Layman asks about Quantum "interaction"

[PeterDonis]

There's only really the state. So, let's delete "behavior" and say "collapse" is a change of state of the electron.
Now, technically, the electron's state is continuously evolving with time, under the SDE. This is also called unitary evolution. So, let's call "collapse" a non-unitary change of state. I.e. upon measurement.

Careful. Remember that, if we are talking about the 7 Basic Rules--and that's all we should be talking about at this point, since we have to get that groundwork in place before even trying to talk about anything else--those rules do not say anything about what the electron's "state" actually is. They only say that we use particular states--wave functions, vectors in a Hilbert space--to describe the electron. When no measurement is being made, our description of the electron changes in accordance with unitary evolution--the time-dependent Schrodinger Equation. When a measurement is made, our description of the electron changes in a non-unitary manner. We are not making any commitment at this point about whether those changes in our description of the electron reflect anything that is "really happening" to the electron.

 

[Peter Mole]

A single electron does not form an interference pattern. It just makes a single dot somewhere on the detector screen. The interference pattern only shows up after many electrons have all passed through the apparatus, one by one, and made their dots on the detector screen: the interference pattern is formed by the many dots the many electrons made.

Got it.

If we just talk about the 7 basic rules of QM, as described in the Insights article I linked to, Rule 7, which can be called "collapse", could in principle be applied to each individual electron when it hits the detector screen, but there wouldn't be much point since the electron gets absorbed by the screen and we can't make any further measurements on it. But in any case, that "collapse" is just a mathematical procedure; the 7 basic rules don't say anything about what "really happens" to the electron. They just tell you how to predict the results of experiments. So if you're just using the 7 basic rules, it's pointless to ask whether the electron "changes state" when it hits the screen, or whether it stops being a quantum wave and starts being a classical particle, or any of that. The 7 basic rules simply don't say anything about any of that.

So this the "shut up an calculate" approach?

Rather than saying the basic rules make it pointless to ask whether the electron changes state, could you explain to me why the basic rules make it pointless to ask whether the electron changes state?

This logic feels circular, not unlike when you ask a christian "if god can do anything then can he create a stone so heavy even he can't carry it?" and then the christian answers the bible (rules) says god can do anything without explaining why the rules are valid.

If you insist on trying to say things about "what really happens" to the electron, then any question you ask will have multiple possible answers which are inconsistent with each other, since there are multiple interpretations of QM in the literature and they are inconsistent with each other. There are interpretations that say that "collapse" is a real physical process that happens to the electron when it hits the screen (but none of them say that real process turns the electron from a quantum wave into a classical particle). There are other interpretations, like the many worlds interpretation, that say there is no such thing as "collapse" at all.

You keep telling me that I'm trying to look at this in terms of "what really happens." My resistance to that has been because I felt you were trying to say I was leading up to saying "god" or "consciousness" did it or something else of that nature. This is why I have gone out of my way to say this is not my conclusion and why I have stated that I don't know or understand "what's really happening". To be clear, there is also a difference between describing what's happening on its face, and assigning meaning to what's happening or describing why it's happening. I don't think that's what you're getting at here, but at times my comments have been wrongly defined as my assigning "meaning".

All that said, and to your point, I do find it hard not to ask the question about "what's happening" at least in terms of explaining why the addition of the which-way detectors changes the experiments results from an interference pattern to a double bar. Are you not also asking this question about what's happening?

We have to start somewhere, don't we? I didn't want or try to start the conversation based on my clumsy concept of what "collapse" meant. I only explored that on your relentless insistence. I can (barely) grasp that the collapse is just a change in math and put the implications or lack of implications about that aside for now. My curiosity was about pinning down the physical interaction that was required to change the result of the experiment. This is why I asked you to describe the nature of the detectors. Is it not logical to think that the introduction of the dectectors is what changed the results of the experiment? Can I ask this question without making determinations or considerations about "many worlds" or whether or not there is a "real physical process"?

Am I any closer? Was I a little closer for a moment? lol.

 

[PeterDonis]

So this the "shut up an calculate" approach?

That's more or less what the 7 Basic Rules amount to, yes.

could you explain to me why the basic rules make it pointless to ask whether the electron changes state?

That should be obvious: because the basic rules make no commitment whatever about what "really happens" to the electron.

A better question would be why the basic rules make no such commitment. And the answer is that, as I've already said, there is no agreement on what "really happens" to the electron: there are multiple different interpretations of QM that say different things about that that are inconsistent with each other. So the reason the basic rules are the way they are is that that is the only thing there is general agreement on among physicists. There is no general agreement on what "really happens" to the electron. The only general agreement is about the basic rules we can use to make predictions about the results of experiments.

Are you not also asking this question about what's happening?

Everybody asks that question. But, as above, there is no general agreement among physicists on what the answer is; there are different interpretations of QM that say different, inconsistent things about it. The only thing there is general agreement on is the basic rules for making predictions.

That means you have to make a choice if you want to have a discussion at all. You can either choose to stick to just the basic rules, which means any questions about "what really happens" are out of bounds. That is what the regular QM forum here at PF is for. Or you can pick a particular interpretation of QM, and ask what that interpretation says "really happens". But whatever interpretation you pick, it will not be telling you anything that is generally agreed upon by physicists. That sort of discussion is what this QM interpretations subforum is for.

 

[PeterDonis]

My curiosity was about pinning down the physical interaction that was required to change the result of the experiment. This is why I asked you to describe the nature of the detectors.

And the answer is that we do not know what it is about "the nature of the detectors" that makes it necessary to apply Rule 7 when a detector registers. We only know the empirical fact that, if we want to make correct predictions, we have to apply Rule 7 when a detector registers.

Is it not logical to think that the introduction of the dectectors is what changed the results of the experiment?

It's not only logical, it's an empirical fact: the experiment with which-way detectors present gives a different observable result than the experiment without which-way detectors present. And we know we need to apply Rule 7 when a which-way detector registers in order to correctly predict that difference in observable results.

What we do not know is how to predict from first principles what kinds of physical objects or physical interactions will make it necessary to apply Rule 7 to make correct predictions. Our knowledge of that is entirely empirical, based on what we've seen in experiments so far. We have some heuristic rules, that contain words like "macroscopic", but those are just heuristics and are obviously incomplete: after all, as I think you pointed out earlier in this thread, the screen with the slits in it is "macroscopic", but somehow it doesn't force us to apply Rule 7 when an electron goes through the slits if there are no which-way detectors present. So clearly our knowledge is incomplete and we have more to learn.

 

[Peter Mole]

Pero/Peter,
I'm going to try to stop answering inline and go back and try to re-read your post and links to the numbered rules and see if it sinks in. Given a desire to respond to this thread in a timely fashion, I'm not sure I have the intellect to completely wrap my head around all the vocabulary and concepts, while avoiding rational intuitive reality grounded conclusions about ambiguous terms like "measurement" or "interaction" as defined at a quantum scale. But I'll try!

I'll may try to parse together both your comments in a single post and answer to them as this thread is starting to look like a gerrymandered district. If I don't specifically answer to something you said it may be because I didn't understand it's relevance, but it won't be because I didn't read or re-read it or re-re-read it.

I'll be back.

 

[EPR]

Another philosophy thread...

So you are essentially trying to bridge qm with classical mechanics and form an intuitive picture? Lol good luck with that..
Consider qm the theoretical aspect of this world and classical mechanics - the practical/physical. You can adopt this attitude(be content with what we can say about the world) as have done many physicists before you were born. It still holds.
Many bright scientists will flat out refuse to discuss these issues(what constitutes measurement, detector, observer, collapse, etc) as they are laden and philosophical in nature and have no definite resolution.

 

[EPR]

So unless there's a physical interaction, the wave will not collapse?

With one version of the double slit experiment, if you wait until after the wave passes through the double slits before trying to detect them (but before they hit the screen), the wave will still collapse and create the two bar pattern. (Feel free to correct me if I'm describing this wrong).

So there is no physical interaction until after the "wave" went through the slits. If I understand, the explanation is that the wave went back in time and collapsed before it was interacted with physically by "interaction" that only happened after the wave/particles passed through the slits.

How can interaction AFTER the event cause the wave to collapse in the past? We know the wave collapsed before it went through the slits but there was no interaction until after it when through the slits.

Why is it more logical to think a present action changes the past than to say that information gained collapsed the wave without interaction? Neither explanation seems at all logical to me.

You should not think in classical mechanics terms as things down there are not definite and fixed. They are fuzzy. If it's confusing(it is), be sure that most physicists are still baffled at the way things are at the lowest level and how they manifest up here. What the mentors and science advisors appear to be telling you is to pull back on the assumptions and stay in safer territories. Especially using your daily 'pedestrian' intuition(sorry for the word).

 

[Peter Mole]

Okay, I've read and re-read.

Peter Mole said:
Are you not also asking this question about what's happening?

Everybody asks that question.

Well, you're part of everybody.

But, as above, there is no general agreement among physicists on what the answer is; there are different interpretations of QM that say different, inconsistent things about it. The only thing there is general agreement on is the basic rules for making predictions.

Good lord if you only knew how many times I've typed and retyped this response. Hours.

There's a difference between asking what's happening in terms of what's occurring in reality in front of our eyes, verses what's happening behind the scenes. In terms of what's happening in front of our eyes, it makes no difference whatsoever whether or not there's a scientific agreement about what's "really" happening or what's we believe or don't believe is happening behind the scenes. In the context of what I'm saying here observable reality is something that's really happening.

I don't pretend to understand what's "really" happening when the which-way detectors are being used. (You still haven't described the physically of how that works.) Just because I'm not able to describe what's happening, that does not mean that something isn't happening. Something IS really happening and whatever is happening is happening because the detectors were added to the experiment and the reason I know SOMETHING REALLY HAPPENED is because the pattern changed from an interference pattern to a double bar. Just because I can't explain or don't know what "really" happened, that doesn't change the observable reality that something indeed did happen.

That means you have to make a choice if you want to have a discussion at all. You can either choose to stick to just the basic rules, which means any questions about "what really happens" are out of bounds. That is what the regular QM forum here at PF is for. Or you can pick a particular interpretation of QM, and ask what that interpretation says "really happens". But whatever interpretation you pick, it will not be telling you anything that is generally agreed upon by physicists. That sort of discussion is what this QM interpretations subforum is for.

