Brief Encounters
I think the hardest thing to understand from your Lifebook Online Review standpoint is that "There simply is no lack of space for worlds, dimensions, planes and universes to exist. The physical properties of any world is only an appearance, and appearances do not take up space. Period!Physical systems only take up space within your own frame of reference, but other systems share the same space as your world and you will never bump into them in your journeys. They are just as real, just as physical and concrete within their own dimension as is your own world within your dimension.
Many dimensions can co-exist within what you call your own space, moving through each other, oblivious of each others existence. Probable worlds exist in these multi-dimensional aspects, and in another gross oversimplification, I am afraid, probable worlds exist in what might be considered, sympathetic clusters around your world, in the same cosmic neighborhood so to speak, but in another dimension entirely.
From your standpoint, you will always rationally consider your world, the "Real World" and the others as probable worlds. Of course, you can assume that identities that exist in the other probable worlds consider their worlds the "Real Worlds" and you're world, to them, would then be considered the probable world. In other words, distance wise, keeping in mind that distance does not apply to other dimensions, they are close, but in psychic terms they are very distant indeed. In the same way, the universe of anti-matter exists as real as your own, but in another dimension entirely, and you will never visit it in your space vehicles.