A new preprint by renowned physicist Roy Kerr challenges the long-held assumption that black holes contain singularities – regions where the laws of physics break down. Kerr, famous for discovering the Kerr metric that describes spinning black holes, argues that there is still no definitive proof that singularities exist inside event horizons.
The paper examines various key solutions of Einstein’s equations like the Schwarzschild, Kerr, and Kruskal metrics. It focuses on light rays called Principal Null Vectors (PNVs) that have bounded affine length as they approach event horizons asymptotically. Many physicists have assumed these must end at singularities, but Kerr shows through counterexamples that they may not. This contradicts a basic premise behind various “singularity theorems” proposed in the past.
Kerr suggests that when realistic matter is considered, rotating black holes formed from collapsed stars could be non-singular, with centrifugal forces overcoming gravitational collapse at small scales. While incredibly dense, neutron stars are likewise believed to be non-singular. He argues the mathematical extensions used to demonstrate singularities are physically irrelevant.
The paper does not rule out the possible existence of singularities. However, it forces researchers to re-evaluate longstanding assumptions in general relativity. If correct, it implies a need to better understand the quantum nature of matter at extreme densities, as classical assumptions can break down. It also opens the doors for new approaches to phenomena like black hole interiors and the very early universe.
The concept of singularities has profoundly shaped our understanding of cosmology and astrophysics over the past decades. As telescopes peer deeper into cosmic history and the era of gravitational wave astronomy unfolds, Kerr’s heterodox ideas could stimulate breakthroughs at the interface of relativity, quantum theory, and observation. Even if further evidence favors the standard view, questioning orthodoxy often leads to progress.