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| ==Origin== | | ==Origin== |
| [[Latin]] ''trepidātiōn-em'', n. of [[action]]; ''trepidāre'' | | [[Latin]] ''trepidātiōn-em'', n. of [[action]]; ''trepidāre'' |
− | *[http://en.wikipedia.org/wiki/17th_century 1605] | + | *[https://en.wikipedia.org/wiki/17th_century 1605] |
| ==Definitions== | | ==Definitions== |
| * 1. Tremulous [[agitation]]; confused hurry or [[alarm]]; [[confusion]]; flurry; perturbation. | | * 1. Tremulous [[agitation]]; confused hurry or [[alarm]]; [[confusion]]; flurry; perturbation. |
− | *2. Tremulous, [[vibratory]], or reciprocating movement; vibration; [http://en.wikipedia.org/wiki/Oscillation oscillation], rocking; an instance of this; also, involuntary trembling of the limbs, as in paralytic affections; tremor. | + | *2. Tremulous, [[vibratory]], or reciprocating movement; vibration; [https://en.wikipedia.org/wiki/Oscillation oscillation], rocking; an instance of this; also, involuntary trembling of the limbs, as in paralytic affections; tremor. |
− | *3. Astronomy. A libration of the eighth (or ninth) [[sphere]], added to the system of [http://en.wikipedia.org/wiki/Ptolemy Ptolemy] by the Arab astronomer [http://www.worldcat.org/title/notice-sur-une-theorie-ajoutee-par-abul-hasan-thabit-ben-korrah-al-harrani-a-larithmetique-speculative-des-grecs/oclc/493040850 Thabet ben Korrah], c950, in order to account for certain [[phenomena]], esp. precession, really due to [[motion]] of the [[earth]]'s [[axis]] | + | *3. Astronomy. A libration of the eighth (or ninth) [[sphere]], added to the system of [https://en.wikipedia.org/wiki/Ptolemy Ptolemy] by the Arab astronomer [https://www.worldcat.org/title/notice-sur-une-theorie-ajoutee-par-abul-hasan-thabit-ben-korrah-al-harrani-a-larithmetique-speculative-des-grecs/oclc/493040850 Thabet ben Korrah], c950, in order to account for certain [[phenomena]], esp. precession, really due to [[motion]] of the [[earth]]'s [[axis]] |
| ==Description== | | ==Description== |
− | According to a [http://en.wikipedia.org/wiki/Middle_Ages medieval theory] of [[astronomy]], '''trepidation''' is [http://en.wikipedia.org/wiki/Oscillation oscillation] in the [http://en.wikipedia.org/wiki/Precession_of_the_equinoxes precession of the equinoxes]. The [[theory]] was popular from the 9th to the 16th centuries. | + | According to a [https://en.wikipedia.org/wiki/Middle_Ages medieval theory] of [[astronomy]], '''trepidation''' is [https://en.wikipedia.org/wiki/Oscillation oscillation] in the [https://en.wikipedia.org/wiki/Precession_of_the_equinoxes precession of the equinoxes]. The [[theory]] was popular from the 9th to the 16th centuries. |
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− | The origin of the [[theory]] of trepidation comes from the Small Commentary to the Handy Tables written by [http://en.wikipedia.org/wiki/Theon_of_Alexandria Theon of Alexandria] in the 4th century CE. In [http://en.wikipedia.org/wiki/Precession precession], the [http://en.wikipedia.org/wiki/Equinoxes equinoxes] appear to move slowly through the [http://en.wikipedia.org/wiki/Ecliptic ecliptic], completing a revolution in approximately 25,800 years (according to [[modern]] astronomers). Theon states that certain (unnamed) ancient astrologers believed that the precession, rather than being a steady unending [[motion]], instead reverses direction every 640 years. The equinoxes, in this [[theory]], move through the ecliptic at the rate of 1 degree in 80 years over a span of 8 degrees, after which they suddenly reverse direction and travel back over the same 8 degrees. Theon describes but did not endorse this [[theory]]. | + | The origin of the [[theory]] of trepidation comes from the Small Commentary to the Handy Tables written by [https://en.wikipedia.org/wiki/Theon_of_Alexandria Theon of Alexandria] in the 4th century CE. In [https://en.wikipedia.org/wiki/Precession precession], the [https://en.wikipedia.org/wiki/Equinoxes equinoxes] appear to move slowly through the [https://en.wikipedia.org/wiki/Ecliptic ecliptic], completing a revolution in approximately 25,800 years (according to [[modern]] astronomers). Theon states that certain (unnamed) ancient astrologers believed that the precession, rather than being a steady unending [[motion]], instead reverses direction every 640 years. The equinoxes, in this [[theory]], move through the ecliptic at the rate of 1 degree in 80 years over a span of 8 degrees, after which they suddenly reverse direction and travel back over the same 8 degrees. Theon describes but did not endorse this [[theory]]. |
