  Despite conventional wisdom that spin-1/2 systems have no classical analog,
we introduce a set of classical coupled oscillators with solutions that exactly
map onto the dynamics of an unmeasured electron spin state in an arbitrary,
time-varying, magnetic field. While not addressing the quantum measurement
problem (discrete outcomes and their associated probabilities), this new
classical analog yields a classical, physical interpretation of Zeeman
splitting, geometric phase, the electron's doubled gyromagnetic ratio, and
other quantum phenomena. This Lagrangian-based model can be used to clarify the
division between classical and quantum systems, and might also serve as a
guidepost for certain approaches to quantum foundations.
