The direct answer
Schrödinger's cat is a thought experiment that connects a microscopic quantum event to a macroscopic consequence. A radioactive atom, a detector, and a mechanism that releases poison are sealed with a cat. If the atom is described as a superposition of decayed and not decayed states, then the combined system appears to place the cat in a corresponding combination of outcomes.
Erwin Schrödinger introduced the scenario in 1935 to make a problem vivid. Quantum mechanics describes superpositions with extraordinary precision at small scales, yet daily experience presents definite outcomes. The cat asks where and how that transition occurs.
Superposition is a state, not ordinary uncertainty
A classical coin hidden under a cup has already landed on heads or tails even if you do not know which. A quantum superposition is different. The state contains amplitudes for multiple possible measurement outcomes, and those amplitudes can interfere. That interference is what separates a coherent superposition from a simple lack of information.
When a measurement is made, one outcome is recorded. Different interpretations of quantum mechanics disagree about what that transition says about reality, but they agree on the probabilities that experiments observe.
Observation does not require consciousness
In quantum mechanics, observation means a physical interaction that can carry information about the system. A detector, an atom, a photon, or the surrounding environment can all play that role. A human mind is not required.
Large systems interact with their environments constantly. Those interactions rapidly destroy the phase relationships that make interference possible, a process called decoherence. This is why cat scale superpositions are not part of ordinary experience.
What experiments have actually shown
The 2012 Nobel Prize in Physics recognized Serge Haroche and David Wineland for methods that let researchers measure and control individual quantum systems. Their teams created and tracked cat like states in trapped ions and microwave fields while studying how those states lose their quantum character.
The 2025 Nobel Prize in Physics recognized experiments that demonstrated macroscopic quantum tunnelling and quantized energy levels in an electrical circuit. These systems remain far smaller and more controlled than a living animal, but they show that collective systems can display quantum behavior when sufficiently isolated.
Frequently asked questions
Did Schrödinger believe a real cat could be both alive and dead?
The scenario was a critique and a challenge. It was intended to show how strange it becomes to extend a microscopic superposition directly to an everyday object.
Does looking at a quantum system require a person?
No. Measurement is a physical interaction that produces or can produce information about the system. Conscious awareness is not part of the experimental requirement.
What is decoherence?
Decoherence is the loss of observable quantum coherence as a system becomes entangled with its environment. It helps explain why interference becomes extremely difficult to observe in large systems.