Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
An event horizon is the boundary surrounding a black hole beyond which no light or other information can escape. It marks the point at which gravitational pull becomes so strong that escape velocity exceeds the speed of light.
5 Must Know Facts For Your Next Test
The event horizon is defined by the Schwarzschild radius, calculated as $R_s = \frac{2GM}{c^2}$ where $G$ is the gravitational constant, $M$ is the mass of the black hole, and $c$ is the speed of light.
Within the event horizon, all paths lead to the singularity at the center of the black hole.
The event horizon appears as a perfect sphere in non-rotating black holes but can be distorted in rotating (Kerr) black holes.
Hawking radiation theorizes that particle-antiparticle pairs near the event horizon can result in one particle escaping, leading to gradual black hole evaporation.
Information paradox: The fate of information that crosses an event horizon remains an unresolved issue in theoretical physics.
A point at which density becomes infinite and space-time curvature becomes infinitely large, typically found at the center of a black hole.
Hawking Radiation: Hypothetical radiation predicted by Stephen Hawking that results from quantum effects near a black hole’s event horizon, leading to slow loss of mass and energy from the black hole.