Einstein's theory of relativity, both special relativity and general relativity, provides a comprehensive explanation for the phenomenon of time dilation.
In special relativity, time dilation occurs due to the postulate that the speed of light is constant in all inertial reference frames. This postulate leads to the concept of spacetime, where time and space are interconnected. Special relativity introduces the concept of "proper time," which is the time interval measured by an observer in a reference frame where an event occurs at the same location. According to special relativity, the proper time experienced by an object or observer moving relative to another frame of reference is dilated or stretched compared to the proper time of a stationary observer.
The time dilation effect arises from the fact that the speed of light is the same for all observers, regardless of their relative motion. As an object approaches the speed of light, time appears to slow down from the perspective of a stationary observer. This effect becomes more significant as the relative velocity increases.
General relativity extends the concept of time dilation to include gravitational effects. According to general relativity, gravity is not merely a force but a curvature of spacetime caused by mass and energy. In a gravitational field, the curvature of spacetime affects the passage of time. Clocks in a stronger gravitational field run slower compared to clocks in a weaker gravitational field.
This gravitational time dilation is due to the fact that space and time are influenced by the distribution of mass and energy. The curvature of spacetime near a massive object, such as a planet or a black hole, causes time to pass more slowly. This effect is observed, for example, in experiments where atomic clocks placed at different elevations (with different gravitational potentials) show slight differences in their ticking rates.
In summary, Einstein's theory of relativity explains time dilation as a consequence of the interplay between the constant speed of light and the curvature of spacetime caused by relative motion and gravitational fields. It provides a mathematical framework to understand and predict the observed effects of time dilation in various scenarios.