[deleted]
Frank,
It would appear that but you and ARRL have overlooked a very important point.
While light is comprised on super-positioned EM wave of various wavelength the longitudinal waves produced by spark gaps etc. are not of the same nature.
Each photon comprising the EM wave they form lines up one behind the other.
Note that even Planar 2D waves have a some minuscule Z component [else you couldn't have Pos charge on one side with Neg on the other to satisfy Lorentz co-ordinate changes]
As the photons don't super-position they they line up like quantum railway motor-carriages and create a 'rod' of co-linear momentum.
Once this 'rigid rod' of Energy momenta is established any momenta added at one end of it will 'instantaneously' cause the momenta at the other to respond - just like pushing the end of a stick.
ACTION can be transferred in either direction along this wave as the momenta are lined up bidirectionally [like little carriages or rods] but any additional EM information added to the wave (apart from the co-linear momenta noted) is forced to propagate at c along its length
LWs form the basis of Newtons 'action-at-a-distance' and the reason why Tesla's spark gap waves stung his face [but were revealed NOT to be electrons]
Of course longitudinal waves can be super-positioned but that doesn't enhance the effect (just allows it to operate over a larger surface of action at each end]
Why has this been overlooked by the Science community for so long? - the wave equations for both are identical, only their sources and E-field polarisations are different [another sad case of doing Maths without physical Models].
When the photo-electric effect was discovered they moved from Spark gaps to oscillating charged particles to produce EM waves, then Einstein's SR explanation of Electrodynamics drove the scientific community down a blind alley [again because his model of mass-ENERGY-Matter was wrong]
Longitudinal waves form the basis for electrostatic CHARGE in our Universe, and it is the separation of Charges that gives us the electromotive force for Electricity in our World.
see attached.Attachment #1: Figure_21.05__Volts_and_EMF_800x600.jpgAttachment #2: Figure_28.17__Longitudinal_Action_at_a_Distance_800x600.jpg