Time dilation is a phenomenon in which time appears to pass differently for observers in different frames of reference, particularly when there is relative motion between them or when they are in the presence of strong gravitational fields. It is a consequence of Einstein's theory of relativity.
The two main factors that can cause time dilation are:
Relative velocity: According to the theory of special relativity, when two observers are in relative motion, their perception of time will differ. If one observer is moving at a significant fraction of the speed of light relative to the other, time will appear to pass slower for the moving observer as observed by the stationary observer. This effect is known as time dilation due to relative velocity or "kinematic time dilation."
Gravitational fields: In the theory of general relativity, the presence of a massive object, such as a planet, star, or black hole, can also cause time dilation. In the vicinity of a massive object, the curvature of spacetime is greater, leading to a slowing down of time. The stronger the gravitational field, the greater the time dilation effect. This effect is known as gravitational time dilation.
Both types of time dilation have been experimentally confirmed. For example, atomic clocks flown in airplanes or placed in satellites experience minuscule but measurable time dilation due to their high speeds relative to observers on the Earth's surface. Similarly, gravitational time dilation has been observed by comparing clocks at different elevations, with lower clocks running slightly slower than higher clocks due to the influence of Earth's gravitational field.
It is important to note that time dilation is a relative effect, meaning it depends on the relative motion or gravitational fields between observers. The experienced time dilation will be different for different observers, depending on their relative situations.