Pentcho Valev wrote:

Doppler effect - when an observer moves toward a stationary source
https://www.youtube.com/watch?v=bg7O4rtlwEE

I'm well aware of what Doppler effect is.

"Now let's see what this does to the frequency of the light. We know that
even without special relativity, observers moving at different velocities
measure different frequencies. (This is the reason the pitch of an
ambulance changes as it passes you it doesn't change if you're on the
ambulance). This is called the Doppler shift, and for small relative
velocity v it is easy to show that the frequency shifts from f to
f(1+v/c)... There are relativistic corrections, but these are negligible
here." http://galileo.phys.virginia.edu/~pf7a/modd35.pdf

The frequency shifts from f to f' = f(1+v/c) = (c+v)/d, where d is the
distance between the pulses and f is the frequency measured by the
stationary observer. Accordingly, the speed of the pulses as measured by
the moving observer is

c'= df' = c + v

Negligible is NOT the same as non-existent. At low speeds,
c'= df' = c + v is an acceptable approximation. Not at 0.2 c.

in violation of Einstein's relativity.

Which, as I pointed out, you ignore accounting for relativity.
Enter time dilation and Lorentz contraction and c can be constant.

The conclusion remains essentially the same even if the relative velocity
v is great and the relativistic corrections are not negligible.

Your calculations are purely Newtionian and thus irrelevant at
relativistic speeds since you don't do the relativistic corrections.
But you don't acknowledge their consequenses, so why bother?


--
I recommend Macs to my friends, and Windows machines
to those whom I don't mind billing by the hour