# Is quantum mechanics just an approximation? | Roger Penrose, Jacob Barandes, Alyssa Ney

Source: https://www.youtube.com/watch?v=7XtTDZeNvMc
Recap page: https://rapidrecap.app/video/7XtTDZeNvMc
Generated: 2025-09-27T14:33:54.716+00:00

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## Quick Overview

The discussion concludes that the Everett Many-Worlds Interpretation (MWI) of quantum mechanics, which avoids the collapse postulate, is not necessarily superior to the standard Born rule approach because the MWI itself introduces circularity and relies on unproven assumptions about probabilities, making the question of which theory is correct highly complex and unresolved.

**Key Points:**
- Jacob Barandes questions whether simplifying quantum theory by removing the measurement postulate (as in MWI) still yields a working theory, arguing that MWI has its own inherent difficulties.
- Alyssa Ney argues that the MWI, which posits that all possible outcomes of a measurement occur in different branches of reality, is not necessarily better than the standard interpretation which uses the Born rule for probabilities.
- Barandes points out that the MWI approach, while deterministic in its evolution of the universal wave function, still requires deriving probabilities for measurement results, leading to circular arguments.
- Ney suggests that the MWI approach, which avoids the collapse postulate and hidden variables, still contains assumptions about probability that are difficult to test or justify rigorously.
- Roger Penrose (via video link) expresses disagreement with the notion that the Schrödinger equation alone describes reality, suggesting it only works well for small phenomena but fails for large systems where relativistic effects become important.
- The discussion centers on the philosophical and physical implications of different quantum interpretations, particularly the difficulty of testing theories that rely on unobservable branches of reality (MWI) versus those that retain a measurement postulate.
- The panelists acknowledge that both major interpretations—MWI and the standard interpretation involving collapse—face significant philosophical hurdles regarding the nature of reality and probability.

![Screenshot at 00:15: Jacob Barandes questioning whether removing the measurement axioms to simplify quantum theory still allows the theory to yield empirical results like probabilistic predictions of measurement outcomes.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-00-15.png)

**Context:** This video features a panel discussion involving theoretical physicist and philosopher Jacob A. Barandes, philosopher of science Alyssa Ney, and Nobel Laureate Roger Penrose (appearing via video link), moderated by an unseen host. The central theme is the philosophical interpretation of quantum mechanics, specifically contrasting the standard approach involving wavefunction collapse (Born rule) with the Many-Worlds Interpretation (MWI) proposed by Hugh Everett. The panelists debate the relative merits and inherent challenges of each framework when explaining observed reality and measurement outcomes.

## Detailed Analysis

The discussion tackles the fundamental question of whether quantum mechanics, when stripped down to its core mathematical axioms, remains empirically sound, particularly contrasting the standard interpretation with the Many-Worlds Interpretation (MWI). Jacob Barandes initiates the debate by asking if removing the measurement axioms to simplify the theory (a key feature of MWI) still allows the theory to predict the probabilistic content of measurement results. He argues that MWI, despite being fully deterministic in its wave function evolution, still runs into circularity when trying to derive probabilities, essentially having to presuppose the very notion of probability it seeks to explain. Alyssa Ney agrees that the MWI interpretation, which suggests all possible outcomes occur in branching realities, is not necessarily superior to the standard interpretation that uses the Born rule. She points out that MWI still contains unstated assumptions about probability and that the existence of countless unobservable copies of oneself in different branches does not necessarily make the theory more coherent or empirically grounded. Roger Penrose, appearing remotely, reiterates his long-held view that the Schrödinger equation alone is insufficient to describe reality, especially when dealing with large systems where gravitational effects become relevant, implying that quantum mechanics needs further revision beyond interpretations of measurement.

### Questioning Simplification

- Jacob Barandes asks if removing measurement axioms for simplicity (MWI) still yields empirical content
- The MWI wave function evolves deterministically, but deriving probabilities remains circular
- Barandes notes that the Everett approach seems to presuppose the probability it tries to derive.

### Critique of Many-Worlds

- Alyssa Ney argues that MWI does not automatically solve philosophical issues; it posits unobservable parallel worlds for every outcome
- Ney finds that MWI is not clearly superior to the standard interpretation relying on the Born rule.

### Penrose's Stance

- Roger Penrose insists that the Schrödinger equation is not the whole story, arguing it fails for large systems where gravity matters
- Penrose suggests that the mathematical framework must account for large-scale, non-quantum phenomena.

### The Role of Probability

- Barandes points out that MWI proponents often derive probabilities in a way that requires assuming the probabilities exist beforehand, leading to circular reasoning.

### Conclusion on Interpretations

- Ney concludes that both the Everett interpretation and the standard interpretation face significant philosophical challenges regarding what constitutes 'real' and how to connect quantum formalism to empirical observations.

![Screenshot at 00:00: Jacob A. Barandes introducing the central question about the validity of quantum theory axioms.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-00-00.png)
![Screenshot at 00:06: Alyssa Ney responding to Barandes, stating her strong view that the theory might not work if simplified by removing measurement axioms.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-00-06.png)
![Screenshot at 00:16: A wide shot of the panel setup, with Roger Penrose visible on the screen, indicating his remote participation.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-00-16.png)
![Screenshot at 00:30: Roger Penrose speaking remotely, arguing against the completeness of the Schrödinger equation for large-scale systems.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-00-30.png)
![Screenshot at 00:50: Close-up of Roger Penrose expressing his skepticism about the Schrödinger equation alone being sufficient.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-00-50.png)
![Screenshot at 01:18: The moderator posing a question to the panel about the philosophical meaning of the interpretations of reality.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-01-18.png)
![Screenshot at 02:00: Jacob Barandes detailing the circularity issue in deriving probabilities within the Everett approach.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-02-00.png)
![Screenshot at 03:39: Alyssa Ney explaining her objection to the MWI, focusing on the concept of unobservable branching realities.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-03-39.png)
![Screenshot at 04:50: Jacob Barandes emphasizing that different interpretations lead to different predictions about what is physically real.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-04-50.png)
![Screenshot at 06:36: Jacob Barandes pointing emphatically while discussing the circularity of probability derivation in MWI arguments.](https://ss.rapidrecap.app/screens/7XtTDZeNvMc/00-06-36.png)