http://www.wired.com/2014/06/the-new-quantum-reality/
Have We Been Interpreting Quantum Mechanics Wrong This Whole Time?
265 thoughts on “Bohm Lives Again–(aka was Krishnamurti right? ;>} )”
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The Skeptical Zone
"I beseech you, in the bowels of Christ, think it possible that you may be mistaken."
If the thing is “quantum state” and experience has to involve measurement, then I understand that is essentially what QM says: namely, measuring the state changes the state (unless you repeatedly measure the same thing). I don’t thing there is much controversy about that.
For example, if the state was spin X direction up (as known by past measurement which will be confirmed by repeated measurements of the same spin direction) then measuring spin in the z direction ends the definiteness of measurements in the x direction.
For entangled systems, measuring the state of one remote component of the system instantaneously changes the state of another component, in the sense of that it changes the distribution of possible outcomes of a measurement of that other component.
That was partly what the EPR paper was about. My understanding is that Bohr’s reply to Einstein was originally taken as conclusive, but is not anymore. Instead, Einstein’s hope for local hidden variables was dashed by experiments using Bell’s work.
BTW, empaist seems to be a fan of Bohr’s philosophy and SEP does claim he was anti-realist.
A small quibble, Bruce: it’s not a state that is measured, it’s a physical observable. In the language of QM, the former is a vector in a Hilbert space, the latter is an operator.
The contingent properties of my teacup (e.g., how it looks to me now) depend on what light is shining on it, what color glasses I am wearing, the medium between me and the cup, etc. But it doesn’t follow from that there is no such thing as “what is real for the object.” Maybe I have to fog up a mirror to look at it closely. Maybe observation of an electron’s momentum alters its position. If those are so, they’re so. What’s “real” for those objects doesn’t disappear as a result–we simply have to recognize that such properties are affected by other stuff going on in the world.
Noted; thanks.
I really need to spend the time to at least understand the basics.
My hands are getting tired from all this waving.
In this context I am restricting it what is inferrable from actual events. This allowance must be made in any case as our observations of most quantities is indirect. In what sense is the inference to wavefunction or quantum state realism grounded in or deduced from emprical facts?
All agree that QM is an immensely successful empirical enterprise whatever its interpretive quandaries might be. How did we manage to reach this conclusion without rigorously defining or at least reaching a consensus understanding of counts as a measurement? Standard QM assumes measurements, they are the objects to which and upon the basis of which the formalism assigns probabilities. Clearly what is presupposed by the formalism cannot have its existence established by the formalism.That the existence of measurements needs to be shown to be consistent with quantum theory is a task that needs to be completed and this requires the development of a consistent treatment of the macroworld. That was a genuine deficiency in the Copenhagen view but I think it can be fixed.
The question is in the direction of inference. Distinguishing ontology from what the world is like may just be a terminological squablbe, but interpreting the real (e.g. reading an ontology off of the formalism) in order toi place the world into direct correspondence with a theoretical item (quantum states) needs a lot of unpacking and I think the interpretative direction should lead back into features of the world, which however nonintuitive motivate and support the empirically testable deliverances of the theory as well as clarify its logical structure. This prompts what, to my mind, are more cogent questions like: Why this theory; why does QM preclude the simultaneous determination of conjugate variables to within a quantum level of accuracy? What does it mean for a particle of system to have a definate position in space? I think these are more interesting questions that seem to go begging perhaps because they lack the wow factor of the multi-verse or the implicate order and also because they are more difficult.
No, the name derives from what my grandkids call me.
I disagree. Holding that physical properties exist only to the extent they are inferrable (whether anyone is around to infer them or not) from actual goings on in the world is anything but a “commitment free instrumentalism”. It is in one obvious sense a complete logical triviality whose mention is only necessary in the context of ongoing reifications of theoretical terms that appear to violate the very categories of their definition and usage. In another sense it is a rather stark statement about the irreducible relationality of the physical world that could be proved wrong, but which appears to be consistent with QM..
Further I do not take the position that tables and sunsets are merely useful theoretical entities. They are, of course, words and like all words we must learn to use them correctly, but what these words designate in correct usage are respectively useful and enjoyable actual entities.
I guess I don’t know what you mean by “inferrable.” I would think that physical properties could be validly inferred only from other physical properties. We kind of “take them” from our experiences, which, if they are also physical (as they well might be) are not so in any obvious way. Naturally we’d want to use only “actual goings on” in the world to do our inferring from. But we either start with physical properties, or I’m afraid we never get them.
I agree with you that tables and sunsets exist, that they are actual entities designated by “table” and “sunset”–but, alas, there are no proofs–and never will be.
Bridging the gap between the quantum and classical worlds and deriving Born’s probabilities rule has been an area of active and fruitful research. Wojciech Zurek has a review of this topic in his paper “Quantum Darwinism,” Nature Physics 5, 181 (2009); arXiv:0903.5082.
I think these questions are less fundamental and more sociological in nature. Answering them will tell more about our limited view of the world (from our classical perch) than about the world itself.
Let me explain this on a “simpler” example from classical physics.
