SauwIs the concept of finite space in infinite time scientifically valid?

[Sauwelios]

Lectori salutem.

Can anyone refute the finite space/energy/matter in infinite time theory?

Finite space/energy/matter implies that the universe is not something endlessly extended, but set in a definite space as a definite force.

Infinite time implies that it will never reach a final state of equilibrium.

This means that the universe consist of a finite amount of energy (in whatever manifestation) that flows on in an infinite stream - not infinitely deep or wide, but infinitely long.

I will welcome any serious thoughts on the subject.

Thanks in advance!

Sauw

 

[heusdens]

Originally posted by Sauwelios
Lectori salutem.

Can anyone refute the finite space/energy/matter in infinite time theory?

Finite space/energy/matter implies that the universe is not something endlessly extended, but set in a definite space as a definite force.

Infinite time implies that it will never reach a final state of equilibrium.

This means that the universe consist of a finite amount of energy (in whatever manifestation) that flows on in an infinite stream - not infinitely deep or wide, but infinitely long.

I will welcome any serious thoughts on the subject.

Thanks in advance!

Sauw

From what perspective, reason, or observation, you conjecture that space is finite in extend.

All we know or assume is that space has no edges or boundaries. Which does not imply it being infinite, but neither disables that option.

I really doubt that space or matter are finite in extend, in more or less the same way as I doubt that time is finite in extend.

If space would be finite in extend, and have no boundaries or edges, this means that space is not flat, but curved. If space is sufficiently large, we might not observe that fact on small distance scales.

Current astronomical observations indicate however that space seems perfectly flat. It is not a proof, but just an indication that space can be infinitely large. And if not, it would need to be very large indeed. Most atronomers assume that we only see a small fraction of all of space.

Infinite space is a real candidate, and not just a theoretical model for the universe.

 

[Sauwelios]

All I need is the POSSIBILITY of finite space; and that possibility exists until it is refuted - i.e. until the infinite-space theory is proven PRACTICE.

 

[heusdens]

Originally posted by Sauwelios
All I need is the POSSIBILITY of finite space; and that possibility exists until it is refuted - i.e. until the infinite-space theory is proven PRACTICE.

Why do you 'need' finite space?

What is your motivation for assuming that space is finite in extend?

 

[Sauwelios]

If space were infinite it could not expand. This is contrary to the big-bang theory.

Simply put, if the universe is a finite force in infinite time, this means that all possible conditions will exhaust themselves and sooner or later the same condition shall come about. From which it follows...

 

[heusdens]

Originally posted by Sauwelios
If space were infinite it could not expand. This is contrary to the big-bang theory.

Why do you think that? The assumption is false.

Take for instance the infinite number set. You can add to it an infinite amount of numbers, without problem. Also you can subtract from it an infinite amount of numbers, while it sill maintains being infinite.

You have to look at space expansion as an expansion of the metrics.
An infinite space that expands still remains infinite.

However, it can be stated that the Big Bang is the expansion of an initial region as small as a infinitesimal small part of the size of a proton. However, in the embedding theory of inflation, this is just one region, and the surrounding space is still infinite space.
Inflation indeed talks about a small region of space that expands, which means that that region, no matter how large and how fast it expands, always will be finite in size.

Simply put, if the universe is a finite force in infinite time, this means that all possible conditions will exhaust themselves and sooner or later the same condition shall come about. From which it follows...

That everything would repeat itself? every moment is an eternal moment? well it explains my feelings of deja-vue... LOL

The situation is however not very different in an infinite space, cause then it could be said that there must be infinite many planets exactly like earth, with the same inhabitants, etc.

 

[Lifegazer]

Originally posted by Sauwelios
Finite space/energy/matter implies that the universe is not something endlessly extended, but set in a definite space as a definite force.

And what would this finite existence be residing within? Nothing? Impossible.

Infinite time implies that it will never reach a final state of equilibrium.

Which implies that all things within the universe have always been effects. No cause. That doesn't make sense either.

 

[heusdens]

Originally posted by Lifegazer
And what would this finite existence be residing within? Nothing? Impossible.

The model of a 2D sphere curved in 3D space, is a good model for a finite, yet unbounded space. For 3D space it must mean it is curved in 4D space. But all astronomical observations conclude that space is almost perfectly flat. From observation we thus concldue that space is indeed very large, possibly infinite.

Which implies that all things within the universe have always been effects. No cause. That doesn't make sense either.

Not realy. All effects are at the same time causes for the next effect. Which doesn't mean that I conclude that a circular chain of cause-and-effect, based on the finitiness of space, makes any sense to me...

 

[Lifegazer]

Originally posted by heusdens
The model of a 2D sphere curved in 3D space, is a good model for a finite, yet unbounded space.

Sure. But what is this "model" residing within? Certainly not 'nothing'. That's a logical impossibility.
Something must have boundless existence. This is clear. But this thing cannot reside within 'nothing'. Therefore, existence itself is not finite.
But infinite-existence imposes singularity upon existence itself. The position of any thing within such an existence is thus subjective.

Not realy. All effects are at the same time causes for the next effect.

No effect can lay-claim to being the true cause of any event.
To say that I (lifegazer) am the absolute-cause of this post, for example, is utterly incorrect.

 

[heusdens]

Originally posted by Lifegazer
Sure. But what is this "model" residing within? Certainly not 'nothing'. That's a logical impossibility.
Something must have boundless existence. This is clear. But this thing cannot reside within 'nothing'. Therefore, existence itself is not finite.
But infinite-existence imposes singularity upon existence itself. The position of any thing within such an existence is thus subjective.

While I agree on the conclusion that space is infinite, this does not mean that your argument against finite space is correct. What is against a 3D sphere curved onto itself as a 4D hypersphere? (except that it implies that time had a beginning)

No effect can lay-claim to being the true cause of any event.
To say that I (lifegazer) am the absolute-cause of this post, for example, is utterly incorrect.

We come here again on the point which you argued against, namely that the chain of cause-and-effect is infinite indeed, that means: it has neither a begin nor an end. A finite circular cause-and-effect chain has neither a begin or end, but this means that everything happened already an infinite number of times.
(hmmmm. it appear to me I already say that many times before? lol)

BTW: Did you change your mind on the beginning-of-time thing?

 

[Sauwelios]

Originally posted by heusdens
You have to look at space expansion as an expansion of the metrics.
An infinite space that expands still remains infinite.

That is a mathematical abstraction. "An infinite space that expands" is an oxymoron: it implies that the space have bounds which expand. However, the word infinite means "without bounds"...

[B}The situation is however not very different in an infinite space, cause then it could be said that there must be infinite many planets exactly like earth, with the same inhabitants, etc. [/B]

That is very interesting. Thank you for submitting your views.

Sauwelios

 

[heusdens]

Originally posted by Sauwelios
That is a mathematical abstraction. "An infinite space that expands" is an oxymoron: it implies that the space have bounds which expand. However, the word infinite means "without bounds"...

That is a incorrect view. Model all of space as a flat sheet, infinite in extend, and draw a grid on that sheet.
The expansion of that infinite sheet can now be visualized as a change in the metrics of that grid. It gets larger.
And the only way we can know about that, is because the objects on the grid (the atoms, and material objects) do not expand themselves.

