An eerie quantum force may one day help separate the surfaces in tiny machines for frictionless movement. More than half-a-century ago, the Dutch theoretical physicist Hendrik Casimir calculated that two mirrors placed facing each other in a vacuum would attract. The mysterious force arises from the energy of virtual particles flitting into and out of existence, as described by quantum theory. Now Norio Inui, a scientist from the University of Hyogo in Japan, has predicted that in certain circumstances a reversal in the direction of the so-called Casimir force would be enough to levitate an extremely thin plate.