Chapter 06 · Black Holes
Black Holes
What happens inside a black hole?
We know black holes exist. We don't know what happens at the center, or whether information that falls in is truly lost. These theories tackle what's going on inside.
Families (3)
- Strongly supportedHawking RadiationHawking proved in 1974 that black holes radiate. The result has been theoretically robust for half a century: every quantum-gravity program reproduces it. No astrophysical observation has yet confirmed it directly.6 variants2 votes
- FrontierSingularity AlternativesFive proposals for what replaces the infinite-density point at the center of a black hole. Regular metrics, gravastars, fuzzballs, quantum bounces, and the violent inner structure of rotating black holes. No observational test has yet discriminated among them.6 variants
- FrontierBlack Hole Information ParadoxFive proposals for how information escapes a black hole. The 2019 Page curve calculations show unitarity can be recovered in semiclassical gravity, but the question of what an infalling observer experiences at the horizon locally is still open.6 variants
Bridged from other chapters (7)
These variants live in their own chapters but also answer this chapter's question.
Ch.03Loop Quantum GravityFrontier
Canonical / Spin-Foam Loop Quantum Gravity
Spacetime is woven from a network of quantum geometric atoms. Area and volume have minimum sizes set by the Planck scale.
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Ch.01Cosmological SelectionSpeculative
Smolin's Cosmological Natural Selection
Universes evolve by natural selection. Black holes are reproductive events, and our universe is descended from ancestors that were good at making black holes.
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Ch.03Emergent Spacetime & GravityFrontier
Holographic Spacetime
A higher-dimensional spacetime with gravity is exactly described by a lower-dimensional quantum theory on its boundary. Geometry emerges from entanglement.
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Ch.01Black Hole GenesisFrontier
Afshordi's Holographic Big Bang
A four-dimensional star collapsed in a five-dimensional bulk, throwing off a three-dimensional membrane that became our expanding universe.
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Ch.01Black Hole GenesisFrontier
Pathria-Good Black Hole Origin
The first proposal that our universe might exist inside the singularity of a black hole in a parent universe.
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Ch.01Black Hole GenesisFrontier
Popławski's Einstein-Cartan Torsion
Spacetime can twist as well as bend if matter has intrinsic spin. At ultra-high density the twist becomes a repulsive force that stops gravitational collapse and bounces the collapsing matter into a new expanding universe inside the parent black hole.
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Ch.01Black Hole GenesisFrontier
Delayed Phase Transition Baby Universe
Our universe may be a baby universe formed inside a primordial black hole during a delayed first-order phase transition.
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Ch. 6 · what readers find most compelling, 2 votes cast
Early days, votes still coming in.
2 votes cast
- ★ 01Hawking Radiation2votes
- 02Black Hole Information Paradox0votes
- 03Black Hole Information Paradox0votes
- 04Black Hole Information Paradox0votes
- 05Black Hole Information Paradox0votes