Someone please help me understand the "Schrödinger's cat" theory?

It didn't make sense to Schrodinger either, and he devised this "experiment" to ridicule the Heisenberg Uncertainty Principle. Obviously, a cat cannot be alive and dead at the same time. It is an illustration of the difficulty in making a precision measurement when the very act of measurement alters the property being measured. As a result, no measurement can ever be exact.

Keep in mind: We do NOT "understand" quantum mechanics, we ""interpret" it. We form mental pictures of what is going on and those pictures are weird. The thing is, those pictures when applied to quantum mechanics give the most accurate answers known to science. Bohr, the creator of the Copenhagen Interpretation, argued that his interpretation was so accurate and dependable, it must be reality.

Now, think about the 2 slit experiment:

Before we start with Schrodinger’s Cat we need to deal with the “Principle of Indeterminacy.” One reason why no one understands QM is that quanta behave differently depending on whether or not they are observed. An example of this is the “2 Slit Experiment. If we let a stream of quanta pass through a barrier with 2 slits then hit a screen they form an interference pattern of light and dark bands (Absolute proof that what we are looking at are waves.) BUT, when we use the photoelectric effect to detect the quanta hitting the screen, we get discrete packets of energy (Absolute proof that what we are looking at are particles). Then it gets really strange. If we put a detector next to either slit so that we know which slit a given quantum went through, but leave both slits open, the pattern disappears. If we know which slit the quantum went through, we get one behavior (no pattern). If we do not know, we get a different behavior (pattern). We must somehow explain how a particle orders of magnitude smaller than the distance between the slits somehow passes through both slits and interferes with itself.

Quantum Mechanics gets out of this mess by introducing the Uncertainty Principle, Indeterminacy, and the Copenhagen Interpretation of QM. If we do NOT know which slit the particle went through, then the particle is "smeared out in equal parts" and goes through both slits. It turns into a fog. As long as it is a fog, it can pass through both slits. That is: The particle occupies a volume of space with some probability. QM says that so long as the position is not known, the particle occupies the entire volume. If we learn its position, the fog condenses into that location and the particle goes through one slit. What indeterminancy says is: The quantum can be in 2 places at once (both slits).

This whole concept extends to radioactive nuclei. If we get a detector, we can say exactly when decay occurs. There is no doubt. The nuclei are always either decayed or not decayed. But, suppose we do not observe, then indeterminacy and according to Copenhagen, the nuclei are both decayed and not decayed until we look. Schrodinger disagreed this view.

There are over 20 ways that give equally valid predictions of quantum behavior. Copenhagen is only one. But, since it worked so well and MUST be reality, early quantum theorists were left with the conclusion that the cat must be both dead and alive at the same time until it was observed.

Schrodinger had problems with the idea that an isolated quantum system existed in a superposition of all possible states (e.g. alive state and dead state) until the isolated quantum system interacts with some other system (e.g. observer opens the box) at which time the quantum state collapses to a 'real' value (either dead or alive).

This clearly can be demonstrated with individual quantum particles, and quantum mechanics says that you can continue to draw bigger and bigger 'isolation' boxes and continue to get larger and larger superpositions until you arrive at macroscopic quantum states such as Schrodinger's. Interestingly, you could actually scale this up to the entire universe.

Schrodinger clearly thought that the idea was ridiculous and certainly our perception of the macroscopic world would lead us to believe that distinct superposition at the macro level doesn't exist. The leading explanation is something called 'decoherence'. This is basically the idea that all of the individual quantum states that make up a macro object are out of 'phase' with each other so at the large scale it looks like the superposition has collapsed to a 'real' value

You've got it. "It's just a matter of when the cat will die."

The issue is, until you look, the cat could be dead or alive at any given moment.

Poker players deal with this daily, it doesn't take some stuffed shirt like Schrödinger or his cat.

You have three Kings, your opponent is showing two Aces. Does he have the third Ace or not? Gambling is dealing with the fact that the third (or fourth) Ace simultaneously can exist in your opponents hand or in the deck.

To hell with Schrödinger, I raise $50.00.