In middle school terms what is the schrodingers cat experiment?

Answer 1

"Schroedinger's Cat" is a Gedankenexperiment (German for "no funding available"*).

It runs something like this:

Suppose we have a box we cannot see through. Inside that box we place a cat, and a device containing a cyanide generator and a radioactive sample. The cyanide generator will be triggered if the sample emits radiation. We now seal the box and wait.

There is some chance that an atom in the sample will decay. Since we're doing this all in our imagination, we'll suppose that we have carefully chosen the material and the sample size so that there's a 50/50 chance that an atom will decay in one hour.

Schroedinger points out that, after one hour, the box contains a quantum superposition of states. That's a fancy term for saying that the cat inside is neither dead, nor alive, but half of each, kind of "smeared" into each other.

This was intended as a scathing criticism of the Copenhagen interpretation of quantum mechanics, which basically says that that a superposition of states only collapses into a definite state when it is actually observed (per Schroedinger, when the box is opened and we see either a 100% living or 100% dead cat).

A scientist named Wigner pointed out that this is not really a valid criticism using a different thought experiment usually called "Wigner's Friend". Wigner basically said let's get a bigger box and put a person in it instead. From our point of view (outside the box), there may be an uncollapsed "superposition of states", but to our friend (inside the box) there's no such thing: either he's alive or he's dead.

More to the point, the trigger that either starts the cyanide generator or does not can be counted as an "observer" in the Copenhagen interpretation. The real criticism of the (original) Copenhagen interpretation is that it doesn't define what the word "observe" means clearly enough.

* Actually, it means "thought experiment."