A very basic question about Heisenberg Uncertainty

[PeterDonis]

I don't find non-locality weird, since it doesn't break causation.

No, it just breaks relativity--at least, nobody has ever found a nonlocal theory that is fully compatible with relativity. The de Broglie-Bohm theory is non-relativistic, and AFAIK nobody has been able to construct a consistent relativistic version of it.

 

[PeterDonis]

I suggest you study the single slit experiment and see if you can think of any way that there could EVER be a deterministic theory that would explain how you can get those results.

The de Broglie-Bohm theory can explain it (it duplicates all the experimental predictions of standard QM), and it is deterministic. It's just also nonlocal and non-relativistic.

 

[Ozgen Eren]

But you are not just claiming that there must be multiple possible theories (an infinite number, in fact) that can explain any finite sequence of experimental data. I agree with that. You are making a stronger claim: that of all those possible theories, there must be some that are not as weird as QM. That is the claim I am questioning. My counterclaim is that the weirdness comes from experiments--experiments have shown us that the world just is that weird, so any theory that can explain how the world works must also be that weird.

Yes I agree that the experiment results force weirder theorems, but every explanation we have breaks a major concept. So I just assume among those infinitely many possible explanations, there should be one that doesn't violate position, momentum and similar concepts however complex their equations are. I can't prove it without showing one and I have never heard of Bells theorem before so I'm not sure if he actually disproves what I am saying now, I will check it out more in detail soon.

 

[PeterDonis]

I just assume among those infinitely many possible explanations, there should be one that doesn't violate position, momentum and similar concepts however complex their equations are.

Perhaps one issue is that you are changing your definition of what is "weird" vs. "not weird". First it was non-determinism vs. determinism; now it appears to be "doesn't violate position, momentum, and similar concepts". (Note that the de Broglie-Bohm theory satisfies this latter criterion: all particles have well-defined positions and momenta at all times. But, as I have said, the price you pay is non-locality and violation of relativity.) Of course "weird" is really a subjective term and you can use it however you want; however, that makes it of limited value for discussion unless we can agree on a fixed definition of what it means.

 

[atyy]

(Note that the de Broglie-Bohm theory satisfies this latter criterion: all particles have well-defined positions and momenta at all times. But, as I have said, the price you pay is non-locality and violation of relativity.)

Just a note. Earlier in the thread I asserted that it is impossible (except in special cases) for quantum particles to have well-defined positions and momenta at all times. PeterDonis's statement and mine are not in contradiction, because we are using different definitions of position and momentum. I was referring to the non-commuting canonically conjugate positions and momenta.

 

[PeterDonis]

PeterDonis's statement and mine are not in contradiction, because we are using different definitions of position and momentum. I was referring to the non-commuting canonically conjugate positions and momenta.

Yes, I should have included that the "position" and "momentum" of the particles in de Broglie-Bohm theory, the ones that have well-defined values at all times, are different from the canonically conjugate quantum variables with those names, which are the ones the Uncertainty Principle applies to. Those variables are still there in de Broglie-Bohm theory, but they involve the wave function as well as the particles themselves (so the "particles" themselves are not quite the same as the "quantum particles" that appear in ordinary QM--the latter are more like combinations of the de Broglie-Bohm particles and the de Broglie-Bohm wave function).

 

[bahamagreen]

Ozgen Eren,

There are others here that may be able to explain it better, but what you are confronting in QM is a somewhat different kind of idea about the relationship between a measurement and the attribute measured. The thing is, the measured attribute "does not exist" independently of the measurement... how can that be?

The way I think of it, which is extremely hand wavy, is something like this:

A wave can be decomposed into a set of fundamental sine waves of various frequencies, phases, and amplitudes. Those sine waves combined will reconstruct the original wave. This is Fourier... and the first conclusion might be that any wave is comprised of a set of these sine waves... sine waves are fundamental.

But, the choice of using sine waves to do this is not required; one could also use cosine waves, or triangle waves, or impulse waves, or square waves, or any kind of wave (like the complicated wave of a musical instrument) as the choice of "seed wave" with which to perform the decomposition of the original wave.
Now, think of the "measurement process" as choosing a "seed wave" to use for decomposing into component waves and think of the set of component waves as the "measured attribute".

