That's a good point -- to avoid confusing people, I should mention that my explanations above are sort of the mirror image of how most physicists would think ab

That's a good point -- to avoid confusing people, I should mention that my explanations above are sort of the mirror image of how most physicists would think about this situation. I was trying to be careful to say "appears to be" instead of "is" to leave this interpretive door open :) As you say, the most common interpretation is that time itself slows down as you enter a gravity well, leaving all the physical constants the same (since their locally measured values will appear the same to you). But if you look at things from an imaginary "absolute" viewpoint outside of spacetime, you could think of spacetime itself as a sort of fluid that's denser in regions of high gravity. Light travels more slowly in this denser fluid, and since epsilon zero is inversely proportional to the square of the speed of light, you could interpret it as being larger where gravity is higher. I guess you can tell that fluid dynamics was always easier for me than differential geometry -- whenever I see a system of nonlinear partial differential equations (like general relativity), it's just easier for me to think of them this way.