Consider the circumstances described in Problem 21.8, but now suppose that 2 < 0. Use the

Consider the circumstances described in Problem 21.8, but now suppose that Δ² < 0. Use the transformation defined in Problem 21.7 to show that there is a reference frame traveling at a speed v < c in which the two events occur at the same place, but different times. Show that the time order of the events is the same in all reference frames related by the transformation of Problem 21.7. In this case the event at the earlier time can influence the later event.