planet earth and the sun. in GR, gravity is not a force but simply a manifestation of spacetime curvature. the sun curves spacetime and the earth is simply traveling through geodesic motion through curved spacetime. in string theory, the sun and earth exchange virtual gravitons through a massless spin-2 field that couples to stress-energy tensor. this creates effects identical to gravity. in LQG, which picture explains the attraction the sun and earth have for one another, is earth traveling through curved spacetime or is it via graviton exchange? is there a quantum mechanical description of how mass-energy curves spacetime? i.e how does quantum mechanical matter interact quantum mechanically with quantum spacetime that produces curved space? are there any QG that does not have any notion of gravitons, but explains gravity in terms of curved spacetime?