In our current understanding of the universe, time is considered a fundamental dimension that is intricately connected to the fabric of spacetime. Every object in the universe, including both massive and massless particles, moves through time because time is an inherent part of their existence.
According to Einstein's theory of relativity, the concept of spacetime combines the three dimensions of space with the dimension of time into a four-dimensional framework. This unified spacetime allows us to describe the motion of objects not only in space but also in time.
The motion of an object through time is usually referred to as the object's "worldline" in spacetime. It represents the path traced by the object as it progresses through both space and time. Objects with mass, such as particles, planets, or even galaxies, move along their worldlines in a manner that depends on the distribution of mass and energy in the universe, including gravitational influences.
It's important to note that an object's motion through time is generally perceived as the passage of events or the progression from one state to another. Time provides the framework for ordering and measuring the changes and interactions that occur in the universe.
So, every object in the universe moves through time because time is an inseparable component of the fabric of spacetime, and the motion of objects through spacetime is an essential aspect of their existence and dynamics.