Alain Aspect and the Experiment That Tested Einstein

Einstein called it "spooky action at a distance" and was sure quantum mechanics had to be incomplete. In 1982, in a lab in Orsay, near Paris, French physicist Alain Aspect put the question to nature. Forty years later, he received the Nobel Prize in Physics. What did he find, and what does it really mean? (Spoiler: it does NOT let you send messages faster than light.) In this video we follow the investigation step by step, using the Feynman method: simple images, everyday comparisons, and no complicated equations. 🔎 What you will learn: Local realism: the two "common sense" ideas Einstein believed in Entanglement, and the EPR paper (1935) by Einstein, Podolsky and Rosen The Einstein vs Bohr debate, and why it seemed like philosophy John Bell (CERN, 1964): how a philosophical dispute became a testable experiment Bertlmann's socks, and a simple two-player game that shows Bell's theorem (75% vs about 85%) Clauser and Freedman (1972), the CHSH inequality, and the locality loophole Alain Aspect's experiments (1981-1982): calcium atoms, two lasers, and polarizers switched in flight The numbers: the classical limit is 2, quantum mechanics allows up to about 2.83, Aspect measured about 2.7 What it means (and what it does NOT mean): no faster-than-light signals Loophole-free Bell tests (Delft 2015), cosmic Bell tests, and the Big Bell Test Quantum cryptography, teleportation, and the 2022 Nobel Prize (Aspect, Clauser, Zeilinger) 🎙️ This video is narrated in French. Turn on subtitles (CC) for English. If you enjoyed this, subscribe and turn on the bell. Tell me in the comments which moment surprised you most: the two-player game, Bell's question about a permanent job, or quasar light choosing the settings. Next video: Schrödinger's cat, and how French physicists built a miniature one in Paris. #QuantumPhysics #AlainAspect #Einstein