A breathtaking sensation in 2014 (nowadays completely forgotten):

"A challenge has been thrown down to the consistency of the speed of light, based on an anomaly from the most closely observed supernovae of all time. In 1987 astronomers witnessed the only supernova in 400 years close enough to Earth to see with the naked eye. The first hint of the event came not from telescopes, but neutrino detectors. Neutrinos and photons were assumed to have crossed space between the Large Magellanic Cloud and us at the speed of light. However, light does not always travel at 3x10^8 m/s. Just as glass or water will slow light down, the dense core of a supernova is expected to impede photons so that neutrinos will reach us first. Models of supernovae suggest the delay should be about three hours. However, rather than witnessing a single burst of neutrinos three hours before the first light was observed, detectors picked up two bursts, one 7.7 hours earlier, and the other 4.7 hours. Some models of supernovae predict two collapses, and thus two rounds of neutrinos, but the timing is puzzling since it is the first round that should beat the light by three hours. Professor James Franson of the University of Maryland, Baltimore, believes that these observations require a rewrite of light's behavior. He claims that quantum mechanical effects slow light down under certain circumstances. The effect is very, very small, but over a distance of 163,000 light years could account for the discrepancy in observations." https://www.iflscience.com/could-we-be-wrong-about-speed-light-24917

Franson's theory of how light slows down might be wrong of course, but the observational evidence remains strong: compared with neutrinos, light arrived too late. Either neutrinos travel faster than light, or the speed of light gradually slows down as light travels in a vacuum.

The former possibility was a nightmare that the Einstein Cult successfully suppressed in 2012, with the help of a loose cable. The latter possibility is a nightmare as well - it explains the Hubble redshift and accordingly disproves the Big Bang and the expansion of the universe.

Unfortunately for the Einstein Cult, this second nightmare is getting more and more haunting. Even if the James Webb Telescope didn't exist, the expansion theory would still be doomed - it is too preposterous.

Pentcho Valev https://twitter.com/pentcho_valev

"Some physicists, however, suggest that there might be one other cosmic factor that could influence the speed of light: quantum vacuum fluctuation. This theory holds that so-called empty spaces in the Universe aren't actually empty - they're teeming with particles that are just constantly changing from existent to non-existent states. Quantum fluctuations, therefore, could slow down the speed of light." https://www.sciencealert.com/how-much-do-we-really-know-about-the-speed-of-light

Then the so called cosmological (Hubble) redshift just shows that frequency and speed of light vary proportionally, in accordance with the formula

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

But can the vacuum slow down the speed of light? Yes it can:

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

Pentcho Valev https://twitter.com/pentcho_valev