some people just don't get it
Changes in Gravitational Fields propagate faster than light
When the Moon lines up directly between the Earth and Sun, there is a maximum change in the gravitational field as measured at the Earth's surface. The change is recordable on instruments. The maximum change recorded occurs about forty seconds after the visible alignment of the three celestial bodies because the actual position of the Sun is ahead of its apparent position (note: the moon is also moving).
This is a measurable and well known fact. The Sun really is ahead of where it appears to be visually (relative to the background of stars against which it appears to move because the Earth is orbiting it). The information from the sun is eight minutes retarded. Hence, the "real" gravitational line-up occurs after the visual line-up. So, how can one suppose that the gravitational field changes at the same speed as the electro-magnetic interaction? If it did, the visual in-line point would coincide with the gravitational in-line point. It does not.
Nor can the gravitational field "anticipate" where other bodies will be at some future date. Matter just responds to "things as they are" ... right now.
A demonstration will show this must be the case.
The above rollover image shows an observed mass that has within it an explosive charge that on the observer's command propels two large pieces of the mass away in the direction shown. The result must be a weakening of the measured gravitational force from the initial mass on the observer mass.
What will happen is that the appearance of the explosion will occur ... after ... a change in the gravitational force is measured. This change cannot, in principle, be anticipated because it is a voluntary detonation having no connection with the physical system being observed ...
... unless one wishes to resort to some "mystical" hypothesis to explain away a speed of propagation which vastly exceeds the speed of light.
By the above method one might communicate across the galaxy almost instantaneously ... if ... there was a way found to enhance this tremendously weak signal and differentiate it from all the background noise. (Though I doubt that it's technically possible.)