John,
I agree with Lawrence that the speed of light is measured locally. In fact, I believe that the speed of light, permitivity and permeability exist as characteristics of existent wave-functions. This way, a quantum physicist might calculate a wave-function for a quantum system, but some invisible phenomenon of nature, at the quantum level, actually behaves like the calculated wave-function. That same invisible phenomenon might be small, but it interacts with others like itself in the quantum vacuum. Over the distance of a light year, I think there are invisible wave-functions that pop into existence (and then vanish); such wave-function phenomena should be highly reactive and responsive to the changing conditions of the world (like opening and closing of slits). They would be conductors of energy (like EM waves), but there existence is ghostly. They are there to facilitate the laws of physics.
As horrific as this idea sounds to atheists, it's almost as if some creator of the universe, God, decided to make the laws of physics operate in a certain way, and then used a spirit like thing (the wave-function) to enforce the existence of the laws of physics. Beyond that, there is no natural reason why the physics constants (h, c) would be what they are. I'm not so sure that G isn't an emergent quantity based on the "aetherial material" used to create space-time.
Now that I've put forward a magical (God did it) explanation, I assume someone will shoot back with a logical/natural reason why singularities just come out of nothingness.