 Second, there are the points inside (rather than on) the future or past light cone of \(\mathbf{O}\). We say that these points are timelike separated from \(\mathbf{O}\). If \(\mathbf{B}\) is a point in the spacetime timelike separated from \(\mathbf{O}\) and future to it (that is, inside \(\mathbf{O}\)’s future light cone), then a material particle travelling at some relativistically acceptable speed (that is, less than \(c)\) can travel from \(\mathbf{O}\) to \(\mathbf{B}\). Similarly, a material particle at a point like \(\mathbf{C}\) inside the past light cone of \(\mathbf{O}\), can travel at some speed less than \(c\) from \(\mathbf{C}\) to \(\mathbf{O}\).