If you choose the seed wave to be the sine wave or some other simple wave, that is like preparing a measuring apparatus to measure something like position, or momentum, or some other simple physical attribute. The choice of seed wave (how you design the measurement) determines the nature of the attribute that you measure.

If you chose a complicated seed wave for your decomposition, what you are doing is arraigning a more complicated apparatus and condition, which may be really impossible to construct, but the resulting measurement would correspond to some attribute, which may be bizarrely weird and really impossible to figure out what it corresponds to in physics... but you will get the measure of an attribute.

So, every possible seed wave used to decompose the original into components will result in measurement of some attribute... and there are an infinite number of seed wave forms to use, and an infinite number of resulting attributes, virtually none but a few resulting from the simple seed waves will look like anything we think of as a normal attribute, like position, or momentum.

The designs and implementation of real measuring conditions are pretty much limited to the ones that use the more simple seed waves for deconstruction and those measures result in the basic attributes with which we recognize, and some that are a little weird. If we could design a measurement using a seed wave of great complexity, the attribute measured would be incomprehensible and unrecognizable, but would stand just as "real" as a simple measure that results in a position or momentum.

The quantum object does not have intrinsic attributes apart from measurement in the same way that an original wave does not have a position or momentum attribute until the choice of seed wave used for deconstruction is selected and employed. The original wave does not have any particular set of decomposition components prior to choosing with wave form you want to use to do so... it has no intrinsic attributes before you design and implement a measurement.

It is the familiarity of the simple ones that makes one think they might be there all the time.

 

[DrChinese]

So I just assume among those infinitely many possible explanations, there should be one that doesn't violate position, momentum and similar concepts however complex their equations are. I can't prove it without showing one and I have never heard of Bells theorem before so I'm not sure if he actually disproves what I am saying now, I will check it out more in detail soon.

Heisenberg showed that knowledge of the value of one quantum property (say X) leads non-commuting properties (say Y or Z) to have undefined values in the limit where X is certain. If you attempt to provide values that are consistent with experiment, you will need your theory to be non-local.

So as several have mentioned, you get to make trade-offs between what important concept you must reject: locality, causality, observer independent reality, etc.

To give you an idea of how difficult the experimental regimen is currently: there are experiments in which particles are entangled AFTER they are observed (and no longer even exist). They can be entangled outside each others' light cone as well in the same experiment. So you will find a lot of hoops to jump through in your quest for a viable theory* that is not "weird". *Other than QM, which of course predicts this behavior. If people did not take QM seriously, such behavior could never be even considered.

 

[Ozgen Eren]

Perhaps one issue is that you are changing your definition of what is "weird" vs. "not weird". First it was non-determinism vs. determinism; now it appears to be "doesn't violate position, momentum, and similar concepts". (Note that the de Broglie-Bohm theory satisfies this latter criterion: all particles have well-defined positions and momenta at all times. But, as I have said, the price you pay is non-locality and violation of relativity.) Of course "weird" is really a subjective term and you can use it however you want; however, that makes it of limited value for discussion unless we can agree on a fixed definition of what it means.

I thought it was trivial. When our everyday conception is violated, I call it weird. If you can't apply it to your car for example. That includes the cases where matter don't have defined position, speed or energy. (you can't talk about a car that doesn't have a specified position, speed or energy. you can just say you don't know it in our daily life, but if exists, you know its somewhere and you probably don't assume it may teleport a second later) Or I call it weird when an event don't have a cause. (you can't say the car just moved randomly, I guess you would look for a reason, like a driver right?) Thats what I mean by weird. I understand how quantum dynamics approximate classical physics on large scale. But I just find it really hard to believe every possible explanation for our experimental result set have to be weird.

On wikipedia it summarized Bells theorem by "No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.". So in the manner I just described, I guess he proves a "not weird explanation" do not exist.

 

[Ozgen Eren]

To give you an idea of how difficult the experimental regimen is currently: there are experiments in which particles are entangled AFTER they are observed (and no longer even exist). They can be entangled outside each others' light cone as well in the same experiment. So you will find a lot of hoops to jump through in your quest for a viable theory* that is not "weird".

