How does outer space work in Kingdom Hearts?

Is the place you fly around in with the gummy ship outer space? I always saw that as like a multiverse sort of space, and all the worlds were their own sort of universe with planets and stars and whatnot. However some worlds like deep space and monstro are just things from those worlds floating around in this area, so does that mean the gummy ship segments take place in space? Does that mean by all technicalities that some disney character with access to a rocket could blast off and end up in a different disney world? Could an astronomer from San fransokyo look up into the night sky and see the Caribbean from far away? How does this work?