It very likely exists, somewhere out there in the grand scheme of things, but so far we don't know squat about it. > The parts where it doesn't work are extrem

It very likely exists, somewhere out there in the grand scheme of things, but so far we don't know squat about it. > The parts where it doesn't work are extremes like black holes where GR also breaks apart. Wrong. That scenario is exactly the kind that quantum gravity is supposed to illuminate. Of course, we can't be 100% sure about that yet.