Patreon: https://www.patreon.com/seanmcarroll Blog post with audio player, show notes, and transcript: https://www.preposterousuniverse.com/podcast/2025/07/14/321-david-tong-on-open-questions-in-quantum-field-theory/ Quantum field theory is the basis for our most successful theories of fundamental physics. And yet, there are things we don't understand about it. Some of these puzzles are relatively well-known, while others are less celebrated. David Tong joins us to talk about some of the more interesting and perplexing aspects of quantum field theory. He also discusses his new project to write a series of textbooks covering (all?) important topics in theoretical physics. To date, these include Classical Mechanics, Quantum Mechanics, Fluid Mechanics, and Electromagnetism. David Tong received his Ph.D. in theoretical physics from Swansea University. He is currently a professor of Theoretical Physics in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge. He is a winner of the Adams Prize and a Simons Investigator. In addition to his books, he has written many freely-available sets of lecture notes on topics in physics. Mindscape Podcast playlist: https://www.youtube.com/playlist?list=PLrxfgDEc2NxY_fRExpDXr87tzRbPCaA5x Sean Carroll channel: https://www.youtube.com/c/seancarroll #podcast #ideas #science #philosophy #culture