Is the “Fine-Tuned Universe” an Illusion?

My understanding of the measurement problem is the problem that our measurement outcomes depend on what we measure. As in, the measured result of the double slit depends on what you measure. The result of combining the outcome of reading both slits separately is not the same as the picture we see when we measure both slits together. Reality seems to depend upon what we measure and different measures reveal different realities.

So, indeed does the wave function collapse from a probability distribution to a definite outcome dependent on the measurement being made? How?

Son Goku, you know you should come around and play more often.

Okay so the way you have given it, there are basically two problems:

(a) The collapse of the wavefunction
(b) The fact that different measurements seem to have logically incompatible outcomes

So first of all a wavefunction is just a special case of a quantum state for when you're calculating position measurements. So I'll usually say quantum state instead.

So (a) first.
Looked at mathematically a quantum state has the same units as a probability distribution, obeys virtually all the same theorems as a probability distribution or generalisations there of. It can also be directly proven to be a generalisation of the probability distributions from regular "high-school" probability or statistics. There are a few proofs now in the literature that just assume a gambling agent wants to bet on the world in a coherent way (i.e. without contradicting themselves) and with a few assumptions on how they manage their bets you get a quantum state as a mathematical representation of those bets, but with different assumptions you get an old fashioned probability distribution as how they manage their bets.

For this reason I, along with the vast majority of people who work in QM, consider the quantum state (or wavefunction in the special case) to simply be a catalogue of an agents beliefs/credences/probabilities. It's not a material wave like an ocean wave.

Now probability theory has a method for computing an agent's new probabilities following an observation. You might know this as "Bayesian updating". The "collapse of the wavefunction" can be proven to be exactly this. It's simply the probabilities being updated in light of new information.

Since there are several mathematical proofs of this now, I consider this to be the answer to (a).

Now onto (b)
This is essentially the difference between classical probability and quantum theory.
In classical probability you consider a system to have a set of objective properties independent of observation. A particle has a position, momentum, energy, etc and you use probability theory to manage your ignorance of what values those properties have.
Quantum theory drops this assumption of observation independent objective properties. One's observations of a system produce numbers, but these can't be seen as reflecting properties of your system. Now probability theory is to manage your expectations of future observations, not ignorance of objective properties.

Once probability theory has been generalised to drop the "objective properties" assumption (this was the insight of Heisenberg) the resultant theory predicts the kind of incompatibilities you see in the double slit experiment.
Or one can go in the reverse direction. Simon Kochen and Ernst Specker showed that if certain kinds of incompatibilities show up in your experiments you can derive that there cannot be objective observation independent properties (Kochen-Specker theorem).

So like the vast majority of physicists I view the incompatibilities one sees in the double slit experiment as empirical evidence of the lack of objective properties/lack of an objective description of physical systems. Not a problem, but the insight of QM.

Edited by Son Goku, : Typos

We can use wave function and quantum state interchangeably. At this level it is permissible, yes? Understanding that each quantum state consists of other values like, spin, charge, etc, each with its own wave function of probabilities to be measured.

I hope no one thinks the wave function has a physical manifestation. But it is the reality we experience.

The quantum state is the entanglement of all possible probability values that could be revealed by measurement. It is constantly changing, shifting, updating with each interaction the field (particle(s)) experiences. And the result of a measurement reveals the most probable value we will see at any specific moment in time. The bother comes in when different measurements reveal different values.

I know wave functions are dynamic systems ever changing. But if you freeze time at one slice the probabilities under the wave function should also be set. Yet when we measure the system the “most” probable result will differ depending on how the system is measured. Different measurements seem to consistently alter what is most probable in a set objective system.

If I read your post properly your solution to this is to use Heisenberg’s work to do away with objective reality. How does that work?

Edited by AZPaul3, : No reason given.

Edited by AZPaul3, : No reason given.

Some of what follows might seem pedantic, or maybe stuff you already appreciate. due to it being hard to know what is being followed by somebody else from text alone and for others I will very explicit on certain points.

We can use wave function and quantum state interchangeably. At this level it is permissible, yes?

Yeah the terminology doesn't matter much here.

I hope no one thinks the wave function has a physical manifestation. But it is the reality we experience.

Let me start with an example.

Imagine somebody rolls a dice in a closed room. You who don't know the outcome assign probabilities as follows:

1	2	3	4	5	6
1/6	1/6	1/6	1/6	1/6	1/6

i.e. you give a 1/6 chance of each outcome. That list of 1/6 values in the second row is a probability distribution. The wavefunction is the exact same thing as that list. A list of chances to see certain events.
You wouldn't say that probability list is the "reality you experience". It's a calculational device that encodes expectations of what die roll you might see. The die roll is the actual reality you experience, not the probability list. It's the same with the wavefunction, it has no physical reality at all.

