Chapter 06 · Black Holes
Black Holes
What happens inside a black hole?
General relativity and quantum mechanics disagree about black holes. General relativity says the interior is hidden behind an event horizon, with a singularity at the center where the math breaks down. Quantum mechanics insists that information cannot be destroyed. Both cannot be right at the horizon. This chapter opens with the family of proposals attempting to resolve that contradiction: what happens to the information that falls in? Subsequent families will address formation channels, Hawking radiation, and singularity alternatives.
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.5 variants · PBH variant bridges to Ch. 5 Dark Matter
- 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.5 variants · Fuzzballs and Quantum Bounce complement BHIP and Hawking Radiation
- 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.5 variants · ER=EPR bridges to Ch. 3 Holographic Spacetime
Bridged from other chapters
These variants live in their own chapters but also answer this chapter's question.
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
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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