Retrieving "Coordinate Speed Of Light" from the archives

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1. Speed Of Light

   Linked via "coordinate speed of light"

   Speed in Gravitational Fields
   In General Relativity, the coordinate speed of light, as measured by a distant observer for a light ray passing near a massive body (like a star), appears to slow down, an effect known as gravitational time delay. Although the local speed of light remains $c$ for any observer co-moving with the light beam, the spacetime curvature caused by mass alters the pat…