Roy Lewallen, W7EL wrote:
"With the system on and in steady state, there`s absolutely no way you
can tell the difference between this sum of two waves and no waves at
all."

With the constraint of where Roy would let me check, I think he is
right.

Terman`s first sentence in the 1955 (4th edition) of "Electronics and
Radio Engineering" is: "Electrical energy that has escaped into free
space exisrs in the form of electromagnetic waves."

Other definitions say: "All entities that carry force, whether one
marble striking another or sunlight moving molecules of air, act
sometimes as particles and sometimes as waves."

Thyere is an analogy of Roy`s null plane in public address where two
loudspeakers are placed together and driven out-of-phase. The microphone
is placed on the centerline to avoid feedback.

I agree that two wires in a plane with the plane of the source antennas
perpendicular to the plane of of those wires and the reception point
equidistant from the antennas cannot select between those antennas
without occupying some space outside the plane. A patch antenna might do
it but it has depth or thickness so it partially falls outside the
plane.

Waves may be only a mathematical convenience but are visible in water
and in powders on vibrating surfaces. They are also visible in
synchronized illumination on vibrating surfaces and in synchronized
photos.

Waves in-phase and traveling in the same direction are inseparable so
might as well be a single wave.

Best regards, Richard Harrison, KB5WZI