From what I have read out there, of the four fundamental forces that have been detected in our universe, gravity seems to be the weakest at the atomic level and smaller. I figure this is most likely true because at the atomic level and smaller - the weak and strong forces (those causing beta decay and gluons to hold quarks inside of protons and neutrons) are the forces that build matter at an atomic level. Gravity seems to only rear it's head when the mass of any object is that of an atomic mass or higher. The larger the mass of anything....the more gravity plays a role according to Einstein's general relativity principles. Therefore gravity is a force that needs to be separated from the other three major forces because it doesn't seem to appear or work at levels smaller than anything smaller than an atom. If this is all true....then why the need to even talk about mass-less particles like gravitons even existing in the first place? After all, Einsteins' Gen. Relativity Theory says gravity is nothing more than the physical bending or curving of the space-time fabric which anything that has mass on it does. Thus it's nothing more than a force that only shows up when masses are that of an atom or larger and not at the quantum level.