In fact this situation is similar to the grid not expanding, and all material things on the grid, contracting.
However, I never heard a physical explenation to that, although it must be the same thing, we only changed the definition of our length unit... Physical laws are absolute the same and not dependend on our choise of the length units...

Can anyone explain me this, cause this aspect of "space expansion" I still don't get?

That is very interesting. Thank you for submitting your views.

The fact that either time and/or space is infinite, seems both lead to many contradictionary implications. Either "this moment" happened an infinite number of times already, or "this moment" happens at infinitely many places at once...

 

[Lifegazer]

Originally posted by heusdens
While I agree on the argument that space is infinite, this does not mean that your argument against finite space is correct.

I said that existence was infinite. Not space.
... and why do you disagree with my argument about finite-existence?

We come here again on the point which you argued against, namely that the chain of cause-and-effect is infinite indeed, that means: it has neither a begin nor an end.
A finite circular cause-and-effect chain has neither a begin or end, but this means that everything happened already an infinite number of times.
(hmmmm. it appear to me I already say that many times before? lol)

Yep. A stumbling-block of communication, is this.
My position remains unaltered. If all effects are the product of causality, and causality is infinite in regress, then there cannot be a 'product'. Nothing you have posted has ever convinced me otherwise. Sorry.

 

[Sauwelios]

Originally posted by Lifegazer
And what would this finite existence be residing within? Nothing? Impossible.

Nothingness, ye-e-es. But the idea of something within nothing is a rational impossibility: for, to envision this, one should be able to imagine "The Nothing"... Utter darkness? But that is still something. No, "space enclosed by nothingness" means there is only space, not within something but in itself.

Which implies that all things within the universe have always been effects. No cause. That doesn't make sense either.

It is indeed a vicious circle. But is a circular argument neccesarily a false argument? Or must you really infer a "Creator" as a primary cause. Who, then, invented the Creator? Did He invent Himself? Or has He always been there? - But this is merely a repetition of the question...

 

[Sauwelios]

Originally posted by heusdens
The fact that either time and/or space is infinite, seems both lead to many contradictionary implications. Either "this moment" happened an infinite number of times already, or "this moment" happens at infinitely many places at once...

Or Both?

 

[Lifegazer]

Originally posted by Sauwelios
But the idea of something within nothing is a rational impossibility: for, to envision this, one should be able to imagine "The Nothing"... Utter darkness?

Absolute-nothing is utter nothingness. Not utter colour or colourlessness or any other thing which you'd care to mention.
You cannot have something residing within such a state. It's rationally impossible.

But that is still something.

Then it is not 'nothing', is it? And if you want to put 'something' beyond universal-existence, you just extend existence beyond our material-domain. Hence, existence is boundless and non-finite.

No, "space enclosed by nothingness" means there is only space, not within something but in itself.

Sorry, but this is no longer a rational discussion. You cannot have a finite-entity residing within nothing other than itself. The very-fact that the entity is finite means that it must be embraced by another entity - which cannot be 'nothing'.

It is indeed a vicious circle. But is a circular argument neccesarily a false argument?

Not if the circular argument makes sense.

Or must you really infer a "Creator" as a primary cause.

Personally, I think so. Most here will side with you though.

Who, then, invented the Creator? Did He invent Himself? Or has He always been there? - But this is merely a repetition of the question...

Existence itself is eternal (note: by existence, I do not automatically infer that the material-universe is eternal). This is obviously-apparent when one realizes that something cannot emanate from absolute-nothingness. And since something does exist now (whatever that thing may be), then we can be sure that this thing has always existed, and always shall - since 'nothingness' cannot come of something.
Thus, existence is eternal, and the question about its own causality is shown to be meaningless.

Like other members here, you seem to want to use the term 'nothing' so that it actually is 'something'. This is your base-error, imo.
By the way, welcome to the forums.

 

[Sauwelios]

Originally posted by Lifegazer
Absolute-nothing is utter nothingness. Not utter colour or colourlessness or any other thing which you'd care to mention.
You cannot have something residing within such a state. It's rationally impossible.

Then it is not 'nothing', is it? And if you want to put 'something' beyond universal-existence, you just extend existence beyond our material-domain.

I made the mistake of assuming you could fill in the blanks I intentionally left in this part of my argument. You have, but at the cost of thinking that I could not do so myself. Then you gave the same impression to other readers by cutting my argument into pieces.

Hence, existence is boundless and non-finite.

This conclusion does not follow from the premises. It rather seems to be some kind of idée-fixe you have.

Sorry, but this is no longer a rational discussion. You cannot have a finite-entity residing within nothing other than itself. The very-fact that the entity is finite means that it must be embraced by another entity - which cannot be 'nothing'.

These are all personal opinions, not facts. Why must something be enveloped by something else?

When asked whether you think there is a Creator, you said: "Personally, I think so." That is not very scientific. What makes you think there is one?

Existence itself is eternal (note: by existence, I do not automatically infer that the material-universe is eternal). This is obviously-apparent when one realizes that something cannot emanate from absolute-nothingness. And since something does exist now (whatever that thing may be), then we can be sure that this thing has always existed, and always shall - since 'nothingness' cannot come of something.
Thus, existence is eternal, and the question about its own causality is shown to be meaningless.

This has been my point from the beginning - with the incorporated notion that the essence of existence is to all eternity flux.

Thank you for making me feel at home.

Sauwelios

 

[Sauwelios]

Originally posted by heusdens
Model all of space as a flat sheet, infinite in extend

One can never model all of space if it is infinite...!

 

[heusdens]

Originally posted by Lifegazer
I said that existence was infinite. Not space.
... and why do you disagree with my argument about finite-existence?

Yep. A stumbling-block of communication, is this.
My position remains unaltered. If all effects are the product of causality, and causality is infinite in regress, then there cannot be a 'product'. Nothing you have posted has ever convinced me otherwise. Sorry.

Your reasoning is obviously wrong. Because your reasoning assumes at a certain point there is a begin to the infinite chain of cause-and-effect. From there on you reason that if such a begin is an infinite time from the present, you cannot get from there to the present, and hence there can not be a product.
We been on this point now many times, and the error in your argument is that you put in the conclusion of your argument (time must have a beginning) in the premise to your argument.
Infinity, namely, implies there is no begin to the time line. So, wherever you place your 'begin point' where you start your count, you always leave behind you an infinite amount of time.

So, your reasoning is circular. Your basic (implicit) assumption is that time had a begin. Then you state that if time is infinite, that an infinite amount of time must have been passed since that beginning. You then conclude: that is impossible, so time could not be infinite, hence time must have had a beginning. But that was just the start of your reasoning, the premise you implicitly smuggled into the argument!

Your error: you have assumed that there was a begin (else, where do you start counting?), while in fact, infinity of time in both directions (past and future) means that there is no begin or end to time at either side of the timeline.

Please reread that part of the argument in the text of Friedrich Engels in the thread: https://www.physicsforums.com/showthread.php?s=&threadid=958".

