問題詳情
60. A spacecraft is flying towards Earth at a speed of 0.7 c. When it is 8 light-years away from Earth,
it sends a message to Earth at a speed of 0.5 c (relative to the spacecraft). How long will it take
for Earth to receive this message?
(A) 5 years
(B) 6 years
(C) 7 years
(D) 8 years
(E) 9 years
參考答案
答案：E
統計：A:0,B:0,C:0,D:0,E:0
難度：計算中