Does electromagnetic radiation require a medium to propagate?
Let’s note that this word “medium” refers to some physical substance, be it a solid, a liquid, or a gas, that enables radiation to move from one place to another. We’re thinking here of electromagnetic radiation as a wave. And if we think of other traveling waves, for example, sound waves or water waves or even seismic waves caused by an earthquake, all of these types of waves do indeed require a medium in order to propagate, to move from one place to another.
It turns out however that electromagnetic radiation is an exception to this rule; as these waves travel along through space, they do not require a physical medium in order to do so. This is good because if we think about light from the Sun that has to travel through space to reach the Earth, that radiation has no physical medium to travel through. If electromagnetic radiation did require a medium in order to propagate, light from the Sun wouldn’t be able to reach the Earth. In reality though, the answer to this question is that no, electromagnetic radiation does not require a medium to propagate.