classical physics = 3 space dimensions relativistic physics = 4 dimensions (space+time) braneworld physics = 5 dimension (space+time+mass) http://superstringtheory.com/experm/exper51.html The holy grail of modern theoretical physics is the unification of quantum and relativistic theory. A key idea here is the possibility that there might be extra, hard-to-perceive dimensions. The braneworld theory say that the extra dimension is mass, so the mass of elementary particles might actually be fluctuating, if ever so slightly. Mass dynamics! Who knows, these ultra fine mass experiments may give us a way to test some of these crazy theories.