Schrödinger's Cat
A cat is sealed in a box with a device that may or may not release poison based on a quantum event. Before you open the box, is the cat alive, dead, or somehow both?
Proposed by physicist Erwin Schrödinger in 1935, this thought experiment wasn't meant to prove that cats can be both alive and dead. It was meant to expose an absurdity in the Copenhagen interpretation of quantum mechanics. Schrödinger used it to argue that applying quantum superposition to macroscopic objects leads to a ridiculous conclusion.
Schrödinger, E. (1935). Die gegenwärtige Situation in der Quantenmechanik. Naturwissenschaften, 23(48), 807–812.
What Schrödinger was actually arguing
Schrödinger wasn't delighted by the cat scenario. He was horrified by it. He was pointing out that quantum mechanics, if taken literally at the macroscopic scale, implies the cat is in a superposition of alive and dead until observed. His point: this is obviously absurd, so something must be wrong with the prevailing interpretation.
The experiment forces a question: at what scale does "superposition" stop applying? Electrons seem to behave as if in multiple states at once. Cats don't. Where's the cutoff?
The observation problem
The deeper puzzle is about observation itself. In quantum mechanics, the act of measuring a system seems to collapse its superposition into a definite state. This raises a genuinely unsettling question: does consciousness cause collapse? Is there something special about observation by a mind, or would any physical detector do?
Different interpretations of quantum mechanics give radically different answers:
- Copenhagen: the cat is in superposition; opening the box collapses the wave function.
- Many-Worlds: both outcomes happen; there's a branch of the universe with a live cat and one with a dead cat.
- Pilot Wave: there's always a definite reality; we just can't know it.
Why it matters beyond physics
The cat has become a cultural shorthand for any situation with multiple possible states that "collapse" upon being observed or decided. The philosophy buried inside it, touching measurement, reality, and consciousness, is very much unresolved.