A centre of mass of the Universe.

[Neil Obstat]

8 minutes ago, studiot said:

Yes, I apologise to J.C. MacSwell, I have just found it.

But to whoever said it I still ask the question why not?

It would seem to me that if something that is finite can become infinite, then there is no inherent barrier that exists keeping finite things as finite things, and any one of them or perhaps two of them or more of them (they are finite so their number may be great but never unlimited) could hence become infinite. If there is anything that is finite which CANNOT become infinite but something else finite that CAN become infinite, what is the principle which stands selectively in the way of the one but not in the way of the other?

 

Edited June 26, 2018 by Neil Obstat

[studiot]

3 minutes ago, Neil Obstat said:

It would seem to me that if something that is finite can become infinite, then there is no inherent barrier that exists keeping finite things as finite things, and any one of them or perhaps two of them or more of them (they are finite so their number may be great but never unlimited) could hence become infinite. If there is anything that is finite which CANNOT become infinite but something else finite that CAN become infinite, what is the principle which stands selectively in the way of the one but not in the way of the other?

 

Well mathematically sin(x) is always finite and is considered a 'well behaved' function.

But tan(x) is another matter.

Then again the Gabriel's horn example has a finite volume contained in a 3D shape of infinite surface area.

I don't know how that would scale up a dimension or two.

[Neil Obstat]

12 minutes ago, studiot said:

Well mathematically sin(x) is always finite and is considered a 'well behaved' function.

But tan(x) is another matter.

Then again the Gabriel's horn example has a finite volume contained in a 3D shape of infinite surface area.

I don't know how that would scale up a dimension or two.

It seems to me that you are presuming that mathematics can provide the answer to a question that is utterly beyond the scope of mathematics per se.

I see you have replied to that statement with, "I don't follow this." 

But it seems perhaps while you were posting that, I continued adding to my post here with the following three sentences:

Mathematics can deal with the reality of quantity all right, but when you proceed to other categories beyond the limits of quantity, mathematics fails to cope.

You are wondering here about scaling up a dimension or two, when you ought to be stepping up to a higher realm than that to which mathematics is confined.

It would seem that the question you have (why cannot a finite thing become infinite) is similar to asking why mathematics is confined to quantity.

 

Edited June 26, 2018 by Neil Obstat

[studiot]

6 minutes ago, Neil Obstat said:

It seems to me that you are presuming that mathematics can provide the answer to a question that is utterly beyond the scope of mathematics per se.

 

I don't follow this.

 

[StringJunky]

7 minutes ago, Neil Obstat said:

IYou are wondering here about scaling up a dimension or two, when you ought to be stepping up to a higher realm than that to which mathematics is confined.

 

What language would you be using to describe that?

[Neil Obstat]

5 minutes ago, studiot said:

I don't follow this.

 

Perhaps you didn't notice yet that I added more to the post you're replying to, while you were posting your reply?

[beecee]

28 minutes ago, Neil Obstat said:

Perhaps this conversation is a kind of "big bang" inasmuch as it could go on forever...

If the known universe had a beginning, and at that time it was unknown since there was no one around to know it yet, therefore, the unknown and the known were one and the same thing. If the unknown and the known began as one thing they would consequently continue as the same thing, since what they were was as it was when it was, as it were.

I'm pretty sure that we can logically concur that the universe, all of spacetime is expanding just as our observable portion is.

 

Quote

But then you have: "the remainder of the Universe may have been finite, or may not have been." This would seem to apply to the remainder of the Universe which would not have been included in the "entirety of the universe as we know it," which had been contained in a volume smaller than the nucleus of an atom "at least as far back as t+10^-43 seconds," in other words, the entirety of the universe as we know it did not include the remainder of the Universe. Correct?

Yes....I think! The observable universe is around 95 billion L/years in diameter and obviously finite.

The finite or infinite nature of the whole of the universe/spacetime  is unknown.

The data from WMAP, showed that the universe/spacetime is very nearly flat, to within small tolerances. 

