History of timekeeping devices: Difference between revisions
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The origins of our current [[time]] measurement system go back to the [[Sumer]]ian civilization of approximately 2000 [[BC]]. |
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This is known as the [[sexagesimal]] system based on the number 60. 60 seconds in a minute, 60 minutes in an hour – and possibly a calendar with 360 (60x6) days in a year (with a few more days added on). |
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== Early measurement devices == |
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Man has measured '''[[time]]''' since prehistory. |
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=== Sundial === |
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[[Image:Sundial Taganrog.jpg|thumb|right|Horizontal sundial in [[Taganrog]] (1833)]] |
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A [[sundial]] uses a [[gnomon]] to cast a shadow on a set of markings which were calibrated to the [[hour]]. The position of the shadow marked the hour in [[local time]]. [[Pliny the Elder]] records that the first sundial in Rome was looted from [[Catania]], [[Sicily]] (264 BCE), which gave the incorrect time for a century, until the markings appropriate for the latitude of [[Rome]] were used (164 BCE).<ref>Jo Ellen Barnett, ''Time's Pendulum'' p.31</ref> Noontime was an event which could be marked by the time of the shortest shadow on a sundial. This was used in Rome to judge when a court of law was open; lawyers had to be at the court by that time. An earlier invention also using a cast shadow to determine time is an [[Egypt]]ian device dating to c.1500 BCE, similar in shape to a bent [[T-square]], which measured the passage of time from the shadow cast by its crossbar on a non-linear rule. The T was oriented eastward in the mornings. At [[noon]], the device was turned around so that it could cast its shadow in the evening direction.<ref>Barnett, Jo Ellen ''Time's Pendulum: The Quest to Capture Time - from Sundials to Atomic Clocks'' Plenum, 1998 ISBN 0-306-45787-3 p.28</ref> |
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==Antiquity== |
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During antiquity, [[sundial]]s were used. Later inventions were [[candle clock]]s, [[hourglass]]es and [[water clock]]s. |
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===Waterclock=== |
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The [[mechanical clock]] was invented during the [[middle ages]]. The [[pendulum]] was introduced in the 16th century. |
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The most accurate timekeeping devices of the ancient world were the [[waterclock]] or ''clepsydra'', first found in Egypt. A waterclock was found in the tomb of [[pharaoh]] [[Amenhotep I]] (1525–1504 BCE). They could be used to measure the hours even at night, but required manual timekeeping to replenish the flow of water. [[Plato]] introduced the waterclock to [[Greece]] <ref>{{cite web |url=http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Plato.html |title= Plato biography |accessdate=2007-11-29 |format= |work= }}</ref>, and invented a water-based alarm clock <ref>{{cite web |url=http://www.answers.com/topic/387-bc?cat=technology |title= 387 BC Sci and Tech chronology |accessdate=2007-11-29 |format= |work= }}</ref>. One account says it depended on the nightly overflow of a vessel containing lead balls, which would float in a columnar vat. The vat would hold an increasing supply of water supplied by a cistern. Eventually the vessel would float high enough to tip over. The lead balls would then cascade onto a copper platter. The resultant clangor would then awaken his students at the Academy (378 BCE).<ref>Jo Ellen Barnett, ''Time's Pendulum'' p.38</ref> Another account says that it used two jars and a [[siphon]]. Water empties until it reaches the siphon, which transported the water via the siphon to the other jar. Water rising in the other jar forces air through a whistle, sounding the alarm. The [[Greeks]] and [[Chaldeans]] regularly maintained timekeeping records as an essential part of their astronomical observations. In particular, Arab engineers improved on the use of waterclocks up to the Middle Ages.<ref>Jo Ellen Barnett, ''Time's Pendulum'' p.37</ref> |
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{{technology-stub}} |
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Waterclocks, and later, mechanical clocks, were used to mark the events of the abbeys and monasteries of the Middle Ages. [[Richard of Wallingford]] (1292–1336), abbot of St. Alban's abbey, famously built a [[Clock#Early mechanical clocks|mechanical clock]] as an astronomical [[orrery]] about 1330.<ref>North, J. (2004) ''God's Clockmaker: Richard of Wallingford and the Invention of Time''. Oxbow Books. ISBN 1-85285-451-0</ref><ref>Watson, E (1979) "The St Albans Clock of Richard of Wallingford". ''Antiquarian Horology'' 372-384.</ref> |
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===Hourglass=== |
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Created by the Venetians{{Fact|date=December 2007}}, the [[hourglass]] uses the flow of sand to measure the flow of time. [[Ferdinand Magellan]] used 18 hourglasses on each ship for his circumnavigation of the globe (1522).<ref>Laurence Bergreen, ''Over the Edge of the World: Magellan's Terrifying Circumnavigation of the Globe'', HarperCollins Publishers, 2003, hardcover 480 pages, ISBN 0-06-621173-5</ref> Since the hourglass was one of the few reliable methods of measuring time at sea, it has been speculated that it was in use as far back as the 11th century, where it would have complemented the magnetic compass as an aid to navigation. However, it is not until the 14th century that evidence of their existence was found, appearing in the painting Allegory of Good Government by [[Ambrogio Lorenzetti]] 1338.<ref> {{Cite book |
