What is Gravitational singularity?
[[File:Black_hole_lensing_web.gif|thumb|right|200px|Lensing by a black hole. Animated simulation of gravitational lensing caused by a Schwarzschild black hole going past a background galaxy.]] {{General relativity|cTopic=Phenomena}} A '''gravitational singularity''' (sometimes called a '''spacetime singularity''') is a term used to describe the center of a [[black hole]] where [[gravity]] is thought to approach infinity.<ref>{{cite web|url=http://www.physicsoftheuniverse.com/topics_blackholes_singularities.html|title=Blackholes and Wormholes}}</ref> In the center of each black hole is a singularity, a point where infinite density develops as spacetime approaches it. Spacetime goes toward infinite curvature and matter is crushed to infinite density under the pull of infinite gravity. At a singularity, space and time cease to exist as we know them and current laws of physics cannot be applied to this region.<ref>{{cite web|url=http://www.einstein-online.info/spotlights/singularities|title=Spacetime Singularities|access-date=2015-10-20|archive-date=2017-01-24|archive-url=https://web.archive.org/web/20170124030605/http://www.einstein-online.info/spotlights/singularities|url-status=dead}}</ref> Singularities form by a collapse of a star, where star with high enough mass (above 30 times the sun) would shrink under its own gravity and force until it becomes a single, one dimensional point. When it forms, space and time would be infinite in there. An example would be that if a person were to stand on a collapsing star right before the singularity forms, and they sent a signal every second to a nearby observer, time and space would slow down as the singularity is being formed. The observer would hear the signal slowing down. Let's say the singularity forms at 12:00 exactly. The observer would receive all the signals, one after another, with each new signal slowing down at a very small rate until the 12:00 signal. When the 12:00 signal was sent, time and space would be infinite -- in other words, it would take forever