Regardless of how it’s made, the light has to pass through things - the interstellar medium is not a perfect vacuum. Especially not across one hundred million light-years. The speed of light, as in actual light, goes down in any gas or clear solid. The speed of light, as in C, does not. I think what we just learned is that gravity waves don’t care about stray particles.
If the delay happened the other way around it would be mindboggling.
Regardless of how it’s made, the light has to pass through things - the interstellar medium is not a perfect vacuum. Especially not across one hundred million light-years. The speed of light, as in actual light, goes down in any gas or clear solid. The speed of light, as in C, does not. I think what we just learned is that gravity waves don’t care about stray particles.
If the delay happened the other way around it would be mindboggling.