This article was taken from the August 2014 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.
Regular pendulums? How predictable. Here's how you can build one that never repeats its swing pattern. It embodies chaotic behaviour because any small perturbation of its trajectory could significantly change its future behaviour; this is also known as "the butterfly effect".
In a mathematical world, a chaotic system is deterministic, "but you can't really determine this because of the sensitivities of the initial conditions," says former Manchester Metropolitan University physics lecturer turned- "electronic artist" Mike Cook, whose own homemade contraption sets off sounds and lights as the pendulum swings. Here's how to assemble the basic setup. Get it going and watch it oscillate back and forth, and left, and right, and diagonal, and back, and right, and left...
- Build a stand
Attach a rod to a base at a 90-degree angle. Attach another rod to the first, also at 90 degrees, suspended over the base. Ensure that the material is not magnetic (you don't want it to interfere with your pendulum). Use aluminium, silver, gold or wood. Avoid iron, steel and nickel. - Make a pendulum
Glue a magnet to the end of a non-magnetic rod. The longer and heavier the pendulum, the more obvious its chaotic movement will be. "The size of the dependence on initial conditions increases the longer you swing," says Cook. A lead weight attached to the rod will let it have more kinetic energy, and therefore swing for even longer. - Set it swinging
Place several other magnets on the base of the stand -- choose any formation and combination of north and south poles facing up.
Attach the pendulum to the stand with a piece of twine, so the rod hangs a centimetre above the magnets. The more flexible the thread, the greater the swing.
This article was originally published by WIRED UK
