A thought experiment in which a cat, a flask of poison, and a single radioactive atom are placed in a sealed box. If and when an internal radiation monitor detects the random event of radioactive decay the flask is shattered to release the poison and the cat dies. According to the thought experiement, while the box remains unopened and the cat unobserved, it exists in a quantum superposition of states in which the cat is neither alive nor dead and yet simultaneously alive and dead. Only upon the experimenter opening the box and observing does the state of the cat undergo a ‘collapse of the waveform’ (referring to Schroedinger’s Wave Equation) and the cat is seen to be either alive or dead, but of course not both. This is a classical conceptualization of the Copenhagen interpretation of quantum mechanics which maintains that there is only one universe in which one or the other result occurs, as opposed to the Oxford interpretation of quantum mechanics which maintains we exist in a multiverse and when the box is opened a new universe is split off so that one universe contains a dead cat and in the other universe it remains alive. It should be mentioned that Schroedinger himself conceived this thought experiment as an example of the absurdity of the existing Copenhagen interpretation of quantum mechanics, but since his time some physicists have come to regard it as not absurd at all but that it would be quite real if the experiment were to be performed. Consequently Schroedinger’s Cat has become a way of illustrating and comparing the features, strengths, and weaknesses of each interpretation.