Remember the basics…the medium, any medium, is acting like the dielectric. We can measure the dielectric constant of various material and the word “virtual” is just that. It says something is “almost” but not exactly the same; Nitrogen is virtually a vacuum.
I’m not sure the accuracy and STD deviation of dielectric tests near a vacuum so you got me there. Is the measurement accurate or hidden in the error of the test?
I do understand your idea, any wave that is EM in nature must interact with the medium it is in. And yes, the use of better and better dielectric pretty much proves that to be the case.
The medium the EM field is in absorbs and dissipates the energy in the EM fields hence the words dissipation factor and loss Tangent (a value in the dissipation factor).
I would say once past dry air or VERY high frequencies there are better improvements that could be made. Geometries that cancel EM fields to where we don’t have to worry as much about all that stuf! This shows up in inductance values. Can the EM field be easily created and destroyed in time? It doesn’t change on its own. The energy has to be created and once created it has to be removed.
Inductance just gives you an idea how easy a current can be changed in time.
Curiously pure electric fields (static electricity) or magnetic fields (bar magnets) are kind of cool to play with as they are examples of the extreme isolation of an EM fields two components; electric and magnetic fields at ninety degrees to one another. The are “virtually” separated in pure static or pure magnetic fields.
Each can stay around forever until something interacts with the field (moisture in the air bleeds off static) or randomly re-aligns the atoms in a magnet (heat does it). So we see the relationship you are pointing out. If an EM field is BOTH a B and E field, can we mitigate each one to virtually “zero” change as the composite EM wave moves along.
So we know we need to address BOTH attributes and what interacts with each one. The problem gets harder!