Inanna, Ishtar, and the Oldest Planetary Records

Venus carries the longest documented history of any planet. The Venus tablet of Ammisaduqa, a Mesopotamian record of the risings and settings of the planet over twenty-one years, is one of the earliest surviving astronomical texts and is still used in the argument over Babylonian chronology. The planet was Inanna in Sumer and Ishtar in Akkad, a goddess of both love and war whose descent into the underworld and return was read against the planet's disappearance and reappearance; the double character, gentle and violent, belongs to the planet from the beginning and is not a later complication. The Greeks called the morning star Phosphoros and the evening star Hesperos before recognising them as one body, a recognition later Greek writers credited to Pythagoras or to Babylonian informants. In Mesoamerica the Dresden Codex contains a detailed Venus table, and Venus there was associated with war and with the taking of captives.

The Venus tables of both traditions rest on one number. Venus returns to the same phase relative to the Sun every 583.92 days, and five of those synodic periods come to 2,919.6 days, within two and a half days of eight tropical years. The planet therefore repeats its pattern of appearances against very nearly the same calendar dates on an eight year cycle, and successive conjunctions fall at five points evenly spaced around the zodiac, tracing the figure often called the Venus pentagram. The Mesoamerican Venus round of 584 days is that same synodic period rounded to a whole number, which is why the Dresden Codex table works and why it needed periodic correction.