I don't think that's accurate. We can pretty carefully calculate the forces involved and answer the question as posed. Related: We can calculate how strong a ma

I don't think that's accurate. We can pretty carefully calculate the forces involved and answer the question as posed. Related: We can calculate how strong a magnet has to be to hold your artwork on the fridge in opposition to the force of Earth's gravity. The GR vs Standard Model breakdown occurs at the extreme limits of GR, for example Planck scale regions of space and black hole singularities. A heavy nucleus is way too big to probe these limits and is well within the domain of physics where we don't see a conflict between the two theories.