College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 76

(a) The distance to Polaris, the North Star, is approximately 6.44 × 10 18 m. If Polaris were to burn out today, how many years would it take to see it disappear (b) How long does it take sunlight to reach Earth (c) How long does it take a microwave signal to travel from Earth to the Moon and back (The distance from Earth to the Moon is 3.84 × 10 5 km.)