If Alice stays on Earth while Bob races off in a rocket at a speed close to the speed of light, then, according to special relativity Alice will see a clock on the rocket appear to tick more slowly than the one on her wall. If Bob looks back at Alice's wall clock, then according to the same theory Bob will see the wall clock appear to tick
A) at the same speed as the clock on the rocket.
B) faster than the clock on the rocket.
C) faster or slower than the clock on the rocket, depending on the direction of travel of the rocket compared with Earth.
D) slower than the clock on the rocket.

Question

Quizplus · Accepted Answer

According to the theory of special relativity, time dilation occurs for the observer in motion relative to a stationary observer. Thus, from Bob's perspective in the rocket, time on Earth (including Alice's wall clock) would appear to tick slower, just as Alice sees Bob's clock ticking slower. This reciprocal effect is a fundamental aspect of relativity, illustrating that each observer sees the other's clock as ticking slower.

If Alice Stays on Earth While Bob Races Off in a Rocket