Kinematic time dilation is a consequence of the theory of special relativity, which describes how time and space are affected by the motion of objects relative to each other. According to special relativity, when two observers are in relative motion, they will measure different elapsed times between events.
Kinematic time dilation is a symmetric effect, meaning that it is observed by both observers in relative motion. If two observers, let's call them Observer A and Observer B, are moving relative to each other, they will each perceive the other's clock as running slower compared to their own clock. This phenomenon is often referred to as "time dilation" because it appears as if time is running slower for the moving observer.
The key principle of special relativity is that the laws of physics should be the same for all observers in uniform motion. Therefore, the time dilation effect is symmetric and applies to both observers equally. Each observer will perceive the other's clock as running slower, and the amount of time dilation experienced by each observer is symmetrical.
It's worth noting that when the relative velocities involved are small compared to the speed of light, the effect of time dilation is typically negligible. However, as the relative velocity approaches the speed of light, the effect becomes more significant.