Okay so I got an interesting question about traversing and classifying parallel universes.

So obviously we all know new universes can be born from something as minor as your decision whether you have eggs or toast for breakfast to how fast and how far a particle travels, right?

So I got two questions here. We are somehow able to traverse the multiverse and build a stable portal to the other side before traveling through it. We then go through the portal and go back. If there are infinite number of universes we created from this, would we be able to go back to the same discovered universe we went through or do we go to another universe that we have created? Or is that all futile because technically all the universes we created were from the original since our universe visited that one?

Heres a better question about classification....The TV show Rick and Morty had explored this concept of infinite realities/universes. However, they used a universe classification system. If there are infinite amount of universes and there's a new universe split from each decision, lets hypothetically say if "Rick C - 137" left the Citadel of Ricks (a pocket universe created by Ricks) and went on to some adventure where he had to make a decision right? Well if the two/infinite newly split timelines returns to the citadel, would the two/infinite amount of Ricks still be called Rick from universe C-137?

6058473
...this just got way too heavy for me...

6058473
The creation of new universes with every decision is only a theory, and relies on quantum superposition to work. That's one way to interpret multiple worlds, but isn't necessarily always the case. Some fiction have discrete non-increasing numbers of universes, like Marvel or DC, where the creation of new universes is rare.

If quantum superposition creates new universes with every decision, then it's basically impossible to catalog and classify the many universes because new ones are always being made. In Rick and Morty, I'd expect universe C-137 to be a group of universes rather than a single universe. Not entirely sure, I haven't watched much of it.

6058756
I'd expect that too, even though what confuses me is the same movie/show/media who uses universe classifications also said that new universes are created with every decision which was one of the factors that made me form the question

6058473
This might be related to how Stephen King handles multiple dimensions in his Dark Tower series.
I might be wrong though.
He has this term "Todash".

Basically, an alternate reality is overlayed on ours and could be crossed into if you can see the signs.
One of his chars was able to see a small path and was able to cross into other worlds.
This isn't a sci fi way to handle multiple dimensions but it might still be usable.

There are some great scenes where the char sees his money change depending on where he goes.
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I agree with Inthretis.
Though I wonder if it might be better to group related dimensions by some criteria.
I doubt you can have an objective criteria. You might have to designate a Prime dimension and then count the
other dimensions in relation to it.

In the Flash tv series, there was an Earth Prime and alternate versions of Earth.
I'm not sure they covered why that earth was prime and the others not prime.

6059695
Well I don't know how we would be able to classify where universes came from which universes if we aren't at the metaphysical standpoint and only discovering them by looking through a portal. Even then, it would be futile to still try to classify since it would be probably impossible to classify an infinite amount of universes as each keeps splitting off from each other and therefore eventually creating an endless stream of "characters" (A,B,C,1,2,3,%,$,^, etc.) imo.

Then again, we have yet to invent some sort of system to help us deal with hypothetical infinities built off from other infinities

6060048
Maybe you would have to classify as groups?

This would also depend on your tech or ability too.
Maybe the tech can only pick up major differences between alternate worlds?

Maybe some decisions basically map to one type universe and those just blend
together so they don't produce unique outcomes?

So the decision that Hitler made to become an artist would produce a different world outcome than if he decided to
have oatmeal instead of eggs. And he always has eggs.

And yeah, Hitler did apply to be an artist at some art school.

What if Stalin decided to just be a poet or a bank robber?
Would there be a Soviet Union?

So yeah, a person could create parallel universes by their decisions, but a lot of them could just map back to a Set(inconsequential) vs Set(whole different world).

To play with this a bit, what if Eve didn't eat of the forbidden fruit?
What sort of world would that decision make?

Someone actually played with that idea.
Unfortunately, I don't remember the author and the series.
I guess it might be CS Lewis and his Perelandra series but I'm not sure.

6060836
I think that would still apply to my earlier statement about classifying universes but with groups as well. Don't know which universe came from which and all that

6060836
Perelandria did indeed have Eve not eating the fruit. It's an interesting theological what-if! That whole trilogy is quite fascinating, especially given how early it comes in the history of science fiction. (It's after Burroughs and Wells but before most other folks modern readers are likely to have read.)

Honestly, there's no way to discuss parallel universes in a "this is true" way, because nobody knows what is true. They may not actually exist at all! There's no proof yet one way or another, just theories about what might be true.

So as an author, I take the approach of "It works however the story requires it to work." You can set out rules that suit whatever kind of story you're telling, which is what things like Rick and Morty do.

Consider first that multiverse could potentially brush on infinity. I feel that finite beings like ourselves would try to group what we know. Even if its impossible to catalogue everything, we'd still have names (like the Citadel of Ricks does) for what we have found and would continue to classify as we found more. Further down will explain why splitting wouldn't alter this, possibly.

As for the splitting universe, it gets kinda tricky as you approach infinity due to a few logical reasons. If there are infinite decisions and universes, one of them will eventually end all other universes. This doesn't seem to happen so there is either A. Some kind of fail-safe, maybe related to paradoxes or B. There is something finite about it beyond the fail-safe to where it never occurs or cannot occur.

As for the consequences of leaving a universe, it could work similar to how time travel might. Leaving your universe may forever alter it to where it also becomes an alternate universe and returning to the original is impossible. Mind you that is just a guess based upon the multiple timeline theory (not the real name I'm sure) to where time splits every time someone goes back in time and that is why we have never seen time travelers. This would also explain your Rick issue. If Rick A left and went on an adventure then had to make a decision creating a Rick A and Rick B, neither of them can return to the original timeline/AU. Rick A wouldn't have been able to regardless. Since they can no longer return to the original universe/timeline, you would never see the second Rick because each of them would return to a different alternate universe based upon that decision.

Just my opinion .