The Ekphrasis on the Water Clock: Art, Rhetoric and Measurement of Time in Sixth-Century Gaza

THE MECHANICS OF TIMEKEEPING BY KATHERINE LIU THE DEVELOPMENT AND MECHANICS OF MEASURING TIME IN HUMAN HISTORY S ince the earliest human civilizations, humans have kept time in one form or another, either through water clocks, sundials, hourglasses or candle clocks. Though primitive, these early forms of clocks were the building blocks of modern timekeeping technology. However, even though time is such an essential part of our lives, many people do not understand the mechanics underlying clock function. Archaeological evidence has shown that the Egyptians and Babylonians began measuring time 5,000 years ago. They started by recording the length of a day by following the sun across the sky and noting the phases of the moon. 1 The Egyptians also created calendars that had 12 months with 30 days each. These calendars even included 5 extra days every year to estimate the solar year. The next form of time measurement came with the invention of the sundial. The sundial, which has been invented independently by all major cultures, works by indicating the time of day by the length and direction of a shadow cast by the sun’s light. But because such devices cannot work at night, the sundial’s counterpart, the water clock, was created to tell time during the night. The water clock is a basin of water that lets water drip from a small hole near the base of the basin. Lines were drawn inside the basin walls to denote sections of time so as the water level dropped, it would gradually reveal lines above the water level, thereby indicating the time. 1 The earliest clocks, along with the sundial and water clock, are the hourglass and candle clocks. We often see these in films and animation to give an archaic setting. However, even these seemingly familiar and simplistic clocks are quite impressive in being able to accurately keep time even before the physics regarding water flow and planetary motion were understood. The candle clock works similarly to the water clock in that the wax of a candle is Berkeley Scientific Journal | FALL 2016 melted down and the height of the candle at different moments measure how much time has passed. 1 More modern forms of timekeeping include pendulums, pocket watches, and classroom clocks. These are still relatively simple compared to today’s digital clocks and beyond, but are equally interesting and important. Pendulums are quite distin- guished in function from clocks and pock- et watches in that they don’t have as many small components that aid it in telling time. The main parts of a pendulum are the rod and weight which together swing side to side in an oscillating motion. 2 To maintain the same oscillating rate, there are specific configurations not seen from the outside. But this does not prevent a pendulum clock from eventually lagging in timekeeping. So, occasionally, a clockmak- er or clock owner will need to reconfigure the cogs in a pendulum so they read time accurately. Pocket watches and clocks are unique from pendulums. Clock mechanics

Measuring time as accurately as possible has always represented a significant technological challenge. Rather simple time measurement systems had been developed since antiquity, such as hourglasses, sundials, and water clocks, but it was only with the advent of the first mechanical systems in the late Middle Ages that the way would be paved for the creation of what would become the accurate watches in use today.

The use of divisions of the day by the Chaldaeans marked the beginning of time measurements using sundials, astronomical instruments and water clocks. Ptolemy introduced the “first small parts” and “second small parts”, i.e. the minutes and seconds we use today; however, we argue that back then they represented purely theoretical units since no time measurement had an accuracy higher than 1 minute.

THE history and development of time measurement have already been described in a Science Museum Handbook ("Time Measurement", Part 1). The second part of the handbook which has recently been issued (London: H.M. Stationery Office. 2s. net), contains a detailed description of the objects in "The Time Measurement Collection at the Science Museum, South Kensington". The exhibits, ranging from the ancient Egyptian shadow clocks and water clocks to modern electric time-keepers, include sundials, mechanical clocks, watches and chronometers, escapement models and chronographs, as well as various auxiliary devices such as striking mechanisms, time recorders and time switches. Introductory remarks to each chapter explain the system of classification adopted, and outline the general principles involved in the respective groups of instruments. Many of the exhibits at the Science Museum are shown in continuous operation, while others can be operated by visitors—a facility that appears to receive perpetual appreciation. In addition, several of the more delicate watch mechanisms are illustrated by large-scale models. It may be noted that Harrison's four marine timekeepers (the fourth, completed in 1759, being the chronometer which won for Harrison the British Government prize of £20,000) are now represented in the Museum only by photographs, the originals themselves, long associated with the Royal Observatory, Greenwich, having been transferred to the National Maritime Museum at Greenwich. This handbook with its numerous illustrations provides an admirable introduction to a study of the Time Measurement Collection, and it will also serve as a useful handbook of reference for other occasions.

In the twenty-first century, we take the means to measure time for granted, without contemplating the sophisticated concepts on which our time scales are based. This volume presents the evolution of concepts of time and methods of time keeping up to the present day. It outlines the progression of time based on sundials, water clocks, and the Earth's rotation, to time measurement using pendulum clocks, quartz crystal clocks, and atomic frequency standards. Time scales created as a result of these improvements in technology and the development of general and special relativity are explained. This second edition has been updated throughout to describe twentieth- and twenty-first-century advances and discusses the redefinition of SI units and the future of UTC. A new chapter on time and cosmology has been added. This broad-ranging reference benefits a diverse readership, including historians, scientists, engineers, educators, and it is accessible to general readers.

In the twenty-first century, we take the means to measure time for granted, without contemplating the sophisticated concepts on which our time scales are based. This volume presents the evolution of concepts of time and methods of time keeping up to the present day. It outlines the progression of time based on sundials, water clocks, and the Earth's rotation, to time measurement using pendulum clocks, quartz crystal clocks, and atomic frequency standards. Time scales created as a result of these improvements in technology and the development of general and special relativity are explained. This second edition has been updated throughout to describe twentieth- and twenty-first-century advances and discusses the redefinition of SI units and the future of UTC. A new chapter on time and cosmology has been added. This broad-ranging reference benefits a diverse readership, including historians, scientists, engineers, educators, and it is accessible to general readers.

