The YouTube video "The Strangest Idea in Science: Quantum Immortality" from the "Cool Worlds" channel explores the radical concept of quantum immortality stemming from the many-worlds interpretation of quantum mechanics. This theory suggests that every possible outcome of a quantum event occurs in separate, non-interacting realities, meaning that in scenarios like quantum Russian roulette, a version of an individual would always survive. The video explains foundational quantum concepts like superposition and decoherence, contrasting the many-worlds interpretation with the more traditional Copenhagen interpretation which posits wave function collapse. Ultimately, it examines the philosophical implications of quantum immortality, particularly regarding personal identity and the nature of consciousness, while also acknowledging criticisms and the practical unfeasibility of proving such a phenomenon.