(a) When the Apollo astronauts landed on the moon, it took the radio signal 1.28 s to reach Mission Control on the earth. How far away were the astronauts from the earth?
(b) Since the sun is 1.50 x 1011 from the earth, how much time does it take for light to travel from the sun to the earth?
(c) Light from our next closest star, Alpha Centauri, takes 4.31 years to reach the earth. How far away from the earth, is Alpha Centauri?