Could Planck level physics be driving classical macroscopic physics   through a random walk?
  We examine a very simple conceptual model of stochastic behavior based on a random walk process in velocity space. For objects engaged in classical non-relativistic velocities, this leads under asymmetric conditions to acceleration processes that resemble the behavior of objects subject to Newton's second law, and in three dimensional space, acceleration dependent on an inverse square law emerges. Thus, a non-relativistic random walk would appear to be capable of describing certain prominent features of classical physics; however, this classical behavior appears to be able to take place only for objects with mass exceeding a threshold value which we identify with the Planck mass. Under these circumstances, stochastic space-time displacements would be smaller than the Planck length and the Planck time so that such classically behaved objects would be effectively localized. Lower mass objects exhibit more rapid diffusion and less localization, and a relativistic random walk would seem to be required of objects having masses comparable to and smaller than the threshold mass value. Results suggest the possibility of an intrinsic quantum-classical transition in the microgram mass range. 
C. L. Herzenberg
physics.gen-ph