Topic: Pendulums | Vortex Plates
I suspect somehow pendulum science can be connected with cymatics. Maybe the phase relationship of the pendulum dimensions and the Earth's rotation can be correlated to the dimensions of a material medium and it's resonant frequency.
Pendulum photography is where the pattern created by swinging pendulums is recorded using a light source and camera set on a long time exposure. In the simplest case a point light source is attached to a weight which suspends from the ceiling by a single thin line. A camera is placed underneath the pendulum and the room darkened. As the pendulum swings its motion is recorded by the camera as a moving line which traces out a swirling pattern. One magazine article called the resulting images 'star tracks', and the analogy is in fact apt. The same principle is used to capture the streak of stars (in effect the rotation of the earth) across the night sky.
Also, from Harmonic Vibrations and Vibration Figures, Joseph Goold writes about "Vortex Plates":
A method capable of much more extended application is that which I had the good fortune to discover some years ago.
In this method the necessary excitation of the plate is produced by gently rubbing it on any one of its ventral segments with a specially constructed vibrator which has been described as a "synchronising sound generator."

