Can Quantum Weirdness Be Logically Predicted?

[Max Raker]

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Which makes it wrong. I don't think "close enough, given the proper circumstances" really counts in physics.

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lol, this is all physics is. We never deal with absolute truths, that is for philosophers.

[Max Raker]

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I disagree with this. The position of observers in QM is 100% the result of the universe and not a by product of the way QM is constructed.

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Guess we disagree.

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And there is a 0% chance that quantum mechanics is "wrong", meaning that the worst that can happen to QM is what happened to Newtonian mechanics, ie it becomes a limiting case of a more encompassing theory.

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You contradict yourself.

Your really keen on these 100%, 0% estimates.

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The biggest problem with people learning about QM is that they jump to the hardest parts first. I think here you are attacking a precieved weakness in QM without first knowing what it does and why it was created.


Also I don't think I contradicted myself. To me, quantum mechaincs is just a tool, you use it to figure out how particles behave and it works (well actaully it works better than anything else humans have ever thought of).
I said there is 0% chance that QM is wrong because calling QM wrong is like calling a shovel wrong. How can it be wrong, you just use it to dig.

[Max Raker]

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One of the reasons I and many others reject the "just look around you" argument of Not Ready and others as some type of evidence for a superior being, is that we know that (aside from possibly human consciousness)the seeming magnificence of the Earth is mainly a simple consequence of Newton's laws and fractal geometry.

Furthermore, there is no reason to claim that Newton's Laws were created by this superior being. Because they are basically pure logical common sense. The Inverse Square law, the Law of the Lever, d=gtsquared, F= ma. All these experimental results are not the least bit surprising if you use logical thought. Even much of Einstein's stuff, I believe is a pretty straightforward deduction from the fact that the speed of light is constant.

What I would like to know however is if the strange things about particles that our experiments show, is a logical consequence of anything that makes common sense. I know the equations of quantum theory predict these results. But is their some underlying logical basis for them? In other words was there any way to logically guess that light would behave as a particle when observed but not otherwise or that a radioctive particle would have a 50% chance of decaying in x years regardless of how long it has already gone without decaying. Do results like these follow straighjtforwardly from any assumptions that are commonsensically reasonable? (For example might quantum randumness be necessary for humans to have free will?)

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David,
I have thought about your questions a little bit and I am ready to try to answer some of them. On the wave/particle question, I dont know of a way to explain this without using experimental results. It is clear if you consider the double slit experiment and the photoeletric effect, but I don't know of a way to explain it "on paper".

The particle decay question is not really unique to QM and is just a math problem. Many, non QM based systems follow the same equations.

[madnak]

Not absolute truths, but accurate, reliable patterns. Physics in practice involves a lot of approximation, but physics in theory shouldn't be approximate.

[cambraceres]

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Not absolute truths, but accurate, reliable patterns. Physics in practice involves a lot of approximation, but physics in theory shouldn't be approximate.

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This is a question of epistemology

[Piers]

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The biggest problem with people learning about QM is that they jump to the hardest parts first. I think here you are attacking a precieved weakness in QM without first knowing what it does and why it was created.

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[img]/images/graemlins/confused.gif[/img] [img]/images/graemlins/confused.gif[/img]

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To me, quantum mechaincs is just a tool, you use it to figure out how particles behave and it works (well actaully it works better than anything else humans have ever thought of).

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Agreed.

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I said there is 0% chance that QM is wrong because calling QM wrong is like calling a shovel wrong. How can it be wrong, you just use it to dig.

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I agree with the sentiment but don’t like the phraseology.

You create a model and ask what is the chance this model is correct. The natural interpretation of this is that you are asking what is the chance the model has an isomorphism onto reality (whatever that is). Instead you claim you used it to mean something like what is the chance my model of physics is a model of physics. So is a tautology false?

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And there is a 0% chance that quantum mechanics is "wrong", meaning that the worst that can happen to QM is what happened to Newtonian mechanics, ie it becomes a limiting case of a more encompassing theory.

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I have a street map of London, which was published in 1983. I still use it to travel around London. Is that map of London wrong or not?

[gumpzilla]

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One downside -- he does not discuss Bell's inequalities in these lectures, which are rather profound. However, you should be able to hunt down an intro to this specific topic online without too much trouble.