Did someone grouped all "weird" experimental results that led us to quantum physics, or where can I find them? I know about death spiral of electron, blackbody radiation, photoelectric effect and double slit experiment. But it appears there are a lot more of it.

 

[Ozgen Eren]

Ozgen Eren,

There are others here that may be able to explain it better, but what you are confronting in QM is a somewhat different kind of idea about the relationship between a measurement and the attribute measured. The thing is, the measured attribute "does not exist" independently of the measurement... how can that be?

The way I think of it, which is extremely hand wavy, is something like this:

A wave can be decomposed into a set of fundamental sine waves of various frequencies, phases, and amplitudes. Those sine waves combined will reconstruct the original wave. This is Fourier... and the first conclusion might be that any wave is comprised of a set of these sine waves... sine waves are fundamental.

But, the choice of using sine waves to do this is not required; one could also use cosine waves, or triangle waves, or impulse waves, or square waves, or any kind of wave (like the complicated wave of a musical instrument) as the choice of "seed wave" with which to perform the decomposition of the original wave.
Now, think of the "measurement process" as choosing a "seed wave" to use for decomposing into component waves and think of the set of component waves as the "measured attribute".

If you choose the seed wave to be the sine wave or some other simple wave, that is like preparing a measuring apparatus to measure something like position, or momentum, or some other simple physical attribute. The choice of seed wave (how you design the measurement) determines the nature of the attribute that you measure.

If you chose a complicated seed wave for your decomposition, what you are doing is arraigning a more complicated apparatus and condition, which may be really impossible to construct, but the resulting measurement would correspond to some attribute, which may be bizarrely weird and really impossible to figure out what it corresponds to in physics... but you will get the measure of an attribute.

So, every possible seed wave used to decompose the original into components will result in measurement of some attribute... and there are an infinite number of seed wave forms to use, and an infinite number of resulting attributes, virtually none but a few resulting from the simple seed waves will look like anything we think of as a normal attribute, like position, or momentum.

The designs and implementation of real measuring conditions are pretty much limited to the ones that use the more simple seed waves for deconstruction and those measures result in the basic attributes with which we recognize, and some that are a little weird. If we could design a measurement using a seed wave of great complexity, the attribute measured would be incomprehensible and unrecognizable, but would stand just as "real" as a simple measure that results in a position or momentum.

The quantum object does not have intrinsic attributes apart from measurement in the same way that an original wave does not have a position or momentum attribute until the choice of seed wave used for deconstruction is selected and employed. The original wave does not have any particular set of decomposition components prior to choosing with wave form you want to use to do so... it has no intrinsic attributes before you design and implement a measurement.

It is the familiarity of the simple ones that makes one think they might be there all the time.

This analogy was actually pretty useful thank you. So I guess we also think of uncertainty as taking some Fourier constants of one seed wave, and some Fourier constants of another, given that limited number of constants will construct the original wave. Thus we can never end up knowing both properties at the same time, we just vary their intervals depending on the choice of the constants. And I also guess that this just came out of the modeling of experiments.

 

[PeterDonis]

When our everyday conception is violated, I call it weird.

But you said nonlocality didn't bother you, and nonlocality certainly violates our "everyday conception".

That includes the cases where matter don't have defined position, speed or energy.

Or I call it weird when an event don't have a cause.

The de Broglie-Bohm theory is not "weird" by these criteria. I notice you didn't include nonlocality or violation of relativity in this list, though.

On wikipedia it summarized Bells theorem by "No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.". So in the manner I just described, I guess he proves a "not weird explanation" do not exist.

So nonlocality and violation of relativity are "weird" by your definition?

 

[VantagePoint72]

But you said nonlocality didn't bother you, and nonlocality certainly violates our "everyday conception".

Actually, you'd be surprised how many somewhat physics literate non-physicists (read: people who took high school physics and still remember some of it) are entirely unphased about the notion of non-locality. Until, that is, you remember the Newtonian physics is very non-local, being chock full of instantaneous action-at-a-distance forces. It's a funny thing, but people actually have to be taught first that non-locality is a weird thing in light of special relativity, before appreciating that quantum mechanics is weird for (kind of) having it. For people who haven't been taught to think relativistically, locality is a foreign concept that violates "everyday conception".

