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Sean Carroll cites a recent APS survey where physicists were asked about interpretations of quantum mechanics. A third favored Copenhagen, while Many Worlds placed second.
Carroll argues the Copenhagen definition in the survey - that measurement collapses a multi-state wave function - is ill-defined because it doesn't specify what constitutes a measurement.
In Many Worlds, there is no wave function collapse. The observer is included in the quantum system, and measurement yields a superposition of the observer entangled with each possible outcome, which are interpreted as separate branches.
Quantum mechanics treats the wave function as a superposition of all possible measurement outcomes, not as a classical field in space. Entanglement arises because a two-particle system has a single, combined wave function.
Carroll asserts that position and momentum are not fundamental properties but merely different 'coordinates' or bases used to represent the underlying quantum state in Hilbert space.
The 'problem of structure' in Everettian quantum mechanics asks how the familiar world of objects in space emerges from a bare vector evolving in abstract Hilbert space.
He references a paper by Cotler, Pennington, and Renard showing that locality - where interactions only affect nearest neighbors - is a special, unique way to subdivide Hilbert space, not a generic property.
Carroll's 'quantum mereology' research program aims to derive the subdivision of Hilbert space into subsystems (like 'cat' and 'environment') from criteria like localizability and the system-environment distinction.
A major challenge is that this emergence of structure from Hilbert space dynamics depends on time evolution. The Wheeler-DeWitt equation from quantizing general relativity suggests time may not be fundamental, creating an 'order of operations' problem.
Carroll concludes that if locality and space are emergent approximations, not fundamental, this could have experimental implications, though none are currently known.
His scientific curiosity was reignited at Cornell by observing a spinning plate's wobble in a cafeteria. This playful investigation into a seemingly trivial problem later contributed to his Nobel Prize-winning work on quantum electrodynamics.
Feynman held the Richard P. Feynman Professor of Theoretical Physics chair at Caltech. He influenced a generation of physicists, including John Preskill who was drawn to science by a childhood book based on Feynman's interviews.
Eric Weinstein argues theoretical physics in the US has imploded over the last 42 years, attributing the decline to Edward Witten's 1984 Green-Schwarz anomaly cancellation result that funneled all talent into string theory.
He analogizes the physics community's obsession with unique UV completion to a Wheel of Fortune puzzle where only one player is allowed to guess, stifling alternative approaches like Caitlin Burke's intuitive solve.
Weinstein says physics drives the modern economy through boom (weapons), vroom (energy), and zoom (propulsion, computation, communication), making control of the field geopolitically critical.
He links the 1940s establishment of the Reference Committee within the National Resources Council to the beginning of peer review control, which shunted chain reaction physics research into secrecy.