Does quantum theory really undermine determinism?

[questionposter]

Even if we keep finding the smallest thing, we will just keep asking "well what causes THAT to do what it does?", and the answer will just lead into an infinite amount of questions. Even if things are deterministic on any level, there are infinite levels of determinism, which means no matter what things can't be completely determined, there's always some other smaller or larger level trying to determine things which in turn affect other levels to affect it.

Edited December 24, 2011 by questionposter

[dimreepr]

Ok, this was my main question. If it's the former, then determinism can still hold. If it's the latter, like you say it is, then I see how it undermines determinism. But does HUP really say that particles don't have defined positions and momentums? I thought it was just the principle that they can't be measured together.

 

I know that *later* QM has come up with the idea (after the two-slit experiment) that particles act like waves and thus really only have a "range" of possible positions, but is that really a part of the HUP itself? And even if it's true that a particle has a range of possibilities for position and momentum, isn't this still just a problem with our measurements, and not necessarily of the absolute position or momentum of the particle itself?

 

 

The thing is its range of possible positions, is everywhere in the universe.

 

I think we have to thank hub for refuting determinism, as the exclusion principle would go along way to prooving it.

[IM Egdall]

As Dr. Rocket said, per the modern understanding of quantum mechanics, nature is inherently stochastic (non-deterministic).

 

 

Fowler's link says the act of measurement disturbs the experiment, thus producing the uncertainty. This is a simplification. Per QM, the uncertainty is already there, inherent in nature itself. This is a subtle but very important point, and a change from what the early thinkers on QM believed.

 

I'm trying to remember the details, but I think Bell's theorum test results support this modern point of view. I also recall some careful experiments where the act of measurement produced such small disturbances that they could not possibly cause the randomness -- yet it was still there in the experimental results.

Edited December 26, 2011 by IM Egdall

[jaekwon]

The problem with questions of determinism in QM (which includes elements of non-determinism) is, there exists a "kind of determinism" beyond the inherent non-determinism of QM as long as all real physical phenomena appear to be sufficiently modeled by QM. That is, in repeated experiments it should appear that all experimental results converge towards those as predicted by QM. Then, one can think that QM "determines" the universe.

 

I would argue that no set of theorems consistent with the Universe can have this kind of determinism; that the Universe is non-deterministic under any set of theorems. It follows from an analog of Godel's Incompleteness Theorem; an Incompleteness Theorem of Physics.

 

link to discussion: http://www.scienceforums.net/topic/63883-incompleteness-theorem-of-physics/

[DrRocket]

The problem with questions of determinism in QM (which includes elements of non-determinism) is, there exists a "kind of determinism" beyond the inherent non-determinism of QM as long as all real physical phenomena appear to be sufficiently modeled by QM. That is, in repeated experiments it should appear that all experimental results converge towards those as predicted by QM. Then, one can think that QM "determines" the universe.

 

I would argue that no set of theorems consistent with the Universe can have this kind of determinism; that the Universe is non-deterministic under any set of theorems. It follows from an analog of Godel's Incompleteness Theorem; an Incompleteness Theorem of Physics.

 

link to discussion: http://www.sciencefo...rem-of-physics/

 

rubbish.

 

 

There is no Incompleteness Theorem of Physics, except in your personal delusions, and those delusions have absolutely nothing to do with the Gödell Incompleteness Theorems.

 

The only determinism in evidence is the apparent agreement between observation and the classical theories of general relativity and Newtonian mechanics in limiting cases at the macroscopic level. This is not fully understood, but it not particularly surprising in light of the theorem of probability known as the Law of Large Numbers.

 

So far all experiments agree with quantum mechanics. The only need for repeated experiments is to show that the probability densities predicted by quantum mechanics are accurate -- again a matter of statistics and the Law of Large Numbers. But those results do not, in any meaningful sense, " converge towards those as predicted by quantum mechanics" -- each and every data point is consistent with quantum theory.

[Widdekind]

It fails to what?

