The Original Schrödinger's Cat Revisited: Isolated Systems

Schrödinger's original Cat places a radioactive substance, Geiger counter, relay, hammer, poison, and cat inside a closed steel chamber and leaves “this entire system” to itself for one hour. The construction is commonly treated as an isolated system. This paper examines what isolation means in the thought experiment. Physical isolation, causal connection, and information available about individual members of a system are different conditions. A comparison with human mortality illustrates the distinction. An actuary may possess individual information such as birthdays and living habits, yet has no probability information about when the first death claim will occur; it may come at any time and at any probability. For radioactive atoms, the standard description supplies no comparable individual information and treats atoms of the same isotope as identical or dismisses their differences for radioactive decay. Schrödinger's Cat therefore raises a question beyond the physical isolation of the steel box: what information about individual radioactive atoms is available to determine the first decay?