And actually, yeah, forget about the relative speed, since that is not central to the real issue. The real issue is just that when your light cone changes, the

And actually, yeah, forget about the relative speed, since that is not central to the real issue. The real issue is just that when your light cone changes, the set of points that are simultaneous with you changes (all these points are outside your light cone except for the one you occupy). You cannot observe them directly because they are outside your light cone.