What is Time? The Pendulum Clock

Until the middle of the seventeenth century, clocks did not need a minute or seconds hand because they were only accurate to the hour.

(This is the seventh post of Time and Clocks, the thread that follows Time and Calendars.)

In 1582 CE, in the early years of the scientific revolution of European civilisation Galileo is thought to have studied the pendulum’s motion after watching a lamp swing in the Cathedral of Pisa. His designs were not completed however, leaving Dutchman Christiaan Huygens, in 1656, to make the first pendulum clock. Clocks were only accurate to within 15 minutes at best, but the pendulum device brought this down dramatically to approximately 10 seconds, making the minute hand a useful addition. In 1671, William Clement is said by some to have first used the anchor escapement, using a long pendulum and keeping even better time. These more accurate clocks were then made to go for more than one day, most going for eight days, but some were made to go for a month and some even for a year.

Gothic iron clock with alarm (c. 1580) and one of the first pendulum clocks by Christiaan Huygens, and his treatise on the pendulum, Horologium Oscillatorium published in 1673.

These longer duration pendulum clocks, however, needed much heavier weights, leading to the development of the long case (called the grandfather clock when over six feet tall). The case provided a strong support for the clock mechanism and its now heavy weights while keeping its motion protected from interference.

Science and Ignorance

This quantum leap in accuracy coincided with apogee of the scientific revolution, Issac Newton’s great discoveries concerning the movements of the planets of our solar system, publishing his laws of gravity, light and motion. Our long-accepted position at the centre of the universe was fatally undermined by such dramatic seventeenth-century scientific advances.

Paradoxically, this greater accuracy highlighted the compromise which our 24-hour clock represents. The unit of one day displays an average time from the start of one day to the next, because over the period of one year, the precise measurements of the 24-hour cycle depend on the position of the earth on a given point in its rotation around the sun. Because these vary due to the angle of the earth against the sun and the elliptical, rather than circular rotation, the unit of one day measured by the clock was, and still is, slightly different to the day as experienced by the observer of the sun.

The march of science was characteristically scorned by many of those who still relied on the natural cycles to determine their lives: in a village near Chester, a local memorial for the clockmaker Peter Clare was characteristically mocking:

Here’s the cottage of Peter that cunning old fox,
Who kept the sun right by the time of his clocks.

In spite of such widespread attitudes the believers in science persevered and in 1715 George Graham increased the accuracy to under a second per day, by improving the dead-beat escapement (an invention made in the 1670s). This was one of a number of developments which were designed to reduce the effects of friction and slight irregularities in the motion of the train in the clock mechanism.