# Time Evolution of a Symmetric System

Time Evolution of a Symmetric System

We consider a system of identical, perfectly elastic but otherwise noninteracting particles that are disks in a rigid circular container under the downward influence of gravity. Initially the particles are at rest and placed with mirror symmetry. From the equations of motion of the system, we conclude that the exact particle trajectories would remain mirror-symmetric forever.

This Demonstration shows that accumulating numerical errors break the mirror symmetry rather quickly. The more particles in the container, the sooner the breakdown of symmetry becomes evident.

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