A physicist and biogeochemist gets a kick out of the problem of Brownian motion and diffusion.

The movement of a particle in a gas or fluid, known as Brownian motion, exhibits two different regimes: the ballistic and the diffusive. For illustration, imagine a drunken sailor staggering back to his ship. While taking a few rapid steps, his instantaneous velocity may be quite high (ballistic regime), but his average 'random walk' velocity may be rather low (diffusive regime). If we were to monitor the sailor with a coarse-resolution Global Positioning System device, we would conclude that he is walking leisurely towards the docks, but we wouldn't be able to detect his rapid motions on much shorter timescales.

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