 

When HUP states that there is no way to theoretically ascertain the position and momentum of a particle, what does that mean?:

A. that there is no position and momentum? that no exist?

B. that there are too many positions and momenta? that we cannot decide which is the good pair.

 

 

A quantum particle is represented by a wave-function, which extends throughout some finite volume of space. As such, a quantum-particle is like a "cloud of probability density". You can calculate the "center of probability" of the particle, i.e. its position expectation value:

 

[math]\langle x \rangle = \int d^3x \; \psi^{*}(x) \; x \; \psi(x)[/math]

That expectation value corresponds to the classical "position" of the particle. But, QM'ly, the particle has some statistical spread, in position, about that centroid. That statistical spread, is [math]\Delta x[/math]. Likewise, particles have momentum expectation values [math]\langle p \rangle[/math], which correspond, to the classical "momentum" of the particle; but also, QM'ly, have a statistical spread, of momentum components, [math]\Delta p[/math], about that centroid.

 

I offer, that, in analogy, quantum particles are like "schools of fish", "herds of animals", or "flocks of birds". I.e. the "flock" is generally localized, to some vague region of space, with some semblance of a "center" [math]\langle x \rangle[/math], but also some spatial spread about that center [math]\Delta x[/math]; and, the "flock" is generally moving, in some general direction [math]\langle p \rangle[/math], but some "birds" are moving faster-or-slower, or this-way-and-that [math]\Delta p[/math]. As the particle interacts, with its environment, the "flock" scatters, gathers, roosts, lands, takes flight, swirls, etc.

[questionposter]

rubbish.

 

 

There is no Incompleteness Theorem of Physics, except in your personal delusions, and those delusions have absolutely nothing to do with the Gödell Incompleteness Theorems.

 

Ok, you gotta stop doing this, your going to choke this website with posts of

"rubbish"

"no your rubbish,

"no YOUR rubbish".

Things don't get solved by just saying "rubbish, your delusional because you don't understand my scientific point of view". Not that I think the other guy is right, but this thing doesn't appear to only happen with me. Just give a good explanation and let it play out.

 

It fails to what?

 

When HUP states that there is no way to theoretically ascertain the position and momentum of a particle, what does that mean?:

A. that there is no position and momentum? that no exist?

B. that there are too many positions and momenta? that we cannot decide which is the good pair.

 

The HUP can be translated as other people are describing, but what it means essentially is that if you know the exact position, as in you know only a single point, then that means the momentum is completely unknown, and it has to do with its mathematics. When your mapping out momentum and positions, your using complex equations, but they can be generalized as simple sine waves. Just imagine a sine wave on a graph: let the x axis be distance away form the nucleus, and let y be probability. If we graph y=sin(2x), you'll notice, there's consistant peaks of probability at infinite distances away from the nucleus (which represents exact momentum and undetermined position), however we completely know its momentum which is why we can graph it as y=sin(2x). Where it get's muddy is when you take into account multiple probable energies and add them up. If we add up sine(2x)+ 2sin(x)+4sin(.3x), we get weird looking sine waves, but you will notice that as we take into account more probable positions (representing the unicertainty in momentum, since we aren't just using one momentum to describe the particle's location), we only get peaks in very specific places.

The real math is harder than that though and uses some kind of division to create a horizontal asymtote at x=0.

The exact momentum looks like this

See how the peaks only go up the specific point, yet they contain a whole wide range of distances? THat represents knowing the exact momentum but a completely undefined position.

 

If we know the exact position, then it's a single point and not a sine wave. So knowing the exact position would be the same as

 

The exact position is (1,3), but because we have only 1 exact position, we have no idea what the equation is. There could be any number of different sine waves that pass through that point, and thus the position is known but the momentum is completely uncertain. In order to create a momentum, we need more points, and we only get more points by looking at other probable locations. After enough time of picking points, we see a better pattern for the momentum, but lose a single exact position.

Edited February 7, 2012 by questionposter

[DrRocket]

Ok, you gotta stop doing this, your going to choke this website with posts of

"rubbish"

"no your rubbish,

"no YOUR rubbish".

Things don't get solved by just saying "rubbish, your delusional because you don't understand my scientific point of view". Not that I think the other guy is right, but this thing doesn't appear to only happen with me. Just give a good explanation and let it play out.

 

It is one sensible response to the sort of pile of crap that some people, like you, post. Given such a pile, which is not worthy of the time necessary to address it point by pointless point, it serves the purpose of getting across the aroma of the pile. Hopefully it alerts neophytes who might be reading and lurking that there is nothing to be learned from any attempt to understand the post.

