Yes, time dilation is a real and well-established effect in physics. It is a consequence of the theory of relativity, which has been extensively tested and confirmed through experiments.
The theory of relativity, both special relativity and general relativity, predicts that time can pass differently for observers who are in relative motion or experiencing different gravitational fields. These predictions have been experimentally verified in various ways.
In special relativity, time dilation occurs when objects move relative to each other at significant fractions of the speed of light. Observers in different inertial frames of reference will measure different elapsed times due to the relativistic effects of time dilation. This has been demonstrated through high-speed particle experiments and precise measurements of fast-moving particles.
In general relativity, time dilation arises due to the curvature of spacetime in the presence of mass and energy. Clocks closer to massive objects experience a slower passage of time compared to clocks in weaker gravitational fields. This gravitational time dilation has been observed and confirmed through experiments, such as the Pound-Rebka experiment and the gravitational redshift observations.
The effects of time dilation have practical consequences and are accounted for in various scientific and technological applications. For example, the accuracy of the Global Positioning System (GPS) relies on accounting for both special and gravitational time dilation effects in satellite-based positioning calculations.
In summary, time dilation is a real and measurable effect supported by experimental evidence. It is an essential aspect of the theory of relativity and has been confirmed through a range of experiments and observations.