A pendulum keeps time because its period depends only on its length: longer pendulums swing slower, making them the first precise regulators of seconds.
Equation: \(T = 2\pi \sqrt{L/g}\) (where \(T\) is the period, \(L\) the length, and \(g\) gravitational acceleration).
Keep the pendulum concept in mind when designing intervals, because the natural swing orbits align with seconds and can guide your pacing.