What is Inside a Black Hole?

The theories about the insides of black holes.

Correction (October 2026): A few points in this video need updating. The Planck star is a 2014 proposal by physicists Carlo Rovelli and Francesca Vidotto, named for the Planck length. Planck himself defined that length as a unit of measurement but never described space as pixels. That picture comes loosely from loop quantum gravity. The Planck length is about 1.6 × 10⁻³⁵ meters. A gravastar would have no event horizon at all, just a thin shell around a dark-energy-like core. The "wall of radiation" would hit you at a spinning black hole's inner horizon, not as you cross the event horizon. And rotating black holes are not misbehaving. Every test so far, including the Event Horizon Telescope images of M87* (2019) and Sagittarius A* (2022) and the gravitational-wave event GW250114 (2025), which also confirmed Hawking's prediction that a black hole's horizon area can never shrink, matches Einstein's equations. What happens inside the horizon, though, is still unknown, just as the video says.