The Copenhagen interpretation of quantum mechanics causes paradoxes, at least apparent, when one tries to apply it to the macroscopic world. These two are the best known:
- Schrödinger’s cat paradox. A live cat, a radioactive atom, a vial filled with hydrocyanic acid, and a device that breaks the vial if the radioactive atom decays are placed in an opaque box. If the vial is broken, the cat dies. If it isn’t broken, the cat lives. While the box is closed, the Copenhagen interpretation of quantum mechanics tells us that the radioactive atom is in a superposition of states, decayed and intact, until someone checks it, at which point the superposition of states collapses into one of them. But then, while the box is closed, the cat must be in a superposition of states: alive and dead. Can a cat be alive and dead at the same time? Intuition denies it, but the Copenhagen interpretation of quantum mechanics asserts it. As its name indicates, this paradox was proposed in 1935 by Erwin Schrödinger, one of the fathers of quantum mechanics.