String theory is where the lines of physics become blurred. The real debate is whether it can actually be called a "Theory," because we have no way of testing whether it is true. When you can't construct an experiment that would falisify once and for all your theory, it isn't science, or so goes the thinking of
Karl Popper. I really wouldn't worry about it, as it isn't likely to play into an engineer's life to often, but if theoretical physics is your game, this is where its at. My physics teacher maintains that "string theorists" are really nothing more than philosophers, which, if you want to be pedantic about it, is true.