Black Hole Glossary

• Accretion disk: Hot, rotating matter spiraling toward a compact object.
• Event horizon: A causal boundary beyond which light cannot reach the distant outside universe.
• General relativity: Einstein's theory connecting gravity with spacetime curvature.
• Gravitational wave: A propagating distortion of spacetime, detectable from violent accelerating masses such as merging black holes.
• Hawking radiation: Quantum-theoretical thermal radiation predicted to be emitted by black holes.
• Singularity: A boundary or breakdown in the classical equations where quantities become undefined or divergent.
• Spacetime: The combined four-dimensional structure of space and time.
• Tidal force: A difference in gravitational acceleration across an object.