealt with, without the call for the "supernatural" or "creator" thing.

ie. the world according to humans.
the universe , in reality, could be like an iceberg. because of our human limitations, we can see ONLY the visible part.
I'm sceptic as to find a unification theory, or how it all started, since we can't perceive the hidden part.
our models will be always incomplete/missing something. eg. a mising/invisible/dark mass/energy ...

some say, physicists have already reached their own limit ...

Gotta disagree. The human mind is capable of conceiving of many things beyond human perception.

Do you recall the story of the head of the US Patent Office who resigned because he felt everything worthwhile had been discovered? In the 1890s?

__________________
Never attribute to malice what can be adequately explained by ignorance or stupidity.
Isaac Asimov