system
Given the following post, respond as if you're commenting on Reddit:
human
Why does light move?

Light moves faster than almost anything in the universe, so how does it always move that incredibly fast regardless of what its being emitted from?

Is the speed of a light particle/wave always constant? 

What is the mechanism through which light is emitted from something at light speed, why is it always emitted at light speed?

Thanks, looking forward to the answers.
gpt
Light is composed of an electric and a magnetic field both oscillating sinusoidally. Ampere's and Faraday's laws say that if an electric or magnetic field changes, then the other kind is generated and also changes. It turns out that a sinusoidal change in an electric field will generate a sinusoidal change in the magnetic field. Then the sinusoidal change in magnetic field creates a sinusoidal change in the electric field and the process repeats indefinitely thus creating a light wave.

There are two properties of the universe called electric permittivity and magnetic permeability. These values affect how resistant an area of space is to a changing electric/magnetic field. In a vacuum, these properties have characteristic values which we have empirically measured. 

Permittivity and permeability work together to restrain the propagation speed of light by resisting light's changing electric and magnetic fields. In fact, the speed of light can be derived as simply equal to:

**sqrt(ε0 * μ0)^-1**

Where ε0 and μ0 are permittivity and permeability of the vacuum respectively. So, the speed of light in a vacuum is due to the values of these universal constants.