Pardon me for saying this in capitals, but this thread is full of people getting it wrong.
THE COPENHAGEN INTERPRETATION DOES NOT SAY THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION.
THE COPENHAGEN INTERPRETATION DOES NOT SAY THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION.
THE COPENHAGEN INTERPRETATION DOES NOT SAY THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION.
At least, not in the sense that everyone is assuming, according to which the wavefunction is a real thing.
In the Copenhagen interpretation, the wavefunction is not a physical entity. It has the same sort of ontological status as a probability distribution. It is not itself a probability distribution, but it is the mathematical object from which probability distributions are derived. And it also has this in common with probability distributions, that when new information about the world is obtained, you have to update it. This is the only sense in which “consciousness collapses the wavefunction” in the Copenhagen interpretation.
In the Copenhagen interpretation, the wavefunction is not a physical entity. It has the same sort of ontological status as a probability distribution. It is not itself a probability distribution, but it is the mathematical object from which probability distributions are derived. And it also has this in common with probability distributions, that when new information about the world is obtained, you have to update it.
It sounds like you’re saying the wavefunction represents our uncertainty. My impression is that you know more about grand theories of physics than I do; but I’m confident that the wavefunction does not represent mere uncertainty. Entanglement, the double-slit experiment, the uncertainty principle, etc., can’t be explained by uncertainty.
“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”.
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”.
If the probability distribution collapses, why is that not a physical process? Is it an immaterial, spiritual probability distribution?
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:
THE COPENHAGEN INTERPRETATION DOES [...] SAY THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION.
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.
the examples don’t even claim what you say they do
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.
Look: I did NOT CLAIM THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION. Just READ the post. I am not going to explain it again. It is VERY CLEAR that it is presenting TWO alternatives, ONE of which is that consciousness collapses the waveform.
Almost everyone simply chooses one of the two alternatives, and says, “That’s impossible!”.
Please stop doing that. In general. This is the nature of the post: You have only 2 obvious alternatives, and BOTH of them are impossible.
I am NOT proposing a solution. I am NOT saying that the cat is always dead. I am pointing out that there is no currently viable solution.
If you can’t resolve the situation BY PICKING ONE OF THE TWO ALTERNATIVES—NOT by dismissing one and ignoring the other—you should change your downvote to an upvote.
Note:Mitchell Porter is very smart, and did not actually say that I said that consciousness collapses the waveform.
Phil, this comment was not directed specifically at you. It was my way of saying that all the discussion in the comments was based on the false premise that the choice is between “wavefunctions are real and they collapse” and “wavefunctions are real and they don’t collapse”. Your post offered that as the choice too, but you didn’t originate that misconception, you were just expressing the local paradigm.
Pardon me for saying this in capitals, but this thread is full of people getting it wrong.
THE COPENHAGEN INTERPRETATION DOES NOT SAY THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION.
THE COPENHAGEN INTERPRETATION DOES NOT SAY THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION.
THE COPENHAGEN INTERPRETATION DOES NOT SAY THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION.
At least, not in the sense that everyone is assuming, according to which the wavefunction is a real thing.
In the Copenhagen interpretation, the wavefunction is not a physical entity. It has the same sort of ontological status as a probability distribution. It is not itself a probability distribution, but it is the mathematical object from which probability distributions are derived. And it also has this in common with probability distributions, that when new information about the world is obtained, you have to update it. This is the only sense in which “consciousness collapses the wavefunction” in the Copenhagen interpretation.
It sounds like you’re saying the wavefunction represents our uncertainty. My impression is that you know more about grand theories of physics than I do; but I’m confident that the wavefunction does not represent mere uncertainty. Entanglement, the double-slit experiment, the uncertainty principle, etc., can’t be explained by uncertainty.
You can tell there is really something wrong with the naming conventions when the Uncertainty Principle can’t be explained by uncertainty.
“Everyone” is assuming no such thing.
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.
Look: I did NOT CLAIM THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION. Just READ the post. I am not going to explain it again. It is VERY CLEAR that it is presenting TWO alternatives, ONE of which is that consciousness collapses the waveform.
Almost everyone simply chooses one of the two alternatives, and says, “That’s impossible!”.
Please stop doing that. In general. This is the nature of the post: You have only 2 obvious alternatives, and BOTH of them are impossible.
I am NOT proposing a solution. I am NOT saying that the cat is always dead. I am pointing out that there is no currently viable solution.
If you can’t resolve the situation BY PICKING ONE OF THE TWO ALTERNATIVES—NOT by dismissing one and ignoring the other—you should change your downvote to an upvote.
Note:Mitchell Porter is very smart, and did not actually say that I said that consciousness collapses the waveform.
Phil, this comment was not directed specifically at you. It was my way of saying that all the discussion in the comments was based on the false premise that the choice is between “wavefunctions are real and they collapse” and “wavefunctions are real and they don’t collapse”. Your post offered that as the choice too, but you didn’t originate that misconception, you were just expressing the local paradigm.