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Why did Erwin Schrödinger propose the Schrödinger's cat thought experiment?

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photoelectric effect: Einstein's Nobel Prize-winning discovery — quantum mechanics Brian Greene discusses the key formula in the photoelectric effect, an insight that helped launch the quantum revolution. This video is an episode in his *Daily Equation* series.

Erwin Schrödinger proposed the "Schrödinger's cat" thought experiment in 1935 as a critique of the Copenhagen interpretation of quantum mechanics. He felt that applying quantum principles, which describe the probabilistic nature of subatomic particles, to macroscopic objects led to absurd conclusions.1

The experiment imagines a cat in a sealed box with a radioactive atom, a Geiger counter, a hammer, and a vial of poison. If the atom decays, the Geiger counter triggers the hammer, shattering the vial and killing the cat. According to the Copenhagen interpretation, until the box is opened and observed, the atom exists in a superposition of both decayed and undecayed states. Consequently, the cat would be simultaneously alive and dead. Schrödinger found this idea "quite ridiculous" and used it to highlight what he saw as the limitations and strange implications of quantum theory when scaled up to everyday objects.213