[geordief (OP)]

We believe (with evidential proof?) that in addition to what we can observe by reason of its emitted light  there is a  (expanding?) region containing objects beyond.

If we take that as a given,are there any limits on the size of this area?

Suppose we give a  value of one to the volume of  the region we can observe  what  number could we assign to the region beyond?
2 ?  10? 10^100? Just infinitely larger?

Suppose  we assign the observable universe  the volume of a proton ,is it possible that the volume of the unobservable  universe  might be the same volume (or greater) than that of ,say the Solar System?

Is there perhaps  nothing, no estimation that we can make or do some models attempt to answer this question?

[Halc]

We believe (with evidential proof?) that in addition to what we can observe by reason of its emitted light  there is a  (expanding?) region containing objects beyond.

In classical (non-quantum) physics, this statement is fairly true yes.

If we take that as a given,are there any limits on the size of this area?

There are certainly no limits imposed, which isn't to say that space at a given time is necessarily infinite in volume. It just means we have no evidence to the contrary of that, so it's the working assumption.

Suppose we give a  value of one to the volume of  the region we can observe what  number could we assign to the region beyond?

Per above, no bound to that. Certainly no finite number has been measured.

Suppose  we assign the observable universe  the volume of a proton ,is it possible that the volume of the unobservable  universe  might be the same volume (or greater) than that of ,say the Solar System?

That would be a bounded size if it was that small.  Unbounded doesn't just mean big. It means it isn't bounded.

Is there perhaps  nothing, no estimation that we can make or do some models attempt to answer this question
?

Sure. Create a model where there's a brick wall bounding the universe, only 7 billion LY (proper distance) away, with our solar system at its exact center. Anything that gets to the brick wall disappears, sort of like and edge to a simulation. That model is indistinguishable from the infinite one, unless you wait a lot longer.  No light we see now has ever been more than a proper distance of 7 BLY from here. It is a different way to express the radius of the 'visible universe', defined as the widest proper width of our past light cone.

You can also use a different coordinate system like the inertial frame of our galaxy, which bounds the size of the universe to a diameter of about 28 BLY. The universe still looks isotropic from anywhere, even if you're at a location near the edge. Choosing a different inertial frame changes the size, but can also put Earth near the edge. The model has problems and isn't really a valid one. The entire universe should be visible in such a model, but it isn't. Light emitted from only a finite distance away will never get here ever, and that violates the properties of an inertial frame. The existence of mass at all violates the properties of an inertial frame. But it works for crude purposes.

[geordief (OP)]

That would be a bounded size if it was that small.  Unbounded doesn't just mean big. It means it isn't bounded

Not sure if I was misunderstood.I was just assigning the volume of the observable universe to that of a proton simply as  a scaling mechanism.

It would be the same size as "now" but how many "proton sized"  observable  universes might fit into  the unobservable  universe?

I can't begin to imagine what number might correspond to the number of protons one might fit into the observable  universe  but if we had that number  in our head then could that many observable universes  fit into the  unobservable  universe  in any model?

I am just trying  to get into head the possible scale that is not ruled out as being totally ridiculous

When I say model I mean a model that  has some standing even if we cannot say now or possibly  ever if it is right or wrong.

If we suppose that both the observable  and unobservable  universe shared a common origin would the nature of that origin answer my question  in that it might provide a theoretical  limit to the expansion of both of them?

[alancalverd]

There is no obvious limit to the size of the Universe (note capital U) , only to that portion which can be observed.

This could be a cop-out, of course,but:

It answers questions like "why only protons and electrons when their antiparticles are equally stable?" by saying "they are somewhere else, and if they were here, they'd annihilate with our common particles, so the existence of our finite observable universe (lower case) is conditional on there being an infinity of places where the components of an antiuniverse are in equilibrium".

So equally, it could be the answer to a whole bunch of questions!

[evan_au]

How big could the unknown universe be?

It's unknown, so we don't know!

[geordief (OP)]

So if I  make a claim that the unobservable universe and the observable  universe have a common origin (or meeting point) and that the "present" volume of the former is a trillion  times greater than that of the latter nobody can say this is a priori impossible  but only that (a) I need to show evidence  for this and (b) nobody can  actually assess this except  to say that the ratio is  certainly greater than zero to one because we can  ,I imagine observe galaxies "blinking out of sight if we   look hard and long enough ??

