First posted 31 Oct 2003 - Another wrinkle to follow, if you're interested. Be-ables and Change-ables.
At the end of If you think you understand this, then you don't, I mention Bell's Inequality. Experimental tests of the theorem show that no hidden variable theory can be consistent with quantum mechanics' well documented and highly accurate predictions. Or do they?
Reading the article below in Nature Science Update, I learned that a new theory may show how a deterministic universe is consistent with QM's mathematical formalism and its experimental findings.
Einstein may be smiling in his grave. Having made one of the breakthroughs that led to the quantum revolution, he expressed great dissatisfaction with QM's indeterminacy. He believed that it was simply incomplete, and that a more comprehensive theory would show the indeterminacy to have been simply a result of our earlier ignorance. This looked impossible until recently.
Physicist proposes deeper layer of reality. Nobel winner Gerard 't Hooft says that QM's apparent indeterminacy is due to information loss as we zoom outward from the Planck scale, where deterministic physical laws rule. Although the article says he is not attempting to resurrect hidden variables, he is quoted as saying:
"Contrary to common belief," he says, "it is not difficult to construct deterministic models where quantum mechanics correctly describes stochastic behaviour, in precise accordance with the Copenhagen doctrine."
Where the Copenhagen doctrine is the most widely accepted interpretation of QM, stating that the world really is probabilistic at quantum levels - that there are some things we simply cannot know, some things that we cannot even say exist independent of observation.
't Hooft splits measurable properties into two classes - Be-ables which maintain their precision as one moves from Planck scales to laboratory scales, and Change-ables, which don't. Change-ables really aren't observable properties but rather ways of describing how a system behaves when it is perturbed. The trick is that we can't know in advance whether a property is a Be-able or a Changeable.
No, I don't understand all of this, but it is good to see that the deterministic debate is still alive and well in science as well as philosophy.