Oxymoron

(deleted because my post, though accurately bemoaning the lack of informed debate on this thread wrt randomness etc, added nothing useful).

[ December 20, 2002: Message edited by: Oxymoron ]</p>

Keith Russell

Greetings:

From what I've thus far heard and read, QM does not oppose determinism, nor does it negate causality.

An unknown cause should not be believed to be 'random', any more than an unknown cause should be attributed to 'God'.

Chaos and randomness are words we choose to employ when we don't have all the information about the exact causes of a given event or events.

We call those events 'random' or 'chaotic' because we don't know the cause--not because they have no cause.

Keith.

Oxymoron

The thing is, if you assume that in QM there is a meaningful definition of a 'cause', then because it is a fundamentally unknowable quantity, to posit that there 'is' a cause is just as bonkers as arguing that there 'is' a god.

Chaotic behaviour of a system reflects the fact that in some circumstances the idea of getting quantitative results is meaningless, and the best we can do and that can be doneis go for qualitative ones.

Random events, or random values? Which? They are phenomenologically disparate.

QM f**ks determinism up the a**e with no condom and no lube. Sorry, but it does. Nobody likes the idea that the cosy and relatively tractable world we live in is mad at the smallest scales, but since my microwave still heats my dinner and my laptop continues to execute instructions because of that madness, I just have to get used to it. Some folk on this forum seem to have a real thing about accepting the world as we find it. Surprising, given the nature of II, but there you go.

[ December 20, 2002: Message edited by: Oxymoron ]</p>

Keith Russell

Oxy:

How can you know that it is a 'fundamentally' unknowable cause?

(How can you know that you cannot know?)

Keith.

Oxymoron

Er, because wave functions are complex (as in have real and imaginary components) functions of position and time, and the only meaningful number you can extract from it destroys the information in it (probability density = magnitude of wave function).

Starboy

Kharakov, John, Keith and PotatoError:

<a href="http://fangio.magnet.fsu.edu/~vlad/pr100/100yrs/html/chap/fs2_14023.htm" target="_blank">Experimental Tests of Local Hidden Variable Theories</a>

<a href="http://fangio.magnet.fsu.edu/~vlad/pr100/100yrs/html/chap/fs2_14026.htm" target="_blank">Quantum Mechanics and Hidden Variables: A test of Bell's inequality by measurement of the spin correlation of low energy photon-photon scattering</a>

<a href="http://fangio.magnet.fsu.edu/~vlad/pr100/100yrs/html/chap/fs2_14033.htm" target="_blank">Experimental Realization of Einstien-Podolsky-Rosen-Bohm Gedankenexperiment: A new violation of Bell's inequalities</a>

<a href="http://fangio.magnet.fsu.edu/~vlad/pr100/100yrs/html/chap/fs2_14034.htm" target="_blank">Experimental test of Bell's inequality using time-varying analyzers </a>

Here are some of the experiments supporting the claim that quantum behavior cannot be described by local hidden variables. Please supply experiments to support your claim that what appears to be random behavior could be predicted if the hidden variables were known.

Put up or shut up.

Starboy

[ December 20, 2002: Message edited by: Starboy ]</p>

Kharakov

To posit that there is not a cause is just as bonkers. Lack of knowledge != knowledge.

You haven't made a logical argument against determinism yet.

I agree with you wholeheartedly.

PotatoError

Starboy

I don't understand the links cuz I don't know much (if any) about QM.

Quote: (from the first link)

"It has been shown by a generalization of Bell's inequality that the existence of local hidden variables imposes restrictions on this correlation in conflict with the predictions of quantum mechanics."

I understand what it is saying but I don't know what Bell's inequality is or restrictions that local hidden variables (i know what those are ) impose.

Do you know anywhere on the internet where I could get started learning about Quantum Mechanics? I've tried to look but everywhere I find + the stuff you posted was very high level and relies on lower level stuff which I don't know. I get access to a libary in a few weeks too once I get back to uni so if you know any good basic books that would be nice. But until then I have only the internet.

I am interested because it sounds like there is proof that there are no local hidden variables - in which case it must be random and I have to change my belief but first i need to know about it.

John Page

Hidden variables? I made no such claim. See my responses below.
This experiment compares the output from two other experiments to measure directly any inequalities in the behavior of the systems being measured. (Such as might happen if one assumed that all metals had equal properties, for example).

The result in no way support QM behavior as "truly random". It does support a conclusion that the experimental results are effectively "normalized" through the direct comparison of outputs. All this means is that the conditions required to duplicate the results have indeed been achieved - difficult to know if indirect measurements are made due to the QM-level problems of observation mentioned earlier in this thread.

Again, this experiment in no way proves that quantum events are random. I am confused why you think that an absence of hidden variables entails randomness.

Another coincidence experiment. It concludes that the results are "in favor of non-local properties of microphysics". It makes no conclusion about whether such properties arise through deterministic or random phenomena.
Another coincidence experiment. Conclusions state that the results support nonlocal properties. Nothing about random causation.
Computes an average normalized concidence, so what?

The more I think about your examples, the more they support the assertion that QM experiments show repeatable results, thus supporting causality. If quanta behavior were truly random I suggest our universe would be incoherent to the extent that our existence would not be possible.

In summary, your statement "Here are some of the experiments supporting the claim that quantum behavior cannot be described by local hidden variables." is inappropriate. There may be phenomena unknown that play in quantum level behaviour in ways we have not yet fathomed, but I don't think any of the respondents has claimed that they have local hidden variables up their sleeves, nor do they need to.

Cheers, John

Shadowy Man

QM experiments have results that are repeatable only in a statistical sense. But yes, QM is not completely random; things don't happen just willy-nilly, but they do appear to happen in a manner that we can only describe in terms of probability. Even more so, things appear to be able to exist in indeterminate states!