Definition
The Many-Worlds Interpretation (MWI), also known as the Everett interpretation, is a realist view of quantum mechanics which asserts that the universal wavefunction is objectively real and that there is no “wavefunction collapse.” Instead, all possible outcomes of a quantum measurement are physically realized in a branching structure of quasi-autonomous regions known as the multiverse.
Why It Matters
The Many-Worlds Interpretation forces us to take the full scope of reality seriously; it is the only framework that provides a coherent, ‘realist’ explanation for the quantum effects that power modern technology and define the limits of computation.
Core Concepts
- The Multiverse: A unified physical entity containing more than one universe. Each “universe” is an emergent, coarse-grained history where classical physics approximately holds.
- Fungibility: Initially identical instances of an object (or universe) that are indistinguishable except by their count. As interactions occur, these instances become differentiated, leading to branching histories.
- Interference: The phenomenon where different histories affect each other’s measures (probabilities). Interference is the primary evidence for the multiverse’s existence.
- Autonomy of Histories: Larger, complex systems (like humans) undergo “decoherence,” which suppresses interference and makes different histories behave as if the others did not exist.
- The Measure: The method by which quantum theory assigns unique meanings to proportions and averages over an infinite set of universes, corresponding to what we perceive as “probability.”