Cosmic censorship hypothesis

A conjecture that gravitational collapse does not produce singularities visible to distant observers, because event horizons hide them.

Event horizon: A boundary in spacetime beyond which events cannot influence distant observers. The horizon is the proposed barrier between collapse singularities and distant observers.
Roger Penrose: A British mathematical physicist whose work established major results on gravitational collapse and spacetime singularities. Penrose formulated the censorship conjecture in the context of collapse singularities.
Reissner–Nordström solution: The static, spherically symmetric solution for a charged mass in general relativity. Its inner Cauchy horizon exposes the predictability problem addressed by strong censorship.
Over-extremal Kerr solution: A Kerr geometry with angular momentum too large for its mass to admit an event horizon. It contains a naked ring singularity, though it need not arise from physical collapse.
Gravitational collapse: The contraction of matter under its own gravity, potentially forming a compact object or singularity. The conjecture concerns singularities produced by this process.
Penrose singularity theorem: A theorem showing that trapped surfaces under suitable conditions imply geodesic incompleteness. The theorem made singularity formation plausible, sharpening the question of whether horizons hide it.
Mass inflation: A growth of internal mass-energy near a black hole’s Cauchy horizon caused by counterstreaming radiation. It may destabilize the horizon and help restore deterministic evolution.
Over-extremal Reissner–Nordström solution: A charged spherical vacuum geometry whose charge exceeds its mass in geometric units, leaving no event horizon. It displays a naked singularity in an exact solution, challenging careless versions of censorship.
Naked singularity: A spacetime singularity not hidden behind an event horizon. Its formation would directly violate the conjecture’s central expectation.
Schwarzschild solution: The spherically symmetric vacuum solution of Einstein’s equations describing a nonrotating mass. Its black-hole geometry offers the simplest example of a singularity behind a horizon.

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