A flat universe under normal circumstances denotes an infinite universe, but that would ignore possible topologies such as torus shaped and also the otherwise very small error bars from WMAP, which maybe enough to imply that the flatness measured by WMAP, was just the arc of a much much larger curvature.

Therefor in essence, we cannot know whether the whole universe is finite or infinite.

Those details above are going from memory and open to correction if needed.

[Neil Obstat]

8 minutes ago, StringJunky said:

What language would you be using to describe that?

Last time I checked this is English describing that. Or are you presuming that the topic of the center of mass of the universe must somehow be confined to the language of mathematics?

[studiot]

2 minutes ago, Neil Obstat said:

Last time I checked this is English describing that. Or are you presuming that the topic of the center of mass of the universe must somehow be confined to the language of mathematics?

What ever way you choose to describe it, what do you understand 'the centre of mass to be' ?

[J.C.MacSwell]

26 minutes ago, studiot said:

Again I say why not?

Have you considered Gabriel's horn?

If the model was assumed currently (or initially) finite but expanded for an infinite time the volume of space would tend toward infinite (that IMO would be more in "tune" with Gabriel's Horn if you pardon the pun) but I don't believe that is the context of the quote. Maybe Mordred can chime in and confirm the context. 

[Neil Obstat]

12 minutes ago, beecee said:

I'm pretty sure that we can logically concur that the universe, all of spacetime is expanding just as our observable portion is.

Please excuse me for being pinched here but I'm afraid to attempt any more than one reply to one statement otherwise the platform shuffles the cards and there goes intelligence.

Our observable portion of the universe is the only part that we can verify and test and observe (by definition of "observable").

By what means could we ever arrive at any degree of confidence that SOMETHING ELSE, OTHER THAN this observable "part" exists?

Furthermore, by what means could we ever hope to observe, test, know or verify that which is beyond our ability to observe, test, know or verify?

8 minutes ago, studiot said:

What ever way you choose to describe it, what do you understand 'the centre of mass to be' ?

I personally appreciate the various diagrams you have drawn previously. I think you did a good job.

I'm having some trouble, however, in reconciling concepts being presented here that impute relevance to "parts" of the Universe which are not "parts" of the observable universe.

We can all collectively thank the retarded platform for "merging" my two posts again, effectively DARING you to distinguish between them when or if you quote me.

Edited June 26, 2018 by Neil Obstat

[studiot]

5 minutes ago, J.C.MacSwell said:

If the model was assumed currently (or initially) finite but expanded for an infinite time the volume of space would tend toward infinite (that IMO would be more in "tune" with Gabriel's Horn if you pardon the pun) but I don't believe that is the context of the quote. Maybe Mordred can chime in and confirm the context. 

Yes that would be good. M sometimes says things in shortform that would be understood by another PhD.

5 minutes ago, Neil Obstat said:

Please excuse me for being pinched here but I'm afraid to attempt any more than one reply to one statement otherwise the platform shuffles the cards and there goes intelligence.

Our observable portion of the universe is the only part that we can verify and test and observe (by definition of "observable").

By what means could we ever arrive at any degree of confidence that SOMETHING ELSE, OTHER THAN this observable "part" exists?

Furthermore, by what means could we ever hope to observe, test, know or verify that which is beyond our ability to observe, test, know or verify?

I think the answer to this might lie in considering the overlapping of light-cones on separate world lines.

[J.C.MacSwell]

2 minutes ago, Neil Obstat said:

Please excuse me for being pinched here but I'm afraid to attempt any more than one reply to one statement otherwise the platform shuffles the cards and there goes intelligence.

Our observable portion of the universe is the only part that we can verify and test and observe (by definition of "observable").

By what means could we ever arrive at any degree of confidence that SOMETHING ELSE, OTHER THAN this observable "part" exists?

Furthermore, by what means could we ever hope to observe, test, know or verify that which is beyond our ability to observe, test, know or verify?

 I think it is mostly by default...where nothing at the limits of observation indicate there is not more of the same, and you would expect or require more of the same to explain what you observe near those limits. If say, Space was non existent beyond the observable Universe we would expect to see some effect of that...but we don't...what we see is what we would expect if space continued the same further.