Let me recap a couple things to show I'm following what you're saying (or demonstrate I'm not). With regard to the double slit experiment, the quantum wave function describes the electron, but doesn't say what it is. Is it fair to say the QWF can say where the electron is, even if it said description is only probabilistic? Moving on, we can use the QWF to describe the electron before and after it moves through the double slits. It seems we can also use the QWF to describe the electron at the moment is it detected by the which-way detectors or at the background screen. Doing the math, you say you can update the equation with the information gained by the detectors. I'm a little foggy on what this information is and how it's detected and what happens during the detection process, but for the purpose of the math we can say information is gained and can be added to the equation.

At the moment in time when the electron is being detected by the which-way detectors, can anything be said about the reality of the existence of the electron? Furthermore, and not necessarily pertaining to any experiment, is there ever even a moment in time where we can say the electron actually and physically exists in our reality? Observable reality in the moment?

Let me put or ask this another way using part of Pero's post...

perok:

What does QM have to say about an electron?

1) It's a stable elementary particle with a given mass, unit charge and total spin of 1/2. You can look that up in any table of the standard model of particle physics.

2) It's dynamic properties (position, momentum, energy, angular momentum, spin state etc.) are described by its wave-function. These dynamic properties are also known as the state of the electron.

Your understanding of things like state, superposition and where probabilities (not to mention probability amplitudes) fit in is not solid. I suggest you address these misconceptions in a methodical way.

It's very much NOT solid and less so not having talking with you guys. lol. It seems on the one hand we're saying QT only describes the wave function of the electron, but doesn't describe what it is. So how do we know the electron is a "stable elementary particle with a given mass" and also WHEN do we know it? At the time of measurement? At what moments in time are we allowed to say that an electron is real and existing before us?

the basic rules make no commitment whatever about what "really happens" to the electron.

A better question would be why the basic rules make no such commitment. And the answer is that, as I've already said, there is no agreement on what "really happens" to the electron: there are multiple different interpretations of QM that say different things about that that are inconsistent with each other. So the reason the basic rules are the way they are is that that is the only thing there is general agreement on among physicists. There is no general agreement on what "really happens" to the electron. The only general agreement is about the basic rules we can use to make predictions about the results of experiments.

I can wrap my head around the idea that the basic rule (or the math) doesn't make a commitment to "what really happens" and doesn't need to.

That means you have to make a choice if you want to have a discussion at all. You can either choose to stick to just the basic rules, which means any questions about "what really happens" are out of bounds.

I don't understand why such questions are out of bounds. Put another way, I understand why they aren't necessary to do the math or use the rules, but I don't understand why we're not allowed to speculate whether or not it has anything to do with what's really happening other than some finicky and arbitrary decision to handle things in a certain order and ask certain questions at a later time (in a different forum).

Now consider the second version of the double slit, where we include "which way" detectors. Now we have to apply the Rule 7 mathematical procedure twice for each electron. We apply it once when one of the "which way" detectors registers (only one will register for each electron), and we apply it a second time when the electron makes a dot on the detector screen.

You keep making the point math is only describing the electron, not actually saying what it is. At this point in the experiment, I'm not asking "what's really happening," but I am asking what's observable at the point "when one of the "which way" detectors registers"?

The first question that naturally comes to mind, which I didn't address in post #3 of this thread is: what tells us to apply the Rule 7 procedure when the "which way" detector registers? The answer is simple: because we have to to make correct predictions about what we will see on the detector screen!

Certainly something is happening in observable or experiential reality at the point that the detectors are going off. I understand you're just doing math and the collapse is just a function of the math, but if nothing was happening in observable reality, then the detectors wouldn't be going off and the pattern wouldn't change to a double bar.

Just becasuse you want to confine your answer to a procedural question about math, that doesn't mean nothing is happening and it certainly doesn't mean I cant' ask the question.

If we don't assign a new wave function to the electron based on the "which way" detector registering, we will incorrectly predict that the dots on the detector screen will end up forming an interference pattern. So the general rule for when to apply the Rule 7 procedure is to do it wherever it has to be done to make correct experimental predictions.

It seems like you're applying the math in such a way as to explain the reality rather than using the math to predict the reality.

Of course this is very unsatisfying to people (and it seems like you're one of them--don't worry, you're in good company) who expect QM to tell them from first principles when something like "collapse" is supposed to happen. Many, perhaps most, physicists would agree that the fact that QM cannot tell us from first principles when to apply Rule 7 means that QM, as a physical theory, is incomplete. But in practical terms, the rule given above works quite well. In fact, in practical terms, asking when the theory says you're "supposed" to apply the Rule 7 procedure is looking at things backwards. What actually happens is, experimenters run experiments with quantum systems, and those experiments help us to figure out where the Rule 7 procedure needs to be applied.

But certainly quantum theory can and has been used predictively? Are you saying there's nothing about the math that predicts the collapse of the math at the point the detectors trigger?

And we hope that by doing enough such experiments we will come to a better understanding of what is actually going on "behind the scenes" and we will hopefully be able to come up with a more complete theory of quantum systems, one that will tell us from first principles when the Rule 7 procedure should be applied, instead of us having to put that in by hand in each individual case.

And yet so much working technology is based on QT? I'm confused how this knowledge is utilized to create anything. I'm not sure how to say it. It's like it's not predictive or deterministic.

So one answer to the question of "which physical interactions trigger the Rule 7 procedure, and which don't?" is that we don't know from first principles how to determine that.

Well, full circle in a way. If we don't know how to determine which physical interactions trigger rule 7 (the collapsing of the math wave function), then how do we even know physical interactions play any role at all?

 

[Peter Mole]

One of the things that brought me here was Neil deGrasse Tyson's comments on quantum physical interaction. I know he's keeping it simple and trying to address a wider audience, but is it possible he's a bit mistaken in his understanding? I did a quick transcript of what he's saying followed by video I got it from. Seeking your comments.

It's much simpler than you think. The only reason I can see you is because light is reflecting off you.

I see you . I want to know where you are. If the lights are not on you I can't see you. It's that simple. When you start becoming the size ... of an atom...and I ask the question where are you and I turn on the light to see you there, cause I think you're there, the photon comes in, hits your atom and pops you into another location.. the very act of trying to measure your position prevents me from measuring your position. It has to do with the fact that to know you're there some information has to come from you to me, light shining a light on you. The smaller you are the more susceptible you are to the energy of the light changing your position in space.

NDT then calls this the Heisenberg's Uncertainty Principle.

 

[Peter Mole]

EPR,

I do appreciate your posts, but I'm out of time to reply and will check back later. Thank you.

 

[PeroK]

One of the things that brought me here was Neil deGrasse Tyson's comments on quantum physical interaction. I know he's keeping it simple and trying to address a wider audience, but is it possible he's a bit mistaken in his understanding? I did a quick transcript of what he's saying followed by video I got it from. Seeking your comments.

This forum can give a deeper understanding that can be presented on a radio chat show. This sort of video, regardless of how much Tyson really knows about QM, is not a good basis for discussion.

 

[PeterDonis]

n terms of what's happening in front of our eyes, it makes no difference whatsoever whether or not there's a scientific agreement about what's "really" happening or what's we believe or don't believe is happening behind the scenes. In the context of what I'm saying here observable reality is something that's really happening.

Of course. But observable reality does not include things like an electron changing from a wave to a particle. Nor does it include things in our mathematical models, like wave functions. So if we are going to limit discussion to just observable reality, we're pretty much done, since we already agree on what the observable reality is: there is an interference pattern with no which-way detectors, and there is not when which-way detectors are present.

I don't pretend to understand what's "really" happening when the which-way detectors are being used.

Nobody does. I've already said that.

(You still haven't described the physically of how that works.)

That's because I can't, since nobody knows that. I've already said that. If we knew how, physically, a which-way detector made it necessary to apply Rule 7 to make correct predictions, we would be able to tell, from first principles, what physical objects and what physical configurations would do that. And, as I've already said, we can't tell.

Something IS really happening and whatever is happening is happening because the detectors were added to the experiment and the reason I know SOMETHING REALLY HAPPENED is because the pattern changed from an interference pattern to a double bar.

Yes. I have not denied any of this. But knowing that something happened does not tell us what that something is, or how to tell, from first principles, when we should expect it to happen in experiments we haven't done yet. The latter is the part that nobody knows.

With regard to the double slit experiment, the quantum wave function describes the electron, but doesn't say what it is.

Yes.

Is it fair to say the QWF can say where the electron is, even if it said description is only probabilistic?

If we are using the position basis, which seems to be what we are assuming in this discussion, then the wave function gives the probability (strictly speaking, the probability amplitude, which is a complex number whose squared modulus gives the probability) for detecting the electron as a function of position. However, that is not the same as saying that the electron is "really" at one of those positions, we just don't know which. The description in terms of the wave function just gives the probabilities; it does not make any commitment about what is "really there" underneath the probabilities, not even that the electron is "really at" one of the positions whose probabilities are being given.

At the moment in time when the electron is being detected by the which-way detectors, can anything be said about the reality of the existence of the electron?

Not if we are limiting ourselves to the 7 Basic Rules. Those don't say anything about that.

The various interpretations of QM say things about that, but, as I've already said, the things they say are inconsistent with each other.

is there ever even a moment in time where we can say the electron actually and physically exists in our reality? Observable reality in the moment?

Same answer as I just gave above.

how do we know the electron is a "stable elementary particle with a given mass"

Because we can measure its mass, and we can observe that it never decays into anything else (except for the edge case of electron-positron annihilation).

WHEN do we know it?

When we make the observations I just described.

At what moments in time are we allowed to say that an electron is real and existing before us?

Same answer as I gave above regarding the 7 Basic Rules and the various QM interpretations.

I can wrap my head around the idea that the basic rule (or the math) doesn't make a commitment to "what really happens" and doesn't need to.

If you do, then I don't understand why you even ask your very next question:

I don't understand why such questions are out of bounds.

Because the basic rules don't answer them. So if you want to stick to the basic rules (which was the condition I gave for such questions being out of bounds), then such questions have no answers, which means it's pointless to even ask them, which means here at PF they are out of bounds in such discussions to avoid pointlessly wasting everyone's time.

