大学普通物理相对论,If you (and some friends) allhad telephones that c

这题的条件是你和你的朋友运动速度低于光速,因此相对论对你们的运动有影响；而你和你的朋友们可以发出快于光速的讯息,因此讯息的传递跳出相对论的制约.
假设你在地球上,而你的朋友A驾驶宇宙飞船接近光速飞行.A于2010年自地球启航.地球上2015年时,你打电话给A,此时相对于A时间是2012年,A接到电话立刻将电话中转回地球.这样,在2012年的你就接到了中转自A的,2015年的你的电话.这是所谓的Time dilation.
Based on the conditions from this question.It can be seen that the motions of you and your friends are affected by special relativity,but the transfer of messages between you and your friends aren't.
Assume you are on Earth and your friend A travels in the spaceship.A starts from Earth in 2010.In 2015 on Earth,you call A,who is travelling at a relativistic speed.A picks up the call from you and in A's reference,the time might be 2012 because of time dilation.A instantly transfers the call back to Earth.As a result,you in 2012 gets a call from yourself in 2015,transferred by A.