The phenomenon of time dilation, where time appears to slow down for objects moving at high speeds, is a consequence of Einstein's theory of relativity. It is important to clarify that the speed of light in a vacuum is constant and remains the same for all observers, regardless of their relative motion.
In special relativity, Einstein introduced the concept that the laws of physics, including the propagation of light, are the same for all inertial observers. However, he also proposed that the measurements of time and space are not absolute but depend on the relative motion between observers.
According to special relativity, when an object moves at a significant fraction of the speed of light relative to an observer at rest, the observer will measure time to be dilated or slowed down for the moving object. This effect is reciprocal, meaning that both observers perceive time to be passing slower for the other.
The reason behind this phenomenon lies in the interplay between space and time. Special relativity combines space and time into a four-dimensional structure called spacetime. When an object moves rapidly through space, a portion of its motion is diverted into the time dimension. This diversion causes time to pass more slowly for the moving object as observed by a stationary observer.
The speed of light acts as an "ultimate speed limit" in this theory, but it doesn't directly affect time dilation. Instead, time dilation arises due to the relativistic effects of motion and the consistent speed of light for all observers.