Captain Jirk reports to headquarters that he left the planet Senesca 1.88 × 104 seconds earlier. Headquarters sends back the message: "Was that spaceship proper time?" It will be spaceship proper time if it was
A)measured by one clock fixed at one spot on Senesca.
B)measured by one clock fixed at one spot on the spaceship.
C)measured by a clock on Senesca at departure and by a clock on the spaceship when reporting.
D)measured by a clock on the spaceship when departing and by a clock on Senesca when reporting.
E)calculated by dividing the distance from Senesca according to Senesca by the speed of the spaceship.

Question

Quizplus · Accepted Answer

Proper time is measured by a single clock that is at rest relative to the event being timed. In this case, the event is the spaceship's journey, so the proper time is measured by a clock on the spaceship.

Captain Jirk Reports to Headquarters That He Left the Planet