Pendulum clock

A design for a pendulum clock by Vincenzo Viviani in c. 1637. The clock was never completed.

A German 19th century wallclock made by Gustav Becker

Portrait of Christaan Huygens the creator of the pendulum clock. Portrait made in 1671 by Caspar Netscher.

A pendulum clock is a clock that uses a swinging weight known as a pendulum as its timekeeping element. The pendulum is an approximate harmonic oscillator that swings in a time interval that depends on its length, and that resists swinging at other rates. From its invention in 1656 by Christiaan Huygens, inspired by Galileo Galilei, until the 1930s, the pendulum clock was the world's most precise type of timekeeper. Throughout the 18th and 19th centuries, pendulum clocks in homes, factories, offices, and railroad stations served as primary time standards for scheduling daily life activities, work shifts, and public transportation. Their accuracy allowed for the fast pace of life during the Industrial Revolution. The home pendulum clock, which was replaced by cheaper synchronous electric clocks in the 1930s and 1940s, are now kept mostly for their decorative and antique value.

As pendulum clocks must be stationary in order to avoid affecting the motion of the pendulum, other mechanisms are used in portable timepieces.