Our Mathematical Universe: Brian Greene & Max Tegmark

Brian Greene welcomes viewers to a live session brought by the World Science Festival. He notes that he is broadcasting from New York City, rather than his usual home studio backdrop. Brian provides context that this video builds on a previous discussion about whether math reveals reality. He previews that this session will focus on Max Tegmark's perspective on that topic.

Brian advertises upcoming virtual World Science Festival programs: one on language with various speakers like Noam Chomsky and Stephen Pinker on September 16, and one on cosmology with Alan Guth and Andrei Linde. He requests creative title ideas for the language program from the audience.

Brian introduces his guest Max Tegmark. Max shares about his childhood and early interest in big questions, leading him to study physics and cosmology. He ended up doing grad school in California. Max recounts how he became fascinated by the biggest questions about the origins and size of our universe.

Max summarizes his career trajectory, spending 25 years focused outwardly on physics and cosmology. In the last 5 years, his research has shifted inward to studying intelligence and consciousness with his MIT group on artificial intelligence. He sees math as able to conquer new domains like the mind previously thought impossible to describe mathematically.

Brian takes some audience questions. One asks if physics laws have gotten more complex over time. Max responds they've oscillated between simple and complex in cycles. Brian agrees we're good at finding elegance, expecting an ultimate simple theory. Another asks if humans can definitively determine the mathematical structure of reality. Max thinks it's unknown if we'll fully crack it.

Brian checks his understanding of Max's view - that all mathematical structures exist in reality across a multiverse landscape. Max confirms this controversial idea, which he argues avoids needing any special 'magic' to make one math structure real. He thinks we should be open to reality being larger than we thought.

Max argues that existence of a mathematical structure would imply existence of subjective experience for 'people' in it, so he doesn't distinguish mathematical from physical existence. Brian pushes back that math is our abstract description, not inherent to reality itself.

Brian asks how Gödel's incompleteness theorems limiting provability in math impact Max's view. Max responds that while humans can't prove consistency, our universe seems unfazed by this - so he doesn't think it constrains reality itself.

Brian questions how spacetime fits into Max's framework. Max suggests spacetime could be properties of one mathematical structure we inhabit, rather than separately existing. He argues we should be open to reality being purely mathematical.

Brian doubts the evidence supports extending a mathematical description just within our universe to all conceivable mathematics. Max acknowledges it's controversial but thinks we should explore extreme possibilities. He argues it's humble to accept reality may be larger than we thought.

Brian notes physicists aim for simple explanations whereas Max's view posits endless complexity. Max responds there's a sawtooth of understandings becoming complex then simple again. He thinks humans find complexity at our scale but simplicity from farther out and in.

Brian raises consciousness - how particles produce inner experience. Max excitedly agrees it's key for morality and AI. He suspects subjective experience emerges from certain information processing patterns. Brian notes philosopher David Chalmers' resistance to this view.

Brian asks if Max thinks machines could be conscious. Max says artificial/biological is arbitrary - only complexity of information processing matters. He thinks we need to understand which systems are conscious to avoid creating suffering AI.

Brian states his general agreement with Max but differing on math structures existing concretely. He's glad consciousness is becoming a respectable scientific topic. Max heartily agrees science should increase our humanity.

Brian thanks Max for an enjoyable discussion. He encourages checking out Max's books and the prior math video. He previews upcoming discussions with Chomsky, Guth and Linde. Brian signs off, hoping to continue regular virtual events.