Event horizon

General relativity

$G_{\mu \nu} + \Lambda g_{\mu \nu}= {8\pi G\over c^4} T_{\mu \nu}$

Einstein field equations Important concepts Special relativity Equivalence principle World line · Riemannian geometry Phenomena Kepler problem · Lenses · Waves Frame-dragging · Geodetic effect Event horizon · Singularity Black hole Equations Linearized Gravity Post-Newtonian formalism Einstein field equations Friedmann equations ADM formalism BSSN formalism Advanced theories Kaluza–Klein Quantum gravity |Topic5=[[Exact solutions in general relativity|Solutions]] |Items5=[[Schwarzschild metric|Schwarzschild]] <br />[[Reissner-Nordström metric|Reissner-Nordström]]{{·}}[[Gödel metric|Gödel]]<br />[[Kerr metric|Kerr]]{{·}}[[Kerr-Newman metric|Kerr-Newman]]<br />[[Kasner metric|Kasner]]{{·}}[[Taub-NUT vacuum|Taub-NUT]]{{·}}[[Milne model|Milne]]{{·}}[[Friedmann-Lemaître-Robertson-Walker metric|Robertson-Walker]]<br />[[pp-wave spacetime|pp-wave]] Scientists Einstein · Minkowski · Eddington Lemaître · Schwarzschild Robertson · Kerr · Friedman Chandrasekhar · Hawking Penrose

In general relativity, an event horizon is a part of a black hole. Imagine the black hole to be like a ball that you could see in a large spot of emptiness (like day time blue sky). The event horizon would then be an outer bubble that surrounds that ball. It would be like a little circle inside a bigger circle. The space between the little circle and the big circle would be the event horizon. If an object goes past the event horizon, it can never get away from it. Light that is emitted from the side of the event horizon near the black hole can never reach an observer on the other side. If an observer saw an object fall into a black hole, it would look like the object was stuck at the event horizon forever.