Question

Sam leaves Venus in a spaceship headed to Mars and passes Sally, who is on Earth, with a relative speed of $\mathbf{0}\mathbf{.}\mathbf{5}\mathit{c}$ . (a) Each measures the Venus–Mars voyage time. Who measures a proper time: Sam, Sally, or neither? (b) On the way, Sam sends a pulse of light to Mars. Each measures the travel time of the pulse. Who measures a proper time: Sam, Sally, or neither?

Short answer

(a) The Sam measures the proper time.

(b) Neither, Same nor sally can’t measure the proper time.

Step-by-step solution

Write the given data from the question.

Sam leaves Venus headed to Mars.

The relative speed of the sally is $0.5c$.

Determine who measures the proper time for Venus- mars voyage time.

(a)

Sam is moving from Venus to mars;therefore, he can measure the time of the whole trip by using only one clock but sally is stationary on the earth, therefore she required two clocks to measure the complete time, one clock which measures the time for counting on Venus and other for stopping count on Mars.

Hence Sam measures the proper time.

Determine who measures the proper time when Sam sendsa pulse of light to Mars.

(b)

Since Sam and Sally are stationary relative to the light beam and their relative speed is the same which is $0.5c$. Therefore, they cannot measure the time by using a single clock.

Hence neither Same nor sally can’t measure the proper time.