 

[atyy]

Actually, you'd be surprised how many somewhat physics literate non-physicists (read: people who took high school physics and still remember some of it) are entirely unphased about the notion of non-locality. Until, that is, you remember the Newtonian physics is very non-local, being chock full of instantaneous action-at-a-distance forces. It's a funny thing, but people actually have to be taught first that non-locality is a weird thing in light of special relativity, before appreciating that quantum mechanics is weird for (kind of) having it. For people who haven't been taught to think relativistically, locality is a foreign concept that violates "everyday conception".

The worst of these are the lattice theorists, thinking they can provide a non-perturbative definition of the standard model

 

[PeterDonis]

Until, that is, you remember the Newtonian physics is very non-local, being chock full of instantaneous action-at-a-distance forces.

Hm, good point. Apparently I have done a very good job of retraining my intuitions to be relativistic. ;)

 

[Ken G]

Say we have 1,2 and 3 as experimental result. Then we say most probable function that satisfies it is x=y (like classical physics until it failed). Then we get 1,2,3,7 disproving x=y (7 is like the experiments that disproved classical physics). We can still write infinite functions (theories in this case) to satisfy the experimental data we have. All those infinitely many possible explanations will have different metaphysical assumptions. And I just think quantum physics is like drawing a really weird but valid curve to explain the sequence, instead of trying to fit a smooth polynomial (a theory with our usual perception is a smooth polynomial in this case).

Yes, I think that's a good way to frame the question. So then the question becomes, what are we trying to do-- fit the data with the best polynomial we can, and just tolerate it if we can't do it very exactly (that's more or less what Ptolemy and Copernicus did, when they were stuck with using only circles), or do we generalize our thinking until we can fit it even better (that's more or less what Kepler did when he used ellipses instead of circles). It would have been quite a shock to Ptolemy to imagine ellipses in space, indeed it might have shook him to his core (the ancient Greeks firmly believed in the perfection of the cosmos, and the perfection of circles). Yet today, we teach about ellipses, without batting an eye! Consider this wonderful quote by Feynman:
"We always have had … a great deal of difficulty in understanding the world view that quantum mechanics represents. At least I do, because I'm an old enough man that I haven't got to the point that this stuff is obvious to me. Okay, I still get nervous with it. And therefore, some of the younger students … you know how it always is, every new idea, it takes a generation or two until it becomes obvious that there's no real problem. It has not yet become obvious to me that there's no real problem. I cannot define the real problem, therefore I suspect there's no real problem, but I'm not sure there's no real problem."
In that quote, he seems to agree with you that it would be nice to "fit a polynomial" in your words, but by the same token, he suspects this is just a prejudice of his, that will likely vanish in future generations-- much as the desire for circles in space vanished when ellipses came along.

 

[atyy]

Consider this wonderful quote by Feynman:
"We always have had … a great deal of difficulty in understanding the world view that quantum mechanics represents. At least I do, because I'm an old enough man that I haven't got to the point that this stuff is obvious to me. Okay, I still get nervous with it. And therefore, some of the younger students … you know how it always is, every new idea, it takes a generation or two until it becomes obvious that there's no real problem. It has not yet become obvious to me that there's no real problem. I cannot define the real problem, therefore I suspect there's no real problem, but I'm not sure there's no real problem."

I always consider this to represent Feynman's misunderstanding of quantum mechanics. In his lectures, he says the only weird thing in QM is the double slit. That of course has a local hidden variable model, so yes, there is no real problem.

 

[VantagePoint72]

In his lectures, he says the only weird thing in QM is the double slit.

He actually did acknowledge this omission some years later and said something to the effect of, "Interference and entanglement together cover all the weirdness of quantum mechanics."

 

[Ken G]

It's a funny thing, but people actually have to be taught first that non-locality is a weird thing in light of special relativity, before appreciating that quantum mechanics is weird for (kind of) having it. For people who haven't been taught to think relativistically, locality is a foreign concept that violates "everyday conception".

