That's - well, maybe so! But what you're thinking of, we call those alternate material planes. They're not part of the center. Anyway, it's a big subject and the people who make it their careers to study it tend to go mad.

[And yet they do it anyway. Mortals, what even are you. Some of them, like the elves, do live to be quite old and can probably manage to comprehend some of that madness but unless they're careful about where they go, it claims them all eventually. As it should.]