Scientific American is carried by most public libraries.

A spatial dimension beyond the usual 3 is not necessarily imaginable and not necessarily physical in the sense you are thinking.

To answer the question of where something is requires 3 dimension. I need to supply an x, y, and z coordinate. A fourth dimension is merely a statement that to fully define where something is requires a fourth value. It does not necessarily follow that it is a place, as represented in science fiction movies, where you can go.

DA Morgan