According to this article
http://news.bbc.co.uk/1/hi/sci/tech/4923396.stm
scientists expect soon to be able to see the first evidence of gravitational waves.
The article states that these waves would travel at the speed of light. Since light waves and the speed of light are predicted as a solution to Maxwell’s equations involving electricity and magnetism, and not gravity, why do we expect gravity waves to travel at the same speed? Why couldn’t the speed of gravity be some other value?
IIRC, if gravity isn’t the same speed as light, then we’ve got a serious problem on our hands. I do not, however, have the ability to explain any of this.
The speed of light, c, isn’t really anything that is intrinsic to light or electromagnetic waves - it should perhaps more properly be called “the absolute speed limit of the universe”. In general relativity, gravity is basically identified with curving of spacetime, which creates gravitational waves that propagate at c. In most quantum gravity theories, gravity is believed to be transmitted by a massless particles known as the graviton (which will also behave as a wave, depending on how you look at it), although this particle hasn’t yet been observed. Massless particles always travel at the speed c, and as gravitons are assumed to be massless, like photons, they will always travel at c.
This is why I wish c was taught as “Einstein’s constant” rather than the “speed of light in a vacuum”. Yes, c is the speed of electromagnetic propagation as predicted by Maxwell’s equations, but the constant isn’t fundamentally linked to electromagnetism any more strongly than it is to gravitation. Remember, E = m c[sup]2[/sup]? No electromagnetism there.
AIUI, the “speed of light” (“c”) is the speed at which disturbances in / on the 4-d surface of the universe can propagate. I.e. it is the speed at which ripples in the electromagnetic fields (light) can move, and it is the speed at which ripples in the spatial domains (gravity) can move.
Mind you, I have never been a formal “advanced” physics student. The above may or may not have anything to do with reality. 
I seem to recall a Staff Report on this very topic:
Wow, I’d forgotten I’d written that one. Thanks.
Pleonast, I agree 100% with you on the label attached to c. It’s a Fundamental Constant of the Universe, and it’s just incidental that light is (or seems to be) one of the things that travels at that speed. One could say that c is a combination of the electrical and magnetic constants (this is how it comes out of Maxwell’s equations), but one could more elegantly say that the magnetic constant is a combination of the electric constant and c, and c is in Maxwell’s equations because it’s in everything.