Why do we say gravity [GR] is a theory about ‘spacetime curvature’ and gravitational waves are ‘ripples’ but nobody uses such a description for electromagnetic fields? Don't EM waves 'ripple' spacetime? For example, one might imagine different types of spacetime curvature associated with each phenomena. Don't EM fields ‘ripple’ spacetime as they carry energy, momentum etc? Anything to do with spin? Wikipedia says: https://en.wikipedia.org/wiki/Graviton " If it exists, the graviton is expected to be massless ..... and must be a spin-2 boson. The spin follows from the fact that the source of gravitation is the stress–energy tensor, a second-rank tensor (compared to electromagnetism's spin-1 photon, the source of which is the four-current, a first-rank tensor). What's so different besides the information each field [or massless quanta] may carry?