When a massive star runs out of fuel, its core collapses under its own weight. A black hole forms — a region where gravity is so strong that even light can't escape. For a long time, it was thought that a point of infinite density, a singularity, lurks at the very center. But the equations of quantum physics hint that matter might resist compression and form a smooth, finite core.
Scientists took two descriptions of matter inspired by quantum chromodynamics — the theory of the strong force that glues quarks inside protons and neutrons. The first describes a hot mixture of three quark flavors; the second, a cold 'quark soup' with massive gluons (the particles that carry the strong force). Both were plugged into Einstein's equations to see what happens at the center of collapse.
The result was grim. In the first case, the solution still led to infinite density and spacetime curvature at the center. In the second, temperature grew so fast that near the center the model stopped working. In other words, quark matter alone can't create a safe, regular core. To avoid a singularity, nature would need something more, like a sudden phase transition into a state resembling a vacuum with repulsive gravity.
So the metaphor of a black hole as a whirlpool gets an unexpected twist. Even if water consists of tiny vortices, a void still forms at the center of the funnel — unless some unknown mechanism changes the properties of the fluid at the bottom.
If Earth were compressed into a black hole, its radius would be only about 9 millimeters, the size of a grape.
In Peter Watts's novel 'Blindsight', a ship's crew investigates an anomaly where physical laws break down — a hint that inside a black hole, familiar matter might give way to something entirely different.