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| publisher = Scala Books |
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| isbn = 0935748806 |
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| pages = 83 |
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| last = Frugoni |
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| first = Chiara |
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| title = Pietro et Ambrogio Lorenzetti |
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| date = 1988 |
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| year = 1988 |
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}} </ref><ref> http://www.huntfor.com/absoluteig/lorenzetti_a.htm </ref> |
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<!-- |
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The earliest written records come from the same period and appear in lists of ships stores. --> |
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From the 15th century onwards they were being used in a wide range of applications at sea, in the church, in industry and in cookery. They were the first dependable, reusable and reasonably accurate measure of time. |
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== Modern Devices == |
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[[Image:Swatch Irony angle below.jpg|thumb|left|A contemporary [[quartz watch]]]]The most common devices in day-to-day life are the [[clock]]. Clocks can range from [[watch]]es, to more exotic varieties such as the [[Clock of the Long Now]]. The English word clock actually comes from French, Latin, and German words that mean [[Bell (instrument)|bell]]. The passage of the hours at sea were marked by bells, and denoted the time (see [[ship's bells]]). The hours were marked by bells in the abbeys as well as at sea. They can be driven by a variety of means, including gravity, springs, and various forms of electrical power, and regulated by a variety of means such as a [[pendulum]]. There are also a variety of different calendars, for example the [[Lunar calendar]] and the [[Solar calendar]], although the [[Gregorian calendar]] is the most commonly used. |
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[[Image:ChipScaleClock2 HR.jpg|thumb|A chip-scale atomic clock]] |
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A [[chronometer]] is a portable timekeeper that meets certain precision standards. Initially, the term was used to refer to the [[marine chronometer]], a timepiece used to determine [[longitude]] by means of [[celestial navigation]]. More recently, the term has also been applied to the [[chronometer watch]], a [[wristwatch]] that meets precision standards set by the Swiss agency [[COSC]]. Over 1,000,000 "Officially Certified Chronometer" certificates, mostly for mechanical wrist-chronometers (wristwatches) with sprung balance oscillators, are being delivered each year, after passing the COSC's most severe tests and being singly identified by an officially recorded individual [[serial number]]. According to COSC, a chronometer is a high-precision watch capable of displaying the seconds and housing a movement that has been tested over several days, in different positions, and at different temperatures, by an official, neutral body (COSC). Each movement is individually tested for several consecutive days, in five positions and at three temperatures. Any watch with the denomination "chronometer" is provided with a certified movement. |
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The most accurate type of timekeeping device is currently the [[atomic clock]], which are accurate to seconds in many thousands of years, and are used to calibrate other clock and timekeeping instruments. |
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Atomic clocks use the spin property of the [[caesium]] atom as its basis, and since 1967, the International System of Measurements bases its unit of time, the second, on the properties of caesium. [[International System of Units|SI]] defines the second as 9,192,631,770 cycles of the radiation which corresponds to the transition between two electron spin energy levels of the ground state of the <sup>133</sup>Cs atom. |
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Today, the [[GPS]] global positioning systems in coordination with the [[Network Time Protocol|NTP]] network time protocol can be used to synchronize timekeeping systems across the globe. |
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==See also== |
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* [[Time]] |
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* [[History of measurement]] |
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* [[Calendar]] |
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* [[Horology]] |
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* [[Clockmaker]] |
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* [[Watchmaker]] |
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== References == |
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{{reflist}} |
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[[Category:Time]] |
[[Category:Time]] |
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Revision as of 00:24, 3 December 2007
The origins of our current time measurement system go back to the Sumerian civilization of approximately 2000 BC. This is known as the sexagesimal system based on the number 60. 60 seconds in a minute, 60 minutes in an hour – and possibly a calendar with 360 (60x6) days in a year (with a few more days added on).
