What Is Friction Made Of According to Quantum Physics?

Tonight's question sounds childish: when you push a book across a table and it slows and stops, what is actually doing the stopping? The episode gives the bounded answer early - two surfaces touch at only a tiny scattering of peaks, and at those peaks atoms of one surface pull electrically on atoms of the other - then deepens it by operation: why friction ignores how big the contact looks (the rule written down in 1699), how a single-atom tip on a graphite sheet stutters in stick-slip jumps one lattice spacing at a time, where the lost motion goes (lattice vibrations, quantised as phonons, i.e. heat), and why two mismatched graphite layers can slide with almost no friction at all. It closes on what is still open: how much of the friction electrons in a metal carry away, and the purely theoretical 'quantum friction' between surfaces that never touch. Subscribe to Field & Filament for more calm listening.