The Fertile Crescent

The light of civilization first dawned in the Middle East along what is known by historians as the fertile cresent - a cresent-shaped region stretching from just south of modern-day Jerusalem then northward along the Mediterranean coast to present-day Syria and eastward through present-day Iraq then southward along the Tigris and Euphrates rivers to the Persian Gulf.

Initially, the Fertile Crescent was only sparsely inhabited but around 8000 BC, it was in this fertile valley that agriculture was first believed to have been developed. Wild wheat and barley grew in abundunce and tribes of nomad hunters and herders began to settle down along the lush banks of the rivers and became the world's first farmers. Agriculture was the spark which lit the flame of civilization. Farming gave rise to social planning on a larger scale as groups of nomadic tribes settled down and joined co-operative forces. Irrigation developed as the need increased to feed and support growing populations. Soon towns were built to afford comfort and protection for these early settlers. Towns like Jericho, Jarmo, Ali Kosh, Catal Huyuk, Beidha and Hassuna were the basis of a new form of human social organization and became the foundation for the first civilization.

Around 5,000 B.C. the first cities were constructed in the southern part of this long crescent valley, near the Persian Gulf, by an intelligent, resourceful and energetic people who became known as the Sumerians. Their capital, Sumer, became a rich and vibrant city in which the rudiments of writing and an alphabet were first invented. Another great city established by the Sumerians, where a famous temple, or ziggurat, was excavated is the city of Ur. These people introduced the Bronze Age to civilization; they invented the wheel and the rudiments of mathematics. They gave to humankind one of the first great literary epics -"The Epic of Gilgamesh"; and they also fought the first large-scale wars. They had a religion and built great temples - called ziggurats - to their gods, their primary purpose in life being to serve and please these gods. The priests who administered the temples were the aristocracy and their war leaders became their kings. A rough form of writing called cuneiform developed from the requirements of administering the temples, which included collecting the earliest taxes or tribute to the gods. The Sumerians were also extensive traders of goods and natural resources, exchanging their grain and manufactured products, such as pottery, hand tools and weaponry, for precious metals from surrounding settlements. The Sumerians gradually extended their civilization northward, becoming the first great empire. Mesopotamia, meaning "land between two rivers", was a name given to this geographical area by the ancient Greeks.

Because of its accessibility, the region has seen a constant wave of invaders and conquests. Around 2300 BC the Akkadians invaded the area and for some time the more backward culture of the Akkadians mixed with the more advanced culture of the Sumerians. The Akkadians invented the abacus as a tool for counting and they developed somewhat clumsy methods of arithmetic with addition, subtraction, multiplication and division all playing a part. The Sumerians, however, revolted against Akkadian rule and by 2100 BC they were back in control. Around 2000 BC, the Babylonians, a Semitic people, invaded Mesopotamia and established their capital at Babylon.

This land had deep roots in the Judeo-Christian-Islamic (and hence, the present-day western) tradition. It is said to have hosted the legendary Garden of Eden - if it existed anywhere. To emphasize this the ancient village of Al-Qurna singled out a tree ("Adam's tree") with a sign - in Arabic and English. Abraham prayed here 2,000 years B.C. Throughout Iraq loom ziggurat temples dating from 3,000 B.C. which recall the story of the Tower of Babel. One such ziggurat is Aqar-Quf (a suburb of present day Baghdad) marking the capital of the Cassites. In the south lie the ruins of Sumer where were found tens of thousands of stone tablets from the incredible Sumerian culture which flourished 5,000 years ago. On some of these tablets, which were used for teaching children, are found fascinating descriptions of everyday life, including the first organized and detailed set of instructions on when to plant and when to harvest. Also in the south lie the ruins of Ur from which at God's prodding Abraham set out for the promised land. Here the Akkadians introduced chariots to warfare. In the north of Iraq the gates of Ninevah the Assyrian capital with their imaginative stone winged-bulls mark the place where the prophet Jonah is said to have preached penance to the wicked inhabitants, all of whom repented, much to Jonah's chagrin.

Early Mesopotamian Astronomy

In "History Begins at Sumer", Samuel Kramer tells of the third millennium B.C Sumerian astronomers living along the Tigris River who noticed that there were roughly 360 days in the year. The missing five days were declared occasional holidays. This number 360 was very convenient since it was divisible by many smaller numbers, so they divided each day into 360 gesh, which were later changed by the Babylonians to 24 hours with two levels of subdivisions. Present day use of minute and second is traced to the Latin translations of the Babylonian designations for these subdivisions: small bits (minuta -> minutes) and secondary small bits (secunda minuta -> seconds). Around 2400 B.C. the Sumerians developed an ingenious sexagesimal system to represent all integers from 1 to 59 using 59 different patterns of wedges (cunei . . . cuneiform) which were usually imprinted in soft clay and later hardened. Integers from 60 to 3600 were then represented by a different symbol for 60 which was combined with the other 59 patterns. Like our decimal system it was positional so that the successive symbols were assumed to be multiplied by decreasing powers of 60. For instance, the number 365 in the decimal system would, in the sexagesimal system, be written 6 5 (= 6 times 60 + 5 times 1), just as 65 in our decimal system of base ten means 6 times 10 plus 5 times 1.

