it's absurd because pretty
much every particle of the cat is measured and thus decohered by other particles in the cat
This is obviously impossible... hence, "thought experiment".
If you want to make the argument this makes it ultimately harder to understand rather than easier, well, I'd say the evidence overall would favor that. It seems to confuse more than it casts light on anything.
But if we did have such a box, then the cat could be alive and dead simultaneously. The dead portion of the cat superposition would consistently see the cat as dead, the living portion would consistently see the cat as alive. From within the box nothing could collapse the superposition any further. Once opened you would see only one of them. People are bothered by the macroscopic implications of this violation of our intuition of how the universe works. It is not entirely clear to me that such a violation could ever manifest in reality, though; that is one heck of a box, in a universe with gravity, neutrinos, dark matter, etc.
The cat would not be alive and dead simultaneously regardless of the box because it's totally entangled with and decohered / observed by the other elements in the box.
A single particle, or a coherent system, can be thought of as being isolated though. Do you see what I mean
Is that true? I’ve seen references to observed macro superpositions without such a box: https://en.m.wikipedia.org/wiki/Quantum_superposition
> A double slit experiment has been performed with molecules as large as buckyballs and functionalized oligoporphyrins with up to 2000 atoms.
> An experiment involving a superconducting quantum interference device ("SQUID") has been linked to the theme of the "cat state" thought experiment.
> A piezoelectric "tuning fork" has been constructed, which can be placed into a superposition of vibrating and non-vibrating states. The resonator comprises about 10 trillion atoms.
It seems like a four way black hole merger could possibly leave a space in the middle.
I didn't understand your original reply to my comment; now I understand why, I think.
Perhaps I failed to express myself clearly? I didn't say anything about quantum vs. classical worlds; I made a remark about the purpose for which Herr Schroedinger devised his cat story. His purpose was the opposite of the purpose implied by the article. He thought that the absurdity of a cat being both alive and dead demonstrated the absurdity of a particle being in two states at the same time.
That is, I was talking about Herr Schroedinger's opinions, not my own. IANAPP, but FWIW I'm convinced that quantum theory in the sense of evolution of the wave function is correct. I don't know of any convincing explanation of wave-function collapse as a result of "observation". I don't buy many-worlds, and "just shut up and solve the equations" doesn't cut it for me.
So in fact I'm convinced that we don't live in a classical world.