All celestial bodies (as well as the Earth) travel through the space-time of the Universe along with the distortion (contraction) of the adjacent, warped by the bodies themselves (and belonging to them) time-spatial domains, which we can name “near the surface of the celestial bodies”. The intensity of the gravitational field “near the surface of the celestial body” remains practically the same during the travel of the celestial body through the space, because the gravitational field intensity is determined (dominated) by the mass of the celestial body. The characteristics of any electromagnetic radiation (wavelength, frequency, speed of electromagnetic radiation in a vacuum) depend on the intensity of the gravitational field (depend on the density of the medium) through which it propagates. The speed of electromagnetic radiation (the speed of light) in vacuum in any particular local time-spatial region, corresponds to the intensity of the gravitational field in this time-spatial region. Therefore, during the travel of the celestial body through the distorted by gravity space, the constant intensity of the gravitational field “near the surface of the celestial body” determines the constant “speed of light in vacuum” there.
Therefore, that is the reason why there is no variation in “the speed of light in vacuum” when the Earth moves in its orbit around the Sun and together with the Solar System in the Galaxy.
That is why experiments carried out “near the surface of the Earth” cannot detect any change in the “speed of light in vacuum“ as the Earth travels “through the ether,” which turns out to be the “empty space” itself.
One might say that the speed of light in vacuum is the same for the whole Universe – that it is a fundamental constant. However, it is a big delusion, because actually the speed of light in “empty space” is different in regions with different intensity of the gravitational field. As was mentioned, the “Shapiro time delay effect” and “effect of anomalies in the accelerations of the space-probes “Pioneer 10”, “Pioneer 11”, “Galileo”, and “Ulysses”, are proof of this reality.
Furthermore, using a laser technique, various experiments can be made on board an orbital station, (where the gravity is weaker) – to prove the change (the increase) of the wavelength and frequency of given electromagnetic radiation… and this is actually the proof that aboard the orbital station, the speed of light in vacuum is higher!
On the basis of the “Model of the Physical Reality in the Universe”, a “Thesis about the Behavior of the Electromagnetic Radiation in Gravitational Field” is proposed in chapter 10 of the book “The Special Theory of Relativity – the Biggest Blunder in Physics of the 20th Century”, which actually rejects the accepted by contemporary physics “postulate of the constancy of the speed of light for all inertial frames of reference” and “the constancy of the speed of light for the entire Universe”.
Dear truth-seeker! You will be interested to read the analysis of Einstein’s paper“On the Influence of Gravitation on the Propagation of Light” (Einstein, 1911) given here: