I'm rather new to physics in general, so bear with me in my potential ignorance. Considering we have no idea of the absolute properties of higher dimensions, how is it that they're identified in equations? This especially perplexes me when thinking about the Kaluza-Klein theory, or even Superstring theory. How does one know how many dimensions necessary for the given forces to unify without falling on pure speculation? Assuming it ultimately has to do with spacial limitations, and that in higher dimensions it naturally allows for unification, how do the mechanics of it actually work? I suppose I enjoy the questions more than answers. Hopefully I'm making sense.