I don't understand why we're not allowed to speculate

Speculation is out of bounds period here at PF. We do not discuss people's personal speculations. We discuss mainstream science, as best we can capture it.

If what you really mean by "speculate" is "ask questions that the basic rules don't and can't answer", then I have answered that above as far as discussions that stick to the basic rules are concerned. If you want to have a discussion that goes beyond the basic rules, then you need to pick one of the recognized QM interpretations in the literature as a framework for discussion; otherwise asking questions is pointless because we have no framework from which to answer them.

what's observable at the point "when one of the "which way" detectors registers"?

The fact that that detector registered, i.e., it did something that indicates that the electron passed. What "registered" means in concrete terms depends on the design of the detector: it could make a light flash, or ring a bell, or make a mark on a piece of paper, or make a record in a computer file, etc., etc., as long as it's something that a human can use to tell that the detector registered.

certainly quantum theory can and has been used predictively?

Yes, in scenarios where we already know when we need to apply Rule 7, because either we've tested that scenario before, or we make a correct guess at when to apply it based on some heuristic rule derived from past empirical data.

If QM were able to predict from first principles when to apply Rule 7, experimenters would not have been surprised by things like which-way detectors taking away the interference pattern the first time it was tried. The whole reason such things are so surprising is that the theory cannot tell us from first principles when they will happen.

Are you saying there's nothing about the math that predicts the collapse of the math at the point the detectors trigger?

Yes. The math by itself does not tell you when to apply Rule 7. A human always has to put that in by hand.

And yet so much working technology is based on QT?

Yes, because by the time something is to the point of working technology, it has already been thoroughly studied experimentally and everyone knows when Rule 7 needs to be applied to make correct predictions.

If we don't know how to determine which physical interactions trigger rule 7 (the collapsing of the math wave function), then how do we even know physical interactions play any role at all?

"Physical interactions" is a vague term. Clearly, as you yourself have remarked, there must be something about the which-way detectors that makes it necessary to apply Rule 7, and "physical interactions" is as good a vague term for whatever that something is as anything else. When people say "physical interactions", they are not saying they have anything specific in mind. They are just using a convenient label to avoid having to laboriously explain every time that we don't know what specifically is going on.

 

[PeterDonis]

so long as the requisite non-interference between alternatives is secured by correlating the possible eigenvalues with the possible detector states

I'm not sure what you mean by this. The only way to "secure" non-interference between alternatives is to design the experiment to prevent it. But doing that often would remove the very thing you want the experiment to test.

 

[DrClaude]

It's much simpler than you think. The only reason I can see you is because light is reflecting off you.

I see you . I want to know where you are. If the lights are not on you I can't see you. It's that simple. When you start becoming the size ... of an atom...and I ask the question where are you and I turn on the light to see you there, cause I think you're there, the photon comes in, hits your atom and pops you into another location.. the very act of trying to measure your position prevents me from measuring your position. It has to do with the fact that to know you're there some information has to come from you to me, light shining a light on you. The smaller you are the more susceptible you are to the energy of the light changing your position in space.

This is how the HUP was thought of in the early days of QM. It is reminiscent of the arguments of Niels Bohr.

It is however an outdated view of the HUP. While it can explain the position-momentum uncertainty, you can't use it to understand why spin can be only known with respect to one direction at a time. It also seems to imply that there is a limit to the precision with which you can measure observables, which needs not be the case.

We know nowadays that the HUP says something much more deeper about what can be known about a quantum system, and about how well a system can be prepared with particular attributes (Einstein's "elements of reality") defined simultaneously.

 

[Peter Mole]

You should not think in classical mechanics terms as things down there are not definite and fixed.

If that's how I came off I certainly didn't mean to be.

 

[Peter Mole]

Peter,

First, just thanks again for your patience and attention to detail. I really do appreciate people like you who take the time to engage with people and do this kind of work in forums.

I may get caught up in my own thinking and ask the same question again but it's not intentional. Other times, I'm certain I'm being redundant at this point in my questions, but I am locking this down if you'll just indulge me a little longer. Furthermore, keep in my that I do not know the language of the math and so in places where the math explains it straightfowardly, I'm still not seeing it and am trying to come at it from other angles.

Part of the reason I spent so much time talking about "observable" or "in front of you" really happening reality vs. "what's really happening" behind the scenes is that at times in our conversation I thought I was doing the former when you thought I was doing the later. Other times, I thought I doing the former but might have been doing the later. For me, breaking up these two concepts of "what's really happening," and not letting them bleed into each other has been a fundamental step to keeping myself sober.

Anyway, a few more questions...

#1. What do you call a deer with no eyes?
answer: no idea (say with boston accent)

But observable reality does not include things like an electron changing from a wave to a particle. Nor does it include things in our mathematical models, like wave functions. So if we are going to limit discussion to just observable reality, we're pretty much done, since we already agree on what the observable reality is: there is an interference pattern with no which-way detectors, and there is not when which-way detectors are present.

I'm probably asking the same thing over and over but that's only because I'm confused. I really am trying to nail it down.

Let's say there's a plane flying high above the clouds and my only instrument for detecting it is radar. The radar turns on and off momentarily and I have an image of where the plane is. We have no other way of detecting the plane. We don't know where it is anytime before or after the moment we detected it on radar. We can say in the common way, given what we know of how radar works, that "in reality" at the moment we detected it a physical object there were the radar said it was.

First, in this situation, is it allowable to say "There's a object in the sky where radar detected it." ?

Of course I'm comparing this to:

But observable reality does not include things like an electron changing from a wave to a particle.

Again I come back to... when the detector rings to indicate it's detected the electron.. what can be said about the electron? Can we say we in that moment we knew it's position the same way we knew the position of the plane? I'm guessing your answer is still no. In the common way of planes and radar, what can we cay about what's really happening in the moment? Again, I'm guessing you're going to say nothing.

But observable reality does not include things like an electron changing from a wave to a particle. Nor does it include things in our mathematical models, like wave functions.

Part of the issue here is how we use language. In my imagination, it's much easier for me accept we can't say anything about what's really happening with the electron outside the times when we are measuring is (such as when it's on route to the double slits or after it's on the other side).

When you say the "electron changes from wave to particle", it sounds like you're talking about what's really happening, or otherwise making a statement about a physical object or even teh conversion of a "state," but is that just a description and not a comment on an aspect of reality?

Of your two sentences above, is not the first also nothing more than a mathematical description? If not, please explain.

So if we are going to limit discussion to just observable reality, we're pretty much done, since we already agree on what the observable reality is: there is an interference pattern with no which-way detectors, and there is not when which-way detectors are present.

In talking about the two double slit experiments, one without and one with the detectors, you state the only thing you accept as observable reality is the screen at the back that shows the pattern. Say there's a LED light that flashes when the which-way detector identifies an electron. Isn't that also a form of observable reality... of what's really happening in the moment? We can say the LED light went off. Can we say the detector identified an electron? Can we say at the moment the LED light went off, there was an electron passing by in front of the detector? How is this different from saying we detected the mass of the electron (just as we detected the plane using radar) and so therefore in that moment we know the electron "really was" there in physical particle form?

I can accept that the QWF is just a description of an electron and not a statement on reality itself. It's just a math equation we used (retroactively) to explain what happenings in experiments like the double slit at moments like where the detector lights up.

(You still haven't described the physically of how that works.)

That's because I can't, since nobody knows that. I've already said that. If we knew how, physically, a which-way detector made it necessary to apply Rule 7 to make correct predictions, we would be able to tell, from first principles, what physical objects and what physical configurations would do that. And, as I've already said, we can't tell.

Sorry, in this case I meant technically. Are the detectors looking at the slits like a laser on either side of a garage door seeing if anything's in the way before the door fully closes, or is more like a screen that the election must pass through if it's going through the slit? I'm curious if you could explain this both in hardware and in what's happening on the subatomic level. In other words.. a photon is hitting the electron and bouncing back to the detector, etc.

Let me put my cards on the table. I'm made a list of things I'm struggling to comprehend. At times these things seems to all be referring to the same thing. Part of the confusion is just how we use language. Can you address the differences here in this list or at least use it as a guide to better understand the terms I'm struggling with.

1) electron wave changing to a particle
2) applying Rule 7 to make correct prediction
3) a measurement
4) a record
5) a physical interaction
6) an observation
7) a human observation
9) a pattern on the screen at the end of the double slit experiment
10) a LED indicator going off on the which-way detector indicating it's identified an electron

Okay here's along segment just to get something off the table in my thinking and understanding of what you're saying...

Something IS really happening and whatever is happening is happening because the detectors were added to the experiment and the reason I know SOMETHING REALLY HAPPENED is because the pattern changed from an interference pattern to a double bar.

Yes. I have not denied any of this. But knowing that something happened does not tell us what that something is.,..

To be crystal and redundantly clear... you would NOT say the same thing about the radar and the plane right? The radar my not know for certain it's a "plane" but at least for the radar we can say we know the thing that the radar is detecting is real. In terms of knowing what something is, we know the thing detected by the radar is an object. Right? I say all this just to make sure we aren't playing philosophical existential mind games. For example, I can say I see a coffee cup sitting right side up on my desk, but physically, due to the lenses in my eyes, what I'm really seeing is the image upside down and my brain flips it over for me. And physically, I'm not seeing the coffee cup where it is, I'm seeing it where it was because the photons didn't instantly hit my eyes. It took time for them to travel to my eyes and in that tiny fraction of a moment the coffee cup was in a different position from where I thought I saw it.

My point is, we could state making existential arguments about macroscopic objects and get super technical about physical attributes and what existing in space-time really means, etc.. You could say a macroscopic mountain is in front of you and I could starting taking existential stuff to argue if it was really "there".

But when you say we can't say the electron is "really there", or is there, you're not engaging in this kind of existential whataboutism, right? That's not what's going here.

Also, even if there's no other way to detect it, I could use Netwtonian math to pinpoint the location of Halley's comet far out on the edge of our solar system. It's totally allowable for me to say it's there even though the only reason I can say this is because of math. Right?When it comes to describing the electron as physically "there in reality" at the time it's detected by the which-way detector... you're saying we can't make this statement. Is this because:

1) The very existential nature of "things" at the quantum level is such that we just can't say they "exist".

