Journal of Physics G: Nuclear and Particle Physics, ACCEPTED MANUSCRIPT: Light speed variation from GRB 221009A, Jie Zhu and Bo-Qiang Ma https://iopscience.iop.org/article/10.1088/1361-6471/accebb/pdf

"It is postulated in Einstein's relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed, and a series of previous researches on high-energy photon events from gamma-ray bursts (GRBs) and active galactic nuclei (AGNs) suggest a light speed variation v(E)=c(1−E/ELV) with ELV=3.6×1017 GeV...This result suggests a scenario that high-energy photons travel slower than low-energy photons...This remarkable coincidence between the highest energy photon event observed by Fermi-LAT during the prompt phase and the sharp spike in the low energy light curves of brightest gamma ray burst GRB 221009A supports the light speed variation suggested in previous studies." Light speed variation from GRB 221009A, Jie Zhu , Bo-Qiang Ma https://arxiv.org/pdf/2210.11376.pdf

Again:

"It is postulated in Einstein's relativity that the speed of light in vacuum is a constant for all observers."

This is OBVIOUSLY false. Assume that a light source emits equidistant pulses and an observer starts moving towards the source:

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.

Pentcho Valev https://twitter.com/pentcho_valev

The variation of the speed of light is so obvious that sometimes professors ignore Einstein's nonsense and teach the truth:

Professor Sidney Redner https://sites.santafe.edu/~redner/:

"The Doppler effect is the shift in frequency of a wave that occurs when the wave source, or the detector of the wave, is moving. Applications of the Doppler effect range from medical tests using ultrasound to radar detectors and astronomy (with electromagnetic waves)...We will focus on sound waves in describing the Doppler effect, but it works for other waves too...Let's say you, the observer, now move toward the source with velocity Vo. You encounter more waves per unit time than you did before. RELATIVE TO YOU, THE WAVES TRAVEL AT A HIGHER SPEED: V' = V+Vo. The frequency of the waves you detect is higher, and is given by: f' = V'/λ = (V+Vo)/λ." http://physics.bu.edu/~redner/211-sp06/class19/class19_doppler.html

Pentcho Valev https://twitter.com/pentcho_valev

Lee Smolin, The Trouble With Physics, pp. 226-227: "Einstein's special theory of relativity is based on two postulates: One is the relativity of motion, and the second is the constancy and universality of the speed of light. Could the first postulate be true and the other false? If that was not possible, Einstein would not have had to make two postulates. But I don't think many people realized until recently that you could have a consistent theory in which you changed only the second postulate...The new theory is called deformed or doubly special relativity - DSR for short." http://www.amazon.com/Trouble-Physics-String-Theory-Science/dp/0618551050

No. The consistent theory is called Newton's emission theory of light, and it is not new - it is very very old:

Albert Einstein 1909: "A large body of facts shows undeniably that light has certain fundamental properties that are better explained by Newton's emission theory of light than by the oscillation theory. For this reason, I believe that the next phase in the development of theoretical physics will bring us a theory of light that can be considered a fusion of the oscillation and emission theories." https://en.wikisource.org/wiki/Translation:The_Development_of_Our_Views_on_the_Composition_and_Essence_of_Radiation

The emission theory may have had drawbacks, but insofar as the speed of light is concerned, it is correct and consistent. If judged by their speed alone, photons are Newtonian particles. The speed of light varies, both in presence and absence of gravity, just like the speed of ordinary projectiles (e.g. bullets):

"Emission theory, also called Emitter theory or ballistic theory of light, was a competing theory for the special theory of relativity, explaining the results of the Michelson–Morley experiment of 1887...The name most often associated with emission theory is Isaac Newton. In his corpuscular theory Newton visualized light "corpuscles" being thrown off from hot bodies at a nominal speed of c with respect to the emitting object, and obeying the usual laws of Newtonian mechanics, and we then expect light to be moving towards us with a speed that is offset by the speed of the distant emitter (c ± v)." https://en.wikipedia.org/wiki/Emission_theory

"Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a train at rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus automatically account for the null result of the Michelson-Morley experiment without recourse to contracting lengths, local time, or Lorentz transformations. Yet, as we have seen, Einstein resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas, and introduced as his second postulate something that was more or less obvious when thought of in terms of waves in an ether." Banesh Hoffmann, Relativity and Its Roots, p.92 https://www.amazon.com/Relativity-Its-Roots-Banesh-Hoffmann/dp/0486406768

James Hartle, Gravity: An Introduction to Einstein's General Relativity, p. 113: "If we accept the equivalence principle, we must also accept that light falls in a gravitational field with the same acceleration as material bodies." https://www.amazon.com/Gravity-Introduction-Einsteins-General-Relativity/dp/0805386629

"We conclude, therefore, that A BEAM OF LIGHT WILL ACCELERATE IN A GRAVITATIONAL FIELD AS DO OBJECTS WITH REST MASS. For example, near the surface of Earth light will fall with acceleration 9.8 m/s^2." http://web.pdx.edu/~pmoeck/books/Tipler_Llewellyn.pdf

Pentcho Valev https://twitter.com/pentcho_valev

Speed and frequency vary proportionally as light falls in a gravitational field:

University of Illinois at Urbana-Champaign: "Consider a falling object. Its speed increases as it is falling. Hence, if we were to associate a frequency with that object the frequency should increase accordingly as it falls to earth. Because of the equivalence between gravitational and inertial mass, we should observe the same effect for light. So lets shine a light beam from the top of a very tall building. If we can measure the frequency shift as the light beam descends the building, we should be able to discern how gravity affects a falling light beam. This was done by Pound and Rebka in 1960. They shone a light from the top of the Jefferson tower at Harvard and measured the frequency shift. The frequency shift was tiny but in agreement with the theoretical prediction." https://courses.physics.illinois.edu/phys419/sp2011/lectures/Lecture13/L13r.html

Speed and frequency vary proportionally for the moving observer:

"The Doppler effect is the shift in frequency of a wave that occurs when the wave source, or the detector of the wave, is moving. Applications of the Doppler effect range from medical tests using ultrasound to radar detectors and astronomy (with electromagnetic waves)...We will focus on sound waves in describing the Doppler effect, but it works for other waves too...Let's say you, the observer, now move toward the source with velocity Vo. You encounter more waves per unit time than you did before. Relative to you, the waves travel at a higher speed: V' = V+Vo. The frequency of the waves you detect is higher, and is given by: f' = V'/λ = (V+Vo)/λ." http://physics.bu.edu/~redner/211-sp06/class19/class19_doppler.html

But if speed of light and frequency vary proportionally, the wavelength of light remains constant, in accordance with the formula

(frequency) = (speed of light)/(wavelength)

Additional arguments would show that the wavelength of light is ALWAYS constant (depends only on the nature of the emitting substance and is constant otherwise).

"The wavelength of light is constant" will become the fundamental axiom in future, Einstein-free physics (if it's not too late and the death of physics is not irreversible).

Pentcho Valev https://twitter.com/pentcho_valev