... They include dust, sand, gravel, and various powders [11]. ... e.g., Saturn's) rings, pro toplanetary disks, and interstellar dust clouds [15 ... transportation of dry bulk materials; or dust and sand entrainment by moving air, as ...
... We note, however, that many other effects unaccounted for in the Newton equations (frictional interaction with interstellar dust, relativistic corrections, etc.) must manifest themselves on such a time scale. ...