Light itself does not experience the passage of time. This is a consequence of the theory of relativity, particularly the principle of time dilation. According to special relativity, the perceived passage of time depends on the relative motion between observers.
From the perspective of a light beam, as it travels at the speed of light, time does not elapse. This means that, from the light's frame of reference, its journey from one point to another is instantaneous. This phenomenon is known as "light-like" or "null" geodesics, where the proper time along the path of light is zero.
However, it's important to note that this does not imply that light can travel backward in time or engage in time travel as commonly understood. Time dilation effects are relative and depend on the relative velocities and gravitational fields of different observers. For an observer who is not traveling at the speed of light, they would still perceive the passage of time and see the light beam propagating at the speed of light in their own reference frame.
In summary, while light itself does not experience the passage of time, this does not enable it to engage in time travel or violate the fundamental principles of causality.