There are many nights when I look up and it is not the stars or celestial bodies which puzzle me, it is the space.

I was wondering how much of the research has been spent on the visible since many centuries, even millennia and why is that that the main objects of our research are the things we can actually notice. For instance, if I put a chair in an empty room, this chair becomes an object of observation and if I remove a chair from this room, we can call it an empty space, with nothing to observe. However, in this room, there are many things to measure, such as sounds, a density of the air, the volume or even…