An experiment devised on 1935 where a cat is placed in a steel
box along with a Geiger counter, a vial of
poison, a hammer, and a radioactive substance. When the radioactive substance decays, the Geiger detects it and triggers the hammer to release the
poison, which subsequently kills the cat. The radioactive decay is a random process, and there is no way to predict when it will happen. Physicists say the
atom exists in a state known as a superposition—both decayed and not decayed at the same time.
Until the
box is opened, an observer doesn't know whether the cat is alive or dead—because the cat's
fate is intrinsically tied to whether or not the atom has decayed and the cat would, as Schrödinger put it, be "living and dead ... in equal parts" until it is observed.
