The Casimir force, a result of zero-point electromagnetic fluctuations, is a quantum mechanical effect that can influence the mesoscopic and macroscopic worlds. It acts between any two objects, but it’s so weak that it has typically been considered little more than a theoretical curiosity. Usually, the interaction is attractive. But now, Harvard University’s Federico Capasso and his recently graduated student Jeremy Munday have observed a repulsive Casimir force—even weaker than the attractive version and with possible applications to nanoscale technology. 1
The Casimir force is a close cousin of the van der Waals force between non-polar molecules or larger objects. When the ever-moving charges in one object create a momentary electric dipole, they can induce a dipole in a nearby object such that the two dipoles attract each other. In the van der Waals limit, the objects are close enough that the electric field propagates between them much faster...