I think you have a valid insight here, but I'd say the weirdness of non-locality goes much deeper, and predates relativity. I believe I recall Newton himself saying that no rational person could believe that action at a distance was really true, he just didn't have anything better at the time. So I think he would have been happy to hear about relativity, even though it unseated his theory from the top of the pyramid. To me, the fundamental source of the expectation of locality comes from our most basic experiences, that we only sense reality at a given place and time. We can infer things about elsewhere, but we are just telling a story-- all we actually perceive is entirely local. So if that's the way we ourselves move through our reality, that's also the kind of way for reality to work that would not seem weird to us.

 

[atyy]

He actually did acknowledge this omission some years later and said something to the effect of, "Interference and entanglement together cover all the weirdness of quantum mechanics."

Ah that's interesting. Do you know where I can look that up?

Incidentally, the Quantum Bayesians have made at least a partial defence of the remarks in Feynman's lectures (they acknowledge that nowadays, most Foundations people will think it's the Bell inequalities that epitomize quantum weirdness). It's in the introduction of http://arxiv.org/abs/0906.2187.

 

[VantagePoint72]

I believe I recall Newton himself saying that no rational person could believe that action at a distance was really true, he just didn't have anything better at the time.

True, but I think we can all agree that whatever implications the average student draws from Newton's theories, Newton himself did not have "everyday conceptions" about most things.

 

[Ken G]

I always consider this to represent Feynman's misunderstanding of quantum mechanics. In his lectures, he says the only weird thing in QM is the double slit. That of course has a local hidden variable model, so yes, there is no real problem.

I doubt Feynman would count deBroglie-Bohm as a valid solution to that problem. For example, in his lectures he made the point that you could create a "unified theory of everything" by simply taking every equation of physics, express it as a quantity that must vanish, square that quantity, and add it to all the other such quantities. Then the "theory of everything" would simply say that the sum of all those squared quantities must equal 0, and you have a single equation that includes all the rest. But he pointed out this could not count as a true unification, because it does not have the conceptual status as a unification of disparate phenomenon, it is just a kind of mathematical trick. One can view deBroglie-Bohm in a similar way-- not a conceptual unification, but rather a mathematical trick that allows the known unknowns in the final state to be descendants of the unknown unknowns in the initial state. I don't mean to derail the discussion by turning it into a critique of deBroglie-Bohm as I think that interpretation has interesting insights, I just mean to say that I feel Feynman's quote still holds-- if we don't include solutions that might be regarded simply as mathematical tricks, we still have the fundamental strangeness of the two-slit experiment applied to quanta. The strangeness is we have initial states that as far as we can tell have been prepared identically, which perform differently. It's the usual magic of the Born rule, and brushing that magic back to the initial state is not necessarily a resolution of the quandary.

 

[Ken G]

True, but I think we can all agree that whatever implications the average student draws from Newton's theories, Newton himself did not have "everyday conceptions" about most things.

You mean he was a mystic? That's true, but I still think it is reasonable that he rejected action at a distance because it just doesn't seem like how reality works. I can call to someone across the room, but the sound does not just appear in their head like ESP-- there is a pressure variation in the air in their ear. Since we don't routinely manipulate gravity or electromagnetic forces at a distance, all the influences we have on our environment in our daily lives are like this when we analyze them-- they are all local. So I think it does come as a surprise when we teach students, well before relativity, that mass and charges exert forces on each other at a distance. One way to check this is to ask a student, when they first start out in physics and long before relativity, if they think they can see something in the distance because they are remote sensors, or if they think there is something coming from that distant object that is arriving at their eyes. It would be interesting to check this, I've never tried.

ETA: put differently, this relates to two rather different meanings of "local." Post-relativity, local can mean that signals and influences must propagate slower than the speed of light. But pre-relativity, we still have a concept of local, which is that signals and influences have to propagate at some finite speed, there must be something there that moves from point A to point B to "carry the influence." The speed would have no universal limit, but every signal would have a speed-- that's what rules out action at a distance. And whatever the speed was, some type of entanglement experiment could violate it-- all relativity does is tell us what speed we need to worry about.

 

[VantagePoint72]

Ah that's interesting. Do you know where I can look that up?

Hrmph, one can never escape as easily without a source as one likes. Honestly, it's second hand information—something a colleague told me recently when discussing Feynman and quantum computing—and I hadn't bothered to check it. A bit of cursory research turns up nothing, so perhaps I'm just spreading hearsay by a Feynman admirer.

