Sedimentation-Brownian crossover radius
= Sedimentation-Brownian crossover radius
{title2=$a_c=[3k_BT/(4\pi\Delta\rho g)]^{1/4}$}
Setting the gravitational Péclet number to one gives the displayed particle-scale estimate. A macroscopic sample instead requires its height to be small compared with the <sedimentation scale height>. These different observational criteria give different size thresholds; “no sedimentation” is not an exact universal cutoff.