An observer on Earth sees an alien vessel a
0z-lkpb(1z tc+ota eo*/jc/.fd-m yipproach at a speed of 0.60c. The Enterprise comes to the rescue (Fig
+ m-ozlyibo 1(t-cpet / c*af.k/0jdz. Below), overtaking the aliens while moving directly toward Earth at a speed of 0.90c relative to Earth. What is the relative speed of one vessel as seen by the other? u =
c