You mean he was a mystic? That's true, but I still think it is reasonable that he rejected action at a distance because it just doesn't seem like how reality works. I can call to someone across the room, but the sound does not just appear in their head like ESP-- there is a pressure variation in the air in their ear. Since we don't routinely manipulate gravity or electromagnetic forces at a distance, all the influences we have on our environment in our daily lives are like this when we analyze them-- they are all local.

I mean, I don't disagree with anything you say here, obviously. I think locality is intuitive. As for Newton, all I meant was to say that as a man with his hand uncommonly secure on the pulse of nature, it's not surprising to me that he had intuitive misgivings for the reasons you discuss. I was just suggesting that those without Newton's gifts (which is quite possibly everyone) can probably be forgiven for not jumping to the same intuitive discomfort when they study his theories.

So I think it does come as a surprise when we teach students, well before relativity, that mass and charges exert forces on each other at a distance. One way to check this is to ask a student, when they first start out in physics and long before relativity, if they think they can see something in the distance because they are remote sensors, or if they think there is something coming from that distant object that is arriving at their eyes. It would be interesting to check this, I've never tried.

Well, perhaps your experience with students differs from mine. All I can say is that most of the time when I discuss things like Bell's theorem with people with a high school physics background (which, granted, doesn't happen that often) the "quantum mechanics is non-local!" punchline rarely seems to land.

 

[atyy]

Hrmph, one can never escape as easily without a source as one likes. Honestly, it's second hand information—something a colleague told me recently when discussing Feynman and quantum computing—and I hadn't bothered to check it. A bit of cursory research turns up nothing, so perhaps I'm just spreading hearsay by a Feynman admirer.

I too am a Feynman admirer, and learned a lot from his lectures. The beautiful statements about frogs and composers still resonate with me. Unfortunately, I'm even worse than those lattice theorists, being a biologist, so I simply don't find nonlocality or contextuality weird :) The thing I find weird is the measurement problem, but that's probably because although I read Feynman's Volume III on my own, my first proper introduction to QM was in large part via Landau and Lifshitz. Of course if the lattice theorists actually get a lattice standard model, the measurement problem will probably be solved.

 

[Ken G]

Well, perhaps your experience with students differs from mine. All I can say is that most of the time when I discuss things like Bell's theorem with people with a high school physics background (which, granted, doesn't happen that often) the "quantum mechanics is non-local!" punchline rarely seems to land.

It's an interesting question if introductory students suffer a moment of cognitive dissonance when we tell them about forces that act at a distance, or if they are just fine with it. They probably come in ready to believe almost anything we tell them, so we would need to do a careful probe to discern whether or not that would seem fundamentally surprising to them. It would probably need to happen at the high school level, or else they'll already have been exposed to the notion. It would be an illuminating exercise, well worth reporting in a pedagogy journal.

I agree with you that framing the weirdness of entanglement is tricky, we don't want a kind of "Emperor's New Clothes" phenomenon where students need to act like they are surprised by how weird it is just to seem like they get what we are saying! Personally, I really don't care the time when the correlated observations are taken, whether they are in each other's light cones or not does not impress me because I don't see any signal that is connecting them, so who cares if a non-existent signal is superluminal or not! To me, the "weirdness" is "correlation without signal"-- I take it as a given that there is no signal there because we don't have a signal in the theory. So the weirdness is there even if the correlations are within each other's light cones.

 

[VantagePoint72]

my first proper introduction to QM was in large part via Landau and Lifshitz.

Off topic, but as long as this has strayed into pedagogy, I'm really not a fan of the L&L series. They're a fantastic reference when you already know the material, but I tend to think instructors who use them to complement lectures just have a fetish for conciseness. I recently had lunch with a professor I had way back in the undergrad days who had used an L&L book for both classes I took with him. I always wondered why, because he was a great lecturer and never even bothered to refer to them. We were discussing philosophy of physics and he said, "I never had much interest in it. I can't read the papers. I like stuff loaded up with equations, a page full of text scares me." And I thought, "Well that explains that..."

