When released from nearly the same spot,
the Chaotic Pendulum eventually shows a completely different path.
- Motion of pendula
The chaotic pendulum derives it's name from the kind of motion it displays. While it may seem like the the pendulum is moving about randomly, this is not the case. Instead, the path of the pendulum is highly dependant on where it started and the forces acting upon it. This motion is chaotic, meaning its progress has a complexity beyond standard classical physics.
Let's say you set the pendulum in motion for two separate trials. For both, you try to drop the pendulum in what you believe is the same exact position to begin it's motion. You will almost certainly observe that the pendulum has taken a completely different path on the second trial than it had on the first. This is due to what is widely known as the "butterfly effect". In the butterfly effect, minute changes to the start of a system amplify over time and can result in very different outcomes. The pendulum's path is so sensitive to where it is released from, that (theoretically) it may be totally different if released from two positions that are only an atom's width apart!
Start the chaotic pendulum from different positions and observe the different paths it follows. Then try starting it from the same place multiple times, and watch how it still follows different paths.