Schrodinger's cat gorbe-ye Schrödinger (#) Fr.: chat de Schrödinger A → thought experiment intended to illustrate the → superposition principle in → quantum mechanics. A cat is put in a steel box which is separated from the outside world. The box also contains a vial of lethal acid, a tiny amount of a radioactive substance, a → Geiger counter, and a hammer. If an atom decays and the Geiger counter detects an → alpha particle, the hammer breaks the vial which kills the cat. According to Schrödinger, as long as the box stays closed the cat's fate is tied to the → wave function of the atom, which is itself in a superposition of decayed and un-decayed states. Thus the cat must itself be in a superposition of dead and alive states before the observer opens the box, "observes" the cat, and "collapses" its wave function. However, Schrödinger's argument fails because it rests on the assumption that macroscopic objects can remain unobserved in a superposition state. When an atom decays, its wave function becomes entangled with the enormously complex wave function of the macroscopic Geiger counter. The atom is therefore "observed" by the Geiger counter. Since a Geiger counter cannot, for all practical purposes, be isolated from the rest of the world, the rest of the world observes the atom, and the cat is either dead or alive. → collapse of the wave function. Named after Erwin Schrödinger (1887-1961), → Schrodinger equation, who proposed the thought experiment in 1935 in order to illustrate the inconsistency of the Copenhagen interpretation of quantum mechanics; cat, from M.E. cat, catte; O.E. catt, catte (cf. O.Fris, M.D. katte, O.H.G. kazza, Ir. cat, Welsh cath), probably from L.L. cattus, catta "cat." Gorbé, from Mid.Pers. gurbag "cat;" → Schrodinger equation, |