Time dilation occurs due to the fundamental postulates of special relativity, which state that the speed of light in a vacuum is constant for all observers and that the laws of physics are the same in all inertial reference frames.
The key concept behind time dilation is that the perception of time is not absolute but depends on the relative motion between two observers. When two observers are in relative motion to each other, they will measure different elapsed times for events.
According to special relativity, as an object or observer's velocity approaches the speed of light, time dilation becomes more significant. When an object is moving at a substantial fraction of the speed of light relative to another observer, time appears to slow down for that moving object or observer as perceived by the stationary observer. This means that clocks on the moving object would tick slower compared to clocks at rest in the stationary frame.
The effect of time dilation has been experimentally confirmed and is crucial for numerous practical applications, such as GPS systems that account for the time differences between satellites and receivers moving at different velocities.
As for the theoretical possibility of someone aging slower than others, it is indeed possible. If an individual travels at a high velocity relative to another observer, time dilation would occur for the moving individual. This means that from the perspective of the stationary observer, the moving individual would experience time passing more slowly. Consequently, the moving individual could theoretically age slower than the stationary observer.
However, it's important to note that for significant time dilation effects to occur, velocities close to the speed of light would be required, which is currently beyond our technological capabilities for human travel. Additionally, other factors such as acceleration, gravity, and the relative distances between observers can also influence the overall aging process.