 

I am not trying to "solve" anything. You are quite hopeless. You are not salvageable and I think that no solution exists. But perhaps those lurking neophytes, and every science forum has many of them, can be salvaged and become reasonably informed about matters scientific.

 

You don't have a scientific viewpoint. You have a long history of posting "questions" the answers to which it is abundantly clear that you don't bother to try to understand.

 

Of course it does not happen to only you. You are not only miscreant, but you are rather prolific in your production of tripe. The remainder of your post (not quoted in the interest of conservation of space) only reinforces this point.

[questionposter]

W/e, I don't know about you, but I posted to try and figure things and settle some things down and answer a question. I have no idea what your even doing on this website.

Edited February 7, 2012 by questionposter

[DrRocket]

I have no idea

 

yep

[A Tripolation]

yep

 

I evened out your neg-rep, DrRocket, because you've always taken the time to help me when I need it. Though, I am curious, why aren't you helping to address the misinformation in this thread? I understand that questionposter may be a tad stubborn at times, but, in this, he seems deliberately trying to understand the HUP without the requisite knowledge of probabilities, wave packets, etc. Isn't it better to correct him with a few good links or books or explanations than to call his posts rubbish?

Edited February 7, 2012 by A Tripolation

[questionposter]

I evened out your neg-rep, DrRocket, because you've always taken the time to help me when I need it. Though, I am curious, why aren't you helping to address the misinformation in this thread? I understand that questionposter may be a tad stubborn at times, but, in this, he seems deliberately trying to understand the HUP without the requisite knowledge of probabilities, wave packets, etc. Isn't it better to correct him with a few good links or books or explanations than to call his posts rubbish?

 

I know my understanding isn't completely accurate and I think the way I explained is only generally why it works the way it works ( I wanted to avoid direct usage of quantum fields to make it simpler, but if someone has an explanation is easier for people to understand, I'd definitely like to see it), but the fact that he maybe helped you doesn't give him an excuse to just go around to threads with misunderstandings and say "oh, your crap, and oh, that guy's delusional, no, everything that anyone but me says is complete rubbish and is based on science fiction". It's like saying helping the poor gives you the right to go steal a TV.

Edited February 7, 2012 by questionposter

[A Tripolation]

but the fact that he maybe helped you doesn't give him an excuse to just go around to threads and say "oh, your crap, and oh, that guy's delusional, no, everything that anyone but me says is complete rubbish and is based on science fiction".

 

He helps people a LOT more than he calls ideas rubbish. And, trust me, everything that he says is rubbish IS rubbish.

[questionposter]

He helps people a LOT more than he calls ideas rubbish. And, trust me, everything that he says is rubbish IS rubbish.

 

It might be true that what is being said isn't completely accurate, but the logic for the argument that was false has to of come from somewhere anyway. I run into instances like this where there's misunderstandings and what he's doing only makes it worse. I'll admit that often when I run into it, it's usually with religion, and I just hate it when particularly atheists (OR orthodox religious people) act like they are better than everyone else, and don't even try to help religious people understand their point of view, they just say religious people are genetically inferior or unintelligent or don't have will power or w/e, and that only makes it worse (and I'm currently an atheist, so yeah). It doesn't matter if DR is right if he can't actually communicate it the right way. If Newton only knew how to speak Esperanza I doubt we'd have calculus.

It's also this principal that is partly why I think it is just as important to be a good person as it is a scientist.

Edited February 7, 2012 by questionposter

[DrRocket]

Though, I am curious, why aren't you helping to address the misinformation in this thread?

 

See page 1. The ideas are is relatively easy. I tried, but after that it became clearly futile.

 

Quantum mechanics is stochastic. When one is dealing with someone who cannot grasp that simple idea, there is little that can be done.

Edited February 7, 2012 by DrRocket

[questionposter]

See page 1. The ideas are is relatively easy. I tried, but after that it became clearly futile.

 

Quantum mechanics is stochastic. When one is dealing with someone who cannot grasp that simple idea, there is little that can be done.

 

That is absolutely not true. I've taught algebra to farm girls, music to graphic designers. All you have to do is put the effort into explaining it different ways. It still seems like your in the old way of thinking. I bet even mentally retarded people could have some kind of grasp of the properties of QM. You could show them the wave generated by a pebble in a pond, or run that wave through a panel with two slits to see how it acts for themselves. If you don't want to put the effort into explaining things in a better way, then instead of being rude, find a topic you want to post in.

