This shows how two double pendulum systems varying in the initial positions in the fifth decimal place will diverge after a period of time. At the beginning, the two systems behave almost identically. Eventually, however, the motions of the two pendula will diverge, demonstrating the chaotic nature of this system.
An average of 3 trials (to lessen human error) showed that the two systems' positions vary significantly after 13.51 seconds. This was measured with a stopwatch, starting when the two systems were released and stopping when the paths seemed to diverge to the naked eye.
Try adding energy to one of the systems by clicking on the window to adjust the starting angle. This adjusts the starting potential energy, thus adjusting the total energy in the system.