Chapter 01 · Before the Universe
Before the Universe
What lies outside our space and time?
We don't know what, if anything, existed before the Big Bang. These are the serious proposals, each with a different answer to whether "before" even means anything.
Families (10)
- Strongly supportedEternal InflationOur universe is one bubble in an endlessly inflating ocean that has been spawning universes forever.3 variants4 votes
- FrontierBlack Hole GenesisOur universe was born from the collapse of a black hole in a higher-dimensional parent universe.4 variants2 votes
- SpeculativeMathematical & StructuralReality is fundamentally mathematical or timeless. "Before" is not a meaningful question.2 variants
- SpeculativeQuantum Tunneling OriginOur universe emerged from a quantum process that does not require a pre-existing spacetime.5 variants2 votes
- SpeculativeQuantum Vacuum MechanismOur universe nucleated as a bubble of true vacuum inside a metastable parent vacuum.1 variant
- SpeculativeCyclic & Bouncing CosmologiesOur universe is one phase in an infinite sequence, what came before was a previous cycle.6 variants1 vote
- SpeculativeCosmological SelectionUniverses reproduce through black holes, with physical laws evolving across generations by a process analogous to natural selection.1 variant
- SpeculativeBraneworld & the BulkOur 3D universe is a membrane floating in a higher-dimensional bulk that always existed.2 variants
- SpeculativeAlternatives to InflationTheories that solve the horizon and flatness problems without a period of cosmic inflation.1 variant
- SpeculativeTime-Symmetric CosmologiesThe Big Bang is not a beginning but a midpoint, with time flowing in two directions from it.2 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.03Causal Set TheoryFrontier
Sorkin's Causal Set Program
Spacetime as a discrete partial order. Order plus number equals geometry. The 1987 Bombelli-Lee-Meyer-Sorkin paper is the program's foundational text. Riemann, Finkelstein, and Myrheim are the conceptual predecessors.
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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.02CPT-Symmetric UniverseFrontier
Boyle-Finn-Turok CPT Universe
The Big Bang is a mirror, not a beginning. On the other side is an antimatter universe running backwards in time, and together with ours it forms a CPT-symmetric whole.
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Ch.03Emergent Spacetime & GravityFrontier
Thermodynamics of Spacetime
Einstein's equation is not fundamental but a thermodynamic equation of state for spacetime, analogous to how the ideal gas law emerges from molecules.
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Ch.04String TheoryFrontier
M-Theory
The five seemingly distinct 10D superstring theories are different limits of one deeper 11-dimensional theory. Strings are not fundamental on their own; branes of various dimensions are equally fundamental.
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Ch.03Emergent Spacetime & GravityFrontier
Verlinde Entropic Gravity
Gravity is an entropic force from information on holographic screens. The 2016 dark-matter extension has been substantially constrained by weak-lensing tests.
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Ch. 1 · what readers find most compelling, 9 votes cast
Early days, votes still coming in.
9 votes cast
- ★ 01Eternal Inflation4votes
- 02Quantum Tunneling Origin2votes
- 03Cyclic & Bouncing Cosmologies1vote
- 04Black Hole Genesis1vote
- 05Black Hole Genesis1vote