Our demonstration today is essentially identical to the classic G. I. Taylor demonstration of Stokes flow reversibility at low Reynolds numbers that can be found here. The key is that if inertial and non-hydrodynamic effects (e.g., surface contact, surface tension, etc.) are absent, then reversal in time is the same as reversal in direction: you really can wind the clock backwards! There's always a little loss of memory, of course, which has important implications for suspensions of particles at low Reynolds numbers. A very nice discussion of such memory effects can be found at David Pine's website.