The collisionless nature of high-temperature plasmas

Two phenomena that illustrate the collisionless nature of high temperature plasmas are Landau damping (or, more generally, the resonant wave-particle interaction) and collisionless shock waves. The first half of this paper traces Landau's idea through the years as it is tested experimentally, extended nonlinearly, and applied. The second half traces the progress in understanding collisionless shocks in space and astrophysical plasmas.