[T]hey [scorpions] rely on pressure-sensing organs near the ends of each of their eight walking legs to detect subtle shock waves that propagate outwards, even through sand, when another creature passes by on the desert floor. According to [Philip H.] Brownell, the scorpion orients itself toward the focus of any such disturbance by gauging the minuscule differences in the times at which the shock wave reaches each of its eight spraddled legs.