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Mitchell_Porter comments on Schroedinger's cat is always dead - Less Wrong Discussion
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Here is what I see people saying:
"observation provokes collapse to a random eigenstate, and the result of the collapse determines the result of the observation"
"If you don't say that only conscious agents can collapse waveforms, then you have to agree that something in the box collapses the waveform as seen from inside the box"
"I'm betting that interacting with another subatomic particle is what collapses a waveform"
"The Copenhagen interpretation does say that a certain class of interactions - measurement interactions - produce collapse"
But in the Copenhagen interpretation, "collapse of the wavefunction" has exactly the same sort of reality as "collapse of the probability distribution" does. It is not supposed to be a physical process like "apple falls to the ground".
I don't understand the distinction. If the probability distribution collapses, why is that not a physical process? Is it an immaterial, spiritual probability distribution?
Anyway, Schroedinger is the person who came up with the cat thought-experiment; which shows that he thought at the time that the collapse of the wavefunction had tangible, physical reality.
You may wish to read Schrödinger's original article. It is about whether quantum mechanics could possibly be a complete description of reality. He considers two options: either that the wavefunction is a statistical description of an ensemble of possible states, or that the properties of microphysical systems are objectively undefined prior to observation. The cat shows up (in part 5) as a demonstration that the second option is absurd. This is the part where it may sound (to a modern reader, versed in MWI-think) that he is talking about a physical process of wavefunction collapse, but he's not. He's discussing a situation where the cat goes from "neither alive nor dead" to one or the other, at the moment of observation. At this stage, the wavefunction is not being proposed as a description of the cat's physical state.
Parts 7 through 9 are where he addresses the Copenhagen interpretation, and contrasts it with wavefunction realism: "psi-function as expectation catalog", versus "psi-function as description of state".
Flip a coin but don't look at it. Then look at it. The probability distribution of the coin just "collapsed". The collapse of the wavefunction in the Copenhagen interpretation is the same thing. A wavefunction is like a prior; you adjust it on the basis of information acquired.
I challenged the universality of a claim ("everyone") and you have attempted to support it by selecting anecdotes. This is obviously a mistake. Not only that, the examples don't even claim what you say they do. Although the second example at least alludes to it none of them assumes that:
Say that some people are confused about what the Copenhagen Interpretation says, by all means. But if you are going to throw about grossly exaggerated accusations for the sake of emphasis then at least refrain from trying to defend them!
"Everyone" is an anaphor for the "people getting it wrong" mentioned in my first sentence.
They all affirm that (quoting myself) "the wavefunction is a real thing". So perhaps I should have shouted that part?
THE COPENHAGEN INTERPRETATION DOES NOT SAY THAT THE WAVEFUNCTION IS A REAL THING.
But then - although the Copenhagen interpretation features in Phil's first sentence - it's not ubiquitous in the discussions. So maybe I should just say
THE WAVEFUNCTION MIGHT NOT BE A PHYSICAL THING! MOST PHYSICISTS THINK OF IT AS JUST LIKE A PROBABILITY DISTRIBUTION!
The problem is not just a misapprehension about what the Copenhagen interpretation says. The problem is the ubiquitous background assumption of "wavefunction realism". Either wavefunctions are real, and they collapse under observation, or spontaneously, or because of interaction; or wavefunctions are real, and they don't collapse, and there are many worlds.
You can't obtain clarity about quantum mechanics until you at least understand the perspective, historically identified with the Copenhagen interpretation, according to which wavefunctions are not real, and just provide a formal calculus for obtaining probabilities pertaining to the things that are real, the "observables". Observables are where reality lies in quantum mechanics, not wavefunctions.
Once you understand that, you are then free to note that quantum mechanics is incomplete, you can run off and try to make a better theory in terms of actually existing wavefunctions or in terms of something else, etc. But most discussions on this site are starting off confused, not just about what Copenhagen says, but about what quantum mechanics says, and it's because they start from the premise of wavefunction realism.
Then why did Schroedinger talk about the cat in the box?
I think you must be talking about some new interpretation unknown to Schroedinger.
Even if Schrödinger hadn't known some interpretation when he devised his feline thought experiment in 1935, I don't think it justifies calling it new.