Early measurement devices
Sundial
A sundial uses a gnomon to cast a shadow on a set of markings which were calibrated to the hour. The position of the shadow marked the hour in local time. Pliny the Elder records that the first sundial in Rome was looted from Catania, Sicily (264 BCE), which gave the incorrect time for a century, until the markings appropriate for the latitude of Rome were used (164 BCE).[1] Noontime was an event which could be marked by the time of the shortest shadow on a sundial. This was used in Rome to judge when a court of law was open; lawyers had to be at the court by that time. An earlier invention also using a cast shadow to determine time is an Egyptian device dating to c.1500 BCE, similar in shape to a bent T-square, which measured the passage of time from the shadow cast by its crossbar on a non-linear rule. The T was oriented eastward in the mornings. At noon, the device was turned around so that it could cast its shadow in the evening direction.[2]
Waterclock
The most accurate timekeeping devices of the ancient world were the waterclock or clepsydra, first found in Egypt. A waterclock was found in the tomb of pharaoh Amenhotep I (1525–1504 BCE). They could be used to measure the hours even at night, but required manual timekeeping to replenish the flow of water. Plato introduced the waterclock to Greece [3], and invented a water-based alarm clock [4]. One account says it depended on the nightly overflow of a vessel containing lead balls, which would float in a columnar vat. The vat would hold an increasing supply of water supplied by a cistern. Eventually the vessel would float high enough to tip over. The lead balls would then cascade onto a copper platter. The resultant clangor would then awaken his students at the Academy (378 BCE).[5] Another account says that it used two jars and a siphon. Water empties until it reaches the siphon, which transported the water via the siphon to the other jar. Water rising in the other jar forces air through a whistle, sounding the alarm. The Greeks and Chaldeans regularly maintained timekeeping records as an essential part of their astronomical observations. In particular, Arab engineers improved on the use of waterclocks up to the Middle Ages.[6]
Waterclocks, and later, mechanical clocks, were used to mark the events of the abbeys and monasteries of the Middle Ages. Richard of Wallingford (1292–1336), abbot of St. Alban's abbey, famously built a mechanical clock as an astronomical orrery about 1330.[7][8]
Hourglass
Created by the Venetians[citation needed], the hourglass uses the flow of sand to measure the flow of time. Ferdinand Magellan used 18 hourglasses on each ship for his circumnavigation of the globe (1522).[9] Since the hourglass was one of the few reliable methods of measuring time at sea, it has been speculated that it was in use as far back as the 11th century, where it would have complemented the magnetic compass as an aid to navigation. However, it is not until the 14th century that evidence of their existence was found, appearing in the painting Allegory of Good Government by Ambrogio Lorenzetti 1338.[10][11]
From the 15th century onwards they were being used in a wide range of applications at sea, in the church, in industry and in cookery. They were the first dependable, reusable and reasonably accurate measure of time.
Modern Devices
Mechanical clocks
The most common devices in day-to-day life are the clock. Clocks can range from watches, to more exotic varieties such as the Clock of the Long Now. The English word clock actually comes from French, Latin, and German words that mean bell. The passage of the hours at sea were marked by bells, and denoted the time (see ship's bells). The hours were marked by bells in the abbeys as well as at sea. They can be driven by a variety of means, including gravity, springs, and various forms of electrical power, and regulated by a variety of means such as a pendulum. There are also a variety of different calendars, for example the Lunar calendar and the Solar calendar, although the Gregorian calendar is the most commonly used.
A chronometer is a portable timekeeper that meets certain precision standards. Initially, the term was used to refer to the marine chronometer, a timepiece used to determine longitude by means of celestial navigation. More recently, the term has also been applied to the chronometer watch, a wristwatch that meets precision standards set by the Swiss agency COSC. Over 1,000,000 "Officially Certified Chronometer" certificates, mostly for mechanical wrist-chronometers (wristwatches) with sprung balance oscillators, are being delivered each year, after passing the COSC's most severe tests and being singly identified by an officially recorded individual serial number. According to COSC, a chronometer is a high-precision watch capable of displaying the seconds and housing a movement that has been tested over several days, in different positions, and at different temperatures, by an official, neutral body (COSC). Each movement is individually tested for several consecutive days, in five positions and at three temperatures. Any watch with the denomination "chronometer" is provided with a certified movement.
The most accurate type of timekeeping device is currently the atomic clock, which are accurate to seconds in many thousands of years, and are used to calibrate other clock and timekeeping instruments. Atomic clocks use the spin property of the caesium atom as its basis, and since 1967, the International System of Measurements bases its unit of time, the second, on the properties of caesium. SI defines the second as 9,192,631,770 cycles of the radiation which corresponds to the transition between two electron spin energy levels of the ground state of the 133Cs atom.
Today, the GPS global positioning systems in coordination with the NTP network time protocol can be used to synchronize timekeeping systems across the globe.
See also
References
- ^ Jo Ellen Barnett, Time's Pendulum p.31
- ^ Barnett, Jo Ellen Time's Pendulum: The Quest to Capture Time - from Sundials to Atomic Clocks Plenum, 1998 ISBN 0-306-45787-3 p.28
- ^ "Plato biography". Retrieved 2007-11-29.
- ^ "387 BC Sci and Tech chronology". Retrieved 2007-11-29.
- ^ Jo Ellen Barnett, Time's Pendulum p.38
- ^ Jo Ellen Barnett, Time's Pendulum p.37
- ^ North, J. (2004) God's Clockmaker: Richard of Wallingford and the Invention of Time. Oxbow Books. ISBN 1-85285-451-0
- ^ Watson, E (1979) "The St Albans Clock of Richard of Wallingford". Antiquarian Horology 372-384.
- ^ Laurence Bergreen, Over the Edge of the World: Magellan's Terrifying Circumnavigation of the Globe, HarperCollins Publishers, 2003, hardcover 480 pages, ISBN 0-06-621173-5
- ^ Frugoni, Chiara (1988). Pietro et Ambrogio Lorenzetti. Scala Books. p. 83. ISBN 0935748806.
{{cite book}}: CS1 maint: date and year (link) - ^ http://www.huntfor.com/absoluteig/lorenzetti_a.htm