Time dilation is a phenomenon predicted by the theory of relativity, which states that time can appear to pass differently for observers who are in relative motion or experiencing different gravitational fields. While time dilation is indeed relative, meaning it depends on the relative motion or gravitational fields of the observers involved, it does affect clocks in a measurable way.
There are two main types of time dilation: special relativity time dilation and gravitational time dilation.
Special Relativity Time Dilation: According to special relativity, the passage of time is not absolute but depends on the relative velocity between observers. If two observers are moving relative to each other at high speeds, they will perceive time differently. Specifically, the observer who is moving faster relative to the other will experience time passing more slowly compared to the stationary observer. This effect becomes more pronounced as the speed approaches the speed of light.
Gravitational Time Dilation: Gravitational time dilation occurs due to the gravitational field surrounding massive objects. According to general relativity, the presence of mass and energy warps spacetime, causing it to curve. In regions with stronger gravitational fields, time passes more slowly compared to regions with weaker gravitational fields. This means that clocks closer to massive objects will tick more slowly than clocks farther away.
To understand why time dilation affects clocks, it's important to recognize that time and space are interconnected in a four-dimensional spacetime framework. Objects in motion or in the presence of strong gravitational fields experience a distortion in the fabric of spacetime, causing time to behave differently.
In practical terms, time dilation has been experimentally confirmed and is taken into account in various scientific applications. For instance, the Global Positioning System (GPS) relies on precise timekeeping to determine the location of GPS receivers accurately. However, due to the high speeds of satellites and the difference in gravitational fields between the satellites and receivers on Earth, the clocks on GPS satellites are affected by both special and gravitational time dilation. If the effects of time dilation were not accounted for, GPS navigation would be significantly less accurate.
In summary, time dilation affects clocks because the relative motion between observers or the presence of strong gravitational fields causes a distortion in the fabric of spacetime, altering the passage of time as observed by different observers. This phenomenon has been experimentally confirmed and is crucial to various scientific applications.