Edited February 7, 2012 by questionposter

[DrRocket]

That is absolutely not true. I've taught algebra to farm girls, music to graphic designers. All you have to do is put the effort into explaining it different ways. It still seems like your in the old way of thinking. I bet even mentally retarded people could have some kind of grasp of the properties of QM. You could show them the wave generated by a pebble in a pond, or run that wave through a panel with two slits to see how it acts for themselves. If you don't want to put the effort into explaining things in a better way, then instead of being rude, find a topic you want to post in.

 

Graduate students I can help.

 

Interested and intelligent undergraduates I can help.

 

Kids from 7-18 I can help.

 

Farm girls are a breeze. (God help the ones that you have "taught".)

 

I can and have helped all of the above.

 

But you are beyond help. You have far too many serious misconceptions and a closed mind towards correcting them. There comes a point at which misconceptions are so numerous and so profound that one's knowledge is actually negative. You are way past that point. Your "explanations" of quantum theory only serve to prove this -- while mentally retarded people, as you state, might have some understanding of QM , you clearly do not.

 

The problem is not that you don't understand. The problem is that you don't understand that you don't understand. You compound that by offering instruction to others and that instruction is almost always just wrong. In fact, in the words of Pauli "It is not even wrong."

 

The best that can be done is to prevent you from confusing other innocent people who are capable of learning, and who are worth the time to try to educate.

[swansont]

Ok, you gotta stop doing this

 

!

Moderator Note

On the contrary, you need to stop dragging the post off-topic with this discussion. If a posted idea is contrary to accepted physics, one is within his/her right to call it rubbish.

 

Back to discussion of quantum mechanics vs determinism, please.

[questionposter]

Graduate students I can help.

 

Interested and intelligent undergraduates I can help.

 

Kids from 7-18 I can help.

 

Farm girls are a breeze. (God help the ones that you have "taught".)

 

I can and have helped all of the above.

 

The problem is not that you don't understand. The problem is that you don't understand that you don't understand. You compound that by offering instruction to others and that instruction is almost always just wrong. In fact, in the words of Pauli "It is not even wrong."

 

The best that can be done is to prevent you from confusing other innocent people who are capable of learning, and who are worth the time to try to educate.

 

I already stated that what I said wasn't 100% accurate, and unless you can find someone that is saying that direct description is wrong, I don't see what's wrong with using it for this topic. If you have an easier description to understand, then as I already also said, post a link. Put the effort into progressing the topic if I'm actually wrong. Every time I've posted "instruction", all the staff members or scientists were free to correct it, and they didn't even after two weeks of so little posting that those posts were in the top "most recent" for two weeks, which leads anyone to believe they are at least over 70% accurate, so what specifically is wrong with my general description considering I already know it's only a very basic general overview?

 

But you are beyond help. You have far too many serious misconceptions and a closed mind towards correcting them. There comes a point at which misconceptions are so numerous and so profound that one's knowledge is actually negative. You are way past that point. Your "explanations" of quantum theory only serve to prove this -- while mentally retarded people, as you state, might have some understanding of QM , you clearly do not.

 

Help progress the topic or stop posting. I asked someone to find what is generally wrong with my description and if you have a better one, so either do that, or stop being rude. I'm not the only person you do this with, you do this with other people whom oppose what your saying, just get over the fact not everyone automatically agrees with every single thing you say. I even interned for a real scientist and they weren't as bad as you.

Edited February 7, 2012 by questionposter

[A Tripolation]

Help progress the topic or stop posting. I asked someone to find what is generally wrong with my description and if you have a better one, so either do that, or stop being rude. I'm not the only person you do this with, you do this with other people whom oppose what your saying, just get over the fact not everyone automatically agrees with every single thing you say. I even interned for a real scientist and they weren't as bad as you.

 

What the uncertainty principle actually says is that for two complementary observables (position and momentum are complimentary) that if one takes particles prepared in identical quantum states and then does repeated measurements of position x followed by momentum p (or momentum p followed by position x) that

 

[math]\sigma_x \sigma_p \ge \frac{\hbar}{2}[/math]

 

where [math]\sigma_x[/math] and [math]\sigma_p[/math] are the standard deviations associated with the random variables x and p respectively.

