Let's say this physical world is A, and the astral world is either B or C. Why B or C? Because it's not yet known whether the astral world is a virtual world streaming in the brain or a parallel universe that includes this one, and more. Which ever way it happens to be is beside the point in this topic. The point is to merely draw up a framework to account for both possibilities for future use.

OK, so, this is sort of what it would look like:

B -> A -> C

World B is the astral world possibility of being a larger universe that includes this one, and world C is the astral world possibility of being a virtual reality constructed by our brains, which would be included by world A, the physical.

Whether or not the astral world is B or C, the framework itself doesn't change. If it happens to be that the astral world is not B but C, then there would merely be a change in representation (for me, anyway, as I think it's B).

World C isn't that interesting at this moment. It's more like a familiar possibility at this time, with the Internet, Second Life, MMORPGs, and massive governmental systems (of which there is no end in legality and bureaucracy that it creates its own kind of "Internet") developing toward that end. World B is the fascinating one at this time because of the things that would be possible if found to be a universe that included this one (there's a way to write that expression in set theory, but this window does not allow that symbol/expression, or I just don't know the correct key combination to type it out).

If you're wondering that the astral world could be neither B nor C, as in, being another world that exists side by side (parallel) to A, then if that were so, somehow B and the world parallel to A (let's call it AA) is acting sort of as a "server" to allow for the connection to happen. So, even then, there must be some world that includes A and AA in order for them to be considered "parallel", and going to and from them would mean, at some point, the passing between a "middleground", "wire", "tube", "plane", whatever (B). Unless, of course, if A and AA intersected in some places/times, then going from one to another wouldn't require going through B first*. But that brings up more interesting questions as well, such as format-compatibility/successful-translation or preservation of yourself when going to and from an intersecting AA. In that possibility, the initiating and ending of an OBE is the processing of consciousness from A to AA and back again.

If A ends up being no world at all ("no world" is a kind of world, too, just ask Data), then that would call for a massive rethinking of what we think about when we sense or experience anything at all, even as you read these words, and we could safely say at this moment that we're in some kind of "cryptospacetime". But the experience of an OBE invalidates that possibilty. An OBE narrows the question down to "what is the astral world, really?" Oh, and also, if A is "no world" (let's call "no world" NULL) after all and not physical, the framework stated above still doesn't change; it merely means A is at the very bottom, the NULL, and there would be no C for NULL. NULL is, in set theory, the empty set; there are no subsets.

OK, that's about it for now.

* - That was my initial thought. To go from A to AA that intersect would still require B in order to make the transportation successful.