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and tried to produce the first
pendulum clock but did not
succeed. In 1649 he died with-
out finishing the clock.
In 1656, Dutch Scientist and
Astronomer Christiaan Huygens
worked with Hague clockmaker
Salomon Coster
The largest piece of the to create the first practical
2,100-year-old Antikythera pendulum controlled clock.
Mechanism, which is on Thanks to the invention of the Illustration showing Christiaan Huygens’s
display at the National cycloidal pendulum. The rod was made from
Archaeological Museum Often referred to as the “World’s First Computer,” the pendulum, accuracy in time- flexible metal with bob (P) which describes
in Athens, Greece. Antikythera Mechanism is shown here in an “exploded” view. keeping increased from about cycloidal arc. The rod is suspended between the
15 minutes per day to 15 two solid cheeks (above) in the form of cycloidal
Consider the complexity of what has been named the “Antikythera seconds per day. Many verge arcs at a tangent to the starting point. As the rod
oscillates, it bends and rests on each arc of the
Mechanism” (dating between 150 BC to 87 BC). This “lump” of metal and foliot clocks were retrofitted cheeks by turn, so diminishing the length of the
was discovered in a shipwreck off the coast of Greece in the early 1900s. with pendulums. pendulum depends on the oscillation.
It is the earliest item known to contain a toothed gear (about 5” in Circa 19th century.
diameter). Through careful restoration, the Mechanism was found to
contain many more gear pieces – some 82 separate fragments. According Huygens observed the time
to historical knowledge at the time, gears like these should not have was only accurate if the swing
appeared in ancient Greece, or anywhere else in the world, until many of the pendulum passed along
centuries after the shipwreck.By turning a crank on the Antikythera a somewhat steeper path than
Mechanism, it could predict the positions of the sun, the moon, and on an arc known as a
the other known planets (5 at that time) for any specific day in the past “cycloidal curve.”
or future. It also predicted eclipses and the moon’s variable motion. To overcome this error, he
suggested the use of “cycloidal
The First Mechanical Clock was created towards the end of the cheeks” on either side of
13th century, the most important component of which was the the suspension of the pendu-
“escapement,” a device that releases a train of wheels at set intervals that lum to modify the arc of the
are used to indicate time. These employed a “verge and foliot” or verge swing. Most early pendulum
and balance wheel escapement. At this point in history, the best accu- clocks were made with
racy one could expect from these clocks was about +/- 15 minutes a day. cycloidal cheeks.
Most of the clockmakers from this era did not bother to add a minute
hand – it was felt that an hour hand alone was sufficient. The Anchor Escapement –
A further leap forward took
place a few years later with the
development of the “anchor
Diagram of simple escapement.” This device
gravity pendulum, an maintains the time of a pendu-
ideal model of a The first pendulum clock, invented by lum swing by giving it a small
pendulum. It consists of Christiaan Huygens in 1656. “push” at the end of each
a massive bob suspended swing, allowing the clock’s
by a weightless rod from wheels to advance a fixed amount of space with each swing. The anchor
a frictionless pivot, with- escapement soon became the standard escapement used in almost all
out air friction. When pendulum clocks.
given an initial impulse, Even though the anchor
it oscillates at constant
amplitude, forever. escapement is reliable and
tolerant of large geometrical
errors in its
construction, its operation
retains two of the major dis-
advantages of
the verge escapement.
The Pendulum – The next major development was the use of the 1: The pendulum is
Pendulum – a swinging weight (“bob”) suspended from a pivot (usually always being pushed by an
by a string, stick, or rod) that swings freely. The time interval for a escape wheel tooth through-
swing of the pendulum (a harmonic oscillator) is dependent upon the out its cycle and is never
length of the pendulum’s center of gravity (the center of the bob) to the allowed to swing freely,
pivot point. making the clock’s pace
Around 1602, Galileo ran many experiments with a pendulum to sensitive to changes in the
study its qualities. He found the key property that makes pendulums drive force. Any small
useful timekeepers: isochronism – that the period of swing of a changes in the force
pendulum is approximately the same for different sized bobs if the applied to the pallets —for
length is the same. With this knowledge, he originally used the example by a change in
pendulum to produce accurate tables for the motions of the moons of lubrication due to oil
Jupiter. In 1637, he proposed that a geared mechanism might be used aging—will change the peri-
to record the swings of the pendulum, and if driven by a weight, it od of the pendulum’s swing.
could also give “pushes” to the pendulum. He communicated this idea 2: It is a recoil escape-
to his son in 1641, one year before his death. His son took up the idea ment, meaning the momen- Anchor Escapement Pendulum

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