The Meaninglessness of the Concept of Other Worlds and Its Implications
From the dawn of human history, many religions and belief systems have postulated the existence of other worlds that are generally outside of our world. In what follows, I’ll attempt to demonstrate that the concept is actually meaningless based on the fundamental nature of space.
Space as we know it is infinite extendable. There is no limit to it because it is just something that can be filled with any stuff. There may be regions of space that are not easily accessible (as black holes are) but they remain parts of the same space and the same world. Since there is no other meaningful way to conceive of other worlds, the concept is meaningless.
There are two potential objections to this argument:
1) The dominant interpretation of the equations of general relativity is that there is something called space-time that is a four-dimensional object of a certain shape. If it is valid, then there can be other such objects.
I think the GR equations are fine but their interpretation is misguided. It is based on a simple conflation of changes in the length of objects along the direction of movement with the shrinking/extension of space as such and the speed of processes with time as such.
2) Some theories attempting to reconcile GR with quantum mechanics posit the existence of the additional dimensions of space. It may be argued that other worlds may be concealed in them.
In my view, a conflation somewhat similar to that in GR is on display here. Just because something can be analogized to a dimension of space in the narrow sense that it can be assigned a coordinate axis, it doesn't mean that this something has now become a dimension of space.
Hence, the initial argument still stands.
It is interesting, however, to answer the question what human minds actually do when they deal with the idea of other worlds and other such pseudo-concepts, such as immaterial beings and souls, for instance. Don’t religious people feel they muse about something genuine when they contemplate gods, the higher realms, etc.?
While it is not easy to definitively resolve this conundrum, I’d venture to say that human minds probably revert to meaningful concepts. That’s why spirits were imagined as moving collections of fire, smoke or air. When people think about other worlds they probably just entertain states of affairs very different from the one they know.