Fig. 1. Irregular bodies rotate and shift laterally when settling in fluidized granular matter.

(A, E, and I) Photographs of the main three types of intruders under study. (B, F, and J) A sequence of snapshots taken from videos during the settling into a fluidized granular bed (1-cm reference bars are shown at the upper right corner of each sequence.). (C, G, and K) Plots showing the trajectory of the sinking intruders (z = 0 and x = 0 are taken at the initial position of the CM). (D, H, and L) Plots showing the time evolution of the intruders’ angle relative to the upward direction. In the plots, the dotted lines are averages more than 10 repetitions of each experiment; the colored bands indicate experimental fluctuations. Notice that in the initial snapshots of (F) and (J), the rough side is at the right. D stands for either the average lateral size of the rock or the diameter of the Janus intruders.