Black holes are famous for what they swallow, but one of the most surprising things about them is that they glow. In the 1970s, Stephen Hawking showed that black holes emit a faint thermal radiation due to quantum effects near their horizons. What makes this phenomenon extraordinary is not just that it exists, but that it appears to be universal: the radiation depends only on the black hole’s size, not on what it’s made of or how it formed. Even more striking, similar radiation shows up in laboratory “analogue” systems—such as flowing fluids and ultracold atomic gases—that mimic horizons using completely different microscopic ingredients.
That universality turns out to be a powerful clue. If Hawking radiation emerges no matter what the underlying physics is, then not all microscopic structures of space can be compatible with it. In this work, we turn the usual question around. Instead of asking “does a given theory of space produce Hawking radiation?” we ask: what must space be like in order for Hawking radiation to be universal at all?
Hawking Radiation as a Stress Test for Space
Near a black hole’s horizon, space is pushed to an extreme. Quantum modes are violently blueshifted, information is stretched across the point of no return, and correlations must propagate under intense compression. For Hawking radiation to work, space must be able to handle all of this without choking, fragmenting, or developing preferred directions. That immediately rules out many imaginable microscopic structures. Simple grids have built-in directions. Tree-like networks create bottlenecks. Strongly disordered structures trap waves. Sharp cutoffs prevent the cascade of modes Hawking radiation relies on.
What survives this “Hawking stress test” is a much narrower family of possibilities: geometries that are locally isotropic, highly and redundantly connected, free of bottlenecks, and able to smooth themselves into ordinary continuous space at large scales. In information terms, space must be exceptionally good at managing flow, capacity, and entanglement under extreme conditions.
The Best-Fit Geometry: Close-Packed and Hexagonally Coordinated
Within this admissible family, one class stands out as the best overall fit to all the constraints at once: close-packed, high-symmetry connectivity structures. These are not crystals in the everyday sense, and certainly not literal spheres stacked in space. Rather, they represent a pattern of connectivity in which each local degree of freedom is linked to many neighbors (typically about twelve), arranged so that no direction is preferred and no information bottlenecks form.
Hexagonal coordination plays a key role here. Hexagons don’t appear as tiles floating in space; they appear as neighbor relationships. In a close-packed structure, each point has six neighbors arranged at 60-degree angles in a local plane, with additional neighbors above and below. This arrangement is well known in nature—not because it looks pretty, but because it optimally redistributes stress and information. Under compression, nothing snaps, funnels, or localizes. Everything stays connected.
What This Does—and Does Not—Claim
This is not a claim that space is literally made of spheres, or that it is a frozen crystal at a fixed scale. It’s a statement about how space behaves, not what it looks like. The geometry being proposed is best understood as an information-management geometry: a way of organizing spacetime degrees of freedom so that isotropy, connectivity, and entanglement survive even at a black hole horizon.
The broader point is this: black holes are not just exotic objects in the sky. They are diagnostic tools. The fact that horizons glow—universally—tells us something precise about what space can and cannot be made of. If this analysis is right, the microscopic fabric of space belongs to a very specific family of structures, selected not by aesthetic preference, but by the unforgiving functional demands imposed by Hawking radiation itself.