Pendulum Waves
About this video
Swinging pendulums show off hypnotic dance moves in a classic demo.
This mesmerising video produced by Harvard University shows a line of pendulums dancing together to create travelling waves.
What causes the strange patterns?
A pendulum consists of something hung from a fixed point, like a weight on a piece of string. When the pendulum is knocked, the force of gravity causes it to move down, then out and up.
The different lengths of the fifteen single pendulums cause them to swing back and forth (oscillate) at different rates. The dance takes one minute to complete. In these sixty seconds, the longest pendulum oscillates 51 times. The lengths of the shorter pendulums have been altered to make them each oscillate one more time per minute with the 15th (and shortest) pendulum oscillating 65 times.
This movement produces different types of waves, including standing waves, beating waves and waves that move in seemingly random patterns. The effect is mesmerizing and beautiful.
