Schrödinger’s 1935 mic-drop: seal a cat to a 50% radioactive poison trigger and, by quantum rules, it’s both alive and dead. Superposition is real (double-slit), pushed to 2,000‑atom molecules and tiny diamonds, but decoherence blocks cat-sized weirdness. The fight is over meaning—Copenhagen wave-function collapse vs Many Worlds, with Wigner’s mind and Penrose’s gravity—while quantum computers exploit it, where ~300 qubits explore more states than atoms in the observable universe.