Mindscape Ask Me Anything, Sean Carroll | June 2026

Carroll humorously imagines inviting Pope Leo XIV, a fictional American math/statistics major, onto the Mindscape podcast. This hypothetical pope has issued an encyclical questioning AI's dehumanizing potential and its impact on the 'soul,' sparking debate among 'governing classes.' Carroll sees him as a respectable thinker, despite potential disagreements, and believes a conversation on science, religion, and AI would be valuable.

Discussion of Pope Leo XIV's encyclical on AI and dehumanization, his background as a Villanova alumnus and math/statistics major.

Carroll and his team (Nadia Diaenko, Sakshi Dulani) propose a 'phenomenologically acceptable quantum cyclic universe.' Unlike traditional cyclic models where entropy increases with each cycle, their quantum model, set in a finite-dimensional Hilbert space, features exactly repeating cycles. This avoids the Boltzmann brain problem because the recurrence period is much shorter than the time needed for random fluctuations to create Boltzmann brains, and it accommodates the arrow of time without explaining its initial low-entropy state.

Description of the paper 'Toward a Phenomenologically Acceptable Quantum Cyclic Universe,' explanation of cyclic vs. periodic universes, Tolman's entropy argument, and the quantum recurrence theorem loophole.

Carroll suggests that feelings like boredom and tiredness, as described by poet-philosopher Jacobo Leopardi, are not just behavioral markers but point to consciousness requiring ongoing self-relation across time with needs and desires. He links this to Antonio Damasio's concept of homeostatic regulation, where the body and mind drift from desired states, and consciousness helps us recognize and fix these drifts as part of an evolutionary mechanism.

Reference to Leopardi's theory of boredom and Damasio's work on feelings and homeostatic regulation.

Carroll expresses disdain for deepfakes of historical figures like Richard Feynman, arguing they are 'necessarily degraded' and not a genuine way to learn. He believes they do not honor the original person and are a 'silly' form of entertainment, as information quality degrades through such processing.

Carroll's personal feelings about deepfakes of Richard Feynman and the degradation of information.

A localized quantum wave function necessarily involves parts moving at different velocities due to the uncertainty principle (knowing position precisely means not knowing momentum). However, Carroll clarifies that one should not reify the wave function as 'particles at different positions'; rather, it represents a superposition of possible measurement outcomes. When unobserved, a particle has a wave function, not multiple positions or speeds.

Explanation of the uncertainty principle, plane waves, and the Everettian view of wave functions.

Physicists use the word 'matter' with multiple meanings depending on context. For cosmologists, 'matter' distinguishes from 'radiation' and refers to energy density that decreases as the scale factor to the minus three (e.g., dark matter, stars, black holes). Neutrinos, for instance, are 'matter' now but were 'radiation' in the early universe. This ambiguity highlights the challenge of communicating expert jargon to broader audiences.

Examples of astronomers calling oxygen a 'metal' and cosmologists classifying neutrinos differently based on the universe's age.

Carroll argues that 'hard incompatibilists' like Robert Sapolsky often misunderstand compatibilism by trying to refute it with arguments for determinism. Compatibilism, by definition, asserts that free will is compatible with determinism. He notes that fundamental physics is not deterministic due to quantum mechanics, further weakening hard determinist arguments.

Carroll's interactions with Sam Harris and Robert Sapolsky, and the definition of compatibilism.

Carroll dismisses claims of UFOs using 'gravitational propulsion' to 'get rid of gravity' as 'nonsense.' He states that such proponents demonstrate a lack of understanding of general relativity and gravity. While theoretical concepts like the Alcubierre warp drive exist, they are far from technological reality and do not support the 'fuzzy' and inconsistent observations associated with UFOs.

Critique of UFO claims, reference to general relativity and the Alcubierre warp drive.

'Ontology' is defined as the set of ingredients in the most fundamental description of reality (what exists according to a physical theory). 'Reality' is a more contested term. When physicists say 'reality is a vector in Hilbert space,' they mean reality is *represented* mathematically by such a vector, not that the mathematical structure itself is the physical reality. This distinction avoids tedious philosophical debates by clarifying the role of mathematical models.