Sorry for the unwieldy sentence 

[Halc]

The boundary between the observable part and the rest is different for every point of view, so yes, these parts are adjacent. I don't think it is right to say they have a common meeting point because if they did, the entire universe would be causally connected to every other point and the observable universe wouldn't be any smaller than the whole thing.

There isn't a meaningful finite ratio between the volume at a given time and the volume at time zero which is singular and not meaningful.

Galaxies don't blink out of sight over time. Actually new ones come into view over time and never leave it. They do however slowly redshift so far that only super-long wavelength telescopes like JWST can see them.

[evan_au]

...a common meeting point because if they did, the entire universe would be causally connected to every other point

Under the cosmic inflation hypothesis, for a short period the universe expanded faster than c.
So anything happening after this epoch is not causally linked to the whole universe.

https://en.wikipedia.org/wiki/Inflation_(cosmology)

[geordief (OP)]

The boundary between the observable part and the rest is different for every point of view, so yes, these parts are adjacent. I don't think it is right to say they have a common meeting point because if they did, the entire universe would be causally connected to every other point and the observable universe wouldn't be any smaller than the whole thing.

There isn't a meaningful finite ratio between the volume at a given time and the volume at time zero which is singular and not meaningful.

Galaxies don't blink out of sight over time. Actually new ones come into view over time and never leave it. They do however slowly redshift so  far that only super-long wavelength telescopes like JWST can see them.

I meant a common meeting point as in  "meeting  at  their common origins"(if this happened more than once "origin could be a misnomer,)

I think  it is mainstream science that over time with greater than c expansion the galaxies will disappear  from view  and that is why I said "blink out"
(at some point in the future our night sky will be dark and the JWT will see nothing if it is still.in position)

[alancalverd]

The notion of an origin is unnecessary and indeed inconvenient if you allow the Universe to be infinite.

[geordief (OP)]

The notion of an origin is unnecessary and indeed inconvenient if you allow the Universe to be infinite.

But I said (also) "meeting place" .
If the unobservable and the observable universe  "wind back" to a common point when we go back in time then they share a common origin ,even if that "origin" is  not a first point in time.

[alancalverd]

As I see it, the Universe is infinite and has no beginning, but the observable universe is just a local consequence of infinite possibilities, with a traceable history and evolution inside the Universe.

[geordief (OP)]

As I see it, the Universe is infinite and has no beginning, but the observable universe is just a local consequence of infinite possibilities, with a traceable history and evolution inside the Universe.

I think I see it that way too.

It is a bit difficult to  get my head around the "fact" that it is a priori out of the question  to get  an understanding  of the "whole" picture since the mind seems  unable to accept loose ends and always tries to put everything  into a context but the context here refuses to be corralled.

[Deecart]

As I see it, the Universe is infinite and has no beginning, but the observable universe is just a local consequence of infinite possibilities, with a traceable history and evolution inside the Universe.

In fact, the Universe could have some beginning and also be infinite.
In my opinion, the finitude question depend on what value we are speaking of.
Space ? or Time ?
or SpaceTime ?
Energy ? (If the energy remain constant during time and we assimilate the Universe with its energy, we can also consider "the Universe" infinitly existing during time).

For what we actually know :
The observable universe has some finite space (not sure, but i think it is around the billion year) and everything further is out of range definitly, for us, and for "nature". So we can say that every point of space is linked with other points in space in a maximum range of 1 billion year.
What is outside this sphere "do not exists anymore".
Physicaly speaking it is nonsense to talk about what is outside of the portion of space.

Now, we can perhaps say that we can have some bigger sphere using JANUS therory because this theory predict the possibility to go to some second space, travel 1000 times faster in this other space, and come again in our space, so you could have a 1000 billion years sphere as the observable universe.
To do some analogy, if you know minecraft, it is like making some portal to the netherworld, traveling in the netherworld and going back in the "normal" universe. The travel is faster using the portals than traveling normaly in the normal world..