2) The very existential nature of "things" at the quantum level is such that we just can't say they "exist" or "not exist" because the term just doesn't apply.

3) The math doesn't say the electron is "there" not because you can't use the math to describe something exists at some point in reality (as with halley's comet), but because QW math is used retroactively. Unlike math used predictively, it's math used after the fact simply to describe what happened.

So in terms of our discussion, when you say it's not an allowable question to ask if it's really there, you're reason is always #3, or just sometime #3?

I don't understand why such questions are out of bounds.

Because the basic rules don't answer them. So if you want to stick to the basic rules (which was the condition I gave for such questions being out of bounds), then such questions have no answers, which means it's pointless to even ask them, which means here at PF they are out of bounds in such discussions to avoid pointlessly wasting everyone's time.

Again to be redundantly clear, this is not a case of you just arbitrarily limiting the scope of the topic. It's a case where the math, for whatever reason, is only being good for so much and nothing more either by it's scope or by the way in which it's required to be applied. How do I say it... If you have a hypothetical carton containing a dozen eggs and your friend eats two of them and I ask you how many are left, you would say 10. But if I tell you wait.. Here's the basic rules. You're only allowed to use the mathematical rules of addition and multiplication, but not subtraction. Then you could say there's no way to say how many eggs are left because the basic rules don't allow you to answer the question.

Coming at it another way... in the case again of math describing Halley's comet, math can tell us where it is and how fast it's going. Math can tell us what it is. But math can't tell us whether or not an alien spaceship watching it go by thinks the comet is "pretty." What I'm trying to say is, with QWF math describing the electron, it's NOT a case that we are trying to describe an aspect of the electron that's out of bounds for the math to tell us (like whether or not the electron is "pretty") but rather it's all about the fact that the equations are applies after the fact because we don't know (except through experimentation) where the "electron changes from wave to particle". Right?

...certainly quantum theory can and has been used predictively?

Yes, in scenarios where we already know when we need to apply Rule 7, because either we've tested that scenario before, or we make a correct guess at when to apply it based on some heuristic rule derived from past empirical data.

I think I'm starting to get it. This must be of the stuff no commonly understood by pop-science or those like myself who are math-challenged.

I'm still having trouble wrapping my mind around this. It's like learning how to build a house only from trial and error never knowing if it will stand until it's built and then never really learning anything about the process enough to apply your knowledge to a different kind of house. If you want to know it will stand you can only build the same kind of house. If you design a different kind of house you again won't know if it can stand until it's done, but then at least you'll have another blueprint you understand.

I can now better understand why it must be so hard to build a quantum computer through this kind of trial and error.

Thanks for helping me to realize this bizarre aspect Pete. My mind spins. This is why I came here. (Now please don't tell me I've totally misunderstood it. lol)

If QM were able to predict from first principles when to apply Rule 7, experimenters would not have been surprised by things like which-way detectors taking away the interference pattern the first time it was tried. The whole reason such things are so surprising is that the theory cannot tell us from first principles when they will happen.

I still get hung up when qualify it by say "from first principles" the theory cannot tell us what happens. To beat a dead horse, you can argue that the theory can tell us what happens without the "from first principles" qualification, but to do so you have to move into the realm of speculation. (many worlds, etc)

If we don't know how to determine which physical interactions trigger rule 7 (the collapsing of the math wave function), then how do we even know physical interactions play any role at all?

"Physical interactions" is a vague term. Clearly, as you yourself have remarked, there must be something about the which-way detectors that makes it necessary to apply Rule 7, and "physical interactions" is as good a vague term for whatever that something is as anything else.

First, for our topic in this forum, it's fine to talk about when rule 7 is triggered during the double slit experiment. But if we want to start saying rule 7 is triggered by a "physical interaction" then that's speculation and needs to go to a different subforum... Right?

"physical interactions" is as good a vague term for whatever that something is as anything else.

It seems more grounded to say that something physical bumped into something else physical. But you've been firmly and honestly rigid on this for our whole conversation, especially in terms of what we are allowed and not allowed to say. Regarding whatever it was that triggered the use of rule 7, is speculation that it's caused by a "physical interaction" just as valid as speculating that "an invisible purple octopus god poked it from another dimension"? Is it just as valid as speculating that "information was collected by a human" or "another world split off"?

When people say "physical interactions", they are not saying they have anything specific in mind. They are just using a convenient label to avoid having to laboriously explain every time that we don't know what specifically is going on.

You're offering an opinion and I strongly disagree. I think a lot of people either have an agenda or their understanding is crystalized (in good faith) from their world view. In myself, I'm working hard to get to the understanding that we don't know what's going on in cases where rule 7 is applied, full stop. I certainly don't think most people start there and just fill in a term to avoid the laborious explanation.

Also, can you elaborate on why you qualified with "specifically" instead of just saying "we don't know what's going on?" And furthermore, what can be said about what's "generally" going on?

Here's a line I pulled from wiki... (ya, I know, it's wiki)
In quantum mechanics, wave function collapse occurs when a wave function—initially in a superposition of several eigenstates—reduces to a single eigenstate due to interaction with the external world. "

Would this also be considered speculation? I was of the understanding that "interaction" is a QT term describing the point at which rule 7 was applied. I'm not sure if interaction means "real stuff" hitting "real stuff" or subatomic particles hitting subatomic particles or quantum waves hitting quantum waves. And if it is quantum waves hitting quantum waves is that just a description used by the math?

I know I'm backtracking. Now that you've taught me the places where I can't ask "what's really happening" I'm turning that lens back on statements others have made about QT and seeing if my understanding still holds.

 

[PeroK]

My point is, we could state making existential arguments about macroscopic objects and get super technical about physical attributes and what existing in space-time really means, etc.. You could say a macroscopic mountain is in front of you and I could starting taking existential stuff to argue if it was really "there".

This is not the issue with QM. The issue is that if we are talking about the elementary particles in our universe, they themselves cannot be totally analagous to the macroscopic objects composed of huge numbers of them. QM says they are not. QM says that the elementary components have different properties, not seen in the macroscopic world.

Unless you are prepared to accept that things at the subatomic level have laws of nature that do not directly scale up to the macroscopic world, there is no point in studying QM or particle physics.

It doesn't matter how many times you insist an electron must be like a plane or a mountain, Mother Nature ain't listening.

 

[PeterDonis]

#1. What do you call a deer with no eyes?
answer: no idea (say with boston accent)

LOL, I went to college in Boston so I am quite familiar with the accent.

 

[PeterDonis]

in this situation, is it allowable to say "There's a object in the sky where radar detected it." ?

Of course. But, as @PeroK pointed out, quantum objects are not like planes or mountains. And trying to think of them as if they are will only increase your confusion. So the answer I just gave to your question is actually pointless, since it tells you nothing about quantum objects, which is what we're actually discussing.

when the detector rings to indicate it's detected the electron.. what can be said about the electron?

That the detector rang to indicate that it detected an electron. And that, in our mathematical model, we have to apply Rule 7 and update the wave function we use to describe the electron to reflect that the detector rang to indicate that it detected the electron.

Note that this is a very different answer to the one I gave above about the plane detected by radar.

Can we say we in that moment we knew it's position the same way we knew the position of the plane? I'm guessing your answer is still no. In the common way of planes and radar, what can we cay about what's really happening in the moment? Again, I'm guessing you're going to say nothing.

Your guesses are correct.

When you say the "electron changes from wave to particle", it sounds like you're talking about what's really happening

No. I'm saying that the words "electron changes from wave to particle" are meaningless in this discussion. They don't describe anything at all. They don't describe anything that we do in our mathematical model, and they don't describe "what's really happening" in any of the known interpretations of QM. You should forget those words entirely. Dump them from your memory.

In talking about the two double slit experiments, one without and one with the detectors, you state the only thing you accept as observable reality is the screen at the back that shows the pattern.

No, that's not what I said. Go back and read carefully.

Say there's a LED light that flashes when the which-way detector identifies an electron. Isn't that also a form of observable reality... of what's really happening in the moment?

Of course. And I said that. Go back and read carefully.

There are also other things that are obviously part of observable reality: the electron source and whatever knobs and dials and settings we have on it; the first screen and the slits in it, and whatever attributes of it we have measured (such as the width and separation of the slits); the distance from the electron source to the first screen; the distance from the first screen (with the slits) to the second screen (the detector that shows the dots); the presence or absence of the which-way detectors and the configurations of those detectors, if they are present. And a myriad others.

In fact, "what observable reality is" is pretty much the same in QM as in your everyday experience. That's not where the hard part of QM is. It's true that QM predicts (and experiments confirm) that some things you observe in "observable reality" have properties that you didn't expect--for example, what happens if you make successive spin measurements in different directions on a particle. But the actual process of observing "observable reality" works pretty much the same. It's understanding the mathematical model that makes the predictions that can be difficult--still more so understanding the various interpretations and what they say about what is "really happening" behind the scenes.

Can we say the detector identified an electron?

If it's set up to only detect electrons, and to not detect any other kinds of particles, then yes. Otherwise all you can say is that it detected a "particle", which was of one of the types of particles it can detect.

Can we say at the moment the LED light went off, there was an electron passing by in front of the detector?

If this is just a synonym for "the detector detected an electron", then yes. Otherwise I would need to know what you mean by "passing by" and what implications you think it has that "the detector detected an electron" does not have.

How is this different from saying we detected the mass of the electron (just as we detected the plane using radar)

The detector is not measuring the electron's mass. It's just detecting an electron. (The radar is not measuring the plane's mass either; it's just detecting the plane.)

and so therefore in that moment we know the electron "really was" there in physical particle form?

Since you don't appear to mean the same thing by this as "the detector detected an electron" (otherwise why would you be belaboring this point), then no, we cannot say that "the detector detected an electron" implies this. At least, not if we're just sticking to the basic rules. There might be particular QM interpretations that would say that "the detector detected an electron" implies that the electron "really was there in physical particle form", but there are other interpretations that would not.

