Kidinnu

Encyclopedia : K : KI : KID : Kidinnu

Kidinnu (also Kidunnu) (4th century BC? possibly died 14 August 330 BC) was a Chaldean astronomer and mathematician. Strabo of Amaseia called him Kidenas, Pliny the Elder Cidenas, and Vettius Valens Kidynas.

An astronomer with this name is mentioned in some cuneiform and classical Greek and Latin texts, specifically:

The Greek geographer Strabo of Amaseia writes in his Geography 16.1..6: "In Babylon a settlement is set apart for the local philosophers, the Chaldaeans, as they are called, who are concerned mostly with astronomy; but some of these, who are not approved of by the others, profess to be writers of horoscopes. (There is also a tribe of the Chaldaeans, and a territory inhabited by them, in the neighborhood of the Arabs and of the Persian Gulf, as it is called.) There are also several tribes of the Chaldaean astronomers. For example, some are called Orcheni [those from Uruk], others Borsippeni [those from Borsippa], and several others by different names, as though divided into different sects which hold to various different dogmas about the same subjects. And the mathematicians make mention of some of these men; as, for example, Kidenas, Nabourianos and Soudines."

The Roman encyclopaedist Pliny the Elder writes in his Natural History II.vi.39 about the planet Mercury: ... but according to Cidenas and Sosigenes never more than 22 degrees away from the sun.

The Roman astrologer Vettius Valens stated in his Anthology that he used Hipparchus for the Sun, Sudines and Kidynas and Appollonius for the Moon, and again Appollonius for both types (of eclipses, i.e. solar and lunar).

The hellenistic astronomer Ptolemy in his Almagest IV 2 discusses the duration and ratios of several periods related to the Moon, as known to "ancient astronomers" and "the Chaldeans" and improved by Hipparchus. He mentions the equality of 251 (synodic) months to 269 returns in anomaly. In a preserved classical manuscript of the excerpt known as Handy Tables, an anonymous reader in the third century wrote the comment (a scholion) that this relation was discovered by Kidenas.

In the colophon of two "System B" type lunar ephemerides from Babylon (see ACT 122 for 104..101 BC, and ACT 123a for an unknown year), Kidinnu is mentioned as the tersitu.

A damaged cuneiform astronomical diary tablet from Babylon (Babylonian chronicle 8: the Alexander chronicle; BM 36304) mentions that "ki-di-nu was killed by the sword" on day 15 of probably the 5th month of that year, which has been dated as 14 August 330 BC, less than a year after the conquest of Babylon by Alexander the Great. It is not certain if this referred to Kidinnu the astronomer.

These are about all the sources that we have about the Babylonian astronomer Kidinnu, and little can be concluded from them.

P.Schnabel, in a series of papers (1923..1927) argued that Kidinnu was the principal author of the method of ephemeris computation now known as Babylonian "System B". No-one knows what the term tersitu means, but a similar colophon of a "System A" type lunar ephemeris (VAT 209, see ACT 18) carries the name of Nabu-[ri]-man-nu, whom scholars identify with the Nabourianos/Naburianus known also as a famous astronomer from Greek sources. So it seems plausible to interpret tersitu as "author", and that Kidinnu developed System B and Nabu-rimanni developed System A.

Specifically, the relation of 251 synodic months = 269 anomalistic months indeed is implicit in System B, and Greco-Roman tradition attributes its discovery to Kidinnu.

The lunation length used in System B has also been attributed to Kidinnu; it is 29 days + 191 time degrees + 1/72 of a time degree ("barley corn") = 29^d 31:50:8:20 (sexagesimal) = 29^d + 12^h + 793/1080^h (Hebrew chelek) = 29.53059414...^d, but being a rounded value in the archaic unit of "barley corns" it may be even more ancient. In any case, it is very accurate (only 1/3 of a second in error in the 4th century B.C.). This value for the lunation length was confirmed by Hipparchus and used by Ptolemy and later by Hillel in the Hebrew calendar, in which it has been used up to the present day.

It is difficult to put Kidinnu at a time and place. Classical sources like Strabo mention different "schools" and "doctrines" followed in different places (Babylon, Borsippa, Sippar, Uruk). System A and B tablets have been found contemporary in both Babylon and Uruk. System B associated with Kidinnu is mostly found in Uruk, but the elder tablets seem to come predominantly from Babylon; the oldest preserved tablet using System B parameters comes from Babylon and dates from 258/7 BC. This is in the Seleucid era, but it is plausible that the traditional Chaldean astronomical systems have been developed before the Hellenistic period. The Alexander chronicle tells us that a Kidinnu was killed in Babylon right at the beginning of that new age.

Schnabel computed specific years (314 BC and later 379 BC) for the System B lunar theory, but this was disproved later by F.Kugler. Schnabel puts Kidinnu in Sippar but later O.Neugebauer showed that this was a misreading of the cuneiform tablet. Also Schnabels' assertion that Kidinnu discovered precession (when distinguishing sidereal and tropical years) has been considered unfounded by later scholars. The Metonic cycle and saros cycles seem to have been discovered by Babylonian astronomers before the time of Kidinnu.

Literature

O.Neugebauer: A History of Ancient Mathematical Astronomy Part Two IV A 4, 3A (p.602) and IV A 4, 4A (pp.410..11). Springer, Heidelberg 1975 (reprinted 2004).

Herman Hunger and David Pingree: Astral Sciences in Mesopotamia pp.200..1, 214..15, 219, 221, 236, 239 . Brill, Leiden 1999 .

External references

[Article about Kidinnu]

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.