In the special theory of relativity, time dilation refers to the phenomenon where the passage of time is perceived differently by observers moving relative to each other at different speeds. It is one of the fundamental consequences of the theory proposed by Albert Einstein in 1905.
According to the special theory of relativity, the laws of physics are the same for all observers in inertial (non-accelerating) frames of reference. However, the theory introduces the concept of "relative simultaneity" and the notion that the speed of light in a vacuum is constant for all observers, regardless of their relative motion.
Time dilation arises from the invariance of the speed of light. It states that when two observers are in relative motion, each observer measures the passage of time differently for the other observer. Specifically, an observer in motion relative to another observer will measure time as passing slower for the moving observer compared to their own experience.
This effect becomes more significant as the relative velocity between the observers approaches the speed of light. As an object's speed increases, its time appears to slow down from the perspective of a stationary observer. This is often expressed using the concept of a "time dilation factor," which quantifies the ratio of time experienced by the moving observer to the time experienced by the stationary observer.
Time dilation has been experimentally verified and is crucial for numerous practical applications, such as the operation of Global Positioning System (GPS) satellites, particle accelerators, and the understanding of high-speed travel and space exploration.