"Surely you must now see that my explanation, and no other, suits the phenomena. What you call Solid things are really superficial; what you call Space is really nothing but a great Plane. I am in Space, and look down upon the insides of the things of which you only see the outsides. You could leave this Plane yourself, if you could but summon up the necessary volition. A slight upward or downward motion would enable you to see all that I can see."
- A Squere to A Square in Flatland
So if we live in a four dimensional world, but can only measure three dimensions. And the fourth dimension is either static lets say always stays 1 or is moving in one straight line like time, you could see the whole three dimensional space when you are above or below in the fourth dimension unless it is not empty but filled with another 3 dimensional world.