You commented that a lot of this is how we use language. But the only one who knows how you are using language is you. So the answers to a lot of your questions really come down to what you mean by these various expressions you keep using. We seem to have settled on a concrete meaning for "the detector detected an electron"--it means the bell rang, or the LED light came on, or whatever indication the detector is designed to give. But you keep asking whether that is different from, e.g., "the electron really was there in physical particle form", and the real answer is that it depends on what you mean by "the electron really was there in physical particle form". If you just mean "the detector detected an electron", then of course it's the same. But if you mean something else, something that is different from "the detector detected an electron", then of course it's different. And you are the only one who knows what you mean by these different expressions, so it's pointless for you to ask me to tell you whether they mean the same thing or not.

I can accept that the QWF is just a description of an electron and not a statement on reality itself.

It sure doesn't seem like it, since you keep on asking questions that go beyond this.

1) electron wave changing to a particle

Meaningless, as I've already said.

2) applying Rule 7 to make correct prediction

What we do in the mathematical model when empirical knowledge tells us we have to.

3) a measurement

Something that requires us to apply Rule 7.

4) a record

The same as 3), if we assume that we are keeping records of all our measurement results, which is the simplest assumption to make at this point.

5) a physical interaction

Too vague to have a single meaning.

6) an observation
7) a human observation

Probably best to consider these as the same at this point; they both mean a human observing the result of a measurement.

9) a pattern on the screen at the end of the double slit experiment

The result of a measurement (strictly speaking, the aggregate results of a large number of measurements, since each individual dot in the pattern is the result of a single measurement).

10) a LED indicator going off on the which-way detector indicating it's identified an electron

The result of a measurement.

you would NOT say the same thing about the radar and the plane right?

Yes. As @PeroK said, the rules for classical objects are different from the rules for quantum objects. So trying to compare them will only increase your confusion.

when you say we can't say the electron is "really there", or is there, you're not engaging in this kind of existential whataboutism, right? That's not what's going here.

Correct.

I could use Netwtonian math to pinpoint the location of Halley's comet far out on the edge of our solar system. It's totally allowable for me to say it's there even though the only reason I can say this is because of math. Right?

Yes, because the rules for classical objects allow you to do that. But the rules for quantum objects don't.

Is this because:

1) The very existential nature of "things" at the quantum level is such that we just can't say they "exist".

2) The very existential nature of "things" at the quantum level is such that we just can't say they "exist" or "not exist" because the term just doesn't apply.

3) The math doesn't say the electron is "there" not because you can't use the math to describe something exists at some point in reality (as with halley's comet), but because QW math is used retroactively. Unlike math used predictively, it's math used after the fact simply to describe what happened.

No, no, and no. You left out:

4) The basic rules simply don't talk about things like "exist" at all. They don't say 1). They don't say 2). And they certainly can be used to make predictions so 3) is not true either.

So in terms of our discussion, when you say it's not an allowable question to ask if it's really there, you're reason is always #3, or just sometime #3?

No, it's never 1), 2), or 3). It's always 4).

this is not a case of you just arbitrarily limiting the scope of the topic.

No. The scope of the topic is limited by the fact that, so far, we are only talking about the basic rules. We are not talking about any particular interpretation of QM (because you haven't picked one, and at your current level of understanding I don't think you should, you should stick to learning how the basic rules work first). If we were talking about some particular interpretation of QM, the scope of questions would be wider, but the answers would depend on which intepretation you picked and would be inconsistent with the answers you would get if you picked some other interpretation.

in the case again of math describing Halley's comet, math can tell us where it is and how fast it's going.

Yes.

Math can tell us what it is.

No. Math can't tell you what something is. To correctly predict where Halley's comet currently is and how fast it is currently going, by using math (because we can't currently observe it directly), you have to already know that it is Halley's comet you're talking about--that the data from previous observations that you are using to mathematically calculate its orbit are data from observations of Halley's comet and not something else.

Math also can't tell you that Halley's comet is a comet and not some other kind of object (such as an alien spacecraft ). You have to know that from some other source (like direct observation). Nor can math tell you what it is made of.

with QWF math describing the electron, it's NOT a case that we are trying to describe an aspect of the electron that's out of bounds for the math to tell us (like whether or not the electron is "pretty") but rather it's all about the fact that the equations are applies after the fact because we don't know (except through experimentation) where the "electron changes from wave to particle". Right?

Wrong. The phrase "electron changes from wave to particle" is meaningless. I've already said so several times. Things like whether the electron "exists" are out of bounds for the math to tell us. The math doesn't tell us that.

I can now better understand why it must be so hard to build a quantum computer through this kind of trial and error.

The problems with building a quantum computer actually don't have much to do with not knowing how and when to apply Rule 7. Quantum computers use well-understood quantum systems where we already have lots of knowledge about when we need to apply Rule 7.

The problem with quantum computers is that we don't want to have to apply Rule 7; the whole point is to have the computer not require us to apply Rule 7 until the very end of the calculation. In other words, the problem is that there are too many things that we know could cause us to have to apply Rule 7 when we don't want to, so we have to carefully design the quantum computer to make sure that none of those things happen before we want them to. And that is very, very hard, because those things include stuff like "thermal vibration of the computer kicked one of the qubits and forced us to apply Rule 7", which is very hard to prevent from happening.

you can argue that the theory can tell us what happens without the "from first principles" qualification, but to do so you have to move into the realm of speculation

No. The things interpretations tell us about what happens are not derived from the theory. They are not derived from the math. They are just added on. If they could be derived from the math, we wouldn't have different, mutually inconsistent interpretations. We would just have a theory that told us more than QM, the theory, actually does.

if we want to start saying rule 7 is triggered by a "physical interaction" then that's speculation and needs to go to a different subforum... Right?

First, the subforum we are currently in is the subforum where QM intepretation questions are normally discussed. This particular discussion appears to have now limited itself to just the basic rules, but I am keeping it in this subforum because I don't know if it will stay that way.

That said, if by "physical interaction" you mean something different from just "something that forces us to apply Rule 7", then yes, we would be having an intepretation discussion and you would have to pick an interpretation; we would no longer just be discussing the basic rules. If by "physical interaction" you just mean the same as "something that forces us to apply Rule 7", then no, strictly speaking, the term would be OK for a discussion limited to just the basic rules, but I think it would still be a bad choice of terminology, for reasons that I've already explained (though it was a number of posts ago now).

is speculation that it's caused by a "physical interaction" just as valid as speculating that "an invisible purple octopus god poked it from another dimension"?

In terms of QM interpretations, these two are certainly not equally valid, because "physical interaction" at least gestures in the direction of something we know about--it leads to questions like "what interaction? Is it electromagnetic? Strong interaction? Weak interaction? Gravity?" and so on--whereas talk about invisible purple gods does not.

Also, note that when we start asking questions like "which interaction?", we open up possibilities for experimental tests, in which we can potentially expand the scope of the basic rules, by finding out more things that force us to apply Rule 7. So asking such questions can be viewed as exploring experimental possibilities, not just as pure interpretation. It becomes more like pure interpretation when "interactions" are postulated under conditions where we have no way of testing whether they are there.

Is it just as valid as speculating that "information was collected by a human" or "another world split off"?

"Information was collected by a human" is directly observable; it's not speculation.

"Another world split off" is a particular interpretation, yes (a somewhat garbled version of it, but I don't want to go down that rabbit hole here).

I think a lot of people either have an agenda or their understanding is crystalized (in good faith) from their world view. In myself, I'm working hard to get to the understanding that we don't know what's going on in cases where rule 7 is applied, full stop. I certainly don't think most people start there and just fill in a term to avoid the laborious explanation.

See my discussion of the "which interaction?" question above. We certainly don't have to just give up once we know that, say, a particular kind of which-way detector forces us to apply Rule 7. We can always ask further questions about how the detector works (does it sense electric charge? Magnetic fields? etc.). But asking those questions with a view to testing the possibilities is one thing. Simply saying "physical interactions always require us to apply Rule 7" without saying anything about what interactions these are or how we would test the claim that they always require us to apply Rule 7 is another. (Certainly it's not hard to come up with examples where something that most people would call a "physical interaction" does not require us to apply Rule 7; I think someone gave one a while ago in this thread.)

can you elaborate on why you qualified with "specifically" instead of just saying "we don't know what's going on?"

I don't have any useful elaboration to give here. You're getting too hung up on particular words.

I was of the understanding that "interaction" is a QT term describing the point at which rule 7 was applied.

"Interaction" is a vague term that could have lots of possible meanings. Please don't try to disentangle all that by reading Wikipedia articles.

If you really want to learn how all this works, you need to learn it from a QM textbook. I would recommend Ballentine myself, but different people have different preferences. And you will have to bite the bullet and tackle some math; while it might be possible in principle to learn QM without learning any of the math, trying to keep track of which words are meaningful and which aren't will get overwhelming; math is a much better way of organizing the information and making clear what the logic is.

 

[Ibix]

But, as @Ibix pointed out,

@PeroK, I think.

 

[PeterDonis]

@PeroK, I think.

Oops, yes. Fixed.

 

[Peter Mole]

Peter,

I'm back still acting in good faith. Let me regroup and define terms and say some stuff back to you to see if it's landing for me.

Going forward, let's define "collapse," as synonymous with "where rule 7 is applied in the experiment."

If we just talk about the 7 basic rules of QM, as described in the Insights article I linked to, Rule 7, which can be called "collapse", could in principle be applied to each individual electron when it hits the detector screen, but there wouldn't be much point since the electron gets absorbed by the screen and we can't make any further measurements on it. But in any case, that "collapse" is just a mathematical procedure; the 7 basic rules don't say anything about what "really happens" to the electron. They just tell you how to predict the results of experiments. So if you're just using the 7 basic rules, it's pointless to ask whether the electron "changes state" when it hits the screen, or whether it stops being a quantum wave and starts being a classical particle, or any of that. The 7 basic rules simply don't say anything about any of that.

Four our purposes, "collapse" just means the change in the quantum wave function specific to times when rule 7 is applied. It's not known when to apply rule 7 until after the experiment shows where it is to be applied. In any case, "collapse" is just a mathematical procedure and does not an cannot describe "what really happens".

However, some if not most interpretations (which contradict other interpretations) of "what's really happening" will often focus attention on the moment of the collapse as described by the mathematics. (Is that fair?)

