The First Clocks

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The First Clocks

Overview

Water clocks and sundials were the first artificial measures of time. They allowed people to see time in an abstract way, apart from nature, and also helped create an objective, shared view of time that facilitated social cooperation. Combined with other measurements, such as those of space and weight, timekeeping devices ultimately provided the basis for science and contributed to new ways of understanding and controlling nature.

Background

The first timepiece was probably a stick in the ground whose shadow showed the progress of the sun across the sky. Building on this principle were shadow clocks, or gnomon (Greek for "pointer"), which date from around 3500 b.c. This simple measurement, however, was soon insufficient. As humans established settlements and their societies grew, a common estimate of time became necessary for religious observances and to prompt or coordinate tasks, such as the time animals needed to be milked.

Sundials, which assign a numerical value to the position of a shadow cast by the Sun, were a further refinement in time measurement. Although first used simply to determine the local noon (the point during the day when the Sun is highest), early sundials improved upon shadow clocks by dividing the day into twelve equal periods. The sundial's pointer, however, is still called a gnomon.

The first hemispheric sundial, the kind familiar to us today, is attributed to the Chaldean astronomer Berrosus sometime around 300 b.c. It was little more than a bowl-like indentation carved into a cube of stone or wood. A pointer stood in the center of the bowl, creating the shadow that traveled arcs of varying lengths (to compensate for seasonal variations) that were carved into the surface. Each arc was divided into 12 hours. (These were called "temporary" or "temporal" hours because varied in length from summer to winter.) In 30 b.c., the Roman engineer Vitruvius described three types of sundials that were in common use. The most sophisticated took into account the varying length of days throughout the year, and could be adjusted according to the length of the noon shadow, which is shortest in the summer and longest in the fall. Dials were etched onto cones or inside bowls to increase their precision.

Of course, sundials require sunlight, making them unusable in interior rooms, on cloudy days, or at night (although a device known as a merkhet, used as early as 600 b.c., measured the night hours by tracking stars). Hourglasses, which use the regular, controlled action of gravity, were another way to measure time. Sand flowing through a narrow opening is a simple, effective way to measure small, specific units of time. They work anywhere, at any time, and units of time are independent of the Sun's variable motion. The hours of a water clock (or clepsydra, Greek for "water thief") were similarly fixed. However, people weren't used to hourglass or water clock time, whose hours were the same length in every season. A key development in water clocks was the ability to emulate the sundial and vary the hours of each day.

The basic mechanism of a water clock is the regular emptying or filling of a marked vessel by steadily dripping water. The oldest-known model was found in Amenhotep's (1353-36 b.c.) tomb. More sophisticated versions used floats as indicators, siphons to automatically recharge the source vessel, ringing bells, hour hands that turn, and even elaborate gears (at least as early as 270 b.c.). From the beginning, of course, they made a distinctive regular dripping sound that would evolve into the ticking of our own clocks.

Impact

With the sundial and the water clock, the essentials of timekeeping—a regular, repeated process, a means of tracking that process, and a way to display the results—had been introduced to human culture. This had profound social consequences. Timekeeping devices facilitated cooperation, providing appointed times for religious observances, work and community activities. They enabled bureaucracies and, in Athens, became a measure of fairness, allocating time for debates and court proceedings. Until the advent of the pendulum clock, sundials in particular were equated with time itself and were found not just in public areas, but in houses, baths, temples and even tombs. Portable sundials were carried as late as the seventeenth century. King Charles I of Great Britain left his pocket sundial to his son on the eve of his execution in 1649.

One of the most powerful expressions of the social significance of timing devices was the Tower of the Winds in the Agora, the main marketplace in Athens. Built in the first century b.c., a sundial was fixed on each of side of this octagonal tower. It also indicated wind direction, displayed the season of the year and the astrological date, and contained an elaborate 24-hour water clock.

For all the benefit and efficiency sundials and clocks brought, there was a dark side. The dictatorship of the clock was lamented as early as the second century b.c. in a poem written by the Roman poet and playwright Plautus. He asks the gods to confound the inventor of the sundial and "confound him, too, who in this place set up a sundial to cut and hack my days so wretchedly." Clocks told Plautus when to eat, even though his stomach is a better guide. Over 2,000 years later, Mark Twain also reflected on the artificial rule of the clock when he observed "Man is the only animal who goes to bed when he's not sleepy and gets up when he is."

Besides marking time, sundials also revealed nature in new ways. People had long known that the length of days changed throughout the year. With the sundial, they realized how much. These variables in the length of hours and the changing angle of the Sun throughout the year gave them clues about the true nature of the world, which eventually led to a deeper understanding of the heavens. Sundials also encouraged a more careful study of natural phenomena and helped develop ever-more-precise measurement. This, in turn, helped develop a quantitative, scientific approach to knowledge. In fact, timekeeping, combined with other measurements, such as those of volume and mass, ultimately provided the basis for science in the modern sense. Galileo himself used a mercury clepsydra to time the motion of falling bodies. Ultimately, the measurement of time also made navigation and exploration more practical, expanding our view of the world.

Today, sundials give us a gentler view of time, revealing a connection between humans and nature. They are found in parks, forums, and gardens, where they provide a quiet reminder of the past and an aesthetically pleasing sense of order.

Water clocks were the first mechanical devices, the precursors of automation and the applied use of energy. They allowed ancient scientists to understand the regulation, transfer, and use of energy, and also helped establish the essential concept of standardized, fixed units of time that allowed repeated, consistent experimentation. The very idea of measuring time mechanically led to clocks and watches driven by weights and springs, which led to still more advanced mechanical and electrical devices. Ultimately, this mechanical view even informed philosophy and religion, providing the concept of a "clockwork" universe.

The use of timing devices to organize society and synchronize individuals' activity has only intensified over the ages. With the coming of the railroad, the hours of the day became completely standardized. The need for synchronization over larger geographies caused regional times to supplant local ones. Today, time is digital. It ties together our computers and our economies worldwide, with "24–7" the proud boast of every dotcom.

PETER J. ANDREWS