"For most of us, or perhaps all of us, it's impossible to imagine a world consisting of more than three spatial dimensions. Are we correct when we intuit that such a world couldn't exist? Or is it that our brains are simply incapable of imagining additional dimensions—dimensions that may turn out to be as real as other things we can't detect?" - Lit

"The mathematics used in superstring theory requires at least 10 dimensions. That is, for the equations that describe superstring theory to begin to work out—for the equations to connect general relativity to quantum mechanics, to explain the nature of particles, to unify forces, and so on—they need to make use of additional dimensions. These dimensions, string theorists believe, are wrapped up in the curled-up space first described by Kaluza and Klein..." - Lit