The GR Fundamentality Question: A Coarse Grain Description or Fundamental?
Nature doesn’t actually care what we call “fundamental.” This might seem obvious, but it’s worth stating clearly because of a rhetorical trick that often gets deployed in these discussions. When pressed about whether spacetime has microscopic structure underneath it, some physicists reach for a clever-sounding analogy: asking what’s beneath spacetime is like asking “what’s north of the North Pole?” The question itself is supposed to be meaningless, a category error revealing confusion rather than genuine inquiry.
But this analogy commits a subtle sleight of hand. The North Pole is defined as the northernmost point on Earth – we literally constructed it that way through our coordinate system. Asking what’s north of it is redundant by definition, like asking what comes before the starting line or what’s larger than the largest number. It’s a tautology dressed up as profundity. The GR fundamentality question is nothing like this. Spacetime either has microscopic structure or it doesn’t – this is an empirical fact about reality, not a matter of definition. We don’t get to define it away by declaring geometry “fundamental” and then claiming further questions are meaningless. That’s not physics; that’s rhetoric.
The question is coherent: Does smooth, continuous geometry emerge from something discrete, quantum, or otherwise more fundamental? Or does geometry really go “all the way down”? This isn’t asking what’s before the starting point – it’s asking whether what looks like a starting point might actually be mile marker 50, with miles 1-49 hidden from our current view. The thermodynamics-to-statistical-mechanics transition shows exactly this pattern: temperature looked fundamental until we discovered it emerges from molecular motion. Smooth classical spacetime could be exactly analogous – a macroscopic description awaiting its microscopic explanation. The paper’s own evidence (no local energy, coarse-graining required, 80% gauge redundancy) points strongly in this direction. You can’t dismiss that by invoking clever analogies about poles and directions.