Steve, Eckard.
Thank you Steve for your support. Eckard; You claim I "uttered in the last contest: actually superluminal motion." But you disregard what I actually write and said, and continue to do so!
My first axiom in bold type, last year, was; "EM wave speed is controlled by n within a dielectric medium" i.e. c/n with c explained as 'local' c. I protest that you have not understood, and explain, but you just dismiss my explanations and assume you know better a priori.
The secret to understanding lies in the axiom that there are TWO valid cases for all 'speeds', as clarified in my essay. This is 'real' propagation speed, and 'apparent' speed, which is 'observer speed' (or 'frame') dependant.
I'll try yet another analogy, and ask you questions;
You are an observer at rest on a coach travelling at 100kph.
In the opposite direction a coach B approaches also doing 100kph.
A man in coach B is running towards the front at him maximum speed 15kph
You film the coach passing, play it back, and find the man running at 215kph!
Question. Is the man really running at 15kph, 115kph, or 215kph?
Hopefully considering this question will clarify the reality that there is more than one answer subject to observers state of motion and local background.
DFM Answer;
The runner is doing REAL 15kpk in his local background space.
Coach B is doing REAL speed 100kph in IT'S local background space (same as A's).
You will observe APPARENT 215kph from at rest in YOUR local background space.
And there are 3 speeds of sound, all the same, but, like a bullet speed, would be 'apparently' different if observable. One for each coach and one for the road!
The 'apparent' speed you find for the runner can vary infinitely subject to your coach speed (i.e. 'subject to your inertial frame').
Once you start to be comfortable with that very simple but 'different' way of looking at speed, we can finish the ontology be considering the light that moves from one local space to the next.
Let me know how you get on with that one, or, if you still think it's wrong, please point out where. It should suddenly become very simple the moment it's understood.
Peter