Figure 6: (a) Number of particles which diffused a distance in msec from a sample of 15000 trajectory steps. The thin line is a fit to eqn. (16). (b) The evolution in time of the square of the width, , from fits such as that in (a). The linear least-squares fit to eqn. (17) provides a measurement of the spheres' long-time self-diffusion coefficient. The unresolvable offset in this fit is consistent with our estimated measurement error for particle locations for a dilute suspension with minimal caging.