Definitions of ontology and reality, explanation of 'reality is a vector in Hilbert space' statement.

AI's ability to prove or disprove mathematical conjectures is not surprising, akin to its success in chess or protein folding. These are 'well-formed, clearly articulated problem spaces' that computers excel at due to their computational power. However, this does not imply AI can directly contribute to *new* physics in a paradigm-shifting way, as true scientific creativity involves changing how we think about problems, which LLMs currently struggle with.

Comparison of AI's success in math proofs to chess, Go, and protein folding, and its limitations in 'changing the way we think about a certain problem.'

Carroll remains skeptical that AI poses an 'existential risk' (eliminating humanity). He identifies two types of scenarios: vague 'AI outwits us' arguments, which lack detail on AI motivation, and 'humans are stupid' scenarios where AI is given too much control. The latter is plausible (e.g., economic disruption, system failures) but not existential. He prioritizes existing existential threats like nuclear weapons, biological worries, and climate change.

Categorization of AI existential risk scenarios and comparison to other threats.

Carroll deems the project of ranking the 'top five players in NBA history' as 'completely ridiculous' and 'ill-formed.' The game constantly changes, making cross-era comparisons difficult (e.g., three-point shooting). More importantly, basketball is a team sport, and individual greatness is inseparable from team context and results. The focus should be on who wins the game, not metaphysical 'better-ness.'

Analogy to Villanova vs. Georgetown game, Michael Jordan's early struggles, and the team-sport nature of basketball.

When Carroll states that constants of nature 'could have been different,' he means there's no obstacle to imagining possible worlds similar to ours but with different constants. This is distinct from 'necessity' (true in every possible world) or 'actuality' (how the real world works). As scientists, the goal is to understand actuality, not to seek necessity, as the latter is rarely found in fundamental physics.

Definition of necessity and possibility in terms of possible worlds, and the scientific focus on actuality.

The classical limit describes how classical mechanics emerges from quantum mechanics. It involves two steps: starting with a wave function that is 'localized' (concentrated around a classical point, often due to decoherence), and then applying Ehrenfest's theorem, which states that the average value of such a wave function will obey classical equations of motion (Newton's laws) under certain macroscopic conditions.

Explanation of wave function localization, decoherence, and Ehrenfest's theorem.

Carroll advises aspiring physicists to 'study all the physics you can,' emphasizing physics over excessive math (which is often learned within physics courses). He encourages active, self-directed learning beyond formal classes, leveraging abundant online resources. Crucially, he warns against using AI as a 'crutch' that stunts independent thinking. He also stresses engaging with the broader physics discourse, attending seminars, and thinking about open problems, balancing boldness with humility.

Specific recommendations on study habits, use of resources, and engagement with the scientific community.

Carroll laments the societal structures in the US that make personal finance challenging for both young and old. Young people face high student debt, hindering early savings that benefit from compound interest. Older individuals, despite saving, face escalating expenses like healthcare and housing, leading to their accumulated wealth being 'siphoned away' by the system. He views this as a failure of democracy, where the interests of many are not served.

Discussion of student debt, compound interest, healthcare costs, and the 'siphoning' of wealth from the elderly.

Carroll draws a sharp line on AI use in writing: improving existing prose (grammar, punchiness) is acceptable, but having an LLM 'draft' the prose is problematic. He argues that if an LLM drafts the text, the human is merely an editor, not the author. Authorship implies the creation event was in human hands. Journals, by attributing credit, confer professional benefits, which should only go to genuine authors, not those who primarily edit AI-generated content.

Distinction between 'drafting' and 'improving' prose, analogy to human editors, and the role of journals in attributing credit.

Reconciling the subjective experience of time passing with a 'block universe' (where all past, present, and future exist simultaneously) is challenging but not incoherent. Carroll suggests that the 'experience of time passing' is a folk physics concept. In a block universe, each 'instantiation' of a person at a given moment in time holds an unbalanced set of impressions: memories of the past and projections of the future. This imbalance, traceable to the thermodynamic arrow of time, is what we interpret as time's passage.

Critique of 'presentism,' explanation of how an 'instantiation' in a block universe forms impressions of past and future, and its link to the thermodynamic arrow of time.