This visualization shows what the interior of a rotating (Kerr) black hole looks like, from the perspective of an observer who has crossed over the inner event horizon in that spacetime. The pink region illustrates the view down inside the alleged ring singularity that is present in the mathematical formulation of the Kerr spacetime. Whether this represents a physical (curvature) singularity or not has recently been reopened for debate. (Credit: David Madore)

“Singularities don’t exist,” claims black hole pioneer Roy Kerr

The brilliant mind who discovered the spacetime solution for rotating black holes claims singularities don’t physically exist. Is he right?

Here in our Universe, whenever you gather enough mass together in a small enough volume of space, you’re bound to eventually cross a threshold: where the speed at which you’d need to travel to escape the gravitational pull within that region exceeds the speed of light. Whenever that occurs, it’s inevitable that you’ll form an event horizon around that region, which looks, acts, and behaves exactly like a black hole as seen from the outside. Meanwhile, inside, all that matter gets inexorably drawn towards the central region inside that black hole. With finite amounts of mass compressed to an infinitesimal volume, the existence of a singularity is all but assured.

The predictions for what we should observe outside the event horizon match extraordinarily well with observations, as we’ve not only seen many luminous objects in orbit around black holes, but have even now imaged the event horizons of multiple black holes directly. The theorist who laid the foundation for how realistic black holes form in the Universe, Roger Penrose, subsequently won the Nobel Prize in Physics in 2020 for…