If there is more than one 'universe'

I was thinking of this, a bit. If there is more than one universe, and if (which does not have to follow on all cases) there are "larger" and "smaller" universes, and the smaller are parts of the always invisible level of the microcosm of the larger one (by which i mean that you cannot break up matter enough if you are in the larger universe, so as to reach the outer part of the smaller universe), then wouldn't there have to be, at least in some cases, a specific (maybe even constant, or analogous) ratio of the size of the "parent" universe to the immediately smaller universes contained within it but not reachable from it?

I mean some ratio such as 1 to a trillion trillion trillion etc (just to give an example).

In some cases this won't have to be so (and i suspect in almost all of them). In some cases though, it could.

What do you think of this? Do note that the universes in this model do not have to expand infinitely. They can even have a circular/spheric relation to the smaller and smallest ones, and so just co-exist without expanding. Same goes for the overall 'mass' (it will be another way to view mass, obviously) of each universe in relation to its "density" or some similar quality, they can all be 'equal' in that too.

If the smaller universe can never be observed by yourself in the larger universe, can it really be said to exist at all?

To say something is small assumes you can measure it some way. So if you can't even measure this other universe how can you say it is small?

Why can't the small universe expand infinitely? That is, why can't it just keep on expanding forever without ever encountering the larger universe?

Indeed the smaller universe will remain a concept in this model. However it still might not be able to expand, if the whole system in the model requires a finite "hyper-universe" so to speak.

Protagoras argued that "man is the meter of all things, of those that exist that they exist, of those that do not exist that they do not exist". In a way the smaller universe (or the larger than the one we are in) won't exist, but this too can be factored in the model.

I think (not sure) one could say that the larger universe would be just on the other side of the border of being "infinitely" larger than our own. (iirc we have no model of noting differences larger than an infinity?)

it depends what you mean by universe
if it is like earth then it is nothing new.
if it is different then it is not possible to establish because no one knows what it looks like and therefore calling it universe is deluded.
the word universe as we know is earth size. anything larger or smaller is not.

I was looking for what we have discussed in the philosophy section. This question about other universes is interesting.

Since the big bang likely happened, our universe had a beginning. I think from that we can suspect that there are other universes that we can't currently access that had a beginning as well.

Now we can ask the next question: Are all those other universes capable of having life like ours? There are two answers based on one's beliefs, theistic or atheistic: (1) Yes, they all contain life. (2) No, those beginnings are the result of random processes and so some do not contain life.