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David Mermin wrote a pretty nice article on this; here is a link. It's very approachable.

[prosellis]

Wave/particle duality is emphasized only to get a single point across -- a system's state vector is typically in a superposition of eigenstates of a particular observable. In the case of a particle satisfying the Schroedinger equation, this superposition looks like (has the functional form of) a wave. Superstring theory is a quantum theory, though, so it inherits this same type of "duality," though the observables do not include position operators of a pointlike particle. This is not something fundamentally new -- in quantum field theory one already stops dealing with simple position operators and starts dealing with observables of fields.

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Thanks for the response. I have taken a few introductory classes on theoretical physics but am relatively inexperienced with any of the string theories.

You seem to have some knowledge on the subject so I'll try a few more:

In string theories do the string vibration frequencies serve to replace the particle spin rates of classic Quantum Theory or are they in addition to?

Second, do you happen to know how Schwarz resolved the Yang-Mills anomaly that occurs in classic QM? The Clay Math Institute is still offering a Millenium prize for the mathematical proof of the mass-gap, but I've read (without having the background to understand) that Schwarz and Greene resolved this anamoly in the mid-seventies.

Don't mean to hijack the thread, just curious.

And to whoever it was that was curious about books regarding quantum mechanics, I loved David Bohm's "Quantum Theory."

[Metric]

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In string theories do the string vibration frequencies serve to replace the particle spin rates of classic Quantum Theory or are they in addition to?

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I should say that I am not a string theorist, but I have a little knowledge of the general picture. Basically, spin (and mass) correspond to different excitations of a string -- this is part of what makes the theory attractive to some people. There is no need to postulate spin and mass as external paramenters that simply go into building a theory -- every particle is essentially the same string, merely excited differently.

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Second, do you happen to know how Schwarz resolved the Yang-Mills anomaly that occurs in classic QM? The Clay Math Institute is still offering a Millenium prize for the mathematical proof of the mass-gap, but I've read (without having the background to understand) that Schwarz and Greene resolved this anamoly in the mid-seventies.

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Schwarz and Green showed that superstring theory was free of anomalies (hence interest in the theory exploded after this discovery). The Yang-Mills mass gap problem is apparently still open, but exists in the setting of quantum field theory. As for the details of Schwarz and Green's proof, I basically don't know anything about it, though you've got me curious about it now -- I may have to look it up.

[MadScientist]

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...we will be able to analyze more variables than we can currently account for (because we have advanced in that field) and say exactly when it will decay.

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This was the view of of many physicists before Bell's inequalities, which basically show that "not taking into account every variable" is not sufficient to account for all of the predictions of QM.

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We seem to revist this regularly but here goes again [img]/images/graemlins/smile.gif[/img]

If an experiments could confirm Bells inequality point then it would prove action at a distance (one particle 'knows' about the other one without any information passing between them).

However no finite experiment can tell the difference between action at a distance and information that travels sufficiently fast.

Hence all experimental validation of bells inequalities can do is demonstrate action at a distance or set the a lower bound on the speed at which information is transferred.

Is this confused or plain wrong?

chez

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plain wrong.

There is no information transmitted in experiments that show violations of Bell's inequality.
For instance, take a source that emitts two particles whose net spin must be zero. One up. One down.

<- e spin up *source* spin down e->

However, until measured, whether the leftmost particle has spin up or down is not known, but when it is measured, the rightmost particle's spin must then instantaneously be known.

There is no message sent between particles.

Phase velocities may exceed the speed of light. Only the tranmission of energy (related to the transmission of information), the so called group velocity, can not exceed the speed of light for massive particles.

For those interested in so called quantum weirdness which is just a wrong way to look at quantum mechanics, a well understood and tested part of modern physics, I would refer you to the experiments of Aspect et al., Phys Rev Lett. 49, 91, 1982. He shows by a series of rapidly varying measurement apparatus at a large separation that there can be no "hidden variable" theory at work whereby the orientations of the two particles are predetermined before hand. Rather, he shows that a quantum mechanical theory where the states are determined upon measurement must be correct and that the correlation between states between the two instruments occurs instantaneously.

After reviewing the experimental data, I think you will have a better understanding of QM. It will seem very concrete and indisputable rather than weird.