The texts below imply that, if the speed of light is VARIABLE (it is!), modern physics, predicated on Einstein's 1905 constant-speed-of-light falsehood, is long dead (exists in a zombie state):
"He opened by explaining how Einstein's theory of relativity is the foundation of every other theory in modern physics and that the assumption that the speed of light is constant is the foundation of that theory. Thus a constant speed of light is embedded in all of modern physics and to propose a varying speed of light (VSL) is worse than swearing! It is like proposing a language without vowels."
http://www.thegreatdebate.org.uk/VSLRevPrnt.html
"If there's one thing every schoolboy knows about Einstein and his theory of relativity, it is that the speed of light in vacuum is constant. No matter what the circumstances, light in vacuum travels at the same speed...The speed of light is the very keystone of physics, the seemingly sure foundation upon which every modern cosmological theory is built, the yardstick by which everything in the universe is measured...The constancy of the speed of light has been woven into the very fabric of physics, into the way physics equations are written, even into the notation used. Nowadays, to "vary" the speed of light is not even a swear word: It is simply not present in the vocabulary of physics."
https://www.amazon.com/Faster-Than-Speed-Light-Speculation/dp/0738205257
"The whole of physics is predicated on the constancy of the speed of light...So we had to find ways to change the speed of light without wrecking the whole thing too much."
https://motherboard.vice.com/en_us/article/8q87gk/light-speed-slowed
Assume that a light source emits equidistant pulses and an observer starts moving towards the source:
View: https://youtube.com/watch?v=bg7O4rtlwEE
The speed of the light pulses relative to the stationary observer is
c = df
where d is the distance between subsequent pulses and f is the frequency at the stationary observer. The speed of the pulses relative to the moving observer is
c'= df' > c
"
where f' > f is the frequency at the moving observer.
That is, the speed of light relative to the observer VARIES with the speed of the observer.