A star is moving toward Earth at 90% the speed of light.The star emits light,which moves away from the star at the speed of light.What do Earth-based astronomers measure for the speed of this light?
A)c
B)1.9c
C)1.2c
D)0.98c
E)0.95c

Question

Quizplus · Accepted Answer

According to the theory of relativity, the speed of light is constant for all observers, regardless of their relative motion. Therefore, Earth-based astronomers will measure the speed of light emitted by the star to be c (the speed of light in a vacuum), regardless of the speed of the star itself. The fact that the star is moving toward Earth at 90% the speed of light does not affect the speed of the light it emits.

A Star Is Moving Toward Earth at 90% the Speed