Water clock

Ancient Klepsydra - The upper vessel is shaped so that the falling water level is proportional to the time that has passed. The water flows through a hole in the bottom into the lower vessel.

Envoys from Caliph Harun al-Raschid bring Charlemagne a water clock

A water meter refers to a device for measuring time that uses water as an auxiliary medium. Their principle, which has been used in numerous cultures for thousands of years, that parts of the medium flow from one container into another and thereby define constant time units, was later also used for the hourglasses . The simple water clock was also called Klepsydra in Greece .

Cultural expansion

The functional principle has been used in numerous cultures for several millennia, particularly from Greece to China . The respective implementations are partly compact and simple, but can also be very large and be provided with additional, complex mechanical components.

Antique Persian clock

On the basis of the simple water clock - in Greece called "water thief" (Greek κλεψύδρα, Klepsydra or Klepshydra) - early scientific attempts to explain the phenomena of pressure, negative pressure and vacuum were made. From these simple inlet clocks and outlet clocks of antiquity , large mechanical devices developed in China and the Middle Ages at the latest . The existence of the Orient is still there, but no details of the construction of special short-term water clocks that were used in early astronomy have survived . The caliph Harun al-Raschid gave Charlemagne a water clock. Regular water clocks typically covered periods on the order of fractions of an hour.

The advantage of water clocks over sundials was that they were not dependent on sunlight or the weather and were also functional at night, in closed rooms or in the shade. However, frost hindered the flow of water and thus the accuracy of all water meters, so that torches had to be set up or the water had to be replaced with mercury ( melting point : -38.8 ° C).

history

According to his funerary inscription, it was made around 1500 BC. BC the keeper of the seal Amenemhet for King Amenophis I in ancient Egypt a technically sophisticated water clock.

The oldest preserved water clock is about 100 years younger. It was found in the Temple of Amun in Karnak and was discovered during the reign of Amenhotep III. in the first half of the 14th century BC Manufactured. It is an alabaster leak water clock and is now in the Egyptian Museum in Cairo .

In the 3rd century BC Chr. Built Ktesibios water meters, water organs, a compressed air gun, and a double-acting pump with air chamber.

In ancient Greece and Rome , speaking time in court was measured with water meters, for example with a Klepsydra.
In China , the monk Yixing built an astronomical instrument around 725 that also served as a clock. It was moved by a water-powered paddle wheel that made one complete revolution within 24 hours. The sun, moon and celestial sphere moved in circles, a bell rang automatically every hour, a drum beat every quarter of an hour. All movements were controlled by a mechanism with a mechanical escapement (not by weights and spiral springs, but escapement moved by water power). The mechanism soon began to rust, so that the machine had to be shut down. Yixing died too early to design a successor model.
The Chinese Su Song built and described a water clock around 1090 that had an escapement on the drive wheel. Their construction has been handed down in every detail. It was based on a previous model by Zhang Sixun from 976 and had a water wheel equipped with bowls. These bowls were filled with water in such a way that the wheel continued to turn one bowl every quarter of an hour, while a pawl prevented unwanted forward turning and another one from unwanted backward turning . The Su Songs watch was in use in Kaifeng from 1092 to 1127 , and then for some time in Beijing .
In the 12th century, the Arab engineer al-Jazari designed his elephant clock . With the help of water, several figures are driven that show the hours and minutes.
In the Korean Empire , the inventor Jang Yeong-sil built various water clocks for his King Taejong (1367–1422). In his water clock from 1424, the rise of a float in the lower water vessel initially triggered a small ball every two hours. This started the movement of a larger ball. This enabled a bell to be struck and figures to be moved to indicate the hours.

Bernard Gitton type water clock in the “Noria, Maison de l'Eau” watermill museum in Saint-Jean-du-Bruel in the south of France

The French Bernard Gitton has designed a modern water clock construction, which he describes as Horloge à voir le temps couler (somewhat loosely : "clock where you can see the time flow"). A water-driven pendulum serves as a frequency generator and uses a frequency divider as well as a minute and hour counter to display a discrete time display. The clock is largely made of glass and filled with colored water. Minutes and hours are read from the water level in two columns, which consist of connected glass spheres and are provided with scales ; the water level in these columns does not increase constantly, but at the right rate. Gitton has set up clocks of this type as scientific and artistic installations in numerous cities in shopping centers , public facilities and other places. In Germany, Gitton's 13 meter high clock of flowing time, built in 1982, is located in the Europa Center in Berlin .

The water clock has lost its importance in everyday life due to its rather moderate accuracy and its locality in favor of other techniques, but is occasionally the subject of an artistic-decorative implementation in various modern, mostly large-format versions.

literature

Ulrich Alertz: The Horologium of Harûn al-Raschîd for Charlemagne - An attempt at identification and reconstruction according to the building instructions of al-Gazarî . In: Wolfgang Dreßen, Georg Minkenberg , Adam C. Oellers (eds.): Ex Oriente - Isaak and the white elephant. Baghdad - Jerusalem - Aachen . Volume I, von Zabern, Mainz 2003, pp. 234–249, 10 illustrations
Daniela Wuensch , Klaus P. Sommer (ed.): The ancient Egyptian time measurement / Ludwig Borchardt. New ed. by Daniela Wuensch & Klaus P. Sommer. (With an introduction by Daniela Wuensch " What the ancient Egyptians knew about clocks and time measurement .") Reprint of the edition from 1920, Termessos, Göttingen 2013, ISBN 978-3-938016-14-5 .

Web links

Commons : Water Clock - Collection of pictures, videos and audio files

Wiktionary: Wasseruhr - explanations of meanings, word origins, synonyms, translations

Individual evidence

^ Rudolf Wendorff : Time and Culture. History of time consciousness in Europe . 3. Edition. Westdeutscher Verlag, Opladen 1985, p. 51.
^ Rudolff Wendorff : Time and Culture. History of time consciousness in Europe . 3. Edition. Westdeutscher Verlag, Opladen 1985, p. 51.
^ Moon-Hyon Nam: Yeong-sil Jang (Unknown) . In: Marco Ceccarelli (Ed.): Distinguished Figures in Mechanism and Machine Science . tape 26 . Springer Netherlands, Dordrecht 2014, ISBN 978-94-017-8946-2 , pp. 87-113 , doi : 10.1007 / 978-94-017-8947-9_6 ( springer.com ).
↑ David M. MacMillan: Bernard Gitton's Liquid Science. September 18, 2000, accessed August 5, 2015 .
^ Advertising community Europa-Center: The clock of flowing time. Retrieved August 5, 2015 .

[1] Rudolf Wendorff : Time and Culture. History of time consciousness in Europe . 3. Edition. Westdeutscher Verlag, Opladen 1985, p. 51.

[2] Rudolff Wendorff : Time and Culture. History of time consciousness in Europe . 3. Edition. Westdeutscher Verlag, Opladen 1985, p. 51.

[3] Moon-Hyon Nam: Yeong-sil Jang (Unknown) . In: Marco Ceccarelli (Ed.): Distinguished Figures in Mechanism and Machine Science . tape 26 . Springer Netherlands, Dordrecht 2014, ISBN 978-94-017-8946-2 , pp. 87-113 , doi : 10.1007 / 978-94-017-8947-9_6 ( springer.com ).

[4] David M. MacMillan: Bernard Gitton's Liquid Science. September 18, 2000, accessed August 5, 2015 .

[5] Advertising community Europa-Center: The clock of flowing time. Retrieved August 5, 2015 .