Same with how the odds on a horse race have no physical reality. The horses, jockeys, the race track do, but not the odds.

And the result of a measurement reveals the most probable value we will see at any specific moment in time

It reveals one of the possible values, not necessarily the most probable one. It's not always the horse with the best odds that wins.

Yet when we measure the system the “most” probable result will differ depending on how the system is measured. Different measurements seem to alter what is most probable in a set objective system.

So I'll take as a case the double slit experiment. You mean for example if you check the slits vs don't check the slits the locations where the electron/photon/etc will most likely land changes? If so then the next quote deals with this....

If I read your post properly your solution to this is to use Heisenberg’s work to do away with objective reality. How does that work?

Because the only way the double slit experiment is contradictory is if you think there is some system with objective properties evolving under certain rules/laws and your measurements merely record where it happened to be by the time it hit the screen.
Consider the passage through the slit to be a variable with two possible values:
Slit = Upper
or
Slit = Lower

If you don't check the Slit it leaves this variable undefined:
Slit = NULL

And Quantum Mechanics gives different answers for how likely it is to strike different parts of the screen depending on whether the Slit value was measured vs if it wasn't. It keeps track of which variables have obtained a value due to you measuring them and which haven't and the calculations get altered depending on which variables have become defined/gained a truth value.

This is paradoxical if you think these things have truth values independent of observation. It is not when you realise they only have truth values because of observation*.

Heisenberg conjectured, unlike everybody else at the time, that the issues with atomic spectra were not problems with formulating new laws or equations. Instead he said keep the old equations but drop the assumption that the variables have values at all times independent of observation. Removing that assumption gave him Quantum Theory. A new way of keeping track of your probabilities that doesn't assume objective properties exist.

*And note there is not some mechanical process to be found which "generates" the observed values. You select which variables are going to obtain values by your choice of observations and they will be given a value, but there is no process producing that value to be discovered. Observation/Measurement is a primitive in QM not a derived/emergent outcome of "deeper" properties or processes.

The die roll is the actual reality you experience, not the probability list. It's the same with the wavefunction, it has no physical reality at all.

Yeah, bad language on my part. Not clear for the peanut gallery. It’s ok, though, I knew what I meant.

This is paradoxical if you think these things have truth values independent of observation.

Ok. So the way to make QM consistent and meaningful is to ditch objective reality. Nothing exists other than through observation. And that observation may not be consistent with the result of other observations. Got it.

Actually, no I don’t. I certainly cannot argue your point. But, from a long time trying, the more I study QM the more EPR-like I become. We’re missing something.

Even with QM’s stellar performance in describing this universe it is good to see you QM folks haven’t lost any of your philosophical nuttiness. Yes, I know, I’m the nutty one. Objective reality? What am I smokin’?

[abe] This half-time show sucks.

Edited by AZPaul3, : No reason given.

Edited by AZPaul3, : cite EPR

So the way to make QM consistent and meaningful is to ditch objective reality.

I have not ditched "objective reality". But I have changed what I mean by that term.

From the way that I look at it, there isn't a way that the world is. But there is a way that I experience the world. And there's a way that you experience the world. But I cannot have your experiences and you cannot have my experiences.

So I talk about how I experience the world. And you talk about how you experience it. And we find that we can communicate, and we can agree about a lot of what we experience. So I see "objective reality" as those aspects of our experience about which there is widespread agreement.

Actually, no I don’t. I certainly cannot argue your point. But, from a long time trying, the more I study QM the more EPR-like I become. We’re missing something.

That's a common feeling, but I want to strongly emphasise how wrong it is.

The lack of an objective description for physical systems first showed up in probing atomic spectra and required quantum mechanics. Quantum Mechanics was then converted into Quantum Field Theory to handle subatomic phenomena and has continued to hold down to length scales over a billion times smaller than what QM was originally created for. And yet still the idea of the lack of an objective description holds. Not just holds up, but in fact predicts the correct observations.

In fact the lack of an objective description in QM is strengthened even more in QFT. In QM there might not have been an objective description of an electron but at least you could say there was an electron or your system had 3 or 4 or 5 electrons in it etc.

In QFT even particle number has no objective content to it. The Unruh effect for example shows that if I perform a scan on your body to count the number of atoms, the exact number I get has a probabilistic distribution, i.e. there is no actual number of atoms in your body until I perform the scan. Even further an observer accelerating with respect to you has a different "most likely number of atoms", a different probability distribution for atom count and can sometimes produce a count an stationary observer never would.

