There is absolute truth in science. Of the following two statements one is absolutely true, the other is false:

(A) The speed of light, as measured by the observer (receiver), varies with the speed of the emitter.

(B) The speed of light, as measured by the observer (receiver), does not vary with the speed of the emitter.

Einstein hesitated between (A), a tenet of Newton's theory, and (B), a tenet of the ether theory, and finally chose (B) as his 1905 second postulate:

Einstein: "I introduced the principle of the constancy of the velocity of light, which I borrowed from H. A. Lorentz's theory of the stationary luminiferous ether." https://en.wikipedia.org/wiki/Lorentz_ether_theory

The true statement is (A):

https://qph.cf2.quoracdn.net/main-qimg-f10f1c25528a4e5edc9bae200640f31c-pjlq

The statement (B) proved extremely malignant. Its metastases killed the whole branch of science called "physics", as the following texts imply:

Bryan Wallace: "Einstein's special relativity theory with his second postulate that the speed of light in space is constant is the linchpin that holds the whole range of modern physics theories together. Shatter this postulate, and modern physics becomes
an elaborate farce!...The speed of light is c+v." http://www.kritik-relativitaetstheorie.de/2013/02/the-farce-of-physics-2/ Note: Bryan Wallace wrote "The Farce of Physics" on his deathbed so one should not judge him too severely for (numerous)
imperfections.

Joao Magueijo, Niayesh Afshordi: "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

"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

Pentcho Valev https://twitter.com/pentcho_valev

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

(A) The motion of the observer does not change the wavelength of the incoming light, so frequency and speed of light vary proportionally for the observer, in violation of Einstein's relativity.

(B) The motion of the observer does change the wavelength of the incoming light so that the speed of light can gloriously remain constant for the moving observer.

The true statement, of course, is (A). This is obvious even in Einstein's schizophrenic world:

"The wavelength is staying the same in this case." https://www.youtube.com/watch?v=MHepfIIsKcE

"Thus, the moving observer sees a wave possessing the same wavelength...but a different frequency...to that seen by the stationary observer." http://farside.ph.utexas.edu/teaching/315/Waveshtml/node41.html

"Vo is the velocity of an observer moving towards the source. This velocity is independent of the motion of the source. Hence, the velocity of waves relative to the observer is c + Vo...The motion of an observer does not alter the wavelength. The
increase in frequency is a result of the observer encountering more wavelengths in a given time." http://a-levelphysicstutor.com/wav-doppler.php

The statement (B) is too preposterous, even by the standards of the Einstein Cult, so Einsteinians do not teach it explicitly. Sometimes high priests in the Einstein Cult do teach it but, in order to confuse the public and paralyse any criticism, they
say that that the observer "sees" the wavelength changed (the public should desperately commute between "there is no real change" and "there IS real change"):

Kip Thorne: "If you move toward the [light] source, you see the wavelength shortened but you don't see the speed changed." https://youtu.be/mvdlN4H4T54?t=296

John Norton: "Here's a light wave and an observer. If the observer were to hurry towards the source of the light, the observer would now pass wavecrests more frequently than the resting observer. That would mean that moving observer would find the
frequency of the light to have increased (and correspondingly for the wavelength - the distance between crests - to have decreased)." http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/big_bang_observed/index.html

Pentcho Valev https://twitter.com/pentcho_valev

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You seem to be right about the Doppler Effect, I never saw that before. I asked ChatGPT to clarify the situation.

Question:
A light source at rest and observer at rest are located on a straight line in space, 1 light year apart. The source emits light at frequency of blue light towards the observer, which the observer then receives as blue light with no change in frequency,
one year later. The source then starts moving towards the observer with velocity 1000 metres per second, how long until the observer sees the change in frequency?

Answer:
If the light source and observer are initially at rest, then the observer will detect the light from the source as blue light with no change in frequency, one year after it was emitted.

Once the source starts moving towards the observer with a velocity of 1000 meters per second, the observer will detect a change in frequency due to the Doppler effect. The amount of change in frequency can be calculated using the Doppler effect formula:

Δf/f = v/c * √((c+v)/(c-v))

where Δf is the change in frequency, f is the original frequency of the light (in this case, the frequency of blue light), v is the relative velocity between the source and observer (in this case, 1000 meters per second), and c is the speed of light.

Plugging in the values, we get:

Δf/f = (1000 m/s) / (3 x 10^8 m/s) * √((3 x 10^8 m/s + 1000 m/s) / (3 x 10^8 m/s - 1000 m/s)) ≈ 3.33 x 10^-6

This means that the frequency of the light will increase by a factor of approximately 3.33 x 10^-6. The time it takes for the observer to detect this change in frequency can be calculated using the same formula, but solving for time:

time = distance / (v/c * √((c+v)/(c-v))) ≈ 2.84 years

Therefore, it will take approximately 2.84 years after the source starts moving towards the observer for the observer to detect the change in frequency of the light emitted by the source.

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