In 1935, Austrian physicist Erwin Schrödinger came up with the infamous thought experiment, which he would be best remembered for, while discussing with Albert Einstein the problems of the Copenhagen interpretation of quantum mechanics.
The thought experiment, known as Schrödinger’s Cat, consists of three items sealed inside a box: a cat, a flask of poison, and a radioactive source. Should the internal Geiger counter detect radioactivity, the contraption would break the flask open, releasing the poison. According to the Copenhagen interpretation, the cat would be simultaneously alive and dead at this point; it would remain in this state until the box is opened.
Today, in the garden of Schrödinger’s former house at Huttenstrasse 9 in Zurich, a life-size figure of a cat can be found. Depending on the light conditions of the day, it may appear alive or dead, just like the famous thought experiment.