LambdaCalculator

Blueskyboris in an EVC thread said:

and in reponse to Tracy P. Hamilton, who said....

Blueskyboris said:

Well then, why don't we debate it?

I've always been under the impression that Bell's Theorem prohibits purely local theories in QM, and that the Heisenburg Uncertainty principle is not an error in measurement. What do the experts here think?

OdysseusTheInnkeeper

Didn't the Aspect experiment demonstrate non-local, EPR type interactions between photons?
OTIK

Blueskyboris

"I'm game"

That means you go first. Explain how the Uncertainty Principle proves randomness as a fundamental characteristic of the universe.

You know my statement on Bell's inequality.

Jesse

Yes, the violation of Bell's theorem seen in the EPR experiment does rule out local hidden variables, but nonlocal hidden variables interpretations like Bohmian mechanics are still permitted. If a nonlocal hidden variables interpretation is true, then particles would have exact values of position and momentum at any given time, despite the Heisenberg uncertainty principle (I'm not sure what you mean whan you ask if the uncertainty principle is an 'error in measurement' though).

LambdaCalculator

Uh, I never said it did. The Schroedinger Equation describes a wave-function that evolves it a statistically deterministic way. QM doesn't prove that "randomness" is a "fundamental (whatever that means) characteristic of the universe".

I'll leave the rest to the experts, since this is not really my field of expertise.

Blueskyboris

Bluesky:

Explain how the Uncertainty Principle proves randomness as a fundamental characteristic of the universe.

Black Cap:

Uh, I never said it did.

Well then, we have nothing to debate.

Blueskyboris

Tracy,

Very well, what IS delta x in the Heisenberg Uncertainty Principle?

a) Variation in measured values, even though the particle(s) have
well-defined values?
b) Variation in the value that particles with identical states have?
c) ____________________

This is not a college exam, Tracy. Please explain how the uncertainty principle has proved randomness as a fundamental aspect of the universe. Perhaps my understanding is not up to snuff, but I did not object to my assertion.

breezanne

The uncertainty involved is the element of consciousness.

Jesse

But the Schroedinger Equation itself is not enough to make any physical predictions--you must the additional assumption (originated by Max Born and sometimes called the 'projection postulate') that when you make a measurement, the square of the amplitude of the wavefunction on a particular eigenstate represents the probability that you will find the system in that state. Whether this indicates genuine randomness, or just that we lack enough information to explain why such measurements sometimes go one way and sometimes go another, depends on which "interpretation" of quantum mechanics you prefer.

Tracy P. Hamilton

First, there is no proof of any field of science. There is what the
evidence supports among many alternatives. Some have little
evidence to support them. The problem of quantum mechanics is
not one of theory per se, but what things mean.

That is why my question is directly relevant. If you wish to avoid it, very well. I will choose what I think the best interpretation is and give why.

a) is deterministic, and hence causal and not random

b) is the ontological view, with the wave function applying to an ensemble
of identical systems, which I think is the best interpretation. Perhaps
as transactional approach (d) will be best, analogous to "hand shaking" in
modem communications

c) would be something like Bohm's view, where a particle
has all values simultaneously.

Now if you have identical states but variance in the values of
one variable but with NO dependence of that variable on another
variable, that IS randomness.

The example I prefer is radioactive decay. In a pound of uranium-238,
half of the atoms will decay in 4.5 billion years. As far as the
evidence indicates, there is no physical cause that makes one atom
decay and another not. Hence the decay is RANDOM. Perhaps you
have a better explanation. Now this completely random behavior is
based on a constant decay probability per unit time that EVERY
U-238 nucleus has. Integration of this gives the exponential decay.