Event Horizon
The Event Horizon is the boundary in Spacetime surrounding a Black Hole from which no information, matter, or radiation can escape. It marks the point where the Escape Velocity equals the Speed of Light. Once crossed, the future light cones of all particles point inevitably toward the central Singularity.
Properties
- One-way membrane: Acts as a causal boundary; events inside cannot influence the outside universe.
- Surface Gravity: Characterized by the strength of the gravitational field at the horizon.
- Temperature: Associated with Hawking Radiation, implying black holes have a non-zero temperature and entropy proportional to the horizon’s surface area.
Theoretical Implications
- Information Paradox: Conflict between quantum mechanics (unitarity) and general relativity regarding information loss when matter crosses the horizon.
- No-Hair Theorem: The horizon obscures all internal structure, leaving only mass, charge, and angular momentum observable to external observers.
Recent Developments & Singularities
- Current models suggest the singularity is a breakdown of General Relativity requiring Quantum Gravity for resolution.
- See Black Hole Singularities: Frozen Big Bang and Quantum Gravity Solutions for details on alternative models where singularities are replaced by “frozen big bang” states.