The fact is, your conclusion is wrong, cause the 'product' (the here and now) exist (that is for sure). Further we now that all things of the present must be the effects of previous causes, which themselves are also effects of previous causes. Hence it follows that time had no beginning. Otherwise, there would have been effects without causes.

 

[heusdens]

Originally posted by Lifegazer
Absolute-nothing is utter nothingness. Not utter colour or colourlessness or any other thing which you'd care to mention.
You cannot have something residing within such a state. It's rationally impossible.

Then it is not 'nothing', is it? And if you want to put 'something' beyond universal-existence, you just extend existence beyond our material-domain. Hence, existence is boundless and non-finite.

Sorry, but this is no longer a rational discussion. You cannot have a finite-entity residing within nothing other than itself. The very-fact that the entity is finite means that it must be embraced by another entity - which cannot be 'nothing'.

Not if the circular argument makes sense.

Personally, I think so. Most here will side with you though.

Existence itself is eternal (note: by existence, I do not automatically infer that the material-universe is eternal). This is obviously-apparent when one realizes that something cannot emanate from absolute-nothingness. And since something does exist now (whatever that thing may be), then we can be sure that this thing has always existed, and always shall - since 'nothingness' cannot come of something.
Thus, existence is eternal, and the question about its own causality is shown to be meaningless.

Like other members here, you seem to want to use the term 'nothing' so that it actually is 'something'. This is your base-error, imo.
By the way, welcome to the forums.

You are very excellent in this reasoning. And for most part the reasoning is correct, except for the fact that you rob the material basis from existence. What can exist if no matter in whatever form (mass, energy, fields, whatever there is that can move/change in time and space) would exist?

 

[Eh]

Actually, the reasoning is crap. The claim that a finite manifold must be embedded in external space has been repeated often, but is not founded on logic or any reasoning at all. But maybe you missed that part.

 

[heusdens]

Originally posted by Eh
Actually, the reasoning is crap. The claim that a finite manifold must be embedded in external space has been repeated often, but is not founded on logic or any reasoning at all. But maybe you missed that part.

I already pointed that out. The 2D anology of space, modeled as the surface of a sphere, which is of course a finite size, but has no boundaries or edges; mathematically that is perfectly possible, and does not need 'outside' space.

Nevertheless, from observation and theory, I do not think that real space is finite.

 

[quantumdude]

Originally posted by Sauwelios
I made the mistake of assuming you could fill in the blanks I intentionally left in this part of my argument. You have, but at the cost of thinking that I could not do so myself. Then you gave the same impression to other readers by cutting my argument into pieces.

Don't worry: He doesn't give that impression to any of the regular readers.

When asked whether you think there is a Creator, you said: "Personally, I think so." That is not very scientific. What makes you think there is one?

Ugh--Please, let's not. This was a big enough mess the first time. You can read about it here, if you are so inclined:
https://www.physicsforums.com/showthread.php?s=&threadid=1307

 

[Eh]

Originally posted by heusdens
I already pointed that out. The 2D anology of space, modeled as the surface of a sphere, which is of course a finite size, but has no boundaries or edges; mathematically that is perfectly possible, and does not need 'outside' space.

Nevertheless, from observation and theory, I do not think that real space is finite.

Edges aren't even the problem. The claim that finite space must be embedded in something external is where the argument falls apart. Even if some models of the expanding universe found by Georges Lemaître (with a center and edge) were correct, the claim is still wrong.

But I guess intuition takes priority over reason with some.

 

[heusdens]

Originally posted by Eh
Edges aren't even the problem. The claim that finite space must be embedded in something external is where the argument falls apart. Even if some models of the expanding universe found by Georges Lemaître (with a center and edge) were correct, the claim is still wrong.

But I guess intuition takes priority over reason with some.

Apart from the false argument against a finite extend of space, do you really think that space is finite, and for what reason?

To state that space is infinite is somehow difficult, because that aspect of space can not be observed directly. The only observational point is the "flatness" of space. But since we can not distinguish between an exactly flat space and space that is very near to flat (meaining: space is very big), how can we find out wether or not space is infinite?

 

[Eh]

It's not really something testible, though in theory a finite universe could be proven with the right technology. But in the mean time, I would say finite is more likely, if only because nature does not seem to contain infinities anywhere else. In the past, it was believed that space and time were infinite in extent, while matter and space were infinitely divisible. Quantum theory showed us matter is not continuous, modern cosmology gives difficulty to the idea of infinite time, and it is expected by many that a quantum theory of gravity will do away with the notion of continuous space-time. The only infinity left is that of space.

Is space an oddball, or does nature truly contain no infinities? I vote for the second.

 

[heusdens]

Originally posted by Eh
It's not really something testible, though in theory a finite universe could be proven with the right technology. But in the mean time, I would say finite is more likely, if only because nature does not seem to contain infinities anywhere else. In the past, it was believed that space and time were infinite in extent, while matter and space were infinitely divisible. Quantum theory showed us matter is not continuous, modern cosmology gives difficulty to the idea of infinite time, and it is expected by many that a quantum theory of gravity will do away with the notion of continuous space-time. The only infinity left is that of space.

Is space an oddball, or does nature truly contain no infinities? I vote for the second.

Cosmology does not model time as having a begin.
In fact there has been only one such hypothese (Hawking-Turok these) which modeled universe as having a begin in real time.
This hypothese however has been dropped. Alternative hypothesis are built on the assumptions that time had no beginning.

I suspect that time and space are closely linked together, and that either must be finite or infinite. As to my argument, I would therefore state that both are infinite.

Notice that a finite time and a finite space would not form a very consistent world. Because in the first place, it would not be possible to exist on it's own.

 

[Eh]

Originally posted by heusdens
Cosmology does not model time as having a begin.
In fact there has been only one such hypothese (Hawking-Turok these) which modeled universe as having a begin in real time.
This hypothese however has been dropped. Alternative hypothesis are built on the assumptions that time had no beginning.

Actually, the standard model of cosmology predicts a beginning to the universe. Alternative models such as chaotic inflation build on that, but they still seem to require a beginning after all. For a while, it seemed that some self reproducing universes could be eternal, but now it seems even those must have a beginning. Perhaps theories based on extra dimensions may yield the possibility of an infinitely old universe, but the models based on 4D space-time do not seem to do the trick.

I suspect that time and space are closely linked together, and that either must be finite or infinite. As to my argument, I would therefore state that both are infinite.

Yes, that is why I would suspect finite.

Notice that a finite time and a finite space would not form a very consistent world. Because in the first place, it would not be possible to exist on it's own.

Not necessarily. You can model a beginning to the universe that does not have a before without suffering from any logical inconsistancy. The same applies to finite space. Of course this position goes against intuition, but that isn't a problem with logic.

Philosophical notions aside, modern cosmology does indeed give an infinite universe problems. Perhaps a cyclic model would work, but there is no guarantee such a universe did not have a first cycle.

 

[wimms]

Originally posted by Eh
Actually, the reasoning is crap. The claim that a finite manifold must be embedded in external space has been repeated often, but is not founded on logic or any reasoning at all. But maybe you missed that part.

Eh, this IS coming up often. Would you, as one of the pros care to explain it slow and understandably, why such reasoning is crap? Or if that has been beaten to death already, where's a link?

