(Revised 28 March 2024.) The Venus Tablet(s) of Ammi-şaduqa is a collection of records of this planet’s first and last observations over 21 years. Over a century ago, historians began to recognize that these records had the potential to assist researchers in determining the absolute chronology of King Ammi-şaduqa’s Babylonian Amorite Dynasty.
As an inner planet, Venus first rises in the east in the morning and remains visible each night for about eight months. Then, it later appears in the west each evening for a similar duration. This cycle lasts 583.9 days, and five cycles equal 7.994 solar years, just two days short of eight average tropical years (or 99 average lunar cycles minus four days). Thus, long-term observation records could potentially match sets of dates every eight years. However, since the Babylonian astronomers recorded the rising and setting dates using their lunar calendar, the combination of Venusian and lunar cycles fits only some multiples of eight-year cycles. Over four decades ago, astronomers proposed the starting date of Ammi-şaduqa’s reign must have been in 1702, 1646, 1582, or 1550 BCE. Historians call these models the High, Middle, Low, and Ultra-Low Chronologies. Since the formulation of these original models, astronomers have proposed variations of two models offset by eight years, specifically 1638 and 1574 BCE.
The Middle Chronology is the correct model. Although king list data between Ammi-şaduqa and his more famous great-great-grandfather Hammurabi is somewhat unreliable, a complete set of year-name records during this interim is extant. Other indirect astronomical evidence confirms Hammurabi’s reign began in 1792 BCE. (See The Six Pillars, Chapters 3 and 4, to be published soon.) Furthermore, Hammurabi’s first official year started halfway through the 17th year of Assyrian King Šamši-Adad I. Radiocarbon dating of logs associated with Šamši-Adad’s reign, dendrochronology, and related artifacts confirm the approximate accuracy of the Middle Chronology. More importantly, three astronomical records from his ruling period directly prove the precise timing of this Assyrian king’s absolute regnal period. (See The Six Pillars, Chapter 5.)
All extant copies of the Venus Tablets originated in the eighth century BCE or later. During the intervening centuries from the original observations until then, Mesopotamian astrologers repeatedly copied them and accidentally introduced many transcription errors. However, more significant problems existed. Many of the original records had delayed rising dates and early setting dates due to seasonal cloudy weather, particularly in the winter and spring. Even worse, two large volcanic eruptions affected viewing conditions, making the sky hazy. (The eruptions of Thera and Aniakchak were in 1650 and the early 1620s BCE, respectively.) The resulting poorer viewing conditions delayed observations of the rising of Venus and caused setting dates to be earlier than usual.
Neo-Mesopotamian astrologers were unaware of these problems. They must have assumed that the records that did not conform to a standard eight-year cycle of Venus were due to copyist errors. Consequently, they tried to “fix” them by calculating and inserting the correct dates. However, they had to arbitrarily choose which records they considered the most accurate and calculate earlier and later dates from them. The result is a mishmash of confused variations.
Modern astronomers have recognized that cloudy conditions offset some dates. However, they have failed to realize that volcanic eruptions seriously affected viewing conditions, especially in the early years of Ammi-şaduqa’s tenure. When they tried to determine which of the models best matched the ideal rising and setting dates of Venus, they chose to use the variant dates that seemed the most realistic. They failed to appreciate that they primarily used the later retro-calculated dates based on an idealized eight-year Venus cycle.
Thus, the Venus Tablets’ Middle Chronology Model is correct, as verified through multiple other lines of evidence. The irony is that astronomers proposed the various models over four decades ago principally based on later Mesopotamian astrologers’ retro-calculations rather than original data. Serendipitously, one of them proved to be correct.
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