In the twenty-first century, we take the means to measure time for granted, without contemplating the sophisticated concepts on which our time scales are based. This volume presents the evolution of concepts of time and methods of time keeping up to the present day. It outlines the progression of time based on sundials, water clocks, and the Earth's rotation, to time measurement using pendulum clocks, quartz crystal clocks, and atomic frequency standards. Time scales created as a result of these improvements in technology and the development of general and special relativity are explained. This second edition has been updated throughout to describe twentieth- and twenty-first-century advances and discusses the redefinition of SI units and the future of UTC. A new chapter on time and cosmology has been added. This broad-ranging reference benefits a diverse readership, including historians, scientists, engineers, educators, and it is accessible to general readers.

Astronomical phenomena, such as the waxing and waning of the Moon, the succession of days and nights and the pattern of the seasons define a time which is basically cyclical. During many centuries, rather simple devices, such as water clocks or astrolabs and, later on, mechanical clocks, have been used by astronomers for defining realistic but low accuracy time scales. Lately, the atomic time, with its unprecedented precision, has open the way to a more accurate investigation of astronomical phenomena. From cyclical, the time of mankind has become definitely linear and the astronomers seem to have lost its control ...

Following the prescriptions of the ancient authors such as Palladius and Varro, Daniele Barbaro planned some device for timekeeping in the process of remodelling the family villa in Maser. The two large square surfaces on the villa’s two lateral towers, obtained at the expense of the harmony and hierarchy in the general composition, are an indication of the will to install devices for the measurement of time. However, Barbaro’s shortcomings in the geometrical methodology for the design of sundials on a declining wall raises some doubts about the original presence of sundials like the early twentieth-century ones seen today. The older iconographic sources show two original painted frescoes in which appear the dials of mechanical clocks. Finally, series of contact points with Ctesibius’s hydraulic clock described by Barbaro in Vitruvius makes the hypothesis of a water clock plausible, even if not proved at a documentary level.

A discussion about the meaning of time that took place in a combined grade 3 and 4 classroom in Toronto, Ontario, Canada is described and analyzed. The paper begins by explaining how a failed classroom demonstration of a water clock resulted in an animated class discussion that led to the successful redesign of the clock. Next, recent work in sociocultural theory is reviewed as it applies to learning and teaching. After the school and classroom context are described, the discussion about the meaning of time is summarized and analyzed. The discussion was to serve as an occasion for the children and their teacher to make connections between the various activities in which they had engaged and the artifacts of various kinds that had mediated their practical study. It began with the teacher inviting the students to think about what they had learned during the preceding 5 weeks. The invitation led to discussions of the need for a standard, accurate measure of time; scientific processes; units of time; work with pendulums; sources of power for clocks; bases for units of time in the earth's movements; and time zones. Short excerpts from the discussion are presented. The role of teachers in the co-cGastruction of knowledge is discussed next, followed by concluding comments about the themes and findings of the analysis. (AC) *********************************************************************** Reproductions supplied by EDRS are the best that can be made * from the original document. * *********************************************************************** 'WHAT HAVE YOU LEARNED?': CO-CONSTRUCTING THE MEANING OF TIME oo ff) U.S. DEPARTMENT Of EDUCATION Office of Educahonat Research and Improvement EDUCATIONAL RESOURCES INFORMATION CENTER (ERIC) Xl'hts document has peen reproduce° as reCatved trom the person or Orgarzation ongmabng d b Minor changes have been made to .mprove reproduchon Quahty Pomts of mew or opmlons stated )5 INSCIOCU ment do not necessaray represent otitcust OE RI posItion or pohcy Gordon Wells Ontario Institute for Studies in Education Gen Ling Chang-Wells Toronto Board of Education PERMISSION TO REPRODUCE THIS MATERIAL HAS BEEN GRANTED BY eorcitr WQ.kk5 Gen Lvc30rva.r1-WittkS TO THE EDUCATIONAL RESOURCES INFORMATION CENTER (ERIC).

Time, including its experience, definition, and measurement, has interested the human species for centuries. Shadow clocks, sundials, sandglasses, and water clocks represent but a few of the ancient timekeeping devices ingeniously created by our early counterparts. Prisoners, hostages, and others held in dark, windowless dwellings for long periods frequently develop a disrupted and disjointed sense of time perception, robbed of the cues and time measurement strategies available to the rest of us. Becoming agitated, confused, and depressed in this state of time disorientation, many devise makeshift timetracking systems, cutting marks into their bedposts or belts fashioning a type of time tabulation calendar. The extent to which this time scheme actually reflects the “real” time experienced in the outside world seems less important than the degree to which it provides a framework of consistency, regularity, and predictability for the disoriented individual. We, as human organisms-at least here in Western culture-seem to be uniquely motivated to anchor ourselves in, and orient ourselves in relation to, time.

Archaeological remains yield remarkable information concerning the Nabataeans’ timing system; excavations and surveys revealed water clocks, sundials and ground shadow clocks in Nabataean sites, namely Petra and Hegra. Besides, certain Nabataean inscriptions expose a good deal of evidence regarding the Nabataean timing terminology: ywm ‘day’; šnt ‘year’; yrḥ ‘month’; šch ‘hour’; šbc ‘week’, lyly’ ‘night’ and zmn ‘time’ are the most frequently used terms found in the different Nabataean texts. Moreover, the excavations uncovered some archaeological evidence concerning the Nabataean annual calendar. The study adopts a comparative historical and linguistic perspective in investigating the different aspects of time measurement in Nabataean civilisation.