Nice answer JP. As for the question of gravitons, if they exist then gravity would be a force, is that not so?

Pete can go into it in more detail, but gravity

*is certainly* a force. Our best model for gravity just works differently (space-time geometry) than our best models for other forces (particles). I think most physicists assume that an improved model of gravity will contain particles, but who knows? Maybe the particle model will be superseded.

Part of this comes back to the point I harp on a lot: in mid-19th century physics, a lot of terms had a single, precise, classical defiinition: mass, particle, force, length, etc. But modern physics in the form of quantum mechanics and relativity (general and special) changed the game. Now there are multiple definitions of these quantities that, in the limits of slow speeds, weak gravity or large objects, agree with our classical definitions. But in the extended, modern theories, we have to be more precise and they can take on multiple definitions. Not everyone agrees with these definitions.

Force is another example of this: Newton's gravity is defnitely a force as much as is electromagnetic force. But extending this to modern physics, these forces are described completely differently: gravity in terms of space-time geometry and electromagnetism in terms of particle exchanges. Does this mean gravity is suddenly not a force? Of course not. But it means we have to be careful when describing it to lay persons so that they know what makes it unique among the forces (at least in current models).