Apples and Oranges? Comparing Quantum and Classical Theories

Even among specialists, quantum mechanics is notorious for being difficult—or even impossible—to understand. Nevertheless, no theorist worth their salt would readily accept that one of the pillars of modern physics lies beyond human comprehension. The standard approach to this problem is to explain the numerous idiosyncrasies of quantum theory by comparing and contrasting it with classical theories: one formulates both a quantum-mechanical and an analogous classical description of a given phenomenon, and then points out the glaring discrepancies between the two.

This tried-and-true strategy relies, of course, on our solid understanding of classical theories—contrasting the classical with the quantum can shed light on the latter only if there are no doubts about the former. However, is our confidence in classical physics truly justified? How well do we actually understand classical theories?

In this talk, I will present a critical examination of our current understanding of classical theories in the context of their comparison with quantum mechanics. I will argue that this understanding is far from complete, and that much remains to be learned. Finally, I will outline a systematic strategy for addressing this issue and show that many classical features can, in fact, be best explained through comparison with quantum mechanics—an ironic turn of events, given the context.