At the center of a black hole lies a singularity — a point where spacetime is crushed infinitely. Black holes can change state, much like water freezing or boiling. Usually, these transitions are noticed by observing the hole's surroundings. But new research suggests listening to the pulse of the singularity itself.
When the hole is calm, this exponent changes smoothly, like a steady rhythm. When it undergoes a phase transition, the pulse becomes erratic, chaotic. At the critical point where the distinction between phases vanishes, the two rhythms merge. Most unexpectedly, beyond this point, a smooth line appears that does not coincide with any known boundary between states. Thus, by the singularity's pulse, one can discern the overall state of the black hole without peering inside.
The Kasner exponent, originally devised to describe the contraction of the Universe in a Big Crunch, has become a tool for studying black holes.
In Carl Sagan's novel 'Contact,' the singularity served as a bridge to other worlds; now this fantasy gains a measurable foundation.