173
mainspring. By the 16th century, a pendulum clock had been devised, but the pendulum swung in a large arc
and thus was not very efficient.
G
To
address this, a variation on the original escapement was invented in 1670, in England. It was called the
anchor escapement, which was a lever-based device shaped like a ship's anchor. The motion of a pendulum
rocks this device so that it catches and then releases each tooth of the escape wheel, in turn allowing it to turn
a precise amount. Unlike the original form used in early pendulum clocks, the
anchor escapement permitted
the pendulum to travel in a very small arc. Moreover, this invention allowed the use of a long pendulum which
could beat once a second and thus led to the development of a new floorstanding case design, which became
known as the grandfather clock.
H
Today, highly accurate timekeeping instruments set the beat for most electronic devices.
Nearly all computers
contain a quartz-crystal clock to regulate their operation. Moreover, not only do time signals beamed down
from Global Positioning System satellites calibrate the functions of precision navigation equipment, they do so
as well for mobile phones, instant stock-trading systems and nationwide power-distribution grids.
So integral have these time-based technologies become to day-to-day existence that our dependency on them is
recognised only when they fail to work.
