Schrödinger's cat

"Schrödinger's cat" was a famous thought experiment devised by Human physicist Edwin Schrödinger in the early 20th century to illustrate the uncertainty principle. In this scenario, a cat is in an enclosed box with a device that, if an atom of a radioactive substance decays, the cat will be killed. While in the box and unobserved, the scenario suggests the cat is both alive and dead, and only assumes a single state of being once observed.

A similar thought experiment in Vulcan science was called T'Pral's Sehlat.