The underlying geometry of spacetime algebra allows one to derive a force by contracting the relativistic generalization of angular momentum, M, with the mass-current, m., where w is a proper 4-vector velocity. By applying this force to a cosmological object, a repulsive inverse distance-square law is found, which is proportional to the velocity dispersion squared of that structure. It is speculated if this finding may be relevant to the recent suggestion, that such a force may accelerate the expanding universe with no need for a cosmological constant.