Schrödinger’s Cat

One of the most famous thought experiments in physics, one that kindled a passion for thought experiments in myself. Let’s dive in.

Picture this: a cat is placed inside a sealed box with a tiny bit of radioactive material, a Geiger counter, a vial of poison, and a hammer. If the atom decays, the counter triggers the hammer, breaks the vial, and—well, it’s bad news for the cat. If the atom doesn’t decay, the cat is fine. Now here’s the catch: according to quantum mechanics, until you open the box and observe it, the atom is both decayed and not decayed—meaning the cat is somehow both alive and dead at the same time.

This strange setup was proposed by Erwin Schrödinger in 1935, not because he believed cats could actually be half-dead, but to highlight how bizarre quantum physics sounds when applied to everyday objects. In the microscopic world, particles can exist in superposition—multiple states at once—until they’re observed. Schrödinger used the cat to mock the idea of scaling that logic up to the real world. After all, no one’s ever seen a half-alive cat.

The point was to show the tension between quantum theory and classical reality. At atomic scales, uncertainty and probabilities rule. But when you open the box—when you measure or observe—the wave of possibilities “collapses” into one outcome: alive or dead.

Over the years, Schrödinger’s cat has become a symbol for how mysterious the universe really is. It challenges how we think about observation, existence, and reality itself. Are things real before we look at them? Or does looking make them real?