A cat is put in a box, together with a radioactive atom. A Geiger counter linked to a poison canister is attached to the box. If the atom decays, and the geiger-counter detects an alpha particle, poison is released, killing the cat. Before some observer opens the box, the cat's fate is tied to the wave function of the atom, described as a superposition of decayed and undecayed 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.
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Paradoxes like this lead some researchers to suggest that every possible path of "execution" does happen, but we only observe one of the paths and are isolated from the others. Thus, there may be parallel universes where nerds get dates.
What have you done to the cat? It looks half-dead. -- Schroedinger's wife
NoAnimalsWereHarmed in making this page. Only human fingers and joints.