In science we attempt to classify everything. And everything seems to be a subset of something else. Planet is a part of a solar system, solar system is a part of a galaxy, galaxy is part of the universe, universe is a part of our dimension, etc.
Obviously there are exceptions to this, rogue planets, but we still consider them contained.
I understand the idea of multidimensions is theoretical, but if they exist, do we have a name or even a theory what might contain them?
No problem! I was worried it might end up a bit of a word salad lol, so I’m glad you found it informative and easy to digest!
The extra dimensions in string theory are actually spatial dimensions, as far as I know, they’re just “compact.” So, for analogy, consider the surface of an infinitely long pencil (or straw or other cylinder). It’s two dimensional. One of its dimensions is pretty large: the one along the length of the infinite pencil. It’s unbounded, infinite, and flat. The other spatial dimension is the one that goes around the pencil: it’s unbounded, but finite and curved (convex, like the dimensions on a sphere). That one that goes around is more like what string theorists are taking about, I think.
I also don’t put that much stock in string theory, for whatever my opinion is worth (and it shouldn’t be worth too much, because again I’m not a physicist). Mainly because we can’t actually test it, and I think testability is important.
This I know much less about, unfortunately. I’ve seen this idea come up in, eg, the many worlds interpretation of quantum mechanics, but my sketchy understanding is that what they’re actually talking about is something very different from the sort of multiverse as portrayed on TV and in novels. I have a bit of a suspicion that the answer might be the same (they’re not contained in anything), but I really don’t know for sure.