Following on from the previous blog — where we explored how General Relativity is a map, not the mechanics — this new paper takes the next logical step. If Einstein’s equations describe the large-scale geometry of gravity rather than the machinery that produces it, then what is that machinery made of? What lies beneath the elegant curvature?
The new work argues that, once we impose only the minimal physical requirements — locality, Lorentz symmetry, isotropy, the equivalence principle, and lossless gravitational-wave propagation — all possible underlying structures collapse to a single surviving option. The substrate that can reproduce General Relativity at macroscopic scales must be a shift-symmetric scalar field whose collective behaviour is that of a superfluid. In other words, space itself has to flow — frictionlessly, coherently, and universally — with its gentle phase gradients giving rise to the geometry we call spacetime.
This doesn’t mean we’ve solved gravity, but it does narrow the field dramatically. If GR is the map, this scalar superfluid is the terrain — the minimal, self-consistent way for geometry to emerge from something deeper. It’s a picture where the universe is not built from rigid scaffolding but from a vast, quantum-coherent medium, and gravity is the rhythm of its flow.