Kidinnu

Definition

Kidinnu (Akkadian; transliterated into Greek as Κιδηνᾶς / Kidenas, sometimes Kidin) is a Late Babylonian astronomer historically attributed by Schnabel (1923) as the inventor of System B of the Moon, one of the two arithmetical computation systems of Seleucid Babylonian mathematical astronomy. The attribution rests on the colophons of ACT 122 (covering -103/2 to -101/0) and ACT 123a, both identified as the teršītu (compilation) of Kidinnu, together with Greek doxographic mentions in Strabo and an early-third-century-CE commentator on Ptolemy.

In Tradition

In the historiography of Babylonian mathematical astronomy Kidinnu is treated as a name-attached-by-colophon rather than a securely individuated scholar. Hunger and Pingree preserve the Schnabel-attribution while reporting that the only direct evidence is the teršītu-colophon of two ACT tablets. Neugebauer emphasises caution: the names occur on only three late tablets, the colophons are difficult, and the classical sources say nothing about authorship.

In Practice

For students of how Babylonian mathematical astronomy is historiographically reconstructed, Kidinnu is the canonical test case. Hunger and Pingree report Schnabel's argument step-by-step: an anonymous early-third-century-CE commentator on Ptolemy's Handy Tables attributed the period-relation 251 synodic months = 269 anomalistic months to Κιδηνᾶς, and Schnabel identified this Greek name with the Kidinnu of the ACT 122 + 123a teršītu-colophons, dating him to -313 (later redated to -378) and locating him in Sippar. Schnabel further claimed Kidinnu discovered the precession of the equinoxes in 379 BCE — the so-called "Schnabel-Kidinnu Debate" that Neugebauer's essay [16] in *Astronomy and History* refuted point-by-point in 1950. The careful reader treats "Kidinnu invented System B" as a Schnabel-via-colophon hypothesis the evidence supports but does not prove, paired with Nabû-rimannu as the parallel attribution for System A.

Historical Origin

Kidinnu is named in the colophons of ACT 122 and ACT 123a (Late Babylonian Uruk and Babylon, c. 4th-1st c. BCE) and in Greek doxographic sources (Strabo *Geographica* XVI 1, 6 listing him as Cidenas among Babylonian μαθηματικοί; an early-third-century-CE Ptolemy commentator). Modern critical treatments: Hunger & Pingree, *Astral Sciences in Mesopotamia* (Brill 1999), pp. 232-233 §C4.1; Neugebauer, *Astronomy and History: Selected Essays* (Springer 1983), essay [16] section 3, vol. p. 248; Schnabel, *Berossos und die babylonisch-hellenistische Literatur* (Leipzig 1923).

Further Reading

• Hermann Hunger & David Pingree, Astral Sciences in Mesopotamia
• Otto Neugebauer, Astronomy and History: Selected Essays