All throughout the Universe, different types of signals propagate. Some of them, like sound waves, require a medium to travel through: the waves are fundamentally disturbances in a medium of particles, and in the absence of those particles, an initial “disturbance” has nowhere to go. Others, like light or gravitational waves, are perfectly content to traverse the vacuum of space, seemingly defying the need for a medium altogether. Irrespective of how they do it, all of these signals can be detected from the effects they have on all the matter and energy that they interact with: both along their journey through space all the way up until their eventual arrival at their final destination. But is it truly possible for waves to travel through the vacuum of space itself, without any need for a “medium” to propagate through at all? What would that even mean for the nature of space itself ?…