What is "gravitational singularity"

n. (context physics English) 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 gravitational singularity or space-time singularity is a location where the quantities that are used to measure the gravitational field of a celestial body become infinite in a way that does not depend on the coordinate system. These quantities are the scalar invariant curvatures of space-time, which includes a measure of the density of matter. The laws of normal space-time could not exist within a singularity.

For the purposes of proving the Penrose–Hawking singularity theorems, a space-time with a singularity is defined to be one that contains geodesics that cannot be extended in a smooth manner. The end of such a geodesic is considered to be the singularity. This is a different definition, useful for proving theorems.

The two most important types of space-time singularities are curvature singularities and conical singularities. Singularities can also be divided according to whether or not they are covered by an event horizon ( naked singularities are not covered). According to modern general relativity, the initial state of the universe, at the beginning of the Big Bang, was a singularity. Both general relativity and quantum mechanics break down in describing the earliest moments of the Big Bang, but in general, quantum mechanics does not permit particles to inhabit a space smaller than their wavelengths. Another type of singularity predicted by general relativity is inside a black hole: any star collapsing beyond a certain point (the Schwarzschild radius) would form a black hole, inside which a singularity (covered by an event horizon) would be formed, as all the matter would flow into a certain point (or a circular line, if the black hole is rotating). This is again according to general relativity without quantum mechanics, which forbids wavelike particles entering a space smaller than their wavelength. These hypothetical singularities are also known as curvature singularities.