The Schrödinger’s cat is an experiment based on thought considerations, proposed by the Austrian physicist Erwin Schrödinger around 1935. The experiment establishes that a cat may be simultaneously both alive and dead at the very same time, a state known as #quantum superposition, as a result of being linked to a random subatomic situation that may or may not occur. The thought experiment is also often featured in theoretical discussions of the interpretations of quantum mechanics. Schrödinger coined the term Verschränkung (entanglement) in the course of developing the thought experiment.
In consequence of this proposal, in 1957 Hugh Everett developed the many-worlds theory of quantum mechanics, which does not single out observation as a special process. In the many-worlds interpretation, both alive and dead states of the cat persist after the box is opened, but are decoherent from each other. In other words, when the box is opened, the observer and the possibly-dead cat split into an observer looking at a box with a dead cat, and an observer looking at a box with a live cat. But since the dead and alive states are decoherent, there is no effective communication or interaction between them.