How David Bohm and Hugh Everett changed quantum theory

Status of Bohmian Mechanics and Many‑Worlds

• Several commenters dispute the claim that “science now accepts” Everett and Bohm; both are seen as interpretations, not confirmed new theories.
• Many report that most working physicists they know default to “shut up and calculate” rather than committing to an interpretation.
• Bohmian mechanics is viewed as hard to extend to quantum field theory; many doubt it as a long‑term contender.

Falsifiability and Testing Interpretations

• Strong disagreement over whether Many‑Worlds (MWI) is falsifiable.
• One side: MWI is just standard quantum mechanics (QM) with unitary Schrödinger evolution; it’s falsified if that fails, or if extra variables/collapse are detected.
• Other side: that only distinguishes QM+MWI from non‑QM theories; MWI is not falsifiable against other interpretations that keep the same math.
• Collapse‑type theories are noted to make distinct, in‑principle‑testable predictions, some already constrained by experiment.

Copenhagen vs Many‑Worlds vs Others

• Copenhagen is criticized as vague: “measurement,” “macroscopic,” and collapse are not precisely defined, and it can’t cleanly analyze the measuring device itself.
• Defenders argue it’s the de facto default for historical and pragmatic reasons, and reasonable to use while the measurement problem is unresolved.
• MWI advocates emphasize: wavefunction is real, Schrödinger holds always, and “worlds” are emergent decohered branches.
• Objections to MWI: trouble with probability/Born rule, and claims that it contradicts the observed “single outcome” unless you accept branching as unobservable.

Parsimony and “Theory Cost”

• One camp: MWI is more parsimonious—no special collapse rule, just one dynamical law.
• Critics: positing exponentially many concrete branches massively increases “theory cost” (number of real states/entities), so Copenhagen or collapse may be simpler overall.

Measurement, Decoherence, and Scale

• Ongoing debate on what counts as a “measurement” and whether there is an objective macroscopic threshold.
• Decoherence is seen by some as pushing toward MWI; others think it doesn’t rescue Copenhagen but also doesn’t uniquely select MWI.

Attitudes and Alternatives

• Many see interpretations as largely philosophical given identical predictions; focus should be on new theories with new testable consequences.
• Alternative frameworks mentioned include relational quantum mechanics; some hope future “completion” of QM will clarify these issues.