Relativistic electron trembling from positive/negative energy interference
Zitterbewegung ("trembling motion") arises in Dirac's relativistic quantum mechanics: a free electron wave packet oscillates at frequency ωZB = 2mc²/ℏ due to interference between positive- and negative-energy components. The trembling amplitude is ℏ/(2mc) ≈ λ_C/4π (Compton wavelength scale). Drag on canvas to inject momentum.