## Double

Pendulum

Painting patterns of light with two connected pendulums

**What is it about?**

The pendulum is a fundamental system in physics, its so-called *harmonic oscillations* find relevance in many different fields.

The motion of a single pendulum can be described quite easily. However, if you look at the double pendulum, you quickly see a seemingly random, unpredictable dynamic. In our installation, an ultraviolet laser mounted on the tip of the pendulum creates an afterglow on a phosphorescent film that illuminates the path of the pendulum. The line describing the motion of the pendulum is called its trajectory.

**Details and Theory**

The theoretical description of this trajectory leads to coupled nonlinear equations. Nonlinear systems generally have the property that a small change in the initial conditions causes a large change in the dynamics.

If you drop the pendulum several times from almost the same position, you get a completely different pattern each time. If all initial parameters were exactly adjustable (which is impossible in reality), the chaos of the double pendulum could be controlled – hence it is called deterministic chaos.