The question of "Universe" and "observable universes" has been discussed in a very large number of posts in many, many, threads. to get an idea, just use the search function (the 'magnifying glass' at top right of blue bar above. It is to the right of the ennvelope and the bell symbols). In search, enter universe, and in member enter Catastrophe, or leave it blank.
If you are going to reopen this subject, please first get clear about "Universe" and "observable universes".
First "all there is" is not a sufficient definition. Most of what there is is rapidly moving away from our field of view. When we say "all there is", this can only mean all we are capable of 'observing', which is limited by what our senses can receive, and how our brains process this input. This has been clarified any number of times, and one acceptable definition is here:
I believe there is considerable difference still possible in what we understand by Universe, and this goes beyond what we understand by observable universes. We need to look at the "we". I do believe that "all there is" itself requires clarification. What do we mean by this? Exclude "all we...
forums.space.com
It follows that there as many "observable universes" as there are observers, although millions of beings on one planet, e.g., Earth, would share almost identical observable universes. This sum total could be viewed as (as a close approximation) the observable universe of humanity at present. This observable universe changes over time. Distant galaxies may move away soo quickly that they will be lost to view. Light will not have time to reach us.
Conversely, galaxies already far beyond this limit will never know of us, and vice versa, unless the expansion of the universe reverses, and all start approaching each other.
There is a very useful analogy, which I find very useful into understanding the "
expanding into what" paradox. There are many examples found by searching (as above) "flatlander" / Catastrophe.
Here is a brief sample:
The points I wish to draw from this analogy, are:
That the flatlander's 'universe' is limited to that spherical surface existing in his 'time. For us, as a D+ being, meaning a being able to perceive and process at least one more dimension than the flatlander, it is simply akin to an expanding soap bubble. Note that this is a common analogy for us, but not so in the later example. We should at least be prepared for some differences. Thus a D+ being (e.g., us) could observe a million or more of what a flatlander considers to be 'his' 'universe'. Hence my use of 'around' the word universe. That means that 'universe' is no longer "all there is", but "all that can be perceived or generally recognised by the entity owning that 'universe'.
"Universe" is a relative term, which may be replaced by "observed universe".
Note that the flatlander notices "his universe" expanding, because every point on the spherical surface, which is his world, moves away from every other point. If the Earth expanded, the distance between London and Paris would increase. Every point on Earth would move away from every point. There would be no centre of this expansion.
Being aware of the flatlander's little world, we would see his universe, his spherical surface, expanding. We would also see, which he would not, that his spherical universe was expanding in its radius - a concept completely beyond the flatlander, who could only appreciate the surface. He would be completely mystified because his universe was obviously expanding, but he could not figure "expanding into what?" We would easily see that his universe was expanding into another dimension not accessible to the flatlander. Perhaps that helps us understand into what our universe is expanding. It is expanding into another dimension not accessible to us. String Theory requires 10 dimensions.
Cat
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