3 TABLE I: Time-scales relevant for colloidal suspension; numerical values are for a buoyant colloid of radius a = 1 µm in H 2 O . For H 2 O , the speed of sound is 1 . 48 × 10 $^{9}$µm/s . The kinematic viscosity ν = 1 × 10 $^{6}$µm$^{2}$/s , and measures the diffusion constant with which vorticity diffuses away. Solvent time-scales Solvent collision time over which solvent molecules interact τ col ≈ 10 $_{−}$15 s Solvent relaxation time over which solvent velocity correlations decay τ$_{f}$ ≈ 10 $_{−}$14 − 10 $_{−}$13 s Hydrodynamic time-scales Sonic time over which sound propagates one colloidal radius t cs = a c s ≈ 6 . 7 × 10 $^{$_{−}$10}$s Kinematic time over which momentum (vorticity) diffuses one colloidal radius τ ν = a 2 ν ≈ 10 $^{$_{−}$6}$s Brownian time-scales Fokker-Planck time over which force-force correlations decay τ FP ≈ 10 $^{$_{−}$13}$s Brownian relaxation time over which colloid velocity correlations decay in Langevin Eq. τ B = M c ξ S ≈ 2 . 2 × 10 $^{$_{−}$7}$s Colloid diffusion time over which a colloid diffuses over its radius τ D = a 2 D col ≈ 5 s Ordering of time-scales for colloidal particles τ col < τ$_{f}$ , τ FP < t cs < τ B < τ ν < τ D