The Pendulum

Tick, tock, tick, tock, it keeps going.

The thing about a pendulum is that it always starts off at the golden centre. That is the mid-point of its path and the equilibrium of its existence.

Then some external force comes along and displaces the happy state of affairs. It moves thanks to this external force in one direction, slowly gaining an angle and reciprocatingly losing speed. As it arrives towards its extremity, there is an opposite force that starts working on it which prevents it from keeping on going in the same direction. Soon, kinetic energy converts into potential energy and it comes to a stand still for a microsecond.

The pent up potential energy it has is too much for it too sustain itself at one end of its trajectory. It slowly starts heading back towards its mid-point, its equilibrium. As the mid-point approaches, it rushes faster and faster towards it. But by the time it reaches the equilibrium, it has converted all the potential energy back into kinetic energy and it can't suddenly stop. In fact, the pendulum is at its fastest at its mid-point. Almost as if it wants to stay at the equilibrium for the least possible time.

The momentum doesn't let up and it keeps going. Only this time in the opposite direction, towards the other extreme. Before it is time to turn back and head back to the first extreme. And the same story repeats over and over. But not forever.

The laws of physics do not allow perpetual motion. Tiny frictions during the swing contribute to its gradual slowing. The friction could be in the pivot mechanism or between the bob and the air rushing past it. What's more there is also the force of gravity which constantly acts as a check on every swing of the pendulum, gradually slowing it down to a standstill.

The longer the rod, the heavier the bob, the smoother the pivot, the lesser the air and the lighter the gravity; the longer it will take for the pendulum to stop.

But sooner or later, it has to.