In one minute

J. B. Pendry asks whether two perfectly smooth surfaces at absolute zero, defined only by their dielectric functions and separated by a gap, feel friction when sheared past each other. The aim is the simplest possible system, stripped of every complication, to see how friction arises at all. Quantum fluctuations produce friction between such surfaces even at absolute zero. For materials with resistivity around 1 mΩ in close proximity, the friction is comparable to everyday frictional forces. It depends only on the surfaces' electromagnetic reflection coefficients and falls off as a power law with separation, so it can dominate at large gaps, like the van der Waals force.

Shearing the vacuum – quantum friction