"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.cfa.harvard.edu/news/2017-30

Optical signals (gamma rays) are gravitationally deflected or blocked by cosmic matter. In contrast, gravitational waves "don't care about matter in any way":

"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/startsw...instein-wrong/

Then how can optical signals and gravitational waves arrive "from the same location of the sky", almost simultaneously?

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Pentcho Valev