What is Real?: The Unfinished Quest for the Meaning of Quantum Physics

by Adam Becker

The radiation emitted by the lump of metal is composed of subatomic particles, breaking away from the atoms in the metal and flying off at high speeds. Like all sufficiently tiny things, those particles obey the laws of quantum physics. But, instead of reading Shakespeare, the subatomic particles in the metal have been listening to the Clash—at any particular moment, they don’t know whether they should stay or they should go. So they do both: during the time the box is closed, the indecisive lump of radioactive metal will and won’t emit radiation. Thanks to these punk-rock particles, the Geiger counter will and won’t register radiation, which means the hammer will and won’t smash the vial of cyanide—so the cat will be both dead and alive. And this, Schrödinger pointed out, is a serious problem. Maybe an atom can travel down two paths at once, but a cat certainly can’t be both dead and alive. When we open the box, the cat will be either dead or alive, and it stands to reason that the cat must have been one or the other the moment before we opened the box.

Explanation