I'd vowed that I wouldn't hit this tarbaby yet again. But here I go.

Among the junk science being bandied about here is the following
supposition:

Suppose you have beams from two identical coherent lasers which, by a
system of (presumably partially reflective and partially transmissive)
mirrors, are made to shine in exactly the same direction from the same
point (which I'll call the "summing point"). Further, suppose that the
paths from the two lasers to this summing point differ by an odd number
of half wavelengths. So beyond the summing point, where the laser beams
exactly overlie each other, there is no beam because the two exactly
cancel. Or, in other words, the sum of the two superposed fields is
zero. The recurring argument is that because each laser is producing
energy and yet there is no net field and therefore no energy in the
summed beams, something strange has happened at the summing point (or
"virtual short circuit"), and creative explanations are necessary to
account for the "missing energy". One such proposed explanation is that
the mere meeting of the two beams is the cause of some kind of a
reflection of energy, and that each wave somehow detects and interacts
with the other.

Well, here's what I think. I think that no one will be able to draw a
diagram of such a summing system which doesn't also produce, due solely
to the reflection and transmission of the mirrors, a beam or beams
containing exactly the amount of energy "missing" from the summed beam.
No interaction(*) of the two beams at or beyond the summing point is
necessary to account for the "missing" energy -- you'll find it all at
other places in the system. Just as you do in a phased antenna array,
where the regions of cancelled field are always accompanied by
complementary regions of reinforced field. Somewhere, in some bounce
from a mirror or pass through it, the beams will end up reinforcing each
other is some other direction. My challenge is this: Sketch a system
which will produce this summation of out-of-phase beams, showing the
reflectivity and transmissivity of each mirror, and showing the beams
and their phases going in all directions from the interactions from each
mirror. Then show that simple interaction of the beams with the mirrors
is insufficient to account for the final distribution of energy.

Next, do the same for a transmission line. Show how two coherent
traveling waves can be produced which will propagate together in the
same direction but out of phase with each other, resulting in a net zero
field at all points beyond some summing point. But also calculate the
field from waves reflected at the summing point and elsewhere in the
system due to simple impedance changes. Show that this simple analysis,
assuming no interaction between the traveling waves, is insufficient to
account for all the energy. A single case will do.

Until someone is able to do this, I'll stand firm with the unanimous
findings of countless mathematical and practical analyses which show
superposition of and no interaction between waves or fields in a linear
medium.

(*) By "interaction" I mean that one beam or wave has an effect on the
other, altering it in some way -- for example, causing it to change
amplitude, phase, orientation, or direction. I'm not including
superposition, that is the fact that the net field of the two waves is
the sum of the two, in the meaning of "interaction".

Roy Lewallen, W7EL