So probing deeper scales required abandoning the "objectivity" concept even more.

Further more we now have No-Go theorems such as Hardy's theory, GHZM theorem, Kochen-Specker theorem and newer strong ones that show no theory which postulates an objective description can possibly succeed in matching current evidence.

So we've still plenty to figure out, but if we find out QM is incorrect the only way it is going to go is an even less "objective" theory. Such theories do exist, the most studied is the so-called Popescu-Rohrlich box world, which is far less objective than even QM. So far no such "more subjective" theory has been required empirically so we conservatively stick to QM. They're weird theories, I'll say more about them in responding to nwr's interesting post below.

So this is a very good launching point for discussing objectivity in QM. I'll start by quoting UC Santa Cruz and Rutgers professor Thomas Banks' recent (2018) undergraduate textbook on quantum theory "Quantum Mechanics: An Introduction" where he says on p.16 of the 2021 paperback reprint:

Objectivity Reality is an Emergent Phenomena

Quantum Theory, like any probability theory, is used to model agents updating their expectations in light of experience. We can then model these agents exchanging and communicating information.

In Classical Probability theory under certain very mild conditions these agents when presented with the same data will eventually start to converge on similar probability distributions for future observations. These probability distributions and the process of their convergence is completely consistent with the existence of a single underlying description of physical reality. And so the convergence process can be read as "getting closer and closer" to this objective TRUE description of things.

Quantum Theory is quite different. The way the probabilities behave is not consistent with a single underlying description, i.e. a "way the world is". For this reason agents are not guaranteed to converge on a single set of expectations.
However one can show that the probabilities and expectations concerning large scale features of the world, e.g. the location of a tree, the height of Khufu's pyramid, do show a convergence and other features that are exactly like what you'd have in Classical Probability. And so a "layer" of reality emerges that agents can communicate stably about and agree on.

The existence of such a layer is of certain critical importance since otherwise it would be very hard to imagine how we could do science. The fact that QM requires the emergence of such a layer in order to be scientifically useful was a major concern of Neils Bohr:

"Bohr Collected Works Volume 7 p349" writes: ...that by the word “experiment” we refer to a situation where we can tell others what we have done and what we have learned and that, therefore, the account of the experimental arrangement and of the results of the observations must be expressed in unambiguous language with suitable application of the terminology of classical physics

The emergence of an objective layer is closely tied to thermodynamic processes often called "irreversible" and the large size of macroscopic bodies. Ultimately QM tells us we can only speak objectively about occurrences in this macroscopic layer of the world:

"Bohr Collected Works Volume 7 p390" writes: In this connection, it is also essential to remember that all unambiguous information concerning atomic objects is derived from the permanent marks—such as a spot on a photographic plate, caused by the impact of an electron—left on the bodies which define the experimental conditions. Far from involving any special intricacy, the irreversible amplification effects on which the recording of the presence of atomic objects rests rather remind us of the essential irreversibility inherent in the very concept of observatio

Thomas Banks in the textbook above (p.223 in 2021 reprint) makes a similar point that the scientific content of QM is:

"Banks" writes: To compute the probabilities for future events conditioned on the result of some particular event that affected a collective coordinate of a macroscopic body

"Collective coordinate" is basically jargon for "large scale feature" like the height of Khufu's pyramid rather then specific details of its atoms.

This does have knock on effects such as that it's not strictly correct to say I am "made of atoms" since it is impossible to conceive of an atom as an objective object, as Heisenberg often said:

"Heiseneberg. Physics and Philosophy Penguin Reprint p83" writes: They* would prefer to come back to the idea of an objective real world whose smallest parts exist objectively in the same sense as stones and trees exist, independently of whether or not we observe them. This however is impossible... *He means people who oppose QM

There's a book by the French physicist Roland Omnès "The Interpretation of Quantum Mechanics" where he carefully studies the use of language and logic in QM. He rightly points out the inconsistent of statements like "I'm made of atoms" or "fission works by neutrons splitting atomic nuclei" and has a section devoted to "Reliable Properties" which are essentially stories like this that treat atomic phenomena as if they were objective, i.e. effective metaphors, and he carefully works in what situations the stories work and when they break down. They're surprisingly fragile in the case of fission for example, it's not hard to derive in a few lines a basic contradiction in the typical account of fission. I can do it if anybody wants.