 

[Eh]

It's really just a matter of geometry. The volume of something has nothing to do with the space it is embedded in. And that's just it. The notion of area and volume are well defined geometric concepts that do not need reference to outside space for definition. So the claim that a finite universe must be embedded in some infinite space is founded on intuition and not any logic.

 

[Lifegazer]

Originally posted by Eh
It's really just a matter of geometry.

Geometry is conceptual mathematics. It is formulated within the mind, for practical applications within space.
The difference between concepts of the mind and perceived-objects (finite objects), is that concepts are embraced by the mind, whereas 'objects' are embraced by perceived-space.
In either case, geometry is formulated within something.
It is not formulated within nothing. A finite-object cannot exist within nothing.

 

[Eh]

No, you're wrong. The mathematical field of Geometry is a description of space, which is very real. Space-time does not need to be embedded in any external space, inspite of what intuitionists like yourself would claim.

 

[Sauwelios]

An end to the discussion?

I agree with Eh in this. However, I do not think that we can get much further in the discussion. We all disagree with others in some respects, while being in agreement with others. Therefore I propose to close this correspondence. I will unsubscribe myself from this thread. I want to thank all of you for participating in this discussion: some of your contributions have broadened my perspective, while others have adjusted it a bit. Most importantly, I feel I have discovered with this forum a resource from which I can tap valuable knowledge for the use, and even challenge the conclusions, of my personal investigations. Keep up the good work!

Sauwelios

 

[heusdens]

Originally posted by Eh
Actually, the standard model of cosmology predicts a beginning to the universe.

I don't think that the standard model describes that. The standard model is just the model of the observable universe (which extends beyond our obsevation) which was in the past more dense, smaller and more hot. In the standard model we can calculate back to perhaps the 10 to the minus 43 seconds, but then physical laws aren't able predicting anything. So the standard model can not make predictions about what was before.

Alternative models such as chaotic inflation build on that, but they still seem to require a beginning after all. For a while, it seemed that some self reproducing universes could be eternal, but now it seems even those must have a beginning. Perhaps theories based on extra dimensions may yield the possibility of an infinitely old universe, but the models based on 4D space-time do not seem to do the trick.

Eternal / open or chaotic inflation models are built in such a way that the Big Bang theory becomes part of the inflationary regime.
That what is stated in this theory is that once inflation starts, it can reproduce eternally, and therefore does not need a begin.
I have not seen the 'proof' that such a regime can't be eternal.
But if that is proven, it just means that also that theory can predict about reality in a limited way. It does not urge us however to state then that time must had a beginning, but that some other material form, which can not be described within inflation theory, preceded inflation.

Yes, that is why I would suspect finite.

But a beginning of time is a very weird concept. It would urge us to conclude that everything existing came out of nothing.
No physical law can ever describe that. Physical laws can not be built on 'nothing'.

Not necessarily. You can model a beginning to the universe that does not have a before without suffering from any logical inconsistancy. The same applies to finite space. Of course this position goes against intuition, but that isn't a problem with logic.

The logic inconsistency does occur however. When 'modelling' the state of the universe 'before' the begin of time, in fact we have to conclude that no model can describe it. Because a mere nothingness is either inexistent in time, or is just a concept of pure time, that is a concept of time without any foreign admixtures, without anything changing in time. The logic problem is that in such an eternal unchanging nothingness, a change did occur, 'causing' the material existence, time and space.

There is no logic that can work on that concept, if you ask me.

Philosophical notions aside, modern cosmology does indeed give an infinite universe problems. Perhaps a cyclic model would work, but there is no guarantee such a universe did not have a first cycle.

This is just an indication of how good our models are. If the model comes up with such inconceivable concepts as the 'begin of time' it would merely indicate that a new theory must emerge.


Philosophical note on Infinity of matter

The philosophical notion of the infinity of matter, does not reflect on a determined age or a detemined space. It denotes the eternal transformation of matter, the fact that matter can not be created or destroyed, but only can be transformed from one form, into another.
Infinity of matter means, that all finite development forms of matter in a finite spatial extent with a finite age transforms into another development form of matter, which also has a finite spatial extent and age.

 

[wimms]

Originally posted by Eh
It's really just a matter of geometry. The volume of something has nothing to do with the space it is embedded in. And that's just it. The notion of area and volume are well defined geometric concepts that do not need reference to outside space for definition. So the claim that a finite universe must be embedded in some infinite space is founded on intuition and not any logic.

Sorry, that was too fast for me . Do I understand right, that because volume and area of brick can be well defined without any need for reference to outside space for definition, assumption that there must be something around the brick is plain stupid?

Isn't definition of finite manifold simply postulate that needs no further consideration? As such, isn't it just assumption that is forbidden to be questioned? For working model, no problem. But when suppressing other intellect 'from higher ground'? Patience please, some understanding doesn't come easy.

Logic doesn't reveal truth, it only checks consistency. Any theory is based on assumptions, intuitive or not.
Claim that a finite universe must be embedded in some infinite space may be unfortunate, but claim that universe cannot be finite comes from logical approach. I can't help but draw analogy with claim that set of _all_ integers can be finite.

 

[Eh]

Originally posted by heusdens
I don't think that the standard model describes that. The standard model is just the model of the observable universe (which extends beyond our obsevation) which was in the past more dense, smaller and more hot. In the standard model we can calculate back to perhaps the 10 to the minus 43 seconds, but then physical laws aren't able predicting anything. So the standard model can not make predictions about what was before.

The standard model, as well as comsology as a whole, is based on a classic description of space-time. That is, while general relativity cannot accuratley describe quantum scale events, it is the only theory we have to describe the big bang. And as it is, GR predicts a singularity and a beginning to space and time. While the notion of anything prior to the Planck era may not make much sense, GR does predict this. The singularity is expected to be replaced by something on the Planck scale at t=0, but even then many physicists expect a first moment of time.

Eternal / open or chaotic inflation models are built in such a way that the Big Bang theory becomes part of the inflationary regime.
That what is stated in this theory is that once inflation starts, it can reproduce eternally, and therefore does not need a begin.
I have not seen the 'proof' that such a regime can't be eternal.
But if that is proven, it just means that also that theory can predict about reality in a limited way. It does not urge us however to state then that time must had a beginning, but that some other material form, which can not be described within inflation theory, preceded inflation.

The problem seems to be with the expanding universe. Unless you've got a cyclic universe, eventually you will hit a singularity with those models. I read something authored by Vilenkin that showed that even eternal inflation models would likely require an initial singularity. I did some reading, and it seems this issue has been a popular topic for the past couple of years. I have some papers from the arxiv.org site that discuss some of the associated problems, but the PDF's aren't loading. I'm getting a file error, so I'll have to find the links somewhere else. Again, the expansion seems to be the main problem.

But a beginning of time is a very weird concept. It would urge us to conclude that everything existing came out of nothing.
No physical law can ever describe that. Physical laws can not be built on 'nothing'.

It's not created out of nothing. That there is a beginning does not mean there is a prior state from which the universe is created. The important thing to stress is that there is no before.

