Three quantum-inspired cores leave opposite fingerprints on the ringing of black holes

Every black hole hides a question at its center. Einstein’s theory predicts that whatever falls in is crushed into a singularity, a point of infinite density where the theory itself breaks down. Most physicists expect quantum gravity to replace that point with something finite. But the center lies hidden behind the horizon. How could we ever learn what is there?

Source: Phys.org