I've been reading a lot about gravity lately, trying to understand it as best I can. When I think of gravity, I find it easiest to imagine the rubber sheet analogy to explain the spacetime curvature. Gravity is supposed to be caused by the curvature of spacetime. So the thing that I have no insight on is the 'fabric' of spacetime. What is it? It's talked about like it's a physical object in many texts that I've read. "A tear in the fabric of spacetime." You need something to tear or put a hole in, right? A spinning black hole will spin spacetime near the event horizon - spin what? It's also the medium that gravitational waves travel through. This again requires (in my mind) some kind of physical object, ie. sound waves travel through air - air is the physical object. Another puzzling thing I've seen several times is the idea that the spacetime fabric travels faster than c as the universe expands and has done so since the big bang. The fact that it has always been faster than c satisfies the theory that nothing can CROSS the light barrier, but if the spacetime fabric is some sort of physical object, wouldn't it have mass? How can something with mass go faster than c - that would require infinite energy, wouldn't it? Would a (hypothetical) observer who is outside of our spacetime see the universe and everything in it moving faster than c (relative to their stationary position outside of spacetime) with the 'flow' of the spacetime fabric? I'd appreciate any insight any of you could provide me on this. Any links would be very helpful as well.