It's an interesting question if introductory students suffer a moment of cognitive dissonance when we tell them about forces that act at a distance, or if they are just fine with it. They probably come in ready to believe almost anything we tell them, so we would need to do a careful probe to discern whether or not that would seem fundamentally surprising to them. It would probably need to happen at the high school level, or else they'll already have been exposed to the notion. It would be an illuminating exercise, well worth reporting in a pedagogy journal.

You know, this is a very interesting question. A good friend of mine is a high school physics teacher. I think he's roughly in the part of the semester now where he talks about Coulomb's law (which looks non-local until you learn the rest of Maxwell's equations) and I believe next term he has the course in which Newton's theory of gravitation is introduced. I think I'll talk to him and see if we can set up a series of short surveys and get some insight into how his students react to action-at-a-distance. Probably wouldn't be rigorous enough to get published, but I'd be really interested to see the results.

 

[atyy]

Off topic, but as long as this has strayed into pedagogy, I'm really not a fan of the L&L series. They're a fantastic reference when you already know the material, but I tend to think instructors who use them to complement lectures just have a fetish for conciseness. I recently had lunch with a professor I had way back in the undergrad days who had used an L&L book for both classes I took with him. I always wondered why, because he was a great lecturer and never even bothered to refer to them. We were discussing philosophy of physics and he said, "I never had much interest in it. I can't read the papers. I like stuff loaded up with equations, a page full of text scares me." And I thought, "Well that explains that..."

Actually, I like L&L because their QM book begins with philosophy :) L&L begin with the Heisenberg cut, and mention that it is necessary and that it is strange. It is often said that the great physicists don't care about philosophy, but L&L are a counterexample. As is Weinberg's recent text. Feynman himself obviously cared about it, although he seems to not to quite have put his finger on the problem, being too close in time to Bohm and Bell. Even Dirac in a Scientific American article mentions the measurement problem, and says that it seems too hard to solve, so he will concentrate on the easier one of infinities! He also says he hopes the measurement problem will go away because maybe quantum mechanics is not the final theory.

 

[Ken G]

Probably wouldn't be rigorous enough to get published, but I'd be really interested to see the results.

I'd be interested also, so hopefully you can post the answer in this thread if you get one.

 

[DennisN]

Regarding Newton and the apparent gravitational action-at-a-distance, here's the quote/caveat from the man himself:

"It is inconceivable that inanimate brute matter should, without the mediation of something else, which is not material, operate upon, and affect other matter without mutual contact...[] That gravity should be innate, inherent and essential to matter, so that one body may act upon another at a distance through a vacuum, without the mediation of any thing else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it. Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers."

(source)

 

[DennisN]

Did someone grouped all "weird" experimental results that led us to quantum physics, or where can I find them? I know about death spiral of electron, blackbody radiation, photoelectric effect and double slit experiment. But it appears there are a lot more of it.

You could check out e.g.
http://en.wikipedia.org/wiki/History_of_quantum_mechanics#Founding_experiments

 

[DennisN]

I thought it was trivial. When our everyday conception is violated, I call it weird. If you can't apply it to your car for example. That includes the cases where matter don't have defined position, speed or energy. (you can't talk about a car that doesn't have a specified position, speed or energy. you can just say you don't know it in our daily life, but if exists, you know its somewhere and you probably don't assume it may teleport a second later) Or I call it weird when an event don't have a cause. (you can't say the car just moved randomly, I guess you would look for a reason, like a driver right?) Thats what I mean by weird. I understand how quantum dynamics approximate classical physics on large scale. But I just find it really hard to believe every possible explanation for our experimental result set have to be weird.

Here may be something to think about:

We belong to a species (Homo sapiens) that has evolved to being able to physically and naturally (i.e. without fancy equipment) observe, evaluate and manipulate an environment which involves just a couple of orders of magnitude of length, let's say five (ca 10^-3 m to ca 10⁺¹ m - the exact numbers can be debated, but anyway, roughly five).

Now, take a look at this table:

http://en.wikipedia.org/wiki/Orders_of_magnitude_(length)

There are 50+ orders of magnitude of length listed there.

If we humans can't experience these 45+ other orders of magnitude of length in a natural way, would it not be weird if we expected that physical processes in the domains of these other orders of magnitude would be easy to understand for us?

