Pendulums could go on swinging forever,
Going back & forth in a straight line or
Up,
then down,
then up again
in a curved path infinitely-
It depends on the frame of reference
for which the observation was made.
A constant pulling back & pushing on
between kinetic & potential energy,
More often than not, however,
the other wins over another,
in an unfailing pattern.
But the universe is a place of uncontrolled variables-
Friction exists.
Such brings disorder to the system-
Soon enough,
the pendulum will slow down,
transferring most of its energies to the surroundings-
Eventually, making it stop.
Or one can continue
with the thought experiment
that friction is negligible,
& see this pendulum
in an endless & perfectly timed oscillation.