Let’s ask a similarly deep question: Why do objects not acted upon by a force continue to move along straight lines with undiminished speed, as Newton’s 1st law of motion prescribes? There is no satisfactory answer that science can provide. Sure, one can mumble something about the principle of least action or even derive it from Feynman’s path integrals, but that wouldn’t be the type of answer the questioner seeks.
The short answer is that’s how the world works. We just didn’t know that prior to Newton and Galileo. Our experience in a world with friction had taught us that objects always eventually stop. A deeper investigation uncovered the principle of inertia and that with no force, it’s the velocity that remains constant, not the position.
So the question merely expresses our astonishment at the way the world works, which was hidden from us in the world with inevitable friction forces.
It’s the same with the questions you pose. In classical physics, we take it for granted that we can measure an object’s position and momentum with arbitrary precision. Alas, that’s not how the quantum world works. Asking why isn’t really a deep question. That’s how it is.
Olegt,
I don’t think your comparison to classical physics is a suitable comparison. Nothing in the principle of inertia contradicts what we experience and understand in the observable world. For something to change a direction, or stop, it would need a force to cause this. Force causes either movement or braking, depending on the angle of application. It really requires very little in the way of ignoring of our senses to accept that. Its not counter-intuitive to our life experience.
But to suggest that the act of observing something is tantamount to changing that objects reality is something totally different. We have theories about why forces cause motion, we don’t have theories about why knowing about something changes its fundamental reality (if one accepts this claim of QM).
First of all, inertia is not self-evident. It was long thought that continuous force was required to keep objects moving.
Second, observation is not passive. Observation always involves interaction.
petrushka,
I didn’t say inertia was self-evident, I said it is not counter-intuitive to the theories we have about force.
Secondly, the idea that observation involves interaction is a loaded point. Do we interact with stars that burned out millions of years ago, but whose light is just reaching us. Can we affect that star’s existence?
What theories do we have about why quantum effects occur? We have theories about why force moves things.
For anyone who has not seen it, some Feynman armchair philosophy answering a similar question.
I’ve seen your “theories”.
UD
Yeah, give kids a painful cancer and help them to avoid all that everyday bliss and laziness! I can see the logic in it!
But it seems to me quite clear why quantum effects occur. Jesus want’s it that way!
OMagain,
Awww..you are still mad at God…so sorry.
For the same reason as Coyne?
Thank you for sharing your thoughts, phoodoo.
I am glad that you thoroughly understand Newton’s laws of motion.
Oh, well, it looks like I spoke too soon: you do not understand Newton’s laws of motion. A force does not “cause movement,” it causes a change in the state of motion (movement).
Did you take Physics 101? If not, by all means do.
Think what you like, but get used to being wrong.
Please refer to my previous answer.
olegt,
Ok, but only after you take Thinking 101, fair enough?
OMagain,
Was your Priest a meanie?
Do you tell your cats these secrets?
Yet:
Mote/Beam/Eye.
The Monks were OK actually.
Well, perhaps the reason God made evil is because if all people had in their lives was cosmic bliss, they would never produce anything?
Why don’t you run along and discuss things with your intellectual peers like Joe Gallien? The discussion here is way above your head.
If there was only good in the world, and nothing was bad, why would a person chose to even move? Wouldn’t people simply lay still in one spot forever, because why would anyone ever need to move?
So if a God wanted a world where people produced things, where people were creative or used their minds, then things that are not good would be an almost certain requirement.
Is that one tough for you to comprehend?
I can give you Coyne’s number if you want to commiserate with him?
olegt,
Ohhh, I bet Jerry loves it when you talk sooooo manly. Oooooooo!
No, your “theory” is clear and succinct.
So, kids get cancer because otherwise we’d all be lazy. And you worship the great cancer-giver-in-the-sky?
OMagain,
What problem do you have with cancer? If its just a normal result of natural selection, why are you calling it evil? Heck you should be hailing it as a great filter.
Praise cancer!
Is that the compassion of Jesus in you talking?
I’m calling it good. You have stated that it’s caused by a deity that does not want us to be lazy. Therefore, it must be good, as it’s from your deity, right?
Yes, indeed, as you say at UD:
If we did not bring the evil of the world upon us it must have been imposed from an external source – Jesus!
So you worship the bringer of cancer to this world. I get that.
More to the point, why don’t you have a problem with it?
OMagain,
You are the one who said cancer is evil, now you have to explain why.
Can you, guys, get a room?
Normal programming has resumed.
OMagain,
You have admitted defeat, that you can’t justify why you call cancer evil.
I accept your surrender.
It’s way above anybody’s head. Can you recommend some introductory materials?
I’ve responded in the sandbox thread.
BruceS has mentioned Lenny Susskind’s book Quantum Mechanics: The Theoretical Minimum. It is better than many popular accounts: it lets the uninitiated see how the sausage is made. It requires some effort to absorb.
olegt,
You have to admit, though, olegt, that without these interchanges, we might forever be without such gems as this:
What I love about that is that it shows that, for phoodoo, “good” must mean something like “orgasmic pleasure”. I had no idea that that was the xtian picture, but, live and learn.
