By koantum, Section Commentary Posted on Mon Sep 11, 2006 at 02:37:06 AM PST
Sciencebase suggested that I write a summary of my critique of Quincey's article, which was scooped by Sciencebase.
Here goes.
Many weird ideas try to gain respectability by claiming similarities with some of the weird features of quantum mechanics. So what do you do if you want to debunk a weird idea? Quincey tries to undermine them all at once by trying to show that Quantum Mechanics Is Not So Weird after All. Is he going to succeed? Fat chance, given that the outcome of foundational work on quantum mechanics in the last couple of decades has been that interpretations which try to accommodate classical intuitions necessarily lead to empirical predictions that are at variance with the quantum mechanical predictions.
Quincey begins with a step in the right direction by switching (or, rather, pretending to switch) from the standard high-school formalism of classical physics to an equivalent formalism that replaces Newton's F=ma by the so-called principle of least action. But then things begin to go wrong, and badly so.
In the Newtonian formalism we are given the initial positions and momenta of a physical system. If we know how the momenta change at subsequent times (that is, if we know the forces at work) then we can calculate the path that the system will follow in its configuration space-time. (The latter has one temporal dimension and as many spatial dimensions as the system has degrees of freedom.) In the action formalism we are given instead the initial position X and the final position Y in the system's configuration space-time. If we know the values of the potentials (electromagnetic or gravitational) everywhere and at all intermediate times, then we can calculate the path along which the system evolves from X to Y. The reason why the action formalism is the right formalism for making the transition to or from quantum mechanics, is that quantum mechanics allows us to specify X and Y and to calculate the probability with which the system (for instance, a particle in 3+1 dimensional spacetime) is found at Y given that it was last found at X. What disqualifies the Newtonian formalism is that quantum mechanics does not allow us to specify a position in configuration space and a momentum for the same time.
Instead of actually switching over to the action formalism, Quincey combines these two formalisms in illegitimate ways. In addition he misrepresents Feynman's clever illustration of the quantum-mechanical probability algorithm using a surveyor's wheel. According to Quincey, "if we want to check out destinations that are too close to the start" then this mechanism "can't do its job properly." On the one hand he says that "the mechanism doesn't work" whenever classical mechanics fails and quantum mechanics has to be used, and on the other he claims that "quantum mechanics is... just classical mechanics with [this] mechanism." Go figure!
As a matter of fact, Feynman's (computational) mechanism doesn't fail at any scale. Properly understood and used, it precisely predicts when fuzziness (as in "uncertainty principle") comes into play. Quincey, on the other hand, introduces this fuzziness, which revolutionizes nearly everything that classical physics took for granted, in a manner that is completely ad hoc, and he doesn't have anything else to say about it.
For more, please visit here (with comments by Quincey and my responses to them) and here.
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