An appointment with the future
At the start, every pendulum points in the same direction. Then their individual clocks begin pulling them apart. But each is scheduled to complete a whole number of turns in exactly sixty seconds.
Eighteen pendulums. Eighteen different rhythms. No leader, no communication—and yet they have agreed to meet at precisely the same instant. Watch them keep their promise.
Each row is a pendulum; each column is a moment. Turquoise means moving right, amber moving left. The converging pattern is the clockmaker's signature. Drag on the score to travel through time.
All eighteen arrows point together.
Each dot is one clock, viewed on the unit circle. The long green arrow is their average.
Try the final second with each setting. What matters more—the clocks being individually accurate, or the differences between their frequencies being exactly right?
At the start, every pendulum points in the same direction. Then their individual clocks begin pulling them apart. But each is scheduled to complete a whole number of turns in exactly sixty seconds.
fj = (43 + j + εj) / 60 Hz, j = 0,…,17.
With εⱼ = 0, the phase at sixty seconds is 2π(43+j)—an integer number of turns. All phases agree again, although no pendulum ever changed its speed. Add a small εⱼ or disturb a phase and the reunion can fail. These are ideal harmonic oscillators; the hanging strings are a visual metaphor, not a full model of a gravitational pendulum.