Re: Simple question
Okay I'm definitely not an expert but:
There is a fundamental problem that universe is an archaic term for when we thought what we could see was all there was. That is no longer the case but we still call what we can see (by whatever physically allowed means) the universe. it is, by definition, the only one we can 'know' about.
There are, as you have surmised, several possibilities for other 'universes'. An incomplete list includes:
- universes beyond the observable horizon. There are some theories which allow some inferences to be made from movements of matter within our observable uinverse.
- multiple universes existing in various branes in the multi-dimensional M-theory
- multiple universes generated by (or causing indirectly) quantum weirdness (take your pick).
. . . . and others.
You have selected a specific sub-set of universes that you are happy with and arrived at a (possibly valid) conclusion based on that alone.
As one of the other posters alluded to there are very many books, programmes and web articles on these subjects and you need to do some investigation of your own before you can ask a question that others will find sufficiently well formed/defined to provide an answer to.
I don't want to come off as patronising because I am only too well aware how short my knowledge in this area falls but (I hope I'm not being too presumptious here) the general tenor of your question implies that you are not.
I probably should post this anonymously . . . .