I hear physicists saying that the “quantum of the gravitational force” is something called a graviton. Doesn general relativity say that gravity isn a force at all?
You don’t have to accept that gravity is a “force” in order to believe that gravitons might exist. According to QM, anything that behaves like a harmonic oscillator has discrete energy levels, as I said in part 1. General relativity allows gravitational waves, ripples in the geometry of spacetime which travel at the speed of light. Under a certain definition of gravitational energy (a tricky subject), the wave can be said to carry energy. If QM is ever successfully applied to GR, it seems sensible to expect that these oscillations will also possess discrete “gravitational energies,” corresponding to different numbers of gravitons. Quantum gravity is not yet a complete, established theory, so gravitons are still speculative. It is also unlikely that individual gravitons will be detected any time in the near future. Furthermore, it is not at all clear that it will be useful to think of gravitational “forces,” such as the one that sticks you to the earth’s surface, as mediated by virtual