Everettian Quantum Cosmology
The cosmological wavefunction never collapses. Every possible universe is real, branching off at every quantum event.
Looping ambient scene for Mathematical & Structural. These positions deny that "before our universe" is a coherent question. Tegmark: all mathematical structures exist equally as physical realities. Everett: the cosmological wavefunction never collapses, and every quantum branch is equally real.
§1 · The claim, in one sentence
Everettian Quantum Cosmology applies the Everettian interpretation of quantum mechanics to the universe as a whole: every quantum branching produces a real universe.
§2 · Why it might be true
The Everett 1957 interpretation of quantum mechanics holds that quantum branching is real: when a quantum measurement could yield multiple outcomes, all of them actually occur, in parallel branches of the universal wavefunction. Applied to cosmology, this means our universe is one branch of a vastly larger wavefunction containing all possible universes.
In the cosmological context, the 'multiverse' here is not the bubble-universe multiverse of eternal inflation (which is spatially separated regions of one spacetime) but the branching-quantum multiverse (which is the universal wavefunction having different terms corresponding to different histories). Every quantum event splits the universe; every choice you didn't make is being made in a parallel branch.
David Deutsch has been particularly forceful in arguing that the Everettian interpretation should be taken seriously as a cosmological framework, not just as a theory of measurement. In his view, this is the natural cosmological framework if quantum mechanics is universally correct. The 'before' of our universe is the larger wavefunction from which our particular branch emerged.
The family stance
Either all mathematical structures (Tegmark Level IV), or the universal wavefunction branching into every possible history (Everett). In both cases, the notion of a temporal "before our universe" is rejected.
§2.5 · Evidence
- Consistent with standard quantum mechanics, without invoking wavefunction collapse
- Resolves measurement problem without adding new physics
- Has accumulated philosophical support since the 1970s
§3 · What you'd need to test it
- Quantum mechanics applies to the universe as a whole
- All possible universes exist as branches of the wavefunction
- The "branching" structure is a feature of reality, not just a calculational tool
- No 'preferred' branch; our experience is just the appearance from inside one branch
§4 · Where it breaks
- Most physicists view the proliferation of universes as ontologically extravagant
- No way to test that the other branches exist
- The probability rule of quantum mechanics is harder to derive in many-worlds than in collapse-based interpretations
- Some physicists (notably Penrose, Vilenkin) argue the framework is unfalsifiable
Go deeper
Hugh Everett's 1957 PhD dissertation introduced the relative-state formulation of quantum mechanics, which proposed that quantum branching is real. Bryce DeWitt elaborated and popularized this in the 1960s and 1970s as the 'many-worlds interpretation.'
The cosmological application is straightforward: if quantum mechanics applies to the universe as a whole, then the universal wavefunction contains all possible cosmological histories. Our observed universe is just one branch of this wavefunction, corresponding to a specific sequence of measurement outcomes.
Deutsch and others have argued that this framework is the natural cosmological context for understanding quantum measurement. The 'arrow of time' is the proliferation of branches; the 'reality' is the wavefunction; the 'observed universe' is just our particular branch.
Variants in this family
▸§5 · Who built it, and when(3 sources, 3 established)
- EstablishedEverett, H. (1957). 'Relative state formulation of quantum mechanics.' Rev. Mod. Phys. 29, 454
- EstablishedDeWitt, B. (1970). 'Quantum mechanics and reality.' Physics Today 23(9), 30
- EstablishedDeutsch, D. (1997). 'The Fabric of Reality.' Penguin
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