Advanced Undergraduate Laboratory

Department of Physics

University of Toronto

GRAN: Emergent patterns in shaken granular matter

Emergence is a term used to describe a process by which high-level order appears from the many-body collective behaviour of simple subunits. Familiar examples include the flocking of starlings, the shape of snowflakes and the appearance of superconductivity. In each case, the relatively simple interaction of the subunits (birds, water molecules, electrons) somehow gives rise to quite different, but organized, dynamics the level of the whole. In this experiment, the subunits are sub-millimeter bronze spheres. These particles obey Newton's laws, with dissipative, i.e. frictional and inelastic, interactions during collisions. To keep them in motion requires the steady input of energy, which is constantly dissipated. Our focus is the organized state of motion of a large collection of such grains which is being driven by a shaking plate. The local motion of individual grains is highly random, but their large-scale collective motion is fluid-like and exhibits strikingly ordered patterns. These patterns are universal and are observed in many otherwise quite different systems.

This experiment is related to research carried out in Prof. Stephen Morris's Experimental Nonlinear Physics Group.

Write-Up in PDF Format.

(The experiment is new. Contact Prof. Stephen Morris for help.)

Additional resources:

Photo of pattern

A square pattern with various defects in vertically shaken granular matter.

Last updated on 5 September 2019