So, we're fairly sure that the universe is infinitely large. We're also fairly sure that it is expanding. My question is how do these two facts relate to the multiverse? My favorite interpretation was given by Michio Kaku, who stated that in the multiverse each individual universe is like a bubble, and all of these bubbles are floating around in some space (and sometimes interact?).
How can there be an infinitely large object in a space with other presumably infinitely large objects? Is this in like math where there are different "sizes" of infinities, where some are larger than others? What is the space that the universe is expanding into? Does that have a boundary, or is it also some infinity?