Galileo Galilei discovered in the 1580s that the regular swing of a pendulum could be used to regulate a clock. The first pendulum clock was designed in 1656 by Dutch scientist Christiaan Huygens. Pendulum clocks require stationary placement as any movement affects the pendulum's motion and causes inaccuracies, so other mechanisms are used in portable timepieces. Pendulum clocks are now kept mostly for their decorative and antique value.

1. Pendulum clocks

2. In the 1580s, the Italian polymath Galileo
Galilei investigated the regular swing of
the pendulum, and discovered that it could
be used to regulate a clock. The first
pendulum clock was designed and built
by Dutch scientist Christiaan Huygens, in
1656.

4. First pendulum clock

5. One source of error in clocks is that the pendulum rod
changes length slightly with changes in temperature. An
increase in temperature causes the rod to expand,
making the pendulum longer, so its period increases and
the clock loses time. Wood expands less than metal, so
many older quality clocks had wooden pendulum rods.

6. Pendulum clocks must be stationary to operate;
any motion or accelerations will affect the motion of
the pendulum, causing inaccuracies, so other
mechanisms must be used in portable timepieces.
They are now kept mostly for their decorative
and antiquevalue.