Isn’t it more about QM than about the philosophy of science?
olegt,
Speaking of popular accounts, I recently picked up a copy of Lederman/Hill _Symmetry and the Beautiful Universe_. Do any of you know whether that’s any good? Thanks.
I see they are offering a class on Physics that perhaps you could attend. Its taught by Mr. Collinson, its called Forces Causing Movement.
Its for third graders. I hope its not too far over your head boy genius.
http://www.mrcollinson.ca/3%20science/forces/3_science_forces_complete.htm
walto,
If good means the absence of all bad, then what would the purpose of any movement or thought be? You wouldn’t need to eat. You wouldn’t need to build. You wouldn’t need shelter. You wouldn’t be bored. Why would one move?
I realize its a tough one for you walto, what with your Godphobia and all.
Is this where you learned your physics, phoodoo? Did you go all the way to Grade 4?
olegt,
Get back to me after you have. I am sure Mr Collinson would be happy to have you, if its a bit confusing at first for you.
Thanks for that generous offer, phoodoo. I will be on a sabbatical in the fall and might take it up! 🙂
Do consider Physics 101 for improving your understanding of physics. At the very least it will disabuse you of the notion that force causes motion.
phoodoo,
(A) “good” doesn’t mean the absence of all bad (at least it shouldn’t to Christians).
(B) Even if “good” did mean the absence of all bad (which it doesn’t–see (A)), it wouldn’t follow that nobody would ever want to move. We move for lots of reasons, some having nothing to do with good and evil.
(C) Assuming with you that “boredom” is a bad, I could eliminate it by dying–which I take it even on your non-Christian view of this matter wouldn’t be a good. (Well, maybe in my own case you think it would be, but, hopefully, you don’t take dying to be a good generally.)
(D) Do you ever have any idea what the hell you’re talking about?
Susskind’s book has math for the basics; the math is at a level popularizations lack. It is linear algebra at the sophomore level (or at least that is what level I encountered it when I went to school) supplemented by the Hilbert space and operators stuff you need, but you can follow it with high school algebra supplemented by the explanations in the book.
It does talk about the philosophy as well, but if you want something that is less math but more philosophy, this one is good; it is by the G from the group who developed the GRW approach to QM.
BTW, you can find youttube versions of Susskind’s QM as well as classical mechanics book on YouTube. I prefer books.
I don’t think QM lets you use traditional concepts to talk about properties of individual objects, at least at the quantum level.
First, there is superposition, so that if an object is in superposition of two positions (ignoring that position is continuous), then you cannot say any of “it is here”, “it is there”, or even “it is both here and there”.
Next, there a certain theorems which say it is impossible for an object to possess hidden-variable type properties which can be specified regardless of the measuring context. In other words, there are limitations on properties an object can be said to have on its own which would not apply to analogous properties at a macro level (ie this is not about relational properties).
Finally, there is entanglement. If two objects are allowed to interact in a way which produces entanglement, they can no longer be considered separate objects when things related to the entanglement are measured.
You can allow them to separate and then conduct measurements on each object separately. You will find that there are correlations between the measurements on the two objects which cannot be explained by assuming each object had separate properties set when they were together. The correlations happen even if the measurements are far enough apart so that light could not have traveled between the objects in the time between the two measurements.
walto,
1. What reason do we move, which have nothing to do with good or evil?
2. What is good?
Do you think about the implications of your scenarios before asking questions about them? Let’s review: if there was only good in the world… Umm…if there was only good in the world, people would get up and move and do things because getting up and doing things would be good and enjoyable. Duh…
But even aside from that simple implication, people would get up and move and do things simply because they could. That’s the reason most people do things now, not because they are avoiding pain, evil, or any other negative.
You clearly do not understand not only human dynamics, but social and psychological dynamics as well.
I got out of bed yesterday because the phone was ringing. However, I did not answer the phone. Was the phone ringing good or evil?
You make a good point that in effect I used the word “inference” in two ways at the same time.
The first inference is scientific: inferring the QM formalism as the scientific theory for prediction from the empirical data. Here “wavefunction” and other such terms are just names for the mathematical structures in that theory.
The second inference is philosophical. It relates to what a scientific realist can infer about the world from that scientific theory. I take Walt’s original post to be about that philosophical issue, and in particular why the standard Copenhagen interpretation is not a good starting point for the philosophical inference and what other interpretations have been attempted instead.
Further, I believe the philosophical issue of inferring about the world is not about the things we can see unaided: tables, chairs, the computer displays of the results of the measuring instruments at the LHC. Rather it is about the unobservable entities or structures that the theory implies of the world.
It is those status of those unobservables that distinguish the realist from the instrumentalist.
Based on some of the wording in your first post, I am guessing that you lean to a modal interpretation of QM. Is that a good guess?
Thanks — I was not trying to pry; it was simply that Pais remained a strong proponent of Bohr’s ideas and Copenhagen interpretation, I believe, and you also seem to think highly of Bohr’s philosophy.