"But the greatest confirmation that the speed of gravity equals the speed of light comes from the 2017 observation of a kilonova: the inspiral and merger of two neutron stars. A spectacular example of multi-messenger astronomy, a gravitational wave signal arrived first, recorded in both the LIGO and Virgo detectors. Then, 1.7 seconds later, the first electromagnetic (light) signal arrived: the high-energy gamma rays from the explosive cataclysm....Of course, we think that these two speeds are exactly identical. The speed of gravity should equal the speed of light so long as both gravitational waves and photons have no rest mass associated with them. The 1.7 second delay is very likely explained by the fact that gravitational waves pass through matter unperturbed, while light interacts electromagnetically, potentially slowing it down as it passes through the medium of space by just the smallest amount." https://www.forbes.com/sites/startswithabang/2019/07/06/ask-ethan-why-do-gravitational-waves-travel-exactly-at-the-speed-of-light/

Initially the Einsteinian meant this (perhaps):

"Gravitational waves pass through matter unperturbed, while light IS BLOCKED OR DEFLECTED BY MATTER."

Then he saw the danger and replaced "IS BLOCKED OR DEFLECTED BY MATTER" with the following word salad:

"Gravitational waves pass through matter unperturbed, while light interacts electromagnetically, potentially slowing it down as it passes through the medium of space by just the smallest amount."

See more here: https://twitter.com/pentcho_valev

Pentcho Valev

Photons are gravitationally deflected or blocked by cosmic matter. Gravitational waves are not, Einsteinians teach:

"Unlike light, gravitational waves don’t care about matter in any way. You can pass gravitational waves through the vacuum of space, through a lens, prism, or other material, or even through the solid Earth itself, and they will continue to propagate at the speed of gravity." https://www.forbes.com/sites/startswithabang/2020/12/24/how-gravitational-waves-might-wind-up-proving-einstein-wrong/

But LIGO fakers carelessly announced near-simultaneous arrival of gravitational waves and photons, "from the same location of the sky", which means that gravitational waves and photons travel hand in hand (same gravitationally deflected path, same speed, same passage through matter):

"On 8:41 am EDT August 17, 2017, LIGO detected a new gravitational wave source, dubbed GW170817 to mark its discovery date. Just two seconds later NASA's Fermi satellite detected a weak pulse of gamma rays from the same location of the sky." https://www.si.edu/newsdesk/releases/astronomers-see-light-show-associated-gravitational-waves

So Einsteinians have to camouflage LIGO fakers' gaffe - now they desperately prove that gravitational waves and photons undergo the same gravitational deflection:

"We establish at high confidence (significantly greater than 5σ) that the gravitational waves of GW 170817 underwent gravitational deflection to arrive within 1.7 seconds of the photons." https://arxiv.org/pdf/2001.01710..pdf

LIGO fakers also realized that the hand-in-hand travel of gravitational waves and photons is an Achilles heel, and informed the gullible world that GW 170817 was the first and last time an electromagnetic counterpart was detected. No electromagnetic counterparts anymore:

"The first such observation, which took place in August of 2017, made history for being the first time that both gravitational waves and light were detected from the same cosmic event. The April 25 merger, by contrast, did not result in any light being detected." https://phys.org/news/2020-01-ligo-virgo-gravitational-network-neutron-star.html

"You might wonder why we haven’t seen knockout detections of electromagnetic radiation accompanying gravitational waves since the August 2017 discovery. Unfortunately, we probably just got lucky that time. “It was nearby, well-localized in space, and had everything going for it,” Berger said." https://gizmodo.com/mystery-deepens-around-newly-detected-ripples-in-space-1837581646

"The first binary neutron star to be discovered in GWs, GW170817, came with a bright electromagnetic counterpart...Unfortunately most binary mergers, and in particular binary black hole (BBH) mergers, do not have associated electromagnetic counterparts." https://www.ligo.org/science/Publication-O3Cosmology/

More here: https://twitter.com/pentcho_valev

Pentcho Valev