If the space-time interval is calculated according to: ds2=dx2+dy2+dz2-c2*dt2 what might be an example of 2 events in space-time separated by this interval? Suppose for example ds2 =1 (or a constant) and the first event was at the origin where would the second events lie? Am I looking at the (edge of ) the spacetime cone that I have sometimes heard talk of? What if the first event is not at the origin? Has any one a link where I could read about it in detail? I hope I have the very basic understanding of the situation more or less correct.