Lee Smolin: Quantum Gravity and Einstein's Unfinished Revolution | Lex Fridman Podcast #79
Lex Fridman (host), Lee Smolin (guest)
In this episode of Lex Fridman Podcast, featuring Lex Fridman and Lee Smolin, Lee Smolin: Quantum Gravity and Einstein's Unfinished Revolution | Lex Fridman Podcast #79 explores lee Smolin on Reality, Time, and Fixing Modern Theoretical Physics Lee Smolin and Lex Fridman explore deep questions about what is real, the limits of human perception, and whether an objective external world exists independent of us. Smolin defends a realist position, arguing that science as a community practice—rather than a strict ‘scientific method’—slowly refines our stories to better approximate that real world.
Lee Smolin on Reality, Time, and Fixing Modern Theoretical Physics
Lee Smolin and Lex Fridman explore deep questions about what is real, the limits of human perception, and whether an objective external world exists independent of us. Smolin defends a realist position, arguing that science as a community practice—rather than a strict ‘scientific method’—slowly refines our stories to better approximate that real world.
He lays out his view that time and causality are truly fundamental, while space and spacetime are emergent, higher-level constructs arising from networks of events. This leads him to nonlocal, causal approaches to quantum gravity and to critiques of the standard formulations of quantum mechanics (measurement problem) and of Many-Worlds interpretations.
Smolin sees Einstein’s revolution as unfinished: general relativity and quantum theory remain conceptually incompatible and incomplete, and quantum mechanics itself is, in his view, not a final theory. He also reflects on the sociology of physics, string theory, and the need for unifying principles and cross-community collaboration.
Despite past criticisms of string theory, he emphasizes hope in younger physicists who are less invested in old camps and more open to integrating ideas (loops, strings, causal sets, etc.) to finally make progress on quantum gravity.
Key Takeaways
Science is a community practice, not a rigid ‘method’.
Influenced by Feyerabend, Smolin argues there is no single, universal scientific method; instead, science is a community bound by ethical norms (don’t lie, report all results, rigorous checking) and by the ability to withstand intense peer scrutiny.
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Realism sets the goal: approximate an objective world that exists without us.
Smolin’s realist stance holds that a mind-independent world exists and that ‘being right’ means progressively approaching an exact description of it, even though we never know with certainty that we have arrived.
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Time and causality are fundamental; space and spacetime are emergent.
In Smolin’s causal view, the basic ingredients are events and the causal relations between them; time is the ongoing creation of new events from old ones, while space and spacetime arise only at higher levels of complexity as effective, approximate descriptions.
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Quantum mechanics is consistent but incomplete, especially around measurement.
He emphasizes the measurement problem: quantum theory uses two incompatible evolution rules (smooth Schrödinger evolution vs. ...
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Experimental violations of Bell’s locality force us to rethink ‘locality’, not causality.
Different notions of locality exist: standard quantum field theory maintains a local field structure, but Bell’s notion of locality—requiring distant outcomes to be unaffected by measurement choices elsewhere—fails experimentally, pushing Smolin toward nonlocal yet still causal frameworks.
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Many-Worlds remains conceptually incomplete, particularly about probability.
Smolin finds Everettian and post-Everettian approaches elegant but notes that deriving the Born rule and making sense of probability—without collapse—remains controversial even among experts, and the framework does not answer the particular questions he cares about.
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Future progress in quantum gravity likely requires new principles and sociological shifts.
Smolin believes existing approaches (strings, loops, causal sets, etc. ...
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Notable Quotes
“I think that time, the activity of time, is a continual creation of events from existing events.”
— Lee Smolin
“I don’t believe in a scientific method.”
— Lee Smolin
“Quantum mechanics as it was developed in the late 1920s is consistent but incomplete.”
— Lee Smolin
“There is just one world and it happens once.”
— Lee Smolin
“One possibility is God is nothing but the power of the universe to organize itself.”
