Blackbody Friction: Analytic expressions for velocity and position
  The equations of motion are solved analytically for speed and position for the case of blackbody friction on objects traveling at relativistic speeds with respect to observers fixed in the frame of the blackbody radiation. Two model cases are considered, both assume an object which is a perfect absorber of light, and one of which also assumes that the object maintains a constant rest mass by emitting photons in a momentum neutral process. The maximum distances attained for a light sail and a micron-size sand grain are determined under the assumption that the relevant blackbody source is that of cosmic background radiation. At a temperature of 3000K, the temperature at the time the universe became transparent, cosmic background radiation would cause a significant decay of speed fluctuations in dust clouds. 
Joseph West
physics.class-ph