For the double slit experiment firing electrons and using the which-way detectors, rule 7 is applied when the detectors detect the electron. This is the first collapse. The second collapse is when the background screen registers the pattern, but there's really nothing to apply rule 7 to because rule 7's only purpose is to make a mathematical adjustment to the QWF and at the time of the screen registering the pattern, there's nothing further to calculate because the electron gets absorbed by the screen and we can't make any further measurements on it.

Here's a quote from your response #37.

...observable reality does not include things like an electron changing from a wave to a particle. Nor does it include things in our mathematical models, like wave functions. So if we are going to limit discussion to just observable reality, we're pretty much done, since we already agree on what the observable reality is: there is an interference pattern with no which-way detectors, and there is not when which-way detectors are present.

This is where I got hung up on "electron changing from a wave to a particle". Okay, so I understand that an "electron changing from a wave to a particle" is not observable reality. Not because it's too tiny to see. Not because quantum particles do or don't "exist" as particles on the quantum level. Simply because such claims are beyond the reach of the math and are not a function of what the math is doing. Or...

4) The basic rules simply don't talk about things like "exist" at all.

It's true I've struggled to understand what you mean by this, but maybe not always for the reasons you think. I feel whenever I say anything you're hearing me say it with the prefix of "yes, but what's really happening is..." Perhaps my thinking has been along those lines even when I've been unconscious of acting that way, but other times I think you're just reading me wrong.

I still have some quams about this which I think is due to my total ignorance on the math. Unlike my previous analogy about the radar and plane, my analogy about Halley's Comet was to put the attention on the math aspect. There's nothing "real" about Quantum Wave Theory in the same way there's nothing "real" about Algebra or Calculus. And, as you corrected me, Newtonian math doesn't tell us about what Halley's Comet is, just about where it is and where it's going.

I'm honestly not sure what QT can tell us about where the electron is or where it's going or if it can only tell us one and not the other. But that wasn't the point of me using the Halley's Comet analogy. I was just trying to rule out the idea of the basic rules not talking about things like "exist" as simply a matter of the basic rules being math and math doesn't really determine if things exist or not. As with Halley's Comet far out in the solar system, we can say where it is, but not what it is. However, knowledge of it's properties like location and velocity can be built upon to give us a definition of what it is.

However, QT not being able to tell us what exists is different from Newtonian math not being able to tell us what Hally's Comet is, right? This isn't just because it's math. It's more to do with the basic rules .. how do I say it... the basic rules are not designed to describe "reality" or "what's really happening." I still struggle to explain what QWT is describing without having you jump down my throat. lol. If I say it's describing the behavior of the electron that seems to be okay with you, but I can't say it's describing what's happening with the electron or you freak out and assume I'm equating it with a baseball moving through the batters box.

And there is a difference between descriptions of "what's happening" verses "what's really happening" which is a whole other aspect of confusion of this and every topic of human conversation. Just as when a boys asks a girl if he can walk her home we can say "what's happening" is he's concerned for her safety, but "what's really happening" might be something else romantic in nature.

However, as I understand "the rules," when it comes to the electron, it's neither a case of "what's happening" or "what's really happening". The rules are simply not designed to explain the reality of the electron or the reality of it's actions. As much as scientists would love to develop math that describes the "reality" of what's happening at the quantum level, they have not been able to do so, and people who think that's what QM is doing are wrong. How's that?

you can argue that the theory can tell us what happens without the "from first principles" qualification, but to do so you have to move into the realm of speculation

No. The things interpretations tell us about what happens are not derived from the theory. They are not derived from the math. They are just added on. If they could be derived from the math, we wouldn't have different, mutually inconsistent interpretations. We would just have a theory that told us more than QM, the theory, actually does.

I assume my ignorance of the math itself will continue to keep my comprehension at a disadvantage. More than just saying the math doesn't have anything to say about things what "exists," is it that the math, by it's very nature cannot have anything to say about how things exist? Do you understand my distinction? Sort of like contemplating an image of Ouroboros and trying to separate the eater from the eaten.

Along the same vein, while one form of reputable interpretation might speculate and assign physical reality to the electron in some way, QWF, by its nature, cannot be used to support such an interpretation. Is it fair to say that QWF, likewise by its very nature, does not rule out speculation which assigns physical reality to the electron in some way?

is speculation that it's caused by a "physical interaction" just as valid as speculating that "an invisible purple octopus god poked it from another dimension"?

In terms of QM interpretations, these two are certainly not equally valid, because "physical interaction" at least gestures in the direction of something we know about--it leads to questions like "what interaction? Is it electromagnetic? Strong interaction? Weak interaction? Gravity?" and so on--whereas talk about invisible purple gods does not.

Okay, but, keeping you honest, is it fair to say Quantum theory or "the rules" don't support the "physical interaction" interpretation anymore than they support the "invisible purple god theory"?

Can this also be said about the invisible purple octopus god theory? (yea, just messing with you now)

Also, note that when we start asking questions like "which interaction?", we open up possibilities for experimental tests, in which we can potentially expand the scope of the basic rules, by finding out more things that force us to apply Rule 7. So asking such questions can be viewed as exploring experimental possibilities, not just as pure interpretation. It becomes more like pure interpretation when "interactions" are postulated under conditions where we have no way of testing whether they are there.

Ya ya. I'm looking forward to getting into that at some point.

We certainly don't have to just give up once we know that, say, a particular kind of which-way detector forces us to apply Rule 7. We can always ask further questions about how the detector works (does it sense electric charge? Magnetic fields? etc.). But asking those questions with a view to testing the possibilities is one thing. Simply saying "physical interactions always require us to apply Rule 7" without saying anything about what interactions these are or how we would test the claim that they always require us to apply Rule 7 is another. (Certainly it's not hard to come up with examples where something that most people would call a "physical interaction" does not require us to apply Rule 7; I think someone gave one a while ago in this thread.)

Yes yes, laying the ground rules first, after which I'll be eager to hear more about this. And I really do want a better technical understanding of how those detectors work as some point.

I'm going to call you out here where you said...

we already agree on what the observable reality is: there is an interference pattern with no which-way detectors, and there is not when which-way detectors are present.

...you didn't include the ring of the detectors (or the moment at which the detectors detected an electron). This why I went on and on about it trying to get clarity until you corrected me.

Say there's a LED light that flashes when the which-way detector identifies an electron. Isn't that also a form of observable reality... of what's really happening in the moment?

Of course. And I said that. Go back and read carefully.

Moving on...

This particular discussion appears to have now limited itself to just the basic rules, but I am keeping it in this subforum because I don't know if it will stay that way.

Ha! We'll see. I suspect I had this all right from my second post and since then you're just keeping me around for the jokes.

If you really want to learn how all this works, you need to learn it from a QM textbook. I would recommend Ballentine myself, but different people have different preferences. And you will have to bite the bullet and tackle some math; while it might be possible in principle to learn QM without learning any of the math, trying to keep track of which words are meaningful and which aren't will get overwhelming; math is a much better way of organizing the information and making clear what the logic is.

I know you feel that way and I have read your "I Know the Math Says so, but Is It Really True?" article, but I'm not yet convinced. Although I don't know the math, but it's my belief it would only lead me to a conceptual understanding anyway. Likewise, anything the math offers me that isn't conceptual in nature probably isn't anything I'd be interested in.

This may seem like a paradox, but with regards to my ignorance about the math, can you try to at least explain to me conceptually what you think the math explains only to those who know it. Think in terms of a hearing person explaining music to a deaf person.

 

[PeterDonis]

Going forward, let's define "collapse," as synonymous with "where rule 7 is applied in the experiment."

More precisely, it means:

Four our purposes, "collapse" just means the change in the quantum wave function specific to times when rule 7 is applied.

Please be consistent. A huge issue in any discussion of QM is that people use ordinary language terms with vague and shifting meanings, without even realizing it themselves. Please don't do that.

The bolded language above is a good quick summary of what Rule 7 says to do: change the wave function you use to make predictions about future measurement results, based on the measurement result just observed. That's not just "where Rule 7 is applied"; it's a specific thing that you do in the mathematical model when Rule 7 is applied.

It's not known when to apply rule 7 until after the experiment shows where it is to be applied.

Or if we have knowledge from previous similar experiments of where to apply it. That is much more likely to be the case now, since we have so many previous experiments whose results we can make use of. The early pioneers of QM didn't have that background knowledge, which is why they struggled so much with Rule 7, since the underlying theory didn't give them any help in deciding when to apply it.

In any case, "collapse" is just a mathematical procedure and does not an cannot describe "what really happens".

Yes.

some if not most interpretations (which contradict other interpretations) of "what's really happening" will often focus attention on the moment of the collapse as described by the mathematics. (Is that fair?)

That's where most of the time and effort spent in the QM interpretations literature and in discussions of them is spent, yes.

For the double slit experiment firing electrons and using the which-way detectors, rule 7 is applied when the detectors detect the electron. This is the first collapse.

Yes. More precisely, rule 7 is applied in order to correctly predict probabilities for where a dot will show up on the detector screen for that electron, given the knowledge of which which-way detector registered.

The second collapse is when the background screen registers the pattern, but there's really nothing to apply rule 7 to because rule 7's only purpose is to make a mathematical adjustment to the QWF and at the time of the screen registering the pattern, there's nothing further to calculate because the electron gets absorbed by the screen and we can't make any further measurements on it.

Yes. But, in principle, that is just a technical limitation; we could imagine a scenario where, even though the detector screen absorbs the electron, we still had the technical ability to keep track of what was happening inside the detector screen to a level of detail that would make it necessary to apply Rule 7 based on where the dot showed up in order to correctly predict further measurement results. We just can't do that with today's technology and today's detector screens.

I was just trying to rule out the idea of the basic rules not talking about things like "exist" as simply a matter of the basic rules being math and math doesn't really determine if things exist or not.

The basic rules of QM not saying anything about things like "exist" is something more than just the ordinary "math doesn't really determine if things exist or not", yes.

Here is a simple way to see the difference: there are not multiple, mutually inconsistent interpretations of classical physics, the way there are of QM. Everyone agrees on the interpretation of classical physics. And since classical physics is also subject to the "math doesn't really determine if things exist or not" limitation, that limitation cannot be all that is involved with the basic rules of QM not saying anything about things like "exist".

I assume my ignorance of the math itself will continue to keep my comprehension at a disadvantage.

