Mar 7, 2020, 3:54 PM ETInterview, Fireside Chat

Lee Smolin: Quantum Gravity and Einstein's Unfinished Revolution | Lex Fridman Podcast #79

Smolin identifies as a scientific realist, believing in an external world independent of human perception, knowledge, or existence.
He argues that what humans experience is a highly processed construct of the brain, not the "raw" world.
He rejects the notion of absolute "right" vs. "wrong," proposing a spectrum where theories are "more right" or "less right" based on their proximity to an objective description of reality.
He disputes the existence of a rigid "scientific method," citing philosopher Paul Feyerabend to argue that science is a community of practitioners bound by ethical precepts (e.g., honesty, peer review) rather than a single algorithmic procedure.

Smolin defines Einstein's "unfinished revolution" as the failure to reconcile quantum mechanics with general relativity.
He critiques the standard formulation of quantum mechanics for having two contradictory evolution rules: smooth deterministic evolution (Schrödinger) and discontinuous collapse during measurement.
He argues that space-time is not fundamental but an emergent, approximate description valid only at certain scales.
Fundamental vs. Emergent:
- Time: Smolin posits time is fundamental, defined as the continuous creation of new events from existing ones; the future does not yet exist.
- Space: Space is emergent, arising only in sufficiently complex systems from the underlying network of events.
- Causality: He proposes causality is the most fundamental physical principle, with events triggering other events without a pre-existing spatial background.
He asserts that the principle of "locality" (as defined by Einstein/Bell regarding independent realities of separated particles) is experimentally false, though a different definition of locality used in quantum field theory remains valid.

Smolin co-invented Loop Quantum Gravity, an alternative to string theory, and maintains both communities were historically divided but should collaborate.
In his 2006 book The Trouble with Physics, he criticized the physics community for fixating on mathematical consistency over empirical testability.
He highlights the "landscape problem" in string theory, noting that the theory allows for hundreds of thousands of solutions (vacua), making it impossible to predict unique properties of our specific universe without additional selection principles.
He proposes "Cosmological Natural Selection" as a potential framework, suggesting laws of physics may evolve across a multiverse via a process analogous to biological natural selection to maximize the production of black holes.
He regrets that his critique of string theory was misinterpreted as an attack on individuals, when his intent was to criticize methodological stagnation in the field.

Smolin rejects the Many-Worlds Interpretation (Everett), stating as a foundational principle that "there is just one world."
He identifies a fundamental problem with Many-Worlds: it struggles to derive the Born Rule (probabilities) since the theory eliminates wave function collapse, removing the mechanism for probability generation.
He notes that even prominent defenders of Many-Worlds (e.g., Simon Saunders, David Wallace) admit they have not fully resolved the probability problem.
He expresses openness to the views of Sean Carroll but maintains that the Many-Worlds interpretation does not address his specific agenda regarding the reality of a single universe.

Smolin argues that scientific progress requires a community culture where researchers engage in cross-pollination ("get off their hills") rather than sectarianism.
He observes a hopeful trend among younger physicists, who show less interest in historical debates between theory camps and more interest in synthesizing ideas from Loop Quantum Gravity, String Theory, and Causal Set Theory.
He cites Eric Weinstein's metaphor of the "wheel on luggage" to illustrate that major breakthroughs often involve recognizing obvious solutions that previous generations missed due to conventional thinking.
He suggests that genius and breakthroughs stem from a combination of luck, stubbornness, and a unique capacity to ask deeper questions rather than innate talent alone.

Smolin believes the universe's future is open and that fundamental laws of physics could potentially change, though this remains speculative.
He maintains that while human cognitive limits may eventually exist, we are currently far from reaching the boundaries of what can be understood with current tools.
He advocates for a shift in theoretical physics toward identifying fundamental "principles" (like those Einstein used) before constructing mathematical models.
He predicts that the next major breakthrough in physics will likely come from integrating causality as a primary construct rather than treating space-time as a fundamental stage.