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Gallery 2

Harmonograph

A swinging platform and a pen attached to a pendulum, draw intricate shapes and patterns on paper.

How it works

Watch as a Questacon staff member sets the Harmonograph in motion to draw an intricate pattern on paper . Best of all, you can take a Harmonograph pattern home with you when it’s finished.

Things to try or ask around the exhibit

Can you get the exact same pattern twice?

Background

The four pendulums on this Harmonograph are attached to the platform’s corners so that the platform acts as a giant pendulum that is able to twist as well as swing back and forth. These motions allow the Harmonograph to create intricate patterns (known as harmonograms).

As the pen rubs on the paper, some of the platform’s energy is lost as friction, slowing the platform down. The curves being drawn will get smaller and smaller (decaying), creating an intricate pattern.

Due to subtle differences in the starting position of the Harmonograph pen, platform and paper, it's impossible to reproduce exactly the same pattern in succession, but it's fun to play with differences in starting position to create very different and beautiful harmonogram patterns. Sometimes, these patterns are called Lissajous curves.

Lissajous curves were named after the French physicist Jules Antoine Lissajous. He attached mirrors to tuning forks to make them vibrate at particular frequencies. He then shone a light onto the mirrors, which were set so they were perpendicular to each other. The combination of vibration frequencies caused the light to trace out harmonic Lissajous patterns (seen through persistence of vision). Lissajous curves are also known as Bowditch curves, as they were first investigated by Nathaniel Bowditch.

Finding the science in your world

'Harmonograph-style patterns and Lissajous curves can be found in unexpected places.

Intricate harmonogram-like patterns were used on the old Australian twenty dollar paper bank note (before the production of Australian plastic banknotes) as the harmonogram pattern was difficult to forge.

Lissajous curve patterns are similar to the Australian Broadcasting Corporation’s logo and their creation using mirrors and lasers is used to perform laser light shows at parties and events.