27-03-2005 01:37									#31
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quote: Originally posted by KrazyHorse The fundamental axiom of quantum mechanics in question is the one which states: "any measurement of an observable puts the system into an eigenstate of the associated operator"

Is it that or is it that it is in an eigenstate but we're not sure which one without the measurement?

	27-03-2005 01:39									#32
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quote: Originally posted by Dauphin I find it amusing that PA, an economist by education, is questioning the ability of highly precise physics theories to make accurate predictions.

Ask him some questions about deadweight losses and such. I would not be surprised to find some holes on tough micro questions.

	27-03-2005 01:43									#33
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Okay, in order for a theory to be valid, it must be understandable by PA. PA does not understand it, and according to quantum physics truth is dependent on the observer, therefore quantum physics are false. So you'd better get out the sock puppets and start brewing the coffee, Kuci, or the universe is gonna vanish.

	27-03-2005 01:45									#34
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*poof*

	27-03-2005 01:49									#35
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Coincidently the light just went black for a moment, universe must have restarted.

I think I saw a command prompt for a nanosec.

	27-03-2005 01:50									#36
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God got a BSoD.

	27-03-2005 01:52									#37
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I bet he'll soon switch to Mac.

	27-03-2005 02:06									#39
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quote: Originally posted by TCO Is it that or is it that it is in an eigenstate but we're not sure which one without the measurement?

You yourself mentioned the double slit experiment with single electrons, dude. If it was just that we weren't sure there would be no interference pattern.

Plus, go look at Bell's theorem to see how badly hidden variable theories like the one you seem to favour have been trounced.

It is not impossible for there to be a local hidden-variable theory that is consistent with experimental results. However, we haven't found one yet, so my feeling is that any such theory will be needlessly complex.

	27-03-2005 02:23									#40
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I just don't like the observer being important to events. How does the double slit thing cause problems again?

	27-03-2005 02:32									#41
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"The observer" is only an interaction with the non-quantum world, George. No need for consciousness or even for the observation to be recorded.

Putting a particle into an eigenstate can be done without anybody ever finding out what the value of the associated observable was originally. Think about putting a single electron in a giant magnetic field (in z direction) in a sealed box. After a longish time you open the box. The magnetic moment of the electron will have aligned with the magnetic field (it will be in an eigenstate of Sz), yet you performed no "observation" in the naive sense on the original spin The axiom goes the other way: it simply says that you can't find out what its Sz is without putting it into an eigenstate of Sz (or energy or any other observable).

And as for the double slit thing, if the electron took a single path without us having to measure it (and we simply didn't know what path that was) then why would there be an interference pattern? If we throw pool balls through slits in the dark and record where they hit we don't get an interference pattern...

	27-03-2005 02:43									#42
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quote: And as for the double slit thing, if the electron took a single path without us having to measure it (and we simply didn't know what path that was) then why would there be an interference pattern? If we throw pool balls through slits in the dark and record where they hit we don't get an interference pattern...

I wonder if anyone has tried

	27-03-2005 02:58									#43
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Getting a coherent beam of pool balls may be a problem.

	27-03-2005 03:03									#44
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quote: And as for the double slit thing, if the electron took a single path without us having to measure it (and we simply didn't know what path that was) then why would there be an interference pattern? If we throw pool balls through slits in the dark and record where they hit we don't get an interference pattern...

The electrons in the parallel universe!

Yes, I admit, I am a sucker for this theory coz I hate wave-particle duality with a passion.

	27-03-2005 03:06									#45
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Azazel, there's no problem with the many-universe interpretation.

However you must realise that the universe which we live in is not determined unltil the moment you make the observation.

Universes in that interpretation do not split except at observation points. So saying "the parallel universe" is naive. As a matter of fact, in that interpretation the interference pattern is the result of us remaining in a superposition of universes.

	27-03-2005 03:12									#46
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quote: Originally posted by Dauphin Getting a coherent beam of pool balls may be a problem.

Diffract them through a slit, silly.

	27-03-2005 03:16									#47
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You'd need a damn small slit to diffract a pool ball.