(I keep saying "we". I'm not an expert or participant in any cosmology...just a spectator that assumes the models we have accepted are the best we have. My degree of confidence in much of this would be less than 100%)

[studiot]

2 minutes ago, J.C.MacSwell said:

 I think it is mostly by default...where nothing at the limits of observation indicate there is not more of the same, and you would expect or require more of the same to explain what you observe near those limits. If say, Space was non existent beyond the observable Universe we would expect to see some effect of that...but we don't...what we see is what we would expect if space continued the same further.

(I keep saying "we". I'm not an expert or participant in any cosmology...just a spectator that assumes the models we have accepted are the best we have. My degree of confidence in much of this would be less than 100%)

+1

[beecee]

1 hour ago, Neil Obstat said:

Please excuse me for being pinched here but I'm afraid to attempt any more than one reply to one statement otherwise the platform shuffles the cards and there goes intelligence.

Our observable portion of the universe is the only part that we can verify and test and observe (by definition of "observable").

By what means could we ever arrive at any degree of confidence that SOMETHING ELSE, OTHER THAN this observable "part" exists?

Furthermore, by what means could we ever hope to observe, test, know or verify that which is beyond our ability to observe, test, know or verify?

Our observable universe from our frame of reference, is governed by the speed of light and the expansion rate. I'm sure its a reasonable contingency to assume that the rest of the universe, beyond our observable horizon, should not be any different then what we observe.

And as to the question as to why we should assume anything is beyond, I would say if there wasn't, we would see some evidence of a wall of sorts?

[Neil Obstat]

1 hour ago, studiot said:

What ever way you choose to describe it, what do you understand 'the centre of mass to be' ?

I wrote a nice detailed answer to your question but someone apparently thinks it was somehow unmentionable so it was deleted.

Therefore your question cannot be answered. My apologies. I tried.

[Mordred]

59 minutes ago, J.C.MacSwell said:

 I think it is mostly by default...where nothing at the limits of observation indicate there is not more of the same, and you would expect or require more of the same to explain what you observe near those limits. If say, Space was non existent beyond the observable Universe we would expect to see some effect of that...but we don't...what we see is what we would expect if space continued the same further.

(I keep saying "we". I'm not an expert or participant in any cosmology...just a spectator that assumes the models we have accepted are the best we have. My degree of confidence in much of this would be less than 100%)

Yes we should see variations as one approaches the cosmological event horizon. Let toy model this, by descriptive as most likely few will understand the math but if requested I will happily provide.

Lets assume for a moment the a universe portion just on the outside our observable. Now if this portion has a different mass density this will cause a response by the nearby regions within our observable universe. A higher or lower mass density will result in a net flow of mass, this in turn affects the temperature as well as redshift. The direction of flow will be that which supports an equalization of mass density between the two regions.

 We don't see this as far as we can measure. The temperature distribution of the CMB for example is incredibly uniform. This uniformity also limits a rotating universe. The upper bounds on the rotational speed is such that it needs to be low enough to explain why we haven't bee able to detect a rotating universe. However that's just a side note. We can safely assume the regions of shared causality just outside our observable portion but within another observable portion say just at the edge of our observable portion is of the same uniform distribution.

 As we can see regions that can be affected by regions we cannot see via its shared causality that within this limit we can infer that it is much the same as our observable. Beyond any possible shared causality with our observable portion we have absolutely no clue.

 

 

[geordief]

Can there be any possible relationship between the size of the unobservable universe to that of the entire universe with  the possible curvature of the observable universe that may apparently  (within the margin of error) have been measured?

 

Is it believed there was ever a time that the entire universe may have been observable ?(when expansion was occurring at sub liminal speeds )

[Mordred]

With what little data we have if the mass distribution is much the same as ours then so too will be the curvature term. No the observable portion we have now is the furthest we have ever seen. In the past you would see less and less the further back in time the observer is placed. The observable portion is our region of past and present causality.

