Gravitational singularity

In theoretical physics, a gravitational singularity, spacetime singularity, or simply singularity, is a theoretical condition in which gravity is predicted to be so intense that spacetime itself would break down catastrophically. As such, a singularity is by definition no longer part of the regular spacetime and cannot be determined by "where" or "when". No complete and precise definition of singularities exist in the theory of general relativity, the current theory of gravity. A singularity in general relativity can be defined by the scalar invariant curvature becoming infinite, or by a geodesic being incomplete.

General relativity predicts that any object collapsing beyond its Schwarzschild radius would form a black hole, inside which a singularity will form. A black hole singularity is, however, covered by an event horizon, so it is never in the causal past of any outside observer, and at no time can it be objectively said to have formed. General relativity also predicts that the initial state of the universe, at the beginning of the Big Bang, was a singularity of infinite density and temperature. However, classical gravitational theories are not expected to be accurate under these conditions, and a quantum description is likely needed. For example, quantum mechanics does not permit particles to inhabit a space smaller than their Compton wavelengths.