— Lee Smolin
Questions Answered in This Episode
If time is fundamental and space is emergent, what concrete experimental signatures would distinguish this from conventional spacetime-based theories?
Lee Smolin and Lex Fridman explore deep questions about what is real, the limits of human perception, and whether an objective external world exists independent of us. ...
Get the full analysis with uListen AI
How might a fully realist completion of quantum mechanics resolve the measurement problem without invoking Many-Worlds or observer-dependent collapse?
He lays out his view that time and causality are truly fundamental, while space and spacetime are emergent, higher-level constructs arising from networks of events. ...
Get the full analysis with uListen AI
What new guiding principles, analogous to Einstein’s relativity principles, could unify quantum theory and general relativity into a coherent picture of quantum gravity?
Smolin sees Einstein’s revolution as unfinished: general relativity and quantum theory remain conceptually incompatible and incomplete, and quantum mechanics itself is, in his view, not a final theory. ...
Get the full analysis with uListen AI
In what ways could Smolin’s ideas about evolving laws of physics (cosmological natural selection) be empirically tested or falsified?
Despite past criticisms of string theory, he emphasizes hope in younger physicists who are less invested in old camps and more open to integrating ideas (loops, strings, causal sets, etc. ...
Get the full analysis with uListen AI
How can the physics community practically overcome entrenched camps (strings vs. loops, etc.) to foster the kind of cross-pollination Smolin argues is needed for real progress?
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Transcript Preview
The following is a conversation with Lee Smolin. He's a theoretical physicist, co-inventor of loop quantum gravity, and a contributor of many interesting ideas to cosmology, quantum field theory, the foundations of quantum mechanics, theoretical biology, and the philosophy of science. He's the author of several books, including one that critiques the state of physics and string theory called The Trouble With Physics, and his latest book, Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum. He's an outspoken personality in the public debates on the nature of our universe, among the top minds in the theoretical physics community. This community has its respected academics, its naked emperors, its outcasts, and its revolutionaries, its madmen, and its dreamers. This is why it's an exciting world to explore through long-form conversation. I recommend you listen back to the episodes with Leonard Susskind, Sean Carroll, Michio Kaku, Max Tegmark, Eric Weinstein, and Jim Gates. You might be asking, "Why talk to physicists if you're interested in AI?" To me, creating artificial intelligence systems requires more than Python and deep learning. It requires that we return to exploring the fundamental nature of the universe and the human mind. Theoretical physicists venture out into the dark, mysterious, psychologically challenging place of first principles more than almost any other discipline. This is the Artificial Intelligence Podcast. If you enjoy it, subscribe on YouTube, give it five stars on Apple Podcasts, support it on Patreon, or simply connect with me on Twitter @lexfridman, spelled F-R-I-D-M-A-N. As usual, I'll do one or two minutes of ads now, and never any ads in the middle that can break the flow of the conversation. I hope that works for you and doesn't hurt the listening experience. This show is presented by Cash App, the number one finance app in the App Store. When you get it, use code LEXPODCAST. Cash App lets you send money to friends, buy Bitcoin, and invest in the stock market with as little as $1. Since Cash App allows you to buy Bitcoin, let me mention that cryptocurrency, in the context of the history of money, is fascinating. I recommend A Cent of Money as a great book on this history. Debits and credits on ledgers started around 30,000 years ago. The US dollar of course created over 200 years ago, and Bitcoin, the first decentralized cryptocurrency, was released just over 10 years ago. So given that history, cryptocurrency is still very much in its early days of development, but it still is aiming to, and just might, redefine the nature of money. If you get Cash App from the App Store or Google Play and use the code LEXPODCAST, you'll get $10 and Cash App will also donate $10 to FIRST, one of my favorite organizations that is helping to advance robotics and STEM education for young people around the world. And now, here's my conversation with Lee Smolin. What is real? Let's start with an easy question. Put another way, how do we know what is real and what is merely a creation of our human perception and imagination?
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