 

[Ken G]

If we humans can't experience these 45+ other orders of magnitude of length in a natural way, would it not be weird if we expected that physical processes in the domains of these other orders of magnitude would be easy to understand for us?

Another interesting thing about that table is that there are about 14 orders of magnitude between currently known phenomena (like the de Broglie wavelength of protons at CERN) and the "bottom" at the Planck scale. That's about the same gap as is between that smallest well-studied scale and the wavelength of visible light, the latter being a subject of common study in Newton's day. Since we regard the bigger as being comprised of the smaller, we might then conclude that we are as far from understanding what "underpins" the quantum domain as Newton was from understanding the Higgs mechanism. So if you think quantum is weird, buckle your seatbelt. I doubt we'll cross that chasm in the next few decades, but maybe in the next few centuries...

 

[Demystifier]

We were discussing philosophy of physics and he said, "I never had much interest in it. I can't read the papers. I like stuff loaded up with equations, a page full of text scares me."

That's one of the reasons why I like dBB. It's philosophy of physics, but expressed with equations. :)

 

[Ozgen Eren]

But you said nonlocality didn't bother you, and nonlocality certainly violates our "everyday conception".

The de Broglie-Bohm theory is not "weird" by these criteria. I notice you didn't include nonlocality or violation of relativity in this list, though.

So nonlocality and violation of relativity are "weird" by your definition?

Actually, you'd be surprised how many somewhat physics literate non-physicists (read: people who took high school physics and still remember some of it) are entirely unphased about the notion of non-locality. Until, that is, you remember the Newtonian physics is very non-local, being chock full of instantaneous action-at-a-distance forces. It's a funny thing, but people actually have to be taught first that non-locality is a weird thing in light of special relativity, before appreciating that quantum mechanics is weird for (kind of) having it. For people who haven't been taught to think relativistically, locality is a foreign concept that violates "everyday conception".

No, non locality does not violate the everyday conception. Because you can observe magnets, wireless communication, the interaction of planets. Even though you don't know why, you can actually observe that some objects can affect others from distance instantly (Although its not actually instant, you can't tell the difference. But when you add Maxwell in it, it even sounds more logical to have those effects due to some moving "invisible" things.). Thus its not weird, I know, and have seen that its possible.

And no relativity is also not casual for me, as I haven't seen anything that had a time difference with me. Actually I haven't seen any proof that time itself exists. Its a pretty valid claim for the things that are too small to observe without interfering or close to speed of light, I'm not arguing with that.

All I'm saying is that, there should be a huge evidence that rules out every other claim to give up conceptions like that. That's why I'm approaching with full suspicion on quantum mechanics, not to its accuracy on experiments but to its main perception. It makes me wonder, if every subtle position jump is possible, we should be able to observe at least 1 really weird thing on macro scale. The probability for me to suddenly appear on somewhere else is really really low, I agree. 0,0...as many zeros as you would like...0001 maybe. But every second, there are almost infinitely many random events with really low probability. But if you sum them up for any second, and consider say last 100 years, at least couple random and really weird stuff should have happened.

I am sure both quantum physics and relativity and all other weird theorems works almost perfect with experimental data. All I want to be sure is that the world actually cannot be expressed in terms of what we have already seen.

True, but I think we can all agree that whatever implications the average student draws from Newton's theories, Newton himself did not have "everyday conceptions" about most things.

He did a better everyday conception than most actually. Everyone were able to see "huge rounded bulks" on the sky and everything drops to the ground, whenever they are free on air. This was an everyday conception. The apple moving towards the ground with no apparent connection is something almost everyone have seen. I mean he could have suggested that some particular objects pushed each other, but not all. I claim that you can make a theory experimentally work if you plug enough rules in it. That's what he didn't do. He used three laws and both were somehow familiar and casual(observed by any human). All I am suspecting is that, are we looking for few trivial and strong postulates and derive the rest or are we just making up a new rule in addition to what already is there.

They probably come in ready to believe almost anything we tell them, so we would need to do a careful probe to discern whether or not that would seem fundamentally surprising to them.

I mean no disrespect but in my opinion that's what anyone who didn't ever question quantum mechanics do.