Nabu-rimanni

Nabu-rimanni (also Naburianos, Naburimannu, Naburimani ; * about 560 BC in Babylonia ; † about 480 BC) was a Chaldean astronomer and mathematician .

Nabu-rimanni is the oldest Chaldean astronomer known by name. Important successors are Kidinnu (approx. 400-330), Berossos and Soudines (both 3rd century BC)

As the son of Balatu , Nabu-rimanni worked during the reigns of the Persian kings Darius I (522–486 BC) and his successor Xerxes I (486–465). He was a contemporary of Cleostratus , Aeschylus , Ferehindus and Herodotus .

Numerous written records of Sumerian astronomy have survived from the time of King Nabu-nasir (747 to 734 BC) . The Babylonian priest astronomers calculated the Saros period (cyclical recurrence of solar and lunar eclipses ) to be 6585.33 days (18 years 11 days) on the basis of this and their own long-term data collections . With each new Saros period the earth , sun and moon are again almost in the same relative position.

In addition to these cycles, the Babylonians also observed the periodic change in the movement of the moon (elliptical center-point equation ) and thus specified the length of the anomalous month and the lunar calendar . They also recognized the sun's variable angular velocity and the annual planetary loops .

In the early 6th century BC In addition to the irregular and 5 ° inclined lunar orbit, they also knew the migration of their nodes, which, as points of intersection with the ecliptic, determine the Saros cycle. Around 500 BC Nabu-rimanni improved these values ​​by observations of the eclipse: he received the movement of the moon relative to the sun 10 minutes less per year, the nodal movement 5 minutes less and the movement of the lunar perigee 20 minutes greater. The values, improved by 350 again by Kidinnu (Greek Kidenas), were later used by Hipparchus .

Nabu-rimanni developed the so-called A-system of the ephemeris , which contained the position of the moon, sun and planets for any point in time. Based on the observations of several centuries and calculated with staircase functions , these tables were still too rough and were refined by Kidinnus System B 150 years later. Nabu-rimanni summarized his work in a book on the Akkadian observations of the moon and stars.

Nabu-rimanni determined the solar year to be 365 days, 6 hours, 15 minutes and 41 seconds. He used a water clock to measure the time and calculated the length of the synodic month to be 29d 12h 44 m 5.05s or 29.530614d, only 1.56 s longer than the modern value of 29.530596 days. He also showed how the extent of a lunar eclipse can be determined from the location of the lunar nodes.

literature

• BL van der Waerden : Awakening Science, Volume 2 (The Beginnings of Astronomy), Birkhäuser Verlag, Basel, Boston, Stuttgart, 1980
• Otto Neugebauer : Astronomical cuneiform texts, Lund Humphreys, London 1955