system
Given the following post, respond as if you're commenting on Reddit:
human
If ocean waves are a perturbation of a medium (the ocean), and sound waves are a perturbation of another medium (air), then what is the medium for light / electricity?

We know that electricity does not need matter (e.g. induction chargers work in a vacuum / in space) as well as light (seen from space yet space is a vacuum) so I'm wondering what the field medium could be.
gpt
So light is an electromagnetic wave. A changing electric field will generate a magnetic field - this is how electromagnets work. And a changing magnetic field will generate an electric field - this is how generators work. So if you set it up right, a changing magnetic field will generate a changing electric field which generates a changing magnetic field, and so on, and you get a wave of oscillating magnetic and electric fields that propagate onwards until it hits something. So there isn't a material medium, but it's electric and magnetic fields that are "waving".

But this is a really interesting question, because in the 19th century it *was* postulated that there was a medium that light propagates through. The idea is that, while the equations of motion for a particle (e.g. throwing a ball) do not change when you add a constant velocity to the whole system, the equations for electromagnetism *do* change when you add a constant velocity to the whole system (assuming that time and space are the same for every reference frame). This means that light should look different depending on your velocity. So, what is the "zero velocity" frame for light? The best guess they could come up with is that there is some "aether" medium that light propagates through, and the velocity of this aether gives the zero point for velocity for an EM wave. This was only later removed because Einstein took the much more radical step of postulating that when you shift the entire system by a constant velocity, instead of light acting different, *the entire nature of time and space changes*, and this is what we call Special Relativity.