Wheeler's Cosmic Experiment

Physics: Wheeler's cosmic delayed-choice: quasar ~10 billion light-years away; intervening galaxy acts as gravitational lens, creating two paths separated by kiloparsecs. Photon travels for billions of years. Astronomer's choice: combine paths (wave → interference fringes) or use two separate telescopes (particle → which-path). Result: consistent with QM — photon "retroactively" appears as wave or particle. Philosophical implication: "No phenomenon is a phenomenon until it is an observed phenomenon." (Wheeler). No FTL signaling: choice cannot affect past light cone. Scully quantum eraser and Aspect experiments confirm QM.