Erwin Schrödinger, an Austrian physicist, proposed the famous thought experiment known as "Schrödinger's cat" in 1935 to illustrate the peculiar nature of quantum mechanics. The purpose of the experiment was to highlight what Schrödinger saw as a paradox arising from the Copenhagen interpretation of quantum superposition and the concept of wave-particle duality.
In the thought experiment, Schrödinger imagines a scenario where a cat is placed inside a sealed box along with a radioactive substance, a Geiger counter, and a vial of poison. The radioactive substance has a 50% chance of decaying within a specified time, which triggers the Geiger counter. If the Geiger counter detects radiation, it releases the poison, ultimately leading to the death of the cat. However, if no decay occurs, the cat remains alive.
According to the Copenhagen interpretation, before the box is opened and observed, the cat exists in a superposition of both being alive and being dead. It is in an indeterminate state, a combination of all possible outcomes. It is only upon observation or measurement that the wave function collapses, and the cat's state becomes definite, either alive or dead.
Schrödinger employed this thought experiment to illustrate the apparent absurdity of applying quantum principles to macroscopic objects, such as a cat. By imagining a scenario where a macroscopic object's fate hinges on a quantum event, he aimed to show the potential contradictions or paradoxes arising from the interpretation of quantum mechanics.
Though Schrödinger himself intended the experiment to be provocative and critique the Copenhagen interpretation, it has become widely known and discussed in popular culture as an illustration of the peculiar nature of quantum mechanics and the challenge of interpreting superposition and wave-particle duality at macroscopic scales.