The cosmocalc is far more flexible than this but I focussed the calcs on the particle horizon which is the cosmological event horizon. Here is the range of the observer horizon back in time. I went from from today bottom row to the CMB last surface at redshift 1090. The calc can go earlier but it does reach a limit ie doesn't handle inflation.

[latex]{\small\begin{array}{|c|c|c|c|c|c|}\hline T_{Ho} (Gy) & T_{H\infty} (Gy) & S_{eq} & H_{0} & \Omega_\Lambda & \Omega_m\\ \hline 14.4&17.3&3400&67.9&0.693&0.307\\ \hline \end{array}}[/latex] [latex]{\small\begin{array}{|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|} \hline S&T (Gy)&D_{par}(Gly) \\ \hline 1090.000&0.000373&0.000856\\ \hline 768.343&0.000668&0.001561\\ \hline 541.606&0.001183&0.002822\\ \hline 381.779&0.002074&0.005052\\ \hline 269.117&0.003606&0.008973\\ \hline 189.701&0.006228&0.015819\\ \hline 133.721&0.010698&0.027712\\ \hline 94.260&0.018302&0.048276\\ \hline 66.444&0.031211&0.083704\\ \hline 46.837&0.053094&0.144544\\ \hline 33.015&0.090158&0.248752\\ \hline 23.272&0.152887&0.426844\\ \hline 16.405&0.258995&0.730635\\ \hline 11.564&0.438378&1.247998\\ \hline 8.151&0.741396&2.127725\\ \hline 5.746&1.252327&3.620922\\ \hline 4.050&2.109877&6.148142\\ \hline 2.855&3.531250&10.399216\\ \hline 2.013&5.813076&17.448904\\ \hline 1.419&9.228712&28.800505\\ \hline 1.000&13.787206&46.278944\\ \hline \end{array}}[/latex]

 

Stretch is thee inverse of the scale factor, which will also correspond to the CMB blackbody temperature which is also the inverse of the scale factor.

Edited June 27, 2018 by Mordred

[geordief]

8 hours ago, Mordred said:

With what little data we have if the mass distribution is much the same as ours then so too will be the curvature term. No the observable portion we have now is the furthest we have ever seen. In the past you would see less and less the further back in time the observer is placed. The observable portion is our region of past and present causality.

The cosmocalc is far more flexible than this but I focussed the calcs on the particle horizon which is the cosmological event horizon. Here is the range of the observer horizon back in time. I went from from today bottom row to the CMB last surface at redshift 1090. The calc can go earlier but it does reach a limit ie doesn't handle inflation.

THo(Gy)14.4TH∞(Gy)17.3Seq3400H067.9ΩΛ0.693Ωm0.307 S1090.000768.343541.606381.779269.117189.701133.72194.26066.44446.83733.01523.27216.40511.5648.1515.7464.0502.8552.0131.4191.000T(Gy)0.0003730.0006680.0011830.0020740.0036060.0062280.0106980.0183020.0312110.0530940.0901580.1528870.2589950.4383780.7413961.2523272.1098773.5312505.8130769.22871213.787206Dpar(Gly)0.0008560.0015610.0028220.0050520.0089730.0158190.0277120.0482760.0837040.1445440.2487520.4268440.7306351.2479982.1277253.6209226.14814210.39921617.44890428.80050546.278944

 

Stretch is thee inverse of the scale factor, which will also correspond to the CMB blackbody temperature which is also the inverse of the scale factor.

Probably to much for me to understand or research  but I was basing  my suggestion on the assertion that I have heard (on the BBC) that ,as expansion  continues ,eventually (on a cosmic timescale) our presently observable universe will vanish and our stars/galaxies will switch off one by one as their speed of recession exceeds that of light.

 

It is just fortuitous that we can now see the rest of the (gravity unbound) universe as later it will all be dark.

 

Is not the corollary of this that ,in the past more was visible to us  than is now  and that  it might be the case (if the universe was finite) that all ofit may have been visible to an earlier inhabitant of the Universe?

[Mordred]

In the past we would see less as well and in the future our Observable portion will gradually lessen. This is part of the reasons many cosmologists mention we live at the best times for studying our universe.