You are missing the point of what spacetime is. Think of gravity as the shortest path through spacetime, in other words a field.
And yes the field propagates at the speed of light, but the effects inside the field are instantaneous.
I wrote earlier that if the Sun were to suddenly vanish, Earth wouldn't feel the effects for about 8 minutes. Do you disagree with that?
“You are missing the point of what spacetime is. Think of gravity as the shortest path through spacetime, in other words a field.
And yes the field propagates at the speed of light, but the effects inside the field are instantaneous.”
I think this clears up the confusion very nicely. *Changes* in the field propagate at c whereas the *effects* of the field are instantaneous within the field. The confusion is in confusing the propagation of the field with the effects of the field.
This is looking like a great thread! I’m in a maths tute right now so I’ll catch up with it later tonight.