moving astronauts

[fairylight]

To astronauts pass each other at a relative speed 0.8c. At the instant their spaceships pass they sychronize their clocks and when A reads 10mins, a flash of light will be sent to B. According to B what does clock A read when the flash is sent, and what does B read when A sends the signal?

 

For the first part i used root [1- (v/c)^2] and found the time on A to be 1000seconds. Im confused about how to work out the second half of the question. If the speed of A is relative to B then surely the time on B would be 10mins?? But that seems wrong to me! help!!!! thanx!

[J.C.MacSwell]

To astronauts pass each other at a relative speed 0.8c. At the instant their spaceships pass they sychronize their clocks and when A reads 10mins' date=' a flash of light will be sent to B. According to B what does clock A read when the flash is sent, and what does B read when A sends the signal?

 

For the first part i used root [1- (v/c)^2'] and found the time on A to be 1000seconds. Im confused about how to work out the second half of the question. If the speed of A is relative to B then surely the time on B would be 10mins?? But that seems wrong to me! help!!!! thanx!

 

When B receives the signal he will assume/calculate that it was sent by A at 10 minutes on A's clock or after more than 10 minutes of his own time. A will agree that he sent it at 10 minutes but will feel that less than 10 minutes had expired on B's clock when the signal was made.