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A comment on Milky Way’s Black Hole Just Flared, Growing 75 Times as Bright for a Few Hours. Parent comment

Re:Milky Way’s Black Hole Just Flared, Growing 75 Times as B... by lmilcin on Wednesday August 14, 2019 @08:07AM (#20694614)
The correct way to say it is that the speed of light is the speed of causality only in vacuum. In any medium the speed of light is slower but the causality or other fields (for example gravity field) that are not impeded by matter can and will propagate faster than the speed of light.
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Re:Milky Way’s Black Hole Just Flared, Growing 75 Times as B... by blueprint on Wednesday August 14, 2019 @12:43PM (#20697289)
Where does there exist a vacuum?

How does a particle or its environment measure the particle's traversal of a truly empty space?

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