The logic inconsistency does occur however. When 'modelling' the state of the universe 'before' the begin of time, in fact we have to conclude that no model can describe it. Because a mere nothingness is either inexistent in time, or is just a concept of pure time, that is a concept of time without any foreign admixtures, without anything changing in time. The logic problem is that in such an eternal unchanging nothingness, a change did occur, 'causing' the material existence, time and space.

And therein lies the problem. The proposal is that there is no before at all, and you start talking about the logical problems of a timeless state that existed before the big bang. There is a difference in concepts here.

There is no logic that can work on that concept, if you ask me.

Probably not, but you've got the wrong concept.

This is just an indication of how good our models are. If the model comes up with such inconceivable concepts as the 'begin of time' it would merely indicate that a new theory must emerge.

The point is that if such a beginning suffers from no logical inconsistancy, there is no justification for that indication.

Philosophical note on Infinity of matter

The philosophical notion of the infinity of matter, does not reflect on a determined age or a detemined space. It denotes the eternal transformation of matter, the fact that matter can not be created or destroyed, but only can be transformed from one form, into another.
Infinity of matter means, that all finite development forms of matter in a finite spatial extent with a finite age transforms into another development form of matter, which also has a finite spatial extent and age.

Oddly enough, this old philsophy seems to be in trouble. Matter can be created from the vacuum, and this is an important feature of inflation models where the energy in the universe increases by enormous factors. Of course, this require net energy zero reasoning, and I don't know what relation it has to reality.

 

[Eh]

Originally posted by wimms
Sorry, that was too fast for me . Do I understand right, that because volume and area of brick can be well defined without any need for reference to outside space for definition, assumption that there must be something around the brick is plain stupid?

A brick wall is a bad example, since a building is necessarily embedded in something else. But the gist of it is correct. Since we have can define an area or volume by itself, we don't need infinite space. That doesn't mean the idea of infinite space is wrong, it's just not necessarily required.

Isn't definition of finite manifold simply postulate that needs no further consideration? As such, isn't it just assumption that is forbidden to be questioned? For working model, no problem. But when suppressing other intellect 'from higher ground'? Patience please, some understanding doesn't come easy.

It's not an assumption, it's just the definition. If there is something logically inconsistant about it, no one has of yet been able to show how. Still, the debate of finite vs. infinite space has a long pedegree and goes back as far as the ancient Greeks.
Many philosophers have tried to show why infinite space makes more sense with seeming paradoxes associated with finite space (ie. shooting an arrow at the edge of the universe). But such parodoxes are no longer taken seriously with the advent modern cosmology and such.

Logic doesn't reveal truth, it only checks consistency. Any theory is based on assumptions, intuitive or not.

Correct, and remember that the point I'm stressing is that finite space suffers from no logical inconsistency. Thus either infinite or finite could actually be an accurate description of reality.

Claim that a finite universe must be embedded in some infinite space may be unfortunate, but claim that universe cannot be finite comes from logical approach. I can't help but draw analogy with claim that set of _all_ integers can be finite.

I would seriously like to see a logically supported argument that the universe cannot be finite. Math can describe possible worlds, but only one of those descriptions will actually describe the world we live in. While infinity may be a more intuitive description of space, finite is equally possible.

 

[heusdens]

Originally posted by Eh
The standard model, as well as comsology as a whole, is based on a classic description of space-time. That is, while general relativity cannot accuratley describe quantum scale events, it is the only theory we have to describe the big bang. And as it is, GR predicts a singularity and a beginning to space and time. While the notion of anything prior to the Planck era may not make much sense, GR does predict this. The singularity is expected to be replaced by something on the Planck scale at t=0, but even then many physicists expect a first moment of time.

This is gross and widespread misunderstanding. Ask a physicist how they can make physics laws from nothing. Their answer will be, we can't.

It might be due to the fact that the ideas of Stephen Hawking (A brief history of time) has put forward such concepts. This included concepts like that real time had a definite begin, but imaginary time had not.

I don't think that such ideas will last long. What we have is a barrier to predict anything about what could have been before the Big Bang, cause the laws we an use to describe the event, break down at that instance.

I do not think physics can ever work with a begin of time, in whatever way. It just indicates that our models in that instance are ripped apart and can no longer describe reality.

So we need to look for different approaches to get past the problem.

The problem seems to be with the expanding universe. Unless you've got a cyclic universe, eventually you will hit a singularity with those models. I read something authored by Vilenkin that showed that even eternal inflation models would likely require an initial singularity. I did some reading, and it seems this issue has been a popular topic for the past couple of years. I have some papers from the arxiv.org site that discuss some of the associated problems, but the PDF's aren't loading. I'm getting a file error, so I'll have to find the links somewhere else. Again, the expansion seems to be the main problem.

It is to be expected that there is no material state of the universe or whatever material existing 'thing', that lasts forever.
But that just means that one state of the material universe, is transformed into another material state.
And that can go on without end, and doesn't require a begin either.

It's not created out of nothing. That there is a beginning does not mean there is a prior state from which the universe is created. The important thing to stress is that there is no before.

And therein lies the problem. The proposal is that there is no before at all, and you start talking about the logical problems of a timeless state that existed before the big bang. There is a difference in concepts here.

But this is altogether not much different from, for example a star formation. When the nuclear fusion starts, when the gasses that form the star are dense enough, the star can be said to be 'born'. It will exist for a certain amount of time.

Before the nuclear fusion started, it can be said that the star did not exist. But the gassed that formed the star, did exist.

What is expected from all other examples of the material world, is that such a thing is also true for the universe, that at one time, it started it existence, and can be existent for some definite amount of time.

But although it is difficult to even theoretically define a state prior to the existing universe, we should be confident that also the universe was preceeded by some or other material form. And also that form did not exist eternally, but also was caused by something else.

Probably not, but you've got the wrong concept.


The point is that if such a beginning suffers from no logical inconsistancy, there is no justification for that indication.


Oddly enough, this old philsophy seems to be in trouble. Matter can be created from the vacuum, and this is an important feature of inflation models where the energy in the universe increases by enormous factors. Of course, this require net energy zero reasoning, and I don't know what relation it has to reality.

The important thing to note is, that that vacuum is not empty, but contains fields. Now a field is as material as anyother material form.
It contains the basic properties of motion/change in a spatial and timely way.

So we are not talking about a concept of matter coming into existence from nothing, but from a previous and different material state.

 

[heusdens]

Originally posted by Eh
I would seriously like to see a logically supported argument that the universe cannot be finite. Math can describe possible worlds, but only one of those descriptions will actually describe the world we live in. While infinity may be a more intuitive description of space, finite is equally possible.

In what way would you think the universe is finite or infinite?

The way the material world exists, we see only finite material forms, in a finite space, and with a finite time. This can be stated for all of the material world.

Materialism however, while supporting this fact, says that while every existing material form is finite, it is always precedeed and will be followed by another material form.

Matter as such can not be destroyed or created, it can only be transformed from one form into another form.

In that sense, matter is said to be infinite, or eternal.

 

[Eh]

Originally posted by heusdens
This is gross and widespread misunderstanding. Ask a physicist how they can make physics laws from nothing. Their answer will be, we can't.

I don't of any models that propose such, either.

