We study the transfer of energy from an optical potential to atomic and molecular gases and demonstrate that this process is analogous to collisionless Landau damping of electrostatic potentials in plasmas and gravitational potentials observed on astrophysical scales. We show that a signficant fraction of the light attenuation within a cavity can be attributed to this mechanism when the cavity is filled with a gas at high density. The resulting motion of particles created by optical Landau damping can be used to induce transport when a periodic potential produced by two counterpropagating high-intensity pulsed optical fields is used. Bulk drift of the gas also appears feasible even when the mean kinetic energy is much greater that the maximum optical potential. © 2005 The American Physical Society.