Equal hour

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Equal hours ( äqual / e from Latin aequalis ; meaning corresponding, equal, similar ) are time units of the same duration - that is, they are not different in length in every season of the year, like seasonal and temporal hours .
Special equivalent hours are the 24 equally long equinox hours of a full day on which today's time calculation is based.

Equal hours can be used both for the full day and for parts of a day, for example to divide the total darkness of the night or the core time of the clear day into equally long periods.

Equal hours in ancient Egypt

In ancient Egypt , the earliest use of equivalent hours is given by an inscription from the time of Amenhotep I around 1525 BC. Occupied. The use of water clocks enabled individual hourly units; for example for the division of the dean-star distances , whereby fractions of hours were also taken into account.

Ten equal hours were used for the time between two sunrises.

Equal hours in Babylonia

The temporal hour was the Babylonians until the third century BC. Unknown BC. However, attempts have been made to establish a second ideal calendar with seasonal hours in addition to the astronomical system of the equivalents. Bartel Leendert van der Waerden analyzed the Babylonian system of the ideal calendar in 1974 :

"The conversion of the BERU double hours does not correspond to the later Greek exact method, but only represents a very imprecise division of the day."

- Bartel Leendert van der Waerden

In 1975 Otto Neugebauer confirmed this knowledge as an important distinguishing feature from the later Greek temporal hours. The duration of the light day and night was still measured by the Babylonian astronomers with a gnomon and a water clock in BERU and UŠ . The periods of time were divided into equal time units with regard to the sky observation. The use of a gnomon in connection with a water meter is in the MUL.APIN - cuneiform tablets v already. 700 Occupied.

Its content shows that the values ​​for the duration of the light day and night were recorded during four colors, which were aligned with the longest and shortest day of the year. The records show gnomont tables, but these are only preserved for the 15th Nisan and the 15th Tammuz . The tables for the 15th Tišri and the 15th Tebetu were at the beginning of the broken second column . The gnomon tables are drawn up in such a way that the length of the gnomon corresponds to a Mesopotamian cubit, which measured between 40 and 50 cm.

A 24-hour day included twelve Danna , in turn, taking into account the Babylon model of the mean solar twelve equinoctial units comprised, each lasted 120 minutes. The equivalent hours were based on the Sumerian system of walking on clear day. The unit of measurement, which has a distance of around 10 km as a calculation variable, is incorrectly called double hour in modern literature .

See also

literature

  • Friedrich Karl Ginzel : Handbook of mathematical and technical chronology, Vol. 1 - Time calculation of the Babylonians, Egyptians, Mohammedans, Persians, Indians, Southeast Asians, Chinese, Japanese and Central Americans - , German book export and import, Leipzig 1958 (reprinted Leipzig 1906 )
  • Richard Anthony Parker : Egyptian Astronomy, Astrology and calendrical reckoning In: Charles-Coulson Gillispie: Dictionary of scientific Biography - American Council of Learned Societies - Vol. 15, Supplement 1 (Roger Adams, Ludwik Zejszner: Topical essays) , Scribner, New York 1978, ISBN 0-684-14779-3 , pp. 706-727.
  • François Thureau-Dangin : Itanerare - Babylonian double lesson - . In: Dietz-Otto Edzard : Reallexicon of Assyriology and Near Eastern Archeology . Volume 5: Ia ... - Kizzuwatna. de Gruyter, Berlin 1980, ISBN 3-11-007192-4 , p. 218.
  • François Thureau-Dangin: Rituels Accadiens. Leroux, Paris 1921, p. 133.

Individual evidence

  1. ^ Gustav Bilfinger: The Babylonian double hour . Comm.verl. of the WILDT'schen Buchhandlung, Stuttgart 1888.
  2. ↑ Bartel-Leendert van der Waerden: Science awakening II - The birth of astronomy. International Publishing, Nordhoff 1974, ISBN 90-01-93103-0 , p. 89.
  3. ^ Otto Neugebauer: A History of Ancient Mathematical Astronomy. Volume 1 Springer, Berlin 1975, ISBN 3-540-06995-X , p. 367.
  4. ^ David-Edwin Pingree: The Mesopotamian Origin of early Indian mathematical Astronomy. In: Journal for the History of Astronomy. Volume 4, 1973, p. 5.
  5. ↑ a b Ernst Weidner: A Babylonian Compendium of Celestial Studies . In: The American Journal of Semitic Languages ​​and Literatures. Volume 40, No. 1, 1923, pp. 198-199.
  6. ↑ a b Stefan M. Maul: The Gilgamesh epic . Beck, Munich 2006, ISBN 3-406-52870-8 , p. 156.
  7. ^ François Thureau-Dangin: Itanerare - Babylonian double hour. In: Dietz-Otto Edzard: Reallexicon of Assyriology and Near Eastern Archeology. Volume 5: Ia ... - Kizzuwatna . de Gruyter, Berlin 1980, p. 218.
  8. ^ A b Otto Neugebauer: Some fundamental Concepts in Ancient Astronomy. In: Studies of the history of science. Philadelphia 1941, pp. 16-17. (Reprint in O. Neugebauer: Astronomy and History: Selected Essays. Springer, New York 1983, ISBN 3-540-90844-7 , pp. 5-21.)