Schrödinger’s cat is not actually a paradox at all. It’s what’s called an apparent paradox. Apparent paradoxes are powerful teaching tools in physics, because they serve to break down intuitive ideas that turn out not to be correct or useful.
The point of Schrödinger’s cat is not that it’s possible for a cat to be both alive and dead at the same time. It isn’t possible for a cat to be alive and dead at the same time. The point is that particles are not cats. The rules that apply to macroscopic, everyday life — things continue to exist when they’re not doing anything, for instance — do not apply to particles, and the intuition we’ve built up over a lifetime of interacting with the world at a certain scale is not helpful for understanding smaller scales. Such intuition must be discarded.
Schrödinger’s cat looks like a paradox, because it asks us to accept that two contradictory things are true at the same time: the cat is both alive and not-alive. But it’s not actually a paradox, because if you replace the cat with an electron and the whole box-gas-contrivance thing with a magnetic field, you find that the electron’s magnetic moment is in fact aligned both parallel to and perpendicular to the magnetic field’s orientation right up to the point when you turn the magnetic field on, at which point you either get a photon emitted indicating that the electron has precessed into alignment, or no photon indicating that the electron was already in alignment, with no way of predicting which it will be in a single experiment. All you can do is repeat the experiment many times and see that the average of your results converges toward the expectation value your equations predicted.
Fri 13 Jan
