Penrose-Hawking singularity theorems
Overview
 
The Penrose–Hawking singularity theorems are a set of results in general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...

 which attempt to answer the question of when gravitation produces singularities
Gravitational singularity
A gravitational singularity or spacetime singularity is a location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system...

.

A singularity in solutions of the Einstein field equations
Solutions of the Einstein field equations
Where appropriate, this article will use the abstract index notation.Solutions of the Einstein field equations are spacetimes that result from solving the Einstein field equations of general relativity. Solving the field equations actually gives Lorentz metrics...

 is one of two things:
  1. a situation where matter is forced to be compressed to a point (a space-like singularity)
  2. a situation where certain light rays come from a region with infinite curvature (time-like singularity)


Space-like singularities are a feature of non-rotating uncharged black-hole
Schwarzschild metric
In Einstein's theory of general relativity, the Schwarzschild solution describes the gravitational field outside a spherical, uncharged, non-rotating mass such as a star, planet, or black hole. It is also a good approximation to the gravitational field of a slowly rotating body like the Earth or...

s, while time-like singularities are those that occur in charged or rotating black hole exact solutions.
 
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