Schrodinger's Cat Was a Thought Experiment Against Quantum Theory

While the image of a cat in a box has become a famous symbol of quantum weirdness, its creator intended it as a powerful complaint. In 1935, Erwin Schrödinger was deeply troubled by the prevailing "Copenhagen interpretation" of quantum mechanics. This view stated that a particle, like an atom, exists in a "superposition" of all its possible states simultaneously—for example, both decayed and not decayed—until the moment it is observed. Schrödinger found this acceptable for atoms but wanted to illustrate the ludicrous conclusions it produced when scaled up to the macroscopic world we live in.

The experiment was designed to be a bridge between these two worlds. Inside a sealed box, a cat's fate is linked to a single radioactive atom. If the atom decays, it triggers a Geiger counter, which releases a hammer that smashes a vial of poison, killing the cat. According to the Copenhagen interpretation, until the box is opened and "observed," the atom is in a superposition of both decayed and not-decayed. Therefore, the cat, whose life is entangled with the atom, must also be in a superposition of being simultaneously alive and dead.

Schrödinger, corresponding with a similarly skeptical Albert Einstein, never believed this could be literally true. He used this vivid, morbid example not to explain quantum mechanics, but to argue that any theory leading to such a nonsensical paradox must be incomplete. Ironically, his attempt to highlight a flaw became the most enduring illustration of the very quantum mystery he was protesting: the profound and still-debated problem of where the bizarre rules of the quantum realm end and the classical world we experience begins.