When the Moon in its calculated time is not seen, there will be an invasion of a mighty city. When a comet reaches the path of the Sun, field-flow will be diminished; an uproar will happen twice. When Jupiter goes with Venus, the prayers of the land will reach the heart of the gods. If the Sun stands in the station of the Moon, the king of the land will be secure on the throne.
Even this astrology required comprehensive and accurate astronomical knowledge, without which no omens were possible. The Mesopotamians, possessing such knowledge, distinguished between the "fixed" stars and the planets that "wandered about" and knew that the Sun and the Moon were neither fixed stars nor ordinary planets. They were familiar with comets, meteors, and other celestial phenomena, and could calculate the relationships between the movements of the Sun, Moon, and Earth, and predict eclipses. They followed the motions of the celestial bodies and related them to Earth's orbit and rotation through the heliacal system - the system still in use today, which measures the rising and setting of stars and planets in Earth's skies relative to the Sun.
To keep track of the movements of the celestial bodies and their positions in the heavens relative to Earth and to one another, the Babylonians and Assyrians kept accurate ephemerides. These were tables that listed and predicted the future positions of the celestial bodies. Professor George Sarton (Chaldean Astronomy of the Last Three Centuries B.C.) found that they were computed by two methods: a later one used in Babylon, and an older one from Uruk. His unexpected finding was that the older, Uruk method was more sophisticated and more accurate than the later system. He accounted for this surprising situation by concluding that the erroneous astronomical notions of the Greeks and Romans resulted from a shift to a philosophy that explained the world in geometric terms, while the astronomer-priests of Chaldea followed the prescribed formulas and traditions of Sumer.
The unearthing of the Mesopotamian civilizations in the past one hundred years leaves no doubt that in the field of astronomy, as in so many others, the roots of our knowledge lie deep in Mesopotamia. In this field, too, we draw upon and continue the heritage of Sumer.
Sarton's conclusions have been reinforced by very comprehensive studies by Professor O. Neugebauer (Astronomical Cuneiform Texts), who was astonished to find that the ephemerides, precise as they were, were not based on observations by the Babylonian astronomers who prepared them. Instead, they were calculated "from some fixed arithmetical schemes . . . which were given and were not to be interfered with" by the astronomers who used them.
Such automatic adherence to "arithmetical schemes" was achieved with the aid of "procedure texts" that accompanied the ephemerides, which "gave the rules for computing ephemerides step by step" according to some "strict mathematical theory." Neugebauer concluded that the Babylonian astronomers were ignorant of the theories on which the ephemerides and their mathematical calculations were based. He also admitted that "the empirical and theoretical foundation" of these accurate tables, to a large extent, escapes modern scholars as well. Yet he is convinced that ancient astronomical theories "must have existed, because it is impossible to devise computational schemes of high complication without a very elaborate plan."
Professor Alfred Jeremias (Handbuch der Altorienta-lischen Geistkultur) concluded that the Mesopotamian astronomers were acquainted with the phenomenon of retrograde, the apparent erratic and snakelike course of the planets as seen from Earth, caused by the fact that Earth orbits the Sun either faster or slower than the other planets. The significance of such knowledge lies not only in the fact that retrograde is a phenomenon related to orbits around the Sun, but also in the fact that very long periods of observation were required to grasp and track it.
Where were these complicated theories developed, and who made the observations without which they could not have been developed? Neugebauer pointed out that "in the procedure texts, we meet a great number of technical terms of wholly unknown reading, if not unknown meaning." Someone, much earlier than the Babylonians, possessed astronomical and mathematical knowledge far superior to that of later culture in Babylon, Assyria, Egypt, Greece, and Rome.
The Babylonians and Assyrians devoted a substantial part of their astronomical efforts to keeping an accurate calendar. Like the Jewish calendar to this very day, it was a solar-lunar calendar, correlating ("intercalating") the solar year of just over 365 days with a lunar month of just under 30 days. While a calendar was important for business and other mundane needs, its accuracy was required primarily to determine the precise day and moment of the New Year, and other festivals and worship of the gods. To measure and correlate the intricate movements of Sun, Earth, Moon, and planets, the Mesopotamian astronomer-priests relied on a complex spherical astronomy. Earth was taken to be a sphere with an equator and poles; the heavens, too, were divided by imaginary equatorial and polar lines. The passage of celestial bodies was related to the ecliptic, the projection of the plane of Earth's orbit around the Sun upon the celestial sphere; the equinoxes (the points and the times at which the Sun in its apparent annual movement north and south crosses the celestial equator); and the solstices (the time when the Sun during its apparent annual movement along the ecliptic is at its greatest declination north or south). All these are astronomical concepts used to this very day.
But the Babylonians and Assyrians did not invent the calendar or the ingenious methods for its calculation. Their calendars - as well as our own - originated in Sumer. There the scholars have found a calendar, in use from the very earliest times, that is the basis for all later calendars. The principal calendar and model was the calendar of Nippur, the seat and center of Enlil. Our present-day one is modeled on that Nippurian calendar.
The Sumerians considered the New Year to begin at the exact moment when the Sun crossed the spring equinox. Professor Stephen Langdon (Tablets from the Archives of Drehem) found that records left by Dungi, a ruler of Ur circa 2400 B.C., show that the Nippurian calendar selected a certain celestial body by whose setting against the sunset it was possible to determine the exact moment of the New Year's arrival. This, he concluded, was done "perhaps 2,000 years before the era of Dungi" - that is, circa 4400 B.C.!
Can it really be that the Sumerians, without actual instruments, nevertheless had the sophisticated astronomical and mathematical know-how required by a spherical astronomy and geometry? Indeed they had, as their language shows. They had a term - DUB - that meant (in astronomy) the 360-degree "circumference of the world," in relation to which they spoke of the curvature or arc of the heavens. For their astronomical and mathematical calculations they drew the AN.UR - an imagined "heavenly horizon" against which they could measure the rising and setting of celestial bodies. Perpendicular to this horizon they extended an imagined vertical line, the NU.BU.SAR.DA; with its aid they obtained the zenith point and called it the AN.PA. They traced the lines we call meridians, and called them "the graded yokes"; latitude lines were called "middle lines of heaven." The latitude line marking the summer solstice, for example, was called AN.BIL ("fiery point of the heavens"). The Akkadian, Hurrian, Hittite, and other literary masterpieces of the ancient Near East, being translations or versions of Sumerian originals, were replete with Sumerian loanwords pertaining to celestial bodies and phenomena. Babylonian and Assyrian scholars who drew up star lists or wrote down calculations of planetary movements often noted the Sumerian originals on the tablets that they were copying or translating. The 25,000 texts devoted to astronomy and astrology said to have been included in the Nineveh library of Ashurbanipal frequently bore acknowledgments of Sumerian origins.