I saw an article about physicist testing quantum mechanics in accelerated frames, hoping for insights into quantum gravity. And then I suddenly wondered, is quantum gravity inconsistent with general relativity at the most basic level of the principles of equivalence and relativity?
In general relativity we have the equivalence of a particle at rest on the earth and inside an accelerating rocket, the equivalence of a stationary observer viewing a falling particle and a stationary particle being viewed by an accelerated observer (e.g. an accelerated rocket in special relativity has much of what we call gravity). But a gravitational interaction mediated by gravitons must occur in deBroglian chunks. Like electrons going through the magnets of an accelerator-- rather than accelerating smoothly they're either kicked or not kicked (speaking loosely), and that matters in the design.
So, like, thinking of the "scattering" of a particle under gravity versus moving inertially in an accelerating rocket. Overlooking the weakness of the interaction, it seems like the particle might be kicked by gravity in a way that it wouldn't if it's just sitting there while the rocket accelerates around it.