What phenomenon occurs when time in a moving frame appears to be slower relative to a stationary observer?

The phenomenon where time in a moving frame appears to be slower relative to a stationary observer is known as time dilation. This concept is a fundamental aspect of Einstein's theory of relativity. According to this theory, as an object moves closer to the speed of light, time for that object slows down when observed from a stationary frame.

Time dilation has been confirmed through various experiments, such as observing particles moving near the speed of light and measuring the time experienced by clocks on fast-moving jets compared to stationary clocks. The term effectively captures the essence of how motion affects the passage of time, illustrating that time is not an absolute quantity but is relative to the observer's state of motion.

In contrast, terms like time compression, time shift, or time expansion do not accurately convey the complexities of relativistic effects on time. Time dilation specifically highlights the changes in time perception between different frames of reference, making it the precise term needed to describe this phenomenon.