 

Inherent in this statement are that position and momentum are not deterministic. They are random variables associated with a stochastic system.

 

It is NOT a statement that there will be any definite error in the measurement of either position or momentum. It is in fact a statement that there is no such thing as a definite measurable value of either position or momentum associated with a quantum particle.

 

This was already given to you. It is accurate.

[michel123456]

It is in fact a statement that there is no such thing as a definite measurable value of either position or momentum associated with a quantum particle.

Bolded mine.

What is the word "measurable" doing in this sentence?

 

If I had to follow Dr Rocket, it could be: (paraphrasing Dr's statement)

 

It is in fact a statement that there is no such thing as a definite value of either position or momentum associated with a quantum particle.

[DrRocket]

Bolded mine.

What is the word "measurable" doing in this sentence?

 

If I had to follow Dr Rocket, it could be: (paraphrasing Dr's statement)

 

It is in fact a statement that there is no such thing as a definite value of either position or momentum associated with a quantum particle.

 

I think we are saying the same thing. A quantity in physics is "real" only to the extent that it is either directly measurable or is reflected in a quantity that it directly measurable.

 

If I recall the context (one sentence makes it a bit difficult to do this) the point being made was that quantum mechanics describes random variables that evolve in time -- a stochastic process. Measurements produce samples of that random process and therefore measurements are not reproducible in the deterministic sense, but only in the sense that the statistics of many samples are predictable. When you make a measurement you get a definite value, and that value will be an eigenvalue of the operator associated with the quantity measured. But you cannot predict with certainty which eigenvalue will be produced, but only the relative likelihoods of the possible eigenvalues.

[Xittenn]

Ok, be gentle with me please, my physics is poor and English even worse! What I can't follow with all of this is the following. Schrodinger developed wave equations that model particle behaviour at <macroscopic scale, and these behaviours also tend to be lost at >macroscopic scale. As far as I know or understand, these equations are built on the principles of standing waves. This would suggest to me that there is a defined position. But now HUP comes along and says that defining the areas that a wave-particle will occupy can only be accomplished statistically and through probabilities, which to me contradicts the proposition that such elements could therefor be standing-waves. I have Messiah's book, translated into English (I might like to get the original French version someday) but I can only manage the first few chapters as it stands.

[immortal]

You cannot come to such a conclusion. Alaistair I.M Rae in his book A beginner's guide for QM takes both the analogies i.e a particle in a box analogy as well as the standing waves analogy that can be formed in a pool to arrive at the accurate predictions made by quantum theory.

 

We need those two analogies because of the dual nature of matter, the position of the physical entity like an electron is defined by the particle concept where as the momentum which is associated with the wavelength of the matter waves is defined using the standing wave concept.

 

Both particle -->position and standing waves--> momentum can have a set of possible values. This is where uncertainty creeps in so that we can only predict the possible outcomes or values of a quantum system and we cannot simultaneously know both the values of position and momentum precisely as it will always have an uncertainty equal to (Dirac's constant(h/2pi))/2.

 

Therefore HUP is a direct consequence of standing waves of matter. One advice the postivist approach of Bohr gives is that we should not attempt to attribute some reality to the nature of the quantum system itself, we don't know what those elements are and the aim of QM is just to predict the possible outcomes of the system and not to predict the nature of the physical quantum system itself.

 

 

[MigL]

I believe one of the best explanations was given by Richard Feynman in his lecture series ( They are very easy to find online and may even be here as a sticky ). It arises from the fact that the amplitude of the 'wave' is related to probability.

 

Only an infinitely long wave has a clearly defined wavelength, wave number and amplitude. This amplitude is related to a probability in QM, such that in this case the probability of finding a particle at a certain place is the absolute value of the square of the amplitude. And so, in this case, since the wave is infinitely long, it can be found anywhere; position is uncertain.

 

A wave packet on the other hand, has an increasing/decreasing amplitude BUT the wave number cannot be easily defined. so although the particle is more localised in this case, its energy and also momentum are more undefined.

 

It is basically a trade-off, shortening the wave packet locates the particle with more accuracy, but makes the momentum more indeterminate; conversely lengthening the wave packet introduces more uncertainty in the particle position, but makes the determination of momentum more accurate.

Edited February 9, 2012 by MigL