It might be due to the fact that the ideas of Stephen Hawking (A brief history of time) has put forward such concepts. This included concepts like that real time had a definite begin, but imaginary time had not.

That is also a source of confusion, because in those models, what we experience as "real time" isn't real at all. Imaginary time is, where a timeless 4D space-time exists. Of course that model has problems as well, and was discussed in another thread.

I don't think that such ideas will last long. What we have is a barrier to predict anything about what could have been before the Big Bang, cause the laws we an use to describe the event, break down at that instance.

I do not think physics can ever work with a begin of time, in whatever way. It just indicates that our models in that instance are ripped apart and can no longer describe reality.

But a beginning to time does not actually present a problem, because comsology is based on mathematical models. So long as the model does contain any internal inconsistency, there is no trouble. And that is the point I'm trying to stress. A beginning of time posses no mathematical inconsistency. What DOES give physicists problems is the notion of an infinitely dense point of zero volume.

It is to be expected that there is no material state of the universe or whatever material existing 'thing', that lasts forever.
But that just means that one state of the material universe, is transformed into another material state.
And that can go on without end, and doesn't require a begin either.

I'm not sure many physicists think a quantum theory of gravity will automatically allow the universe to have existed forever. It should give a minimum size for the universe, eliminating the singularity, however.

But this is altogether not much different from, for example a star formation. When the nuclear fusion starts, when the gasses that form the star are dense enough, the star can be said to be 'born'. It will exist for a certain amount of time.

Before the nuclear fusion started, it can be said that the star did not exist. But the gassed that formed the star, did exist.

There is a huge difference. For the star, there was a time when it did not exist. The proposal for the universe is merely that there is no before the big bang. That means exactly what it states. It does not mean there was a prior time (or timeless state) when there was no universe. There is no logical inconsistency with that, even though is goes against our intuition. But this is the same intuition that demands space to be infinite.

And that's really all it comes down to. Effectively, such a universe IS eternal, since it has existed for all time.

 

[Eh]

Originally posted by heusdens
In what way would you think the universe is finite or infinite?

There are the three. Space, time, and the divisibility of both. The infinity of time and the divisibility of both seem to be headed in a finite direction from cosmology and particle physics, so it seems more fitting that space also be finite.

The way the material world exists, we see only finite material forms, in a finite space, and with a finite time. This can be stated for all of the material world.

Materialism however, while supporting this fact, says that while every existing material form is finite, it is always precedeed and will be followed by another material form.

Matter as such can not be destroyed or created, it can only be transformed from one form into another form.

In that sense, matter is said to be infinite, or eternal.

The only problem is with the word matter. In science, matter has a very specific meaning, and it is neither fundamental nor eternal. So for physicalism, I think the word energy would be a better replacement, as energy cannot be created or destroyed and it avoids confusion over the word.

But wait, what if energy is not conserved either? Perhaps then the saying has to be changed again. Maybe some unified field is fundemental, where the geometry is constantly changing, but the field itself is eternal. Time will tell.

 

[heusdens]

Originally posted by Eh
Oddly enough, this old philsophy seems to be in trouble. Matter can be created from the vacuum, and this is an important feature of inflation models where the energy in the universe increases by enormous factors. Of course, this require net energy zero reasoning, and I don't know what relation it has to reality.

Oddly enough, it is not materialism itself that is suffering here, only your concept of matter. Note that the philosophical term matter denotes something different then the physical term matter. For philosophical materialism, matter is just the 'substance' that is in motion (and thus requires time and space to exist; time and/or space without matter would be inconceivable). What this 'substance' is, what form it has, is for science to explore and to define. So far we have the concept of matter in form of mass-having particles (the baryonic stuff and leptons), in form of energy (photons) and in form of fields.

The inflation model is not build on a concept of empty vacuum devoid of anything material., i.e. it is not a concept of 'nothing'.
It does contain 'something' for instance a scalar field that has the property of motion/change, and therefore it is material.
It is devoid however of any kind of 'normal' material stuff, like the atoms and particles and photons we know of, and where everything is made of.

 

[heusdens]

Originally posted by Eh
There is a huge difference. For the star, there was a time when it did not exist. The proposal for the universe is merely that there is no before the big bang. That means exactly what it states. It does not mean there was a prior time (or timeless state) when there was no universe. There is no logical inconsistency with that, even though is goes against our intuition. But this is the same intuition that demands space to be infinite.

And that's really all it comes down to. Effectively, such a universe IS eternal, since it has existed for all time.

What it comes down to that we cannot talk sensibly about the existence of space and time without the concept of matter. If it were not for matter, neither time or space would exist.

What the problem is however, is the problem where did the matter originate from. From 'the nothing'?

There was no existing state prior to the t=0 singularity.
All matter started out from that state, and 'created' time and space for it's existence.

This idea has been put in scientific theory by Hawkings, but also this idea is criticized, precisely because of the inconceivability of such an event.

What is good about this theory (even though it, as any scientific theory, it can be proven wrong) is that at least this is theory is not a form of theological doctrine, but is a scientific theory.
The debate in science is if such a model can explain the universe how it exists today. It must explain the large scale structure of the universe, the homogeneity and size of the universe and flatness.

It has been proven that the initital model (in form of the Hawking-Turok these, the Instanton pea) poses several problems that can not be dealt with in the original theory. Like for instance it would have modeled an universe which would already have crunched, and therefore can't explain the present universe.

There are competiting theories, like the theory of eternal inflation, that do better in the area of explaining observations, and solve some problems in the Big Bang theory.

Further more GR does not require perse that there was a singularity.

See for examle http://xxx.lanl.gov/abs/gr-qc/9810054".

 

[Eh]

Originally posted by heusdens
Oddly enough, it is not materialism itself that is suffering here, only your concept of matter. Note that the philosophical term matter denotes something different then the physical term matter.For philosophical materialism, matter is just the 'substance' that is in motion (and thus requires time and space to exist; time and/or space without matter would be inconceivable). What this 'substance' is, what form it has, is for science to explore and to define. So far we have the concept of matter in form of mass-having particles (the baryonic stuff and leptons), in form of energy (photons) and in form of fields.[/

Yes, I agree it's only a question of definitions. The word matter just seems a bit outdated, and it causes confusion when you use the word with the philosophical meaning for discussions about physics. I would consider myself a physicalist, but avoid using the word 'matter' only because it has a different meaning in science. Clarity is the key.

The inflation model is not build on a concept of empty vacuum devoid of anything material., i.e. it is not a concept of 'nothing'.
It does contain 'something' for instance a scalar field that has the property of motion/change, and therefore it is material.
It is devoid however of any kind of 'normal' material stuff, like the atoms and particles and photons we know of, and where everything is made of.

The vacuum IS a field, or failing a unified field theory, fields. The reason they call inflation a free lunch, is because the energy in the inflated region increases enormously, as if the energy conservation law is being violated. The claim however, is that because the net energy of the universe is zero, no such violation has occured.

 

[Eh]

Originally posted by heusdens
What it comes down to that we cannot talk sensibly about the existence of space and time without the concept of matter. If it were not for matter, neither time or space would exist.