Popescu-Rohrlich theories I mentioned above are more extreme than QM in that they have no "Reliable Properties", i.e. it's never valid to use these stories where you pretend atoms etc are objective objects. You and other agents have to agree to only ever communicate about the objective layer and never say anything beyond that, even as an effective metaphor. It might turn out that's where we have to go for a proper description of gravity. Time perhaps will tell.

The last few days posts in this thread IMHO are full and complete justification for EvC's existence.

The thread has been a classic example of Evolution in action.

I have not ditched "objective reality". But I have changed what I mean by that term.

Just more as a check, Heisenberg did say you have to ditch it below a certain length scale otherwise you'd model Helium wrong. I assume this would be incorporated within what you are saying by saying Helium isn't fully in "objective reality", i.e. you don't ditch objective reality but accept it is verification and communication based and that some things, e.g. Helium, don't fully fall into it.

Edited by Son Goku, : Format

The last few days posts in this thread IMHO are full and complete justification for EvC's existence. The thread has been a classic example of Evolution in action.

I was thinking that exact thing myself, although I suspect QM says I wasn't.

I appreciate Son Goku explaining this to us, and I actually feel like I understood what he's saying, but when I try to conceptualize it my brain exploded (when I measured it). Thanks so much for hanging in here with us!!!

No worries. I had a hard time with QM initially as well.

Later today I'll post the Hardy Paradox as it's usually considered the easiest demonstration of the heart of QM.

So here's the simplest demonstration of QM's odd features.

We consider two electrons and for each one we can measure either the orientation of its spin (clockwise or anticlockwise) or how much Energy it has (high or low).

I'll use shorthand. E1 means Energy of the first particle. S2 means Spin of the second particle. I'll use +,- for each of the two outcomes. "E1 = +" means the Energy of the first particle was high. "S2 = +" means the spin of the second particle was clockwise.

Empirical facts:
A silver oven can be set up to emit electrons in pairs with the following empirical facts following.

(1) "E1 = +" implies "S2 = +" (The first electron being measured as high energy is always accompanied by the second electron spinning clockwise)
(2) "S2 = +" implies "S1 = -" (The second electron spinning clockwise implies the first one is anti-clockwise always)
(3) "S1 = -" implies "E2 = -" (The first electron spinning anti-clockwise implies the second one is at low energy always)

Contradiction:
Now let's say I am going to measure the Energies of both electrons. That is I will measure E1 and E2.

I measure E1 and find the electron has high energy, "E1 = +".

Now I take the three statements above and consider them as statements about objective properties the electrons coming from the oven possess independent of observations.

Since I just measured "E1 = +" I can use the first statement (1) to figure out that "S2 = +", i.e. that the second particle is spinning anti-clockwise.
Knowing that I use statement (2) to infer "S1 = -". Finally I use (3) to infer "E2 = -".

Thus I estimate that the second particle must be in a state of low energy.

However when I measure such systems I find 1/12 of the time the second electron has high energy. This probability is predicted by QM, but is in direct contradiction to the conclusion reached by observation independent properties.

Heisenberg did say you have to ditch it below a certain length scale otherwise you'd model Helium wrong.

I'm not a QM expert. I have been looking at it from the point of view of studying human cognition.

From that perspective, the completely objective reality consists of undifferentiated stuff. It is up to us to make distinctions. So a primary perceptual action is to categorize the world. Maybe it is better to describe that as "thingifying the world" -- dividing the world into things. And reality does not dictate how this should be done. Most of how we do this is driven by pragmatics. But that leaves some uncertainty that is not fixed by reality. And, as an example, we get to Helium by way of this thingifying.

This seems to fit with what I know of the QM point of view. When we thingify the world, that gives us a world of things. But that seems to be pretty much the same idea as collapsing the wave function. All of classical physics is about the things that we come up with as we thingify the world. And the uncertainty in how we do this seems to relate to QM uncertainty.

This seems to fit with what I know of the QM point of view. When we thingify the world, that gives us a world of things. But that seems to be pretty much the same idea as collapsing the wave function. All of classical physics is about the things that we come up with as we thingify the world. And the uncertainty in how we do this seems to relate to QM uncertainty.

Thanks for answering. If you're interested your description here can actually be formalised. "Thingifying" is mathematically formalised as placing statements you make into a Boolean algebra. QM describes the world via a collection of Boolean algebras that don't perfectly overlap/agree and the degree they fail to overlap is exactly Heisenberg's uncertainty. So this seems like a very nice way to approach it to me.

I know the science journalist Amanda Gefter is writing a book sort of bringing together human cognition and QM and from what I've seen of it it sounds very similar to what you are saying. I'm no expert on cognition, but it might be something you'd enjoy once she publishes it.

Edited by Son Goku, : Typos