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The pendulum rotates clockwise and counterclockwise in the most unexpected and surprising fashion, changing directions or suddenly increasing speed just when you think you know what they're going to do next. (A quote from Harvard Natural Sciences Lecture Demonstrations). Timestamps: 00:04 Short pendulum, harmonic motion 00:29 Long pendulum, harmonic motion 00:48 Double pendulum, chaotic motion This is “a simple physical system that exhibits rich dynamic behavior with a strong sensitivity to initial conditions“ (American Journal of Physics, 1993). “A double pendulum executes simple harmonic motion (two normal modes) when displacements from equilibrium are small. However, when large displacements are imposed, the non-linear system becomes dramatically chaotic in its motion and demonstrates that deterministic systems are not necessarily predictable“ (Harvard Natural Sciences Lecture Demonstrations). You can watch additional chaotic pendulums in action at: Triple Pendulum Chaotic Acrobatics:
