Current Attempt in Progress Galaxy A is reported to be receding from us with a speed of 0.50c. Galaxy B, located in precisely the opposite direction, is also found to be receding from us at this same speed. What multiple of c gives the recessional speed an observer on Galaxy A would find for (a) our galaxy and (b) Galaxy B? (a) Number Units (b) Number i Units e Textbook and MediaAn armada of spaceships that is 1.00 ly long (in its rest frame) moves with speed 0.750c relative to the ground station in frame 5. A messenger travels from the rear of the armada to the front with a speed of 0.910c relative to 5. How long does the trip take as measured (a) in the messenger's rest frame, (b) in the armada's rest frame, and (c) by an observer in frame 5? (a) Number a Units v (b) Number n Units v (c) Number n Units v While on board a starship, you intercept signals from four shuttle craft that are moving either directly toward or directly away from you. The signals have the same proper frequency f0. The speed and direction (both relative to you) of the shuttle craft are (a) 0.3c toward, (b) 0.6c toward, (c) 0.3c away, and (d) 0.6c away. Rank the shuttle craft according to the frequency you receive, greatest rst. 0 b>a>c>d O a>b>c>d O a=b=c=d O d>c>a>b