This is what I mean about the use of the word matter. In physics, a field is not considered matter. Neither is energy. So when discussing physics, I don't mean fields or energy when I talk about matter. But just to clear things up, we are in agreement here. Space-time has no existence without fields.

There was no existing state prior to the t=0 singularity.
All matter started out from that state, and 'created' time and space for it's existence.

Since singularities aren't likely to be real, the initial state would have been a finite space-time, so to say time and space were 'created' would not have any meaningful definition. And that is the focus of the topic. A beginning is consistent mathematically and with observations. This doesn't mean it's correct, it just means it can't be discounted on the basis of intuition.

Now you mentioned that inflation and other models are better explanations for the observed universe. They are, but they aren't competing theories! Inflation occurs from a pre-existing space-time, and so is compatible with the big bang. In fact, inflation would be viable whether or not the big bang actually happened. Alas, no such models can deal with the expanding universe as you trace back the clock.

...Further more GR does not require perse that there was a singularity.

See for examle http://xxx.lanl.gov/abs/gr-qc/9810054".

The singularity theorems of Hawking take into account certain assumptions about the mass content in the universe. So if those assumptions are wrong, it has been said the singularity could be avoided. But we've still got a problem.

Let's assume the singularity is avoided, through quantum gravity or some other means. The universe is still expanding and as you go back into the past it gets smaller and denser. Once you hit the minimum size the universe can get (the Planck scale?) what then? Unless you want to argue the universe had existed for an eternity in that small and dense state before expanding, you're facing a beginning. But it's not really an option, because cosmology does not allow such a static state for the universe. So unless there is a mechanism present to allow for a cyclic universe, a minium size is likely to mean a minium time (beginning) for space-time.

 

[heusdens]

Originally posted by Eh
Now you mentioned that inflation and other models are better explanations for the observed universe. They are, but they aren't competing theories! Inflation occurs from a pre-existing space-time, and so is compatible with the big bang. In fact, inflation would be viable whether or not the big bang actually happened. Alas, no such models can deal with the expanding universe as you trace back the clock.



The singularity theorems of Hawking take into account certain assumptions about the mass content in the universe. So if those assumptions are wrong, it has been said the singularity could be avoided. But we've still got a problem.

Let's assume the singularity is avoided, through quantum gravity or some other means. The universe is still expanding and as you go back into the past it gets smaller and denser. Once you hit the minimum size the universe can get (the Planck scale?) what then? Unless you want to argue the universe had existed for an eternity in that small and dense state before expanding, you're facing a beginning. But it's not really an option, because cosmology does not allow such a static state for the universe. So unless there is a mechanism present to allow for a cyclic universe, a minium size is likely to mean a minium time (beginning) for space-time.

The eternal inflation theory, we are talking about, as far as I know it states otherwise. We are then not dealing with a Big bang, in which at the beginning there was inflation, but with an inflationary regime, which as a matter of fact "stands on it's own".
Big bang theory becomes then part of inflation theory, and not the other way around.

But I could be wrong, but this is the interpretation I have read from eternal / chaotic / open inflation, in the theory of Andrei Linde.

 

[Eh]

Apparently the expansion still must start in a singularity with eternal inflation models. Like I said, there have been a lot of papers on the subject of an infinitely old inflationary universe over the past few years, and there seem to be several problems with the idea. But nothing is certain.

 

[heusdens]

Originally posted by Eh
Apparently the expansion still must start in a singularity with eternal inflation models. Like I said, there have been a lot of papers on the subject of an infinitely old inflationary universe over the past few years, and there seem to be several problems with the idea. But nothing is certain.

There ain't anything wrong with that. Inflation theory is not and can not describe the endpoint to physics theories about the early universe.

Matter is eternal, in that it can not be created or destroyed.
But all material forms are always of a finite extend, never will we be able to perceive of infinity.

 

[wimms]

Originally posted by Eh
A brick wall is a bad example, since a building is necessarily embedded in something else. But the gist of it is correct. Since we have can define an area or volume by itself, we don't need infinite space. That doesn't mean the idea of infinite space is wrong, it's just not necessarily required.

No, I don't think brick is bad example. Creatures inside the brick don't know that building is necessarily embedded in something else. They check their math and calmly declare that there is nothing else, because its just enough to describe their existence without considering anything else. Their models work, ergo, they are right. And we outside the brick are puzzled, we knock-knock on the brick 'wait a minute, what about us??' And creatures inside brick doublecheck their math, watch out and say 'nope, sorry, you do not exist..next please..'

It's not an assumption, it's just the definition. If there is something logically inconsistant about it, no one has of yet been able to show how.

Well, how can there be something inconsistent, if that is defined to be true. I'm puzzled about this: we have those beautiful models, consistent with local observation, that don't need infinite space. Thats perfectly okay. But at which point in thinking process does scientist find justification to say that universe IS indeed finite? One thing is model, one thing is limits to our observable universe, but to stand up and say whew, now we know universe is finite??

Correct, and remember that the point I'm stressing is that finite space suffers from no logical inconsistency. Thus either infinite or finite could actually be an accurate description of reality.

Ahha, so we are still talking about assumptions of specific models?

But a beginning to time does not actually present a problem, because comsology is based on mathematical models. So long as the model does contain any internal inconsistency, there is no trouble. And that is the point I'm trying to stress. A beginning of time posses no mathematical inconsistency. What DOES give physicists problems is the notion of an infinitely dense point of zero volume.

Well, sure it does not present problem to a model. Model itself is finite, so its no surprise. I find suprising that we do not view time as something physical, while pondering about notions of infinitely dense point. We step onto infinite one way or other. We have point where time was created which is not a problem, we accept that energy was there, although there exists no meaning of energy that didn't include hidden concept of time.

The proposal for the universe is merely that there is no before the big bang. And that's really all it comes down to. Effectively, such a universe IS eternal, since it has existed for all time.

This can be understood. There are logical arguments to support finite minimum meaningful units of existence. For eg. distance between 2 points can be arbitrarily small, but it cannot be zero, for then there is no 2 points. For us Planck scales are minimum meaningful units, but this doesn't mean there isn't anything below, its just limits of our observable universe. Extrapolating existence to time zero is meaningless, for there is no existence without time.
Thus maybe existence was below Planck scales, but to say that time had a start is effectively creation from nothing. Not that is a problem that our models trace back to start of our observable universe together with our Planck scales, but claim of exact zero point of time. Do models actually predict zero time? They brake down well before that, its we who interpret the models come out and extrapolate.
Btw, we don't have problems with time dilation in SR, but what about that near BB? Observer near BB might not even know that he is part of spectacular BB event. For him its same calm boring expanding universe..

I would seriously like to see a logically supported argument that the universe cannot be finite. Math can describe possible worlds, but only one of those descriptions will actually describe the world we live in. While infinity may be a more intuitive description of space, finite is equally possible.

Well, its not math or physics question, would you agree? Its philosophycal question, besides perfectly working models.
At least by same logic as having no before BB makes universe eternal, having no beyond makes universe infinite. Is it intuitive? Universe, made from finite stuff, of which there is finite/infinite amount, is itself infinite. And growing.

