Fistly, apologies for my earlier version of this writeup, if you didn't see it, well and good.

Any time I refer to c let us take it that it is in vacuo.

Ok the whole rod thing, what actually happens when you move a rod is that you send a compression wave down the rod. We are used to having rods which seem to be rigid but that is because in the domain of use the speed at which it is pushed is usually a lot less than c. If you have a very long rod moving one end is sending the information along the rod as a compression wave. This wave can't move faster than c. A wave in a rod of 4.3 light years in length will probably dissipate into heating parts of the rod and the distant end will probably not move at all. You can't create a perfectly rigid rod, if from nothing else the uncertainty principle so enough with the rods already.

Quantum entanglement does indeed exist. It is known as the Einstein Podolsky Rosen paradox (or EPR for short). It is not a paradox as no information can be sent using this method. This was explained by Bell with Bell's theorm Allthough you may measure an entangled particle and instantaneously know what state it's partner is in this is not a transmission of information. Let us say that I want you to feed my goldfish if you measure spin up and I spin down. The information is really the code of action to take as a function of the measurement. That code has to be prearranged. It is the passing of the code which is the passing of the information and that cannot be done using the entangled particles.

About the Cesium gas experiment, Tiefling's comment says it all.

Ok I have just had a look at the "The Speed of Gravity" stuff. It looks like pseudo-scientific garbage to me. It calims that gravity acts instantaneosly because of the way n which we treat the time retarded potentials (The Lenerd-Wicheard Potentialls. If you learn a little about these fellows you discover that rediation is due to the scceleration of chargesand is the observational effect that this paper claims is absent from gravitatijonal experiments. To claim that binary pulsars orbits decay due to non radial photon pressure is ridiculous. They decay due to the emission of gravitational radiation, radiatioin which is travelling at c I might add. Hmmmm.

Pseudomancer you make a very nice point,
If you don't do physics then perhaps you should. The argument is not correct, at least in the framework of particle physics. In particle physics the particles which transmit, or mediate a force do not have the smae properties as the particles between whoom they communicate.
The best example is electromagnetisim. The electromagnetic force acts between charged particles. If we took your argument and applied it to charged partices we would invoke two mediating particles, one the communicate "attraction" and the other that communicates "repulsion". We woul suppose that this mediating particle has some property of either "attractivness" or "repulsiveness". In fact the particle that carries the electromagnetic force is the photon. It has no charge. The tecnical name for such an object is an intermediating vector boson. (more intersting than proton or electron eh!). I can't tell you why it does what it does, It comes out of the way we describe the electromagnetic field. The process is analagous to when you quantize the simple harmonic oscillator in a second year quantum mechanics course. If i knew my field theory better i might do a better job at explaining, but i am a simple astrophysicist.

My point is that the particle that mediates the graviational field is proabably massless and applying notions of momentum to it is not a valid thing to do. The particle is a manifestation of a field and the test particles dynmics are determined by the shape of the field they find themselves in. (often physics seems like a magical place).

I know that this has not been a very clear explanation, I apologise. I will endeavour to do better in the future. The most elegant description of gravity is through geometry (Einsteins general theory). All of the decriptions, geometric, field, particle, wave, codify the same physcis and are physically equivalent. When thinking about it, it's nice to have many approaches to the problem.

Dear no comply
I can see how I might have pissed you off earlier and I apologise. You did however make a false statement, To date there is no evidence for superluminal communication.

You are right, things might change. The most promising idea on the scence is M-theory. An implication of M-theory is that the global topology of the universe might have extra-dimensions which are foliated onto one another. In this scenario gravity propgates through this higher-dimensional bulk,, while the other forces are constrained the the lower dimensional sub-manifold, (called a brane after membrane). Gravity can effect objects that are not within each others causal light cones. This theory remains just that. Currently experiments are beginning to test it. I may work on some aspect of this in the current year, If I do I will let you know.