An adventuresome, determined and curious reader with a calculator can verify that the Babylonian number 4 23 36 (equals {4 times 60 times 60} + {23 times 60} + {36 times 1}) represents 15,816 in our decimal system. In their grasp of the workings of arithmetic the Babylonians were far superior to the Greeks of later centuries. The latter used letters for numbers (so 888 would be wph) and they would have trouble multiplying a simple problem like 12 times 28 which would be ib times kh. The multiplication rules for letters were beyond the reach of an ordinary person.

Kramer uses as his main source the content of tens of thousands of Sumerian tablets, uncovered in this century from 1902 on, which date back to 2,400 B.C. and reveal a rich literature long before Greek civilization. These remarkable tablets gave us the first Farmer's Almanac filled with astronomical and mathematical data, proving that Sumerian schoolboys were learning the Pythagorean theorem 1,800 years before Pythagoras (circa 585-500 B.C.) was born. In this mainstream of our own cultural background, the Mesopotamian civilization, a fortuitous event in the evolution of arithmetic symbols occurred through the adoption of Sumerian "cuneiform" symbols by the Akkadians to represent their semitic language as it became more popular in Mesopotamia.

About 1600 BC, the Babylonians compiled the first known star catalogs and began long-term records of planetary motions. By 800 BC Babylonian astronomers had fixed planetary locations with respect to the stars of the zodiac and were keeping records of these positions on clay tablets. The objects of their early observations include Venus, Jupiter and Mars. These records often spanned several centuries.

Babylonian clay tablets that have survived since dawn of civilization in the Mesopotamian region record the earliest total solar eclipse seen in Ugarit on May 3, 1375 BC. Like the Chinese, Babylonian astrologers kept careful records about celestial happenings including the motions of Mercury, Venus, the Sun, and the Moon on tablets dating from 1700 to 1681 BC. Later records identified a total solar eclipse on July 31, 1063 BC, that "turned day into night," and the famous eclipse of June 15, 763 BC, recorded by Assyrian observers in Nineveh. Babylonian astronomers are credited with having discovered the 223-month period for lunar eclipses.

The information found on the clay tablets includes both observations and calculations of the motions of the planets. The Chaldeans did less with astronomy than the Babylonians. Nevertheless, one important Chaldean discovery was a method of predicting, within a certain degree of accuracy, the apparent motion of the planets as they sped through the sky. These predictions included times of retrograde (backwards) motion, helical rising and setting, and conjunctions with principal stars. The Chaldeans were also able to calculate the times of Earth's Moon's "new" phase as well as lunar and solar eclipses.

Some of the oldest astronomical artifacts are astrolabe tablets. These clay tablets consisted of three concentric circles divided by twelve radii into twelve sections. Each of the thirty-six fields contained the names of constellations and simple numbers. No one yet understands the significance of these numbers. It is believed that the numbers represented the months of the Babylonian calendar. These calendars are similar to calendars developed by the Egyptians. Astrolabes are still used today to determine the relative positions of stars and planets.

The Babylonian calendar was lunar and based on the appearance of the New Moon, i.e. numbered according to the days elapsed after the Moon reappeared from the end of its waning cycle. Because the seasons were governed by a solar calendar, the Babylonians derived a luni-solar calendar which consisted of twelve months, with a thirteenth one added occasionally to keep the years consistent. Some extant calendrical records also show the presence of a seven-day week system. It varied from place to place throughout Babylon. The final day, with the seventh, fourteenth, twenty-first, and twenty-eighth of each month were considered "cursed". As such, many activities were suspended on these days, and the astronomers-astrologers created rituals to ward off the supposed evil of those dates.

It is from the Babylonian astronomers that the divisions for the 360 degrees of a circle comes. The Babylonians divided the day into twelve intervals called "kaspu". The solar kaspu was the span of thirty degrees which the Sun travels in two hours of daily motion across Earth's sky. The Babylonians used the arc of one degree as a unit of angular space, just as is done today. They expanded their system to include units of time which correspond to four modern minutes, which is approximately the path taken by Earth in one day of its yearly revolution around the Sun.

That the Babylonians became such careful observers was in part a result of the state support for the calendar and for astrology. These political needs induced techniques for predicting planetary positions and for recording long-term observations. Meanwhile, the records the Babylonians kept enabled them to find the basic cycles of periodic celestial motions. They even made detailed observations of solar and lunar eclipses. Such records enabled the Babylonian astronomers to predict eclipses, at least in a rough way.

The Babylonians went beyond recording these basic cycles. Their records helped them discover the variations in them. For instance, they recognized that the angular size of a planet's retrograde loop and the duration of the motion changes from one retrograde loop to the next. The Babylonian astronomers had tables of the major cycles and variations on clay tablets. They used these tables of periods to predict future planetary positions and retrograde motions. This procedure required no explanation of the cycles, only a knowledge of their existence over a long period.

The Babylonian astronomers also served as priests who fostered the continuity of astronomical knowledge. But religion divorced Babylonian cosmology, the grand picture of the universe, from astronomy. In the cosmic picture, the gods created, ordered, and controlled the world. These divine functions were explained in religious myths. Because tables of astronomical cycles functioned strictly for predictions and lacked any geometric or physical framework, Babylonian astronomers could predict but not explain celestial motions in terms of physical causes. They never developed actual scientific models of the heavens, just records of their patterns.

Reference: Some of the text presented above comes from article by Stacey Abrams, which appeared in THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC, Vol. 3, No. 2