Persistent rotation of particles driven by non-inertial Brownian motion

Umeda, Maki ; Chudo, Hiroyuki ; Imai, Masaki  ; Matsuo, Mamoru; Sato, Nana   ; Mori, Michiyasu  ; Maekawa, Sadamichi*; Saito, Eiji

The unidirectional spontaneous rotation of particles caused by Brownian motion rectified by the Coriolis force is reported. Fine magnetic particles dispersed in a revolving liquid were observed using the Barnett effect, and we found that the particles rotated much faster than the liquid. The observed spontaneous extra rotation is attributed to the breaking of the time-reversal symmetry of the Coriolis force, which rectified the random Brownian motion affected by viscosity. Our model considering molecular fluctuations in the medium reproduced the experiments well. The present results also suggest that all objects floating in fluids on Earth rotate spontaneously because of fluctuations.