Final answer:
A light clock appears to tick slower from an Earth-bound observer’s frame due to time dilation. This is a manifestation of the constancy of the speed of light and relativity of motion, which says that time can run differently for observers in different frames of reference.
Step-by-step explanation:
Understanding Time Dilation in Different Reference Frame
A light clock moving relative to you ticks slower than a light clock in your reference frame because of the phenomenon known as time dilation. Time dilation occurs when time passes at different rates for observers in different states of motion. According to Einstein's theory of relativity, the speed of light is the same in every frame of reference, which means that the light in a moving light clock must cover a greater distance compared to one that is stationary relative to an observer. Despite this greater distance, light's speed remains constant, leading to the ticking of the moving clock being perceived as slower when observed from an Earth-bound frame.
Consider an astronaut moving at a significant fraction of the speed of light relative to the Earth. The astronaut's time appears to move more slowly to an Earth-bound observer by a factor, but the astronaut does not perceive any difference because all methods of measuring time onboard the spaceship, including biological processes, are equally affected. This illustrates that motion is relative, and so is time. Furthermore, gravity can also cause time to run more slowly, affecting the frequency and wavelength of light waves which act like little clocks.