APA 7: Çarıkçıoğlu, A. E. (2023, May 2). Kidinnu. PerEXP Teamworks. [Article Link]
His life and contributions
Kidinnu -also spelled “Kidin”, “Kidenas (Greek)”, and “Cidenas (Latin)”-was an astronomer who lived in Babylonia in the fourth and early third centuries BC. The date of his death is estimated as August 14, 330 BC.
It is believed that he was the astronomer who first put forward the theory that modern scientists call “System B”. System B is a theory that describes the speed of the Moon’s movement around the zodiac sign belt as “Gradually increasing”. At the same time, the velocity of the Moon gradually decreases over a month, following a regular “Saw tooth pattern”. According to this enormously successful theory, the Sun also changes its speed in the saw tooth graphical layout. The concept of “Saw tooth” is used to describe that a graph is bumpy. 
The Babylonian Lunar Theory included a diagram for this movement of the Sun since it was involved in the calculation of lunar events, such as phases and eclipses of the Sun. In the easier and probably older System A used to explain the behavior of the Moon, it was assumed that the Sun moved at two different constant speeds at two separate places in the signs.
Kidinnu has also been associated with Deceptions made by later writers about the movement of Mercury and the relationship between the two different Lunar phases. To put the above discoveries, one Earth day equals two days experienced on Mercury. We also know that the Moon has four main phases (New moon, first fourth, full moon, and last fourth). On the other hand, Mercury had two of them observed from Earth at that time. It may be taken naturally to mention Mercury as “Two separate stars” in past ages when its brightness is also taken into the foreground.
Very little is known about Kidinnu’s life. In Babylonia, astronomy was dominated by temple priests. In light of this situation mentioned in various inscriptions, it can be said that Kidinnu was a temple priest. 
References about him, synodic and anomalistic period
Until the deciphering of the Babylonian astronomical texts at the beginning of the twentieth century, what was known about him was limited to references by a few Ancient Greek and Roman authors. The Greek geographer Strabo (64 BC–AD 23) did not neglect to mention Naburimannu (Greek “Nabourianos”), as well as Kidinnu when talking about the astronomers of Babylon. The Greek astrologer Vettius Valens (Second century AD) wrote that he based his calculations on Kidinnu’s calculations when calculating when Lunar eclipses would occur.
The Roman encyclopedist Pliny the Elder (AD 23-79): “According to Kidinnu, the planet Mercury is not seen more than 22 degrees away from the Sun.” he referred to the famous astronomer by saying. An anonymous commentary on Ptolemy from the third century attributed the discovery of the equation “251 synodic (Lunar) months=269 deviant (Anomalistic) periods” to Kidinnu.
The synodic month (About 29.531 days) is the average time from one full moon to the next full moon. The anomalistic period (About 27.555 days) refers to the approximate time elapsed from the moment of the Moon’s rapid movement between the stars to the moment of its next fastest movement. The Moon performs its fast motion when it is on the “Earth”. That’s when it passes closest to the Earth. This period relationship forms the basis of System B and plays a crucial role in eclipse prediction. 
Findings and assumptions about him
At the beginning of the twentieth century, the name “Kidinnu” or “Kidin” was solved on Babylonian cuneiform clay tablets bearing calculations of Lunar phenomena in System B. Such a tablet bears the inscription ”The ‘tersitu’ of “Kidinnu”, where ”Tersitu“ can mean ”Apparatus“, “Preparation”, or perhaps, in this case, simply “Calculated table”. In both systems, mathematical rules have been applied to the changes in the velocities of the Sun and the Moon around the signs. These rules allowed Babylonian writers to solve predictions of Lunar events, including the dates of the new moon and full moon, as well as eclipses. System B was relatively accurate. And it was much better than anything that Greek astronomers could have done before the Lunar theory (Around 130 BC), especially the Permissive Hipparchus (Greek: Hipparkhos).
One of the joint opinions of all historians is that Naburimannu is the creator of System A, and Kidinnu is the creator of System B. Although this situation is satisfactory, it should not be considered final. Since the oldest surviving clay tablets related to System B refer to dates around 260 BC, Kidinnu could not have lived his scientific life later; however, no more precise judgment can be made about his date. 
Kidinnu is named after a crater. This is a crater with a diameter of about 60 kilometers, located on the far side of the Moon. Along with this name, NASA officials must have referred to the hidden windows of Kidinnu and the history of Mesopotamian science. Because it is a crater that has formed somewhat irregularly, with its outer arc forming a rounded polygon. The width of the inner wall of the crater varies. Also, the narrowest part extends along the northeast, bulging outwards. There are no notable craters along the crater’s arc or in the interior. The interior floor appears rugged, with a central ridge extending to the southern edge. 
Inferences on Kidinnu
It is common for historians, philosophers, mathematicians, and astronomers to individually compare the individualism and competitiveness of Ancient Greek society with the anonymity of the Mesopotamian community, where very few scientific discoverers’ names are known about the origins of major theories and discoveries. Even if the view that Ancient Greece laid the foundation for all kinds of science is valid in the society of science, culture, and philosophy, the examples of Kidinnu and Naburimannu show that, at least in a few cases, the names of some Mesopotamian scientists are remembered and respected. 
- DICTIONARY ENTRY Evans, J. (2019, November 7). Kidinnu. Encyclopedia Britannica. [Britannica]
- JOURNAL Reviv, H. (1988). Kidinnu Observations on Privileges of Mesopotamian Cities. Journal of the Economic and Social History of the Orient, 31(3), 286. [JSTOR]
- WEBSITE Pannekoek, A. (1947, October). Planetary Theories – the Planetary Theory of Kidinnu. NASA/ADS. [NASA/ADS]
- BOOK Asimov, I. (1988). Enciclopedia biográfica de ciencia y tecnología: la vida y la obra de 1197 grandes científicos desde la antigüedad hasta nuestros días. Alianza Editorial Mexicana.
- WEBSITE Andersson, L. A., & Whitaker, E. A. (1982, October 1). NASA catalogue of lunar nomenclature. NASA Technical Reports Server (NTRS). [NASA Technical Reports Server (NTRS)]
- WEBSITE Çığ, M. İ. (1995, December). Mezopotamya’da astronomi. Bilim Ve Ütopya. [Bilim Ve Ütopya]