system
Given the following post, respond as if you're commenting on Reddit:
human
What is the force that drives light to move at the speed that it does? Or to put more simply, what propels light?

I understand that light travels really fast. I know that is an understatement but anyway, what is it that propels light forward to move at the speed that it does without ever slowing down?
gpt
There is no propelling force behind light. From a classical perspective, light is two perpendicular waves in the electric and magnetic fields. The changing electric field induces a magnetic field and vice versa, so the wave is constantly perpetuating itself. Waves do not accelerate, they propagate at a constant speed from the time they are emitted to the time they are absorbed. That speed is determined by the permittivity and permeability of the medium, and in the case of a vacuum this gives the speed of light.

From a quantum perspective, light consists of massless particles called photons. In special relativity, a massless particle *must* travel at the speed of light.