Three Ways to Save Reality — Quantum Mechanics (Lecture 5)

Lecture 5 of "Quantum Mechanics and the Crisis of Scientific Realism." Watch the full lecture series:    • Quantum Mechanics and the Crisis of Scient...   Presented by Ergo, a nonprofit that publishes structured philosophical lectures online, free to anyone. https://ergo.org About this lecture Quantum mechanics works extraordinarily well, yet its standard formulation harbors a deep puzzle: the measurement problem. When no one is looking, particles evolve smoothly according to the Schrödinger equation, but measurements seem to force abrupt, random outcomes, and a fundamental theory of nature shouldn't depend on vague notions like "measurement." In this lecture, David Albert examines three ambitious attempts to resolve this tension while preserving a realistic picture of the physical world. GRW theory introduces spontaneous collapses that eliminate macroscopic superpositions. Everett's many-worlds interpretation keeps the smooth evolution but posits a branching universe, raising thorny questions about probability. Bohm's mechanics restores determinism through hidden variables but faces its own challenges, including nonlocality and the role of configuration space. Albert carefully weighs the advantages and costs of each approach, making vivid the intellectual stakes of one of the deepest problems in the foundations of physics. About this course David Albert, professor of philosophy at Columbia University, builds quantum mechanics from the ground up, beginning with simple, undisputed experiments on electrons and arriving at a startling conclusion: a challenge to science's aspiration to describe reality, coming from within science itself. He traces the measurement problem, the apparent need for two incompatible laws of nature, and Bell's theorem with its assault on locality. He then surveys three modern responses: the GRW theory, Everett's many-worlds interpretation, and Bohm's pilot-wave theory. Can science describe reality at all? About David Albert David Albert is Professor of Philosophy at Columbia University, where he directs the MA program in the Philosophical Foundations of Physics. His interests include the foundations of physics, especially quantum mechanics, statistical mechanics, and the nature of time, along with questions about scientific realism. He is the author of Quantum Mechanics and Experience (Harvard, 1992), Time and Chance (Harvard, 2000), After Physics (Harvard, 2015), and A Guess at the Riddle: Essays on the Physical Underpinnings of Quantum Mechanics (Harvard, 2023), as well as articles on the interpretation of quantum theory and the arrow of time. Chapters 00:00 The Measurement Problem and Von Neumann's Two Rules 04:34 Fifty Years of Failed Boundary-Drawing Attempts 05:57 The GRW Spontaneous Collapse Theory 10:17 How GRW Handles Macroscopic Objects 13:30 Entanglement and Measurement in GRW 16:50 The Localization Assumption and Its Worries 20:13 The TV Screen Problem and GRW's Response 26:07 Superposition as a Genuine Physical State 30:46 Assessing GRW as a Scientific Theory 34:04 The Many-Worlds Interpretation 40:46 World-Splitting and the Branching Universe 46:37 The Probability Problem in Many-Worlds 51:38 Probability Puzzles and Quantum Immortality 1:04:59 Bohmian Mechanics: The Hidden Variable Approach 1:10:18 Challenges for Bohmian Mechanics 1:14:11 Why Many-Worlds Appeals to Physicists 1:20:24 Is the Realist Scientific Project Still Alive?