Why not finite? Here's what confuses me, looking like unjust assumptions.
- what happened once, will happen again. assume: it can't happen again, it doesn't.
- energy cannot be created. assume: just once, and net energy is still zero.
- without time, there is no concept of energy, space, existence. No, time is just coordinate in our models. It can't be negative beyond BB though - because it makes no sense, obviously.
- fields are infinite although universe isn't. well, no problem..its big enuf
- there is no center of inflation. well, it was some bigass singularity..
- finite volume means finite radius, what about R+1? postulate: by definition there is no R+1!
- but, er, inflation? R is increasing!? postulate: its possible.
- if there is no beyond, where to does it inflates then? If R increases, there is no need for observable inflation.
- 13b years is like abit on low end. - sorry, that best we could do.

Question is about what is considered infinte? Extent, amount of energy/matter? Amount of differentiable concepts? Universe as Such is unique, single entity. It'd be unique eternally, no matter if it exists or actually doesn't. Similarily, its extent is infinite, has it one part or infinite parts. In same way as set of all reals is unique but has infinite parts. There is no beginning nor end of it, in any direction.

Inflation means that there is increase of differentiable spatial points. Where does this come from? It happens here and now. Is it creation or inflation of Planck scales? BB didn't just happen once, its eternal event?

I stress that I don't want to question validity of any theory, I'm just confused by the confidence with which we are told that BB was pointzero..

 

[Eh]

Originally posted by wimms
No, I don't think brick is bad example. Creatures inside the brick don't know that building is necessarily embedded in something else. They check their math and calmly declare that there is nothing else, because its just enough to describe their existence without considering anything else. Their models work, ergo, they are right. And we outside the brick are puzzled, we knock-knock on the brick 'wait a minute, what about us??' And creatures inside brick doublecheck their math, watch out and say 'nope, sorry, you do not exist..next please..'

It's a bad example because bricks are contingent upon a number of factors. But you're still missing the point. A finite space is logically consistent, but so is infinite space. No one is insisting space must be finite, only that it is a possibility. Nor is anyone suggesting the universe must be infinite, only that it is also a possibility.

Well, how can there be something inconsistent, if that is defined to be true.

I'm puzzled about this: we have those beautiful models, consistent with local observation, that don't need infinite space. Thats perfectly okay. But at which point in thinking process does scientist find justification to say that universe IS indeed finite?[/quote]

They cannot, unless the find that light from the same stars in several locations in the sky, which is only possible in a finite universe. As I said above, only the logical consistency is the subject here. Insisting space must be infinite is not based on reason.

One thing is model, one thing is limits to our observable universe, but to stand up and say whew, now we know universe is finite??

See above.

Ahha, so we are still talking about assumptions of specific models?

No, we're taking about the logical consistency of such models. It has nothing to do with whether or not they reflect reality. Math can describe possible worlds, but observation and experiment can tell us which world we actually live in.

Well, sure it does not present problem to a model. Model itself is finite, so its no surprise. I find suprising that we do not view time as something physical, while pondering about notions of infinitely dense point. We step onto infinite one way or other. We have point where time was created which is not a problem, we accept that energy was there, although there exists no meaning of energy that didn't include hidden concept of time.

No, that isn't what I'm talking about at all. The standard model does not predict a timeless state of energy before the big bang.

This can be understood. There are logical arguments to support finite minimum meaningful units of existence. For eg. distance between 2 points can be arbitrarily small, but it cannot be zero, for then there is no 2 points. For us Planck scales are minimum meaningful units, but this doesn't mean there isn't anything below, its just limits of our observable universe. Extrapolating existence to time zero is meaningless, for there is no existence without time.

Thus maybe existence was below Planck scales, but to say that time had a start is effectively creation from nothing. Not that is a problem that our models trace back to start of our observable universe together with our Planck scales, but claim of exact zero point of time. Do models actually predict zero time? They brake down well before that, its we who interpret the models come out and extrapolate.

No, this is incorrect. Saying time had a beginning is not saying the universe was created from a prior state of nothing. It's just the first moment where no such "before" can have any meaning. The stanard model predicts space and time vanish at t=0, but no one seriously suggests that is an accurate picture of the early universe. A quantum theory of gravity will be needed for that, but there is still likely to be a beginning, for reasons I covered in this thread.

Btw, we don't have problems with time dilation in SR, but what about that near BB? Observer near BB might not even know that he is part of spectacular BB event. For him its same calm boring expanding universe..

He might be a little hot though, with that damn temperature being trillions of degrees.

Well, its not math or physics question, would you agree? Its philosophycal question, besides perfectly working models.

Remember, the topic here is of the logical validity of these models. Math is just another form of logic, so it's certainly in the realm of philosophy.

At least by same logic as having no before BB makes universe eternal, having no beyond makes universe infinite. Is it intuitive? Universe, made from finite stuff, of which there is finite/infinite amount, is itself infinite. And growing.

I tried to point out that "effectively eternal" is not the same as having infinite time. So no, finite space is not infinite.

Why not finite? Here's what confuses me, looking like unjust assumptions.

- what happened once, will happen again. assume: it can't happen again, it doesn't.

I don't understand the meaning of this? How is this an argument against finite space?

energy cannot be created. assume: just once, and net energy is still zero.

Energy can be created from the vacuum. But the big bang does not suppose energy was necessarily created, though the classic singularity has some problems with that.

without time, there is no concept of energy, space, existence. No, time is just coordinate in our models. It can't be negative beyond BB though - because it makes no sense, obviously.

Since no one is proposing a timeless state prior to the big bang, this is a non-issue.

fields are infinite although universe isn't. well, no problem..its big enuf

Who says fields must be intinite? Actually, space-time itself is just the gravitational field. It can be finite or infinite.

there is no center of inflation. well, it was some bigass singularity..

What are you talking about?

finite volume means finite radius, what about R+1? postulate: by definition there is no R+1!

Again, what?

but, er, inflation? R is increasing!? postulate: its possible.
- if there is no beyond, where to does it inflates then? If R increases, there is no need for observable inflation.
- 13b years is like abit on low end. - sorry, that best we could do.

As I pointed out before, the universe expands but does not need to be expanding into something else. Much like how volume is defined without the need for outside space, the volume of the universe increases without the need for space-time to be embedded in some extra dimensional space.

Question is about what is considered infinte? Extent, amount of energy/matter? Amount of differentiable concepts? Universe as Such is unique, single entity. It'd be unique eternally, no matter if it exists or actually doesn't. Similarily, its extent is infinite, has it one part or infinite parts. In same way as set of all reals is unique but has infinite parts. There is no beginning nor end of it, in any direction.

This has already been covered in this thread. 3 potential infinites (spatial extent, time, divisibility space) with addtional infinities that necessarily come with infinite space or infinite time. For example, an infinite universe necessarily has an infinite amount of mass, galaxies, etc.

Inflation means that there is increase of differentiable spatial points. Where does this come from? It happens here and now. Is it creation or inflation of Planck scales? BB didn't just happen once, its eternal event?

I don't know exactly what you're asking here.

I stress that I don't want to question validity of any theory, I'm just confused by the confidence with which we are told that BB was pointzero...

The point I have been stressing is NOT that the BB must have been the beginning of time (though there are good reasons to believe so) but that it is logically consistent.