 Finally, there are the points of the spacetime that are neither in nor on the light cone of \(\mathbf{O}\). We say that such points are spacelike separated from \(\mathbf{O}\). If \(\mathbf{D}\) is spacelike separated from \(\mathbf{O}\), then neither a light signal nor a material body can travel from \(\mathbf{O}\) to \(\mathbf{D}\) or vice versa, because such travel would require superluminal speed. If one makes the natural assumption that information and causal influence are propagated by electromagnetic signals and material particles, then if \(\mathbf{D}\) is spacelike separated from \(\mathbf{O}\), events or occurrences at \(\mathbf{O}\) can have no causal influence at all on events at \(\mathbf{D}\), and vice versa.