Musing aloud,,,,, perhaps there are different flavours of gravity. Weakly interacting and strongly interacting. That given to magnetic interaction where magnetic forces add to the effect, but only to a 'captured' point of equalibrium governed by angular velocity (an electric armature for instance and it's associated field), then that of Mass gravity where the elctro-magnetic affect is modified by sheer weight of numbers of trillions of interacting magnetic fields at the quantum level. That is a field equation stretching from the Planck scale to the universe[-al] scale. I muse because of how small mass particles such as electrons arrange themselves in shell energies growing progressively larger, then smaller for the heavier elements, to interplanetary scales as observed in the stacking of planets in our own solar system. Then there is the perceived anti-gravity or gravity reistance as seen due to gyroscopic motions. If everything is indeed made of 'energy quanta' then E=MC^2 should perhaps be modified to something like E=((M/V)*f)C^2 differentiated by electric field current from 0 to infinty. Where V = velocity in Kilometres per second; f=frequency as cycles per second (with two field equations arising - one for classic frequency that describes the period with respect to a continuous time frame, and another that describes the period in quanta (the quanta frequancy being a modulation of field strength as beats per second ((rather like FM modulation using a planck scale frequency 'beat')). Electric field strength in webers per metre squared divided by area. We then differentiate two equations. One equation being a classically based E=MC^2 energy field, against the Planck scale quantitized FM type equation. I am not a scientist or a mathemetician, but logic tells me that if we cannot find an equation to describe what we are searching for in a unified theory of relativity, then we need to go back to basics of observing causality and the underlying principles of matter observed as we see them (not necessarily experimental observation) but one of logical deduction or even intuition. (Please note the equation I gave is only a muse - sometimes we win on the lottery - though more often I will always accept - we do not). As for the original poster's question - Can Genral Relativity and Quantum Mechanics be two different things,,, Of course they can, but that does not mean that they are not related (like cousins perhaps in a family tree).