	27-03-2005 03:22									#48
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quote: Azazel, there's no problem with the many-universe interpretation. However you must realise that the universe which we live in is not determined unltil the moment you make the observation. Universes in that interpretation do not split except at observation points. So saying "the parallel universe" is naive. As a matter of fact, in that interpretation the interference pattern is the result of us remaining in a superposition of universes.

but why just the universes that are the result of the observation are causing the interference?

	27-03-2005 04:42									#49
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The way I learned wave/particle duality is that particles somehow takes every posible path at the same time, creating the electron interference pattern with the double slits.

	27-03-2005 04:49									#50
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quote: Originally posted by Azazel quote: Azazel, there's no problem with the many-universe interpretation. However you must realise that the universe which we live in is not determined unltil the moment you make the observation. Universes in that interpretation do not split except at observation points. So saying "the parallel universe" is naive. As a matter of fact, in that interpretation the interference pattern is the result of us remaining in a superposition of universes. but why just the universes that are the result of the observation are causing the interference?

Because other choices (for instance what the spin of some other particle in Beijing is) have no effect on the thing being measured...

	27-03-2005 04:50									#51
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Those measurements are independent. Their operators commute....

	27-03-2005 07:58									#52
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quote: Originally posted by KrazyHorse "The observer" is only an interaction with the non-quantum world, George. No need for consciousness or even for the observation to be recorded. Putting a particle into an eigenstate can be done without anybody ever finding out what the value of the associated observable was originally. Think about putting a single electron in a giant magnetic field (in z direction) in a sealed box. After a longish time you open the box. The magnetic moment of the electron will have aligned with the magnetic field (it will be in an eigenstate of Sz), yet you performed no "observation" in the naive sense on the original spin The axiom goes the other way: it simply says that you can't find out what its Sz is without putting it into an eigenstate of Sz (or energy or any other observable). And as for the double slit thing, if the electron took a single path without us having to measure it (and we simply didn't know what path that was) then why would there be an interference pattern? If we throw pool balls through slits in the dark and record where they hit we don't get an interference pattern...

I really haven't sat down and thought about it. But the interference thing seems like wave particle duality to me. Is it really a case of the states being intermediate rather than in some distribution?

	27-03-2005 08:08									#53
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It's both. It's more standard to do the problem from wave mechanical sense, but you can also create an observable (left slit or right slit). If you put the path into an eigenstate of the observable (if it travels through a definite slit) there should be no interference as the electron will propagate as a particle from a fixed point (left slit, say) and you will end up with two peaks and no interference pattern. This is observed when you put a detector on the slits to tell you if the particle has gone through (you perform a measurement on the observable left slit/right slit, which puts you into an eigenstate).

There is no local hidden variable interpretation available right now which is consistent with all experimental results...

	27-03-2005 08:14									#54
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What the bleep do we know? - anybody seen this movie?

	27-03-2005 10:30									#55
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quote: he way I learned wave/particle duality is that particles somehow takes every posible path at the same time, creating the electron interference pattern with the double slits.

behaves like a wave, hence the "wave-particle duality" thing.

quote: Because other choices (for instance what the spin of some other particle in Beijing is) have no effect on the thing being measured...

None whatsoever?

	27-03-2005 11:09									#56
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I get the impression that no-one in physics is intelligent enough to work out the implications, therefore they try to hush up their ignorance with "shut up and calculate" crap.

	27-03-2005 11:52									#57
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I'll repeat my question to you, PA:

what exactly do you think is the dillemma?

	27-03-2005 11:53									#58
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quote: Originally posted by Azazel quote: he way I learned wave/particle duality is that particles somehow takes every posible path at the same time, creating the electron interference pattern with the double slits. behaves like a wave, hence the "wave-particle duality" thing. quote: Because other choices (for instance what the spin of some other particle in Beijing is) have no effect on the thing being measured... None whatsoever?

Not if your experiment is done right...

	27-03-2005 11:53									#59
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quote: Originally posted by Park Avenue I get the impression that no-one in physics is intelligent enough to work out the implications, therefore they try to hush up their ignorance with "shut up and calculate" crap.

I don't know a single physicist as dumb as you.

	27-03-2005 12:27									#60
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PA you are the biggest know nothing sack of **** ever