What is the thought experiment?
Put a cat in a sealed box with a radioactive atom and a vial of poison. If the atom decays, the poison is released and the cat dies. Quantum mechanics says that before measurement the atom is in a superposition of decayed and not decayed. So is the cat, too, both alive and dead until someone looks? Schrödinger meant this as a reductio—a sign something was off.
How do physicists answer it?
The Copenhagen interpretation says measurement collapses the state into one outcome. The many-worlds interpretation says the universe branches into one with a live cat and one with a dead cat. Most physicists today also point to decoherence: big objects constantly interact with their environment, which destroys superposition almost instantly. Quantum computers work by holding off decoherence long enough to compute with superpositions.
FAQ
- Was a real cat ever used?
- No—it's purely a thought experiment.
- What does "Schrödinger's ___" mean in everyday speech?
- Something whose state is undetermined until you check it.
Sources reviewed: 2026-10-25
References
- Schrödinger, E. (1935). Die gegenwärtige Situation in der Quantenmechanik. Naturwissenschaften, 23, 807–812.
- Zurek, W. H. (2003). Decoherence, einselection, and the quantum origins of the classical. Reviews of Modern Physics, 75(3), 715–775.