Most definitely. It's hard enough to learn how QM works when you are learning the math and using it as a tool to help you understand. Trying to do it without learning any of the math at all is, IMO, close to foolhardy. Ordinary language is simply an extremely inadequate tool for the task.

For one thing, you are taking way, way too long to ask what should be simple questions. The one sentence I quoted above, asking about the basic rules not talking about things like "exist", was all you had to say to ask that particular question. You took multiple paragraphs. If you would take some time to learn the math, you would, I think, find it a lot easier to not have to go on and on trying to express yourself in ordinary language.

is it fair to say Quantum theory or "the rules" don't support the "physical interaction" interpretation anymore than they support the "invisible purple god theory"?

This is getting to be ridiculous. I have explained what people generally mean by "physical interaction" and what the limitations of that term are. Continuing to drag invisible purple gods into the discussion is just wasting our time. Don't do it.

you didn't include the ring of the detectors (or the moment at which the detectors detected an electron)

Oh, for goodness' sake. You're the one that made up the scenario. You're basically complaining that I didn't tell you something about a scenario that you made up. Do you see how absurd that is?

I suspect I had this all right from my second post and since then you're just keeping me around for the jokes.

You suspect incorrectly.

with regards to my ignorance about the math, can you try to at least explain to me conceptually what you think the math explains only to those who know it.

Not in this thread. There is a separate thread discussing the Insights article you linked to; you can ask about this there.

 

[PeroK]

Although I don't know the math, but it's my belief it would only lead me to a conceptual understanding anyway. Likewise, anything the math offers me that isn't conceptual in nature probably isn't anything I'd be interested in.

I don't believe you can learn or understand QM purely by getting the right words in the right order. Ultimately, the ability to use the correct words precisely comes from an understanding of the subject; and not vice versa.

 

[Peter Mole]

Peter,

Thanks again for hanging in there. Today's joke will be answered at the end. It's a real thinker. "What's blue, but smells like red paint?"

Four our purposes, "collapse" just means the change in the quantum wave function specific to times when rule 7 is applied.

Please be consistent. A huge issue in any discussion of QM is that people use ordinary language terms with vague and shifting meanings, without even realizing it themselves. Please don't do that.

I'm actually trying very hard to be consistent in a way you'll find acceptable just so we can talk. So... when it comes to referring to things like the detector detecting an electron or the screen recording electrons in whatever pattern, I'll refer to it as "the change in the quantum wave function specific to times when rule 7 is applied". Seems like we could have come up with something a little less wordy, but if that's what it takes to move on, I'm happy to do it.

It's not known when to apply rule 7 until after the experiment shows where it is to be applied.

Or if we have knowledge from previous similar experiments of where to apply it. That is much more likely to be the case now, since we have so many previous experiments whose results we can make use of. The early pioneers of QM didn't have that background knowledge, which is why they struggled so much with Rule 7, since the underlying theory didn't give them any help in deciding when to apply it.

Okay I get what you're saying. I was just trying to be very careful with my words and not suggest that QT was predicting when "the change in the quantum wave function specific to times when rule 7 is applied," or rather, if it was making such predictions, it was able to do so only because of past experiments, not because the math itself has the ability to predict when "the change in the quantum wave function specific to times when rule 7 is applied." If that's still not right, let me know!

For the double slit experiment firing electrons and using the which-way detectors, rule 7 is applied when the detectors detect the electron. This is the first collapse.

Yes. More precisely, rule 7 is applied in order to correctly predict probabilities for where a dot will show up on the detector screen for that electron, given the knowledge of which which-way detector registered.

I believe I understand what you mean. In this case, the change in the quantum wave function specific to times when rule 7 is applied means you've readjusted the equation to account for seeing a double bar pattern instead of an interference pattern.

The second collapse is when the background screen registers the pattern, but there's really nothing to apply rule 7 to because rule 7's only purpose is to make a mathematical adjustment to the QWF and at the time of the screen registering the pattern, there's nothing further to calculate because the electron gets absorbed by the screen and we can't make any further measurements on it.

Yes. But, in principle, that is just a technical limitation; we could imagine a scenario where, even though the detector screen absorbs the electron, we still had the technical ability to keep track of what was happening inside the detector screen to a level of detail that would make it necessary to apply Rule 7 based on where the dot showed up in order to correctly predict further measurement results. We just can't do that with today's technology and today's detector screens.

Yes, I understand.

I was just trying to rule out the idea of the basic rules not talking about things like "exist" as simply a matter of the basic rules being math and math doesn't really determine if things exist or not.

The basic rules of QM not saying anything about things like "exist" is something more than just the ordinary "math doesn't really determine if things exist or not", yes.

Right, I agree with that last "yes." It's more than just because math doesn't tell you stuff exits. I'm sure you never meant it was, but it was a process for me to understand that you didn't.

Here is a simple way to see the difference: there are not multiple, mutually inconsistent interpretations of classical physics, the way there are of QM. Everyone agrees on the interpretation of classical physics. And since classical physics is also subject to the "math doesn't really determine if things exist or not" limitation, that limitation cannot be all that is involved with the basic rules of QM not saying anything about things like "exist".

Certainly the qualifier "...the way there are of QM" makes this a strong statement I agree with. I'm not sure everyone agreeing on the interpretation of classical physics ultimately means anything to me. Even so I'm not looking for an argument. I do accept the limitation of math itself is not all that's involved with the basic rules of QM not saying anything about things like "exist."

is it fair to say Quantum theory or "the rules" don't support the "physical interaction" interpretation anymore than they support the "invisible purple god theory"?

This is getting to be ridiculous. I have explained what people generally mean by "physical interaction" and what the limitations of that term are. Continuing to drag invisible purple gods into the discussion is just wasting our time. Don't do it.

I'm actually surprised by your answer, or rather your decision not to answer. For days, over and over again, you've been trying to hammer into me that I can't draw conclusions about "existence" or "what's really happening" based on the math. Over and over you have set a firewall against using the math to wade into discussions about interpretations. And here I finally come around to accept this and when I ask you a question to solidify the point, you hedge. Either that, or I'm just misunderstanding you again. So I'll ask you again... in terms of "the rules" you insist we confine our conversation to, is there anything about the "rules" that allows for more support of an interpretation about "physical interaction" (however you define it) over an interpretation that involves invisible purple gods?

If your answer is yes, then please explain how so. To my understanding of what I thought you were trying to teach me about the math, regardless of of what interpretations are being compared, the only possible answer to my question should have been no.

you didn't include the ring of the detectors (or the moment at which the detectors detected an electron)

Oh, for goodness' sake. You're the one that made up the scenario. You're basically complaining that I didn't tell you something about a scenario that you made up. Do you see how absurd that is?

Meh. I think I had a valid point, but it feels petty that I even mentioned it and I regret having done so.

I suspect I had this all right from my second post and since then you're just keeping me around for the jokes.

You suspect incorrectly.

Yes, I agree. ;) But I hope you know I was being facetious when I wrote that. Your patience with me has been extraordinary and ignorant though I certainly have been, I really have been acting in good faith.

with regards to my ignorance about the math, can you try to at least explain to me conceptually what you think the math explains only to those who know it.

Not in this thread. There is a separate thread discussing the Insights article you linked to; you can ask about this there.

Well, ya, that's the article I referenced and for which I've already taken a precursory look. After reading that article, I admit I may be more of a cliche case that I would have first thought, but have you considered that that article might well be an inventory of your pre-conceived notions about the ignorant and naive reader who comes to these forums? Maybe not, but something to think about. Speaking for myself, I don't feel threatened by any of the conversations here in the forums about interpretations and certainly there's nothing to be defensive about math that doesn't make any claims about reality. I feel no need to be right over whatever the math says and I especially don't think you or anyone doing the math owes me an explanation, let alone to "prove it". Frankly, the idea of someone demanding that of you makes me LOL. Also, I really don't have a problem accepting someone else explaining to me what the math indicates (or doesn't indicate) so long as that person is qualified and reputable (like you).

Anyway Peter, I'm sorry if I've been frustrating for you. I can honestly say I've been enjoying this thread quite a bit and will keep coming back until you decide you are through with me.

Well, sincerely and in good faith I have tried to show the insight I have gained from our conversation. Have we done enough to lay the ground work? Please say this hasn't really all just been a ploy to get me to learn the math before going on. I have so many non-math questions I'd love to get clarification on... if you think I'm ready.

answer: blue paint

 

[Peter Mole]

I don't believe you can learn or understand QM purely by getting the right words in the right order. Ultimately, the ability to use the correct words precisely comes from an understanding of the subject; and not vice versa.

For the record, I've been reading your posts PeroK but not always responding as it's quite clear PeterDonis has become pretty attached to me at this point and I worry about making him jealous.

Just to show how right you are, I'm not even sure what's meant by Quantum Mechanics. At best I'd say I'm trying to understand some of the fascinating ideas or concepts that it's raised for people like me who aren't even qualified to called laymen on the topic. I've yet to be convinced "the subject" is synonymous with the math. I do promise I'll let you know when/if you convince me... not of the validity of the math, but of the requirement that I understand it by my own self instead of through folks like you. I already, in good faith, accept the validity of the math even if I don't understand it.

 

[PeterDonis]

Seems like we could have come up with something a little less wordy

I thought the less wordy term we had agreed on for this was "collapse".

In this case, the change in the quantum wave function specific to times when rule 7 is applied means you've readjusted the equation to account for seeing a double bar pattern instead of an interference pattern.

No. It means I've changed the wave function I'm using to describe the electron based on my knowledge of which which-way detector registered. I then use that changed wave function to predict a different distribution of probabilities for where a dot on the detector screen will appear for that electron. (Note that this distribution is not a double bar pattern--it is just one of the two "bars", because I am making use of the information about which which-way detector registered. I only get a double bar pattern if I make use of the information that one of the two which-way detectors has fired, but I refuse to make use of the information about which one it was.)

I'm actually surprised by your answer, or rather your decision not to answer.

I didn't make a decision not to answer. I told you I had already answered and you were just wasting our time by belaboring the point. Continuing to belabor the point even further does not help.