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− | A more sophisticated version of this theory was adopted in the 9th century to explain a variation which Islamic astronomers incorrectly believed was affecting the rate of precession.[2] This version of trepidation is described in ''De motu octavae sphaerae'' (''On the Motion of the Eighth Sphere''), a [[Latin]] translation of a lost Arabic original. The book is attributed to the Arab astronomer by [http://en.wikipedia.org/wiki/Ptolemy Ptolemy] by the Arab astronomer [http://www.worldcat.org/title/notice-sur-une-theorie-ajoutee-par-abul-hasan-thabit-ben-korrah-al-harrani-a-larithmetique-speculative-des-grecs/oclc/493040850 Thābit ibn Qurra], but the attribution has been contested in modern times. In this trepidation model, the oscillation is added to the equinoxes as they precess. The [http://en.wikipedia.org/wiki/Oscillation oscillation] occurred over a period of 7000 years, added to the eighth (or ninth) sphere of the [http://en.wikipedia.org/wiki/Ptolemaic_system Ptolemaic system]. "Thabit's" trepidation model was used in the [http://en.wikipedia.org/wiki/Alfonsine_Tables Alfonsine Tables], which assigned a period of 49,000 years to precession. This version of trepidation dominated Latin astronomy in the later Middle Ages. | + | A more sophisticated version of this theory was adopted in the 9th century to explain a variation which Islamic astronomers incorrectly believed was affecting the rate of precession.[2] This version of trepidation is described in ''De motu octavae sphaerae'' (''On the Motion of the Eighth Sphere''), a [[Latin]] translation of a lost Arabic original. The book is attributed to the Arab astronomer by [https://en.wikipedia.org/wiki/Ptolemy Ptolemy] by the Arab astronomer [https://www.worldcat.org/title/notice-sur-une-theorie-ajoutee-par-abul-hasan-thabit-ben-korrah-al-harrani-a-larithmetique-speculative-des-grecs/oclc/493040850 Thābit ibn Qurra], but the attribution has been contested in modern times. In this trepidation model, the oscillation is added to the equinoxes as they precess. The [https://en.wikipedia.org/wiki/Oscillation oscillation] occurred over a period of 7000 years, added to the eighth (or ninth) sphere of the [https://en.wikipedia.org/wiki/Ptolemaic_system Ptolemaic system]. "Thabit's" trepidation model was used in the [https://en.wikipedia.org/wiki/Alfonsine_Tables Alfonsine Tables], which assigned a period of 49,000 years to precession. This version of trepidation dominated Latin astronomy in the later Middle Ages. |
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− | Islamic astronomers described other models of trepidation. In the West, an alternative to ''De motu octavae sphaerae'' was part of the [[theory]] of the [[motion]] of the [[Earth]] published by [http://en.wikipedia.org/wiki/Nicolaus_Copernicus Nicolaus Copernicus] in [http://en.wikipedia.org/wiki/De_revolutionibus_orbium_coelestium ''De revolutionibus orbium coelestium''] (1543). Copernicus' version of trepidation combined the oscillation of the equinoxes (now known to be a spurious [[motion]]) with a change in the obliquity of the ecliptic ([http://en.wikipedia.org/wiki/Axial_tilt axial tilt]), acknowledged today as an authentic motion of the [[Earth]]'s [[axis]]. | + | Islamic astronomers described other models of trepidation. In the West, an alternative to ''De motu octavae sphaerae'' was part of the [[theory]] of the [[motion]] of the [[Earth]] published by [https://en.wikipedia.org/wiki/Nicolaus_Copernicus Nicolaus Copernicus] in [https://en.wikipedia.org/wiki/De_revolutionibus_orbium_coelestium ''De revolutionibus orbium coelestium''] (1543). Copernicus' version of trepidation combined the oscillation of the equinoxes (now known to be a spurious [[motion]]) with a change in the obliquity of the ecliptic ([https://en.wikipedia.org/wiki/Axial_tilt axial tilt]), acknowledged today as an authentic motion of the [[Earth]]'s [[axis]]. |
| ==Notes== | | ==Notes== |
| #a fully quoted translation is found in Jones A., Ancient Rejection and Adoption of Ptolemy’s Frame of Reference for Longitudes in Ptolemy in Perspective, (ed) A. Jones, Spinger, 2010, p.11 | | #a fully quoted translation is found in Jones A., Ancient Rejection and Adoption of Ptolemy’s Frame of Reference for Longitudes in Ptolemy in Perspective, (ed) A. Jones, Spinger, 2010, p.11 |