If a light wave has no medium of propagation then it can have no propagation speed
In classical wave physics, a wave is a disturbance which propagates in a medium. The speed of a wave is determined by the properties of the medium. A wave therefore cannot propagate at any speed if it has no medium to propagate in. Einstein’s 2nd postulate says ‘light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body.’ So he replaces the medium of light wave propagation, the aether, with ‘empty space’, therefore the speed of light c is not defined relative to its medium, aether, but to absolutelly nothing (in which light also propagates, making light a wave of nothing, or a disturbance of nothing). And then claims the exact same thing which classical wave physics said about waves. Taking out the most important thing, which is that the speed of waves is always defined relative to their medium of propagation- which is what causes the wave to propagate and have a definitive speed in the first pla...