What might help would be, if you insist on talking about invisible purple gods, for you to explain what you think the difference is between "physical interactions" and "invisible purple gods" that makes you so persistent about asking me whether the basic rules of QM allow interpretations based on the former but not the latter. Why do you even care what the answer is? I suspect that if you actually took some time to think about that question, it would answer itself and you would be able to stop belaboring the point.

have you considered that that article might well be an inventory of your pre-conceived notions about the ignorant and naive reader who comes to these forums?

I never used the words "ignorant" and "naive" in the article or in that discussion thread. So if those words are coming from anywhere, they're coming from you, not me.

 

[Peter Mole]

to PeterDonis,

I thought the less wordy term we had agreed on for this was "collapse".

I thought so too, but in post #58 you corrected me and so I changed it to try to appease you by phrasing it exactly as I thought you wanted it phrased. Scroll up and see #60 where I was clearly just trying to be accommodating to you.

Specifically, I changed it to "the change in the quantum wave function specific to times when rule 7 is applied", because "where rule 7 is applied in the experiment" wasn't precise enough for you.

ME: For the double slit experiment firing electrons and using the which-way detectors, rule 7 is applied when the detectors detect the electron. This is the first collapse.

YOU: Yes. More precisely, rule 7 is applied in order to correctly predict probabilities for where a dot will show up on the detector screen for that electron, given the knowledge of which which-way detector registered.

ME: I believe I understand what you mean. In this case, the change in the quantum wave function specific to times when rule 7 is applied means you've readjusted the equation to account for seeing a double bar pattern instead of an interference pattern.

YOU: No. It means I've changed the wave function I'm using to describe the electron based on my knowledge of which which-way detector registered.

That's exactly what I meant. The QWF was initially setup for the electron leaving the firing mechanism, but then at the point where the detector detected the electron it was necessary to apply rule 7 which meant you changed the wave function equation which I stated as you readjusted the equation.

I then use that changed wave function to predict a different distribution of probabilities for where a dot on the detector screen will appear for that electron.

Again, that's exactly what I meant. We've been over this. I've been trying to say it back to you to show I've understood, and I dare to say that anyone reading this would see this is all I'm doing.

(Note that this distribution is not a double bar pattern--it is just one of the two "bars", because I am making use of the information about which which-way detector registered. I only get a double bar pattern if I make use of the information that one of the two which-way detectors has fired, but I refuse to make use of the information about which one it was.)

Right, speaking only in terms of the math without describing what "really happened," the QWF for the single electron that got detected by the detector went on to form one of the dots on the back screen that would make up one of the bars of the double bar result. But the reason you readjusted the equation for the electron that was detected by the which way detector was because you were accounting for seeing the double bar pattern instead of the interference pattern. Seeing the results of the experiment told you were to go back an apply rule 7. This is what you taught me.

I'm sorry and a little dumbfounded you found it so confusing, but what you are describing is exactly what I meant.

I'm actually surprised by your answer, or rather your decision not to answer.

I didn't make a decision not to answer.

? Okay, but not only did you refuse to answer it the first time, you are doing it again NOW. Is it possible you really are hedging on this? As I've said more than a couple times I don't have any agenda with how the change in the quantum wave function specific to times when rule 7 is applied is interpreted.

I told you I had already answered and you were just wasting our time by belaboring the point. Continuing to belabor the point even further does not help.

But as I explained I wasn't just belaboring the point. I had a very specific reason for asking the question which you either ignore or just didn't understand. Again, just scroll up and read it. You've now have two opportunities to simply type the two letter word "no" and yet you refuse to do it or explain why you refuse to do it. Who's wasting who's time now? I find your behavior truly puzzling.

What might help would be, if you insist on talking about invisible purple gods, for you to explain what you think the difference is between "physical interactions" and "invisible purple gods" that makes you so persistent about asking me whether the basic rules of QM allow interpretations based on the former but not the latter.

This is bizarre.

1) You've spend DAYS telling me specifically not to wade into interpretations and just to focus on the groundwork and stick with the "rules".

2) Furthermore, I did explain exactly what I thought the difference was between "physical interactions" and "invisible purple gods" with regards to the quantum wave function math and that difference was nothing.. zero... because you've been hammering it into me for days that we can't draw conclusions about "what really happens" or what "exists" based on the math.

Here's what I said exactly about it in #60 after you refused to answer the first time...

For days, over and over again, you've been trying to hammer into me that I can't draw conclusions about "existence" or "what's really happening" based on the math. Over and over you have set a firewall against using the math to wade into discussions about interpretations. And here I finally come around to accept this and when I ask you a question to solidify the point, you hedge. Either that, or I'm just misunderstanding you again.

I suspect that if you actually took some time to think about that question, it would answer itself and you would be able to stop belaboring the point.

I DID THINK ABOUT IT AND I ALREADY TOLD YOU I FULLY EXPECTED THE ANSWER TO BE "NO". Scroll up and read the part you just deleted before answering me.

Is this for real? Are you pranking me right now?

Peter! What's going on with you? Clearly I must have offended you. You're acting needlessly contrarian and argumentative. Is this about what I wrote to PedroK about you? I only meant that as light joking with no animosity whatsoever. I'm truly sorry if I offended you.

have you considered that that article might well be an inventory of your pre-conceived notions about the ignorant and naive reader who comes to these forums?

I never used the words "ignorant" and "naive" in the article or in that discussion thread. So if those words are coming from anywhere, they're coming from you, not me.

I never at all meant to suggest you did. And yes, those words were from me. The words ignorant and naive were words I was using to describe myself coming here trying to talk with people who were and are much wiser on the topic of quantum physics than I am. I feel no shame whatsoever in being ignorant or naive nor would I put shame on anyone else for being so. Regarding the article, clearly, I must have hurt your feelings by suggesting that you consider your own pre-conceived notions about what readers here are saying and, given the tone and attitude your displaying towards me here, it should be clear to anyone reading this that I had a point. I mean, WOW!

As I have said to you already, I really have been enjoying this conversation with you. I mean, I've easily got 6-8 hours into this thread just because I've been so thoughtful in how I've replied while struggling with some of your insights.

I truly don't understand what just happened.

Would you agree it might be best you should take a break from this thread and I'll ask someone else my questions?

 

[almarino dtd]

hate to jump in, but please include the experiment a few years ago where detectors were placed where there should be no recordings if interference and, shore enough, no detections.

 

[PeterDonis]

please include the experiment a few years ago where detectors were placed where there should be no recordings if interference and, shore enough, no detections.

No, please don't. Let's please keep this thread focused only on the experiment described in the OP. If you want to ask questions about a different experiment, please start a separate thread, and please give a specific reference that describes the experiment you want to ask about.

 

[PeterDonis]

I've been trying to say it back to you to show I've understood

Then you're apparently doing a bad job of that, since every time you think you're just saying back what I said, what you say looks to me like you're saying something different.

If we could use math in this discussion, it would be a lot easier to avoid such problems.

Is this for real? Are you pranking me right now?

No.

Clearly I must have offended you.

No, you haven't. I am only trying to help you understand QM better; I have no personal feelings or personal issues involved in this discussion at all. If I am unable to help you, that will be unfortunate, but it won't be any problem for me; I'll just bow out and let someone else try, if anyone else wants to.

I truly don't understand what just happened.

What is happening is that you are repeatedly becoming distracted by irrelevancies. They don't seem to be irrelevancies to you, but they are, and I, who know a lot more about QM than you do, as you have admitted, can easily see that they are irrelevancies. So I am trying to stop you from being distracted by them. Evidently I am not doing a good job of that, but I am doing my best.

(One of the irrelevancies you are being distracted by is worrying about whether you have offended me. Another is worrying about whether I am pranking you.)

The other thing that I think is happening is that, as I have commented several times now, you are persistently refusing to even consider using what has been proven by long experience to be the best tool for the job of understanding QM, or indeed any physical theory: math. And you are repeatedly seeing the drastic limitations that you are imposing on yourself by doing that: we can't even communicate simple ideas because the ordinary language words we are using mean different things to the two of us. When I use them, I am referring to particular specific concepts that are best expressed in math; but you won't look at the math, so I can't just point at a specific piece of math and tell you that this is what I mean by ordinary language expression X. And when you use ordinary language terms, you have nothing to refer them to, because you don't know the math, so they end up not actually meaning anything useful, even though it seems to you that they do.

 

[PeterDonis]

I did explain exactly what I thought the difference was between "physical interactions" and "invisible purple gods" with regards to the quantum wave function math and that difference was nothing.. zero... because you've been hammering it into me for days that we can't draw conclusions about "what really happens" or what "exists" based on the math.

Saying that we can't draw conclusions about "what really happens" or what "exists" based on the math is very different from saying that there is no difference at all between "physical interactions" and "invisible purple gods". Obviously there is, and you know it as well as I do. It's what I said in post #54:

In terms of QM interpretations, these two are certainly not equally valid, because "physical interaction" at least gestures in the direction of something we know about--it leads to questions like "what interaction? Is it electromagnetic? Strong interaction? Weak interaction? Gravity?" and so on--whereas talk about invisible purple gods does not.

Also, note that when we start asking questions like "which interaction?", we open up possibilities for experimental tests, in which we can potentially expand the scope of the basic rules, by finding out more things that force us to apply Rule 7. So asking such questions can be viewed as exploring experimental possibilities, not just as pure interpretation. It becomes more like pure interpretation when "interactions" are postulated under conditions where we have no way of testing whether they are there.

You even picked up on this:

Ya ya. I'm looking forward to getting into that at some point.

But instead of actually getting into it--by, say, asking a further question about it--you kept on about invisible purple gods. This is an example of what I meant in my previous post when I said you are repeatedly getting distracted by irrelevancies.

 

[PeterDonis]

Would you agree it might be best you should take a break from this thread and I'll ask someone else my questions?

Anyone else is already free to respond to your posts.

 

[Morbert]

Can wave collapse occur simply by gaining "information" about the particle without physical interaction?

What interpretation are you operating under? Under some interpretations, collapse is a physical process that can never happen. Under others, collapse is a spontaneous physical process. Under others, collapse is something that happens in the scientist's notebook when she learns new information. Under others, collapse is something that happens in a scientist's notebook when she is constructing logics to characterise the system. etc etc

 

[almarino dtd]

the double slit example i gave was on target, but if you wish to ignore, so be ir.