Everett and the Universal Wave Function

“Everett's proposal: drop the collapse postulate entirely. The wave function never collapses, it always evolves according to the Schrödinger equation. When a measurement occurs, the observer becomes entangled with the measured system: both observer-seeing-spin-up and observer-seeing-spin-down exist in the universal wave function. These branches decohere, become informationally isolated from each other, and from that point forward they are, for all practical purposes, separate worlds. [...] Carroll: 'The Many-Worlds Interpretation is not a hypothesis, it is what you get when you take quantum mechanics seriously.' [...] Wallace: the branching structure of the multiverse is emergent from decoherence, just as tables and chairs emerge from atomic physics. The worlds are real in the way biological species are real, patterns in a more fundamental substrate. — Everett (1957); Carroll, Something Deeply Hidden (2019); Wallace, The Emergent Multiverse (2012); SEP 'Everett's Relative-State Formulation'”