My question is simple. If the equations which govern General Relativity, the deceptively simple looking field equations, can be reduced to Newtonian dynamics where the speed of gravitation is less than the speed of light, and they work because they are transformations of the accepted equations, do we say that the speed of gravity is at or near that of light?
I understand that fundamentally the field equations are intended to have the speed of gravity equal to that of light or near it. Yet there is no definitive speed of gravity which has been proven as rigorously as the speed of light has been studied. I’m only aware of one study which looked at a quasar in line to be lensed by Jupiter and it gave a reading between close to and almost but not quite the speed of light, but that’s still a window rather than a definite quantity.
At the end of the day it is simple to process gravity as a force in mathematical terms, yet famously the exact constant of that force remains elusive. It is known to be approximately the inverse square of the distance between two objects as a vector equation, yet how much the exact force of gravity is pushing or pulling an object isn’t known.
Naturally this is solved by General Relativity which would say gravity is doing neither pushing or pulling, an object hurtling through space has it’s own inertia to do that already. There the speed of gravity is tantamount to instantaneous and would be more about size and speed of the relative objects in a curved spacetime rather than a question of how long does it take to feel the effect of gravity from one point to another. That isn’t my question though. Since the gravitational constant is so hard to pin down does that imply the force is dynamic, that it is better described by an kind of evolutionary value metric beyond the obvious mass/distance relationship?
This isn’t some kind of end around argument for MoND, rather an open question of interpretation. If Einstein can be reduced to Newton, is it not at least possible that gravity is a force that propagates at a variable sub light frequency rather than a fixed frame rate? It certainly seems like the equations already exist which could transform either way.
This derivative variability in the velocity of gravity wouldn’t solve the dark matter problem since all we are talking about are Newtonian equations derived from the field equations giving identical results. This wouldn’t be changing anything, it would just be looking at the problem of describing gravity from another angle. If gravity was a force that wouldn’t invalidate the observation of spatial curvature or gravitational lenses, but neither do those observations mean gravity itself isn’t a force, they simply represent a physical phenomenon no one had noticed before.
So yes, I would be curious to hear why the speed of gravity must be the speed of light, had it been proven empirically through experimentation or is there some subtle aspect in the math which holds the clue? If we can construct equations that can describe the solar system that are literally equivalent to those of General Relativity and they show gravity at less the C, how do we then prove the speed of gravity is moving at C? Doesn’t that violate our equations we derived from the very equations that assume that it does?
So yeah, I guess I’m curious…what exactly is the speed of gravity?