Schrödinger’s Cat

In 1935, physicist Erwin Schrödinger proposed a thought experiment to show how strange quantum mechanics really is. Imagine you put a cat in a sealed box with a tiny bit of radioactive material, a detector, and a vial of poison. If the detector senses a radioactive decay (which is a random quantum event), the vial breaks and the cat dies. If it doesn’t, the cat lives. According to quantum mechanics, until you open the box, the radioactive atom hasn’t decayed or not decayed; it’s in a probabilistic state where both outcomes have some likelihood. That means, following the math strictly, the cat’s fate is tied to that quantum uncertainty.

Schrödinger wasn’t saying cats are actually alive and dead at the same time. His point was the opposite: something seems wrong when you extend quantum rules from tiny particles to everyday objects like cats. At the atomic scale, particles genuinely behave probabilistically, and experiments confirm this. But somewhere between an atom and a cat, those quantum probabilities resolve into the definite reality we experience. Figuring out exactly how and why that transition happens is still one of the open questions in physics. The thought experiment was never meant to be taken literally; it was Schrödinger’s way of saying “this can’t be the whole story,” and physicists are still working on the rest of it.

Looking for a more detailed description? Find it at quera.com/glossary