Gravity propagates at the speed of light.
Yes general relativity says so. But it's confusing just like a spooky action at a distance.
In Einstein's theory of general relativity gravitational interaction is mediated by deformation of space-time geometry. Matter warps the geometry of space-time and these effects are, as with electric and magnetic fields, propagated at the speed of light. In Einstein's theory of motion, matter acts upon space-time geometry, deforming it, and space-time geometry acts upon matter.
Actually gravity
cheats. It acts immediately because of the curvature of space-time. And even tho its speed is finite (c) it acts
faster than light. In quantum mechanics word "faster" means using a shorter route, not having a faster velocity. Cosmic laziness, Geodesic Lines, Non-Euclidean Geometry and all that jazz .... you know.
The speed of gravitational waves in the general theory of relativity is equal to the speed of light in vacuum, c. Within the theory of special relativity, the constant c is not exclusively about light; instead it is the highest possible speed for any physical interaction in nature. Formally, c is a conversion factor for changing the unit of time to the unit of space. This makes it the only speed which does not depend either on the motion of an observer or a source of light and/or gravity. Thus, the speed of "light" is also the speed of gravitational waves and any massless particle. Such particles include the gluon (carrier of the strong force), the photons that light waves consist of, and the theoretical gravitons which make up the associated field particles of gravity (a theory of the graviton requires a theory of quantum gravity, however).
To get the answer we need to know all the theories: General Relativity, Special Relativity, Quantum Mechanics, Quantum Gravity Theory, Theory of Everything, M-Theory, Expanding Space-Time Theory, Supersymmetry, String theory (D-Branes), Unified field theory. Unfortunately the current status of all these theories is incomplete.
for our universe it would be:
x1^2+x2^2+...+xn^2 = r^2, where n is the number of dimensions that the universe really has and r is a constant yet to be discovered.
Now to complicate things even more, I don't think the universe would be an sphere (remember what I really mean by sphere), but some kind of elipsoid. Same concept, various constants.
Ellipsoid has
different r along each axis (for 3D it's a, b, c when a=b=c it's sphere), in that case for every dimension there has to be a separate r.
String theory and supersymmetry theory say that our universe is 10D. After the Big Bang 3 dimensions grew bigger but other extra 7 dimensions remained tiny, hence undetectable.
I digress but here's an interesting snip:
Gravity can be properly localized to a sub-spacetime. Gravity acting in the hidden dimensions affects other non-gravitational forces such as electromagnetism. In fact, Kaluza's early work demonstrated that general relativity in five dimensions actually predicts the existence of electromagnetism. However, because of the nature of Calabi–Yau manifolds, no new forces appear from the small dimensions, but their shape has a profound effect on how the forces between the strings appear in our four-dimensional universe. In principle, therefore, it is possible to deduce the nature of those extra dimensions by requiring consistency with the standard model, but this is not yet a practical possibility. It is also possible to extract information regarding the hidden dimensions by precision tests of gravity, but so far these have only put upper limitations on the size of such hidden dimensions.
In a nutshell: we are stuck in 3D space (there are other dimensions tho), but gravity can "leak" into other dimensions, and even from there it can affect our world. And our world with all its interactions also depends on the shape of those tiny dimensions. Some scientists think that extra dimensions got something to do with dark matter and energy. And maybe it's even possible to create a "shortcut" (wormholes) through the extra dimensions to our world, in that case we could travel with infinite speed and immediatley appear in any desirable spatial and maybe even time destination.
Wow my post is huge