Tzab

Tzab is the Maya name for the Pleiades and it means the rattle of a rattlesnake. The identification is one of the easier ones to accept on sight: the cluster is a small tight group of faint points, and the segments of a rattle are a small tight group of pale rings.

The rattlesnake is not merely a hazard in Maya thought. It appears in iconography with feathers, in the sky, and in association with rain and with the ancestors, and putting its rattle overhead places the animal there by implication, its body running along the sky.

The cluster's zenith passage is one of the events Mesoamerican observers tracked deliberately. At the latitude of much of the Maya area the Pleiades pass directly overhead, and the passage falls near the beginning of the rainy season, which makes it agriculturally useful in the same way the Arabian and Polynesian uses are.

The Aztec use of the same cluster is better documented and is more dramatic. The New Fire ceremony at the close of the fifty-two year calendar round turned on the Pleiades crossing the zenith at midnight, which was taken as the sign that the world would continue, and fires across the empire were extinguished and relit from a single new one.

Maya astronomy was accurate, sustained and written down, and it was aimed at prediction rather than at explanation. The Dresden Codex contains a Venus table tracking the planet's synodic cycle over centuries with a correction mechanism, and an eclipse table giving the intervals at which a solar eclipse is possible. Neither is a model of what the planets are; both work.

Venus mattered most. Its appearances as morning star were tied to warfare and to the taking of captives, and inscriptions record campaigns timed to them. That is astronomy as statecraft, and the tables were maintained because getting the date wrong had consequences.

The sky figures themselves are less well recovered than the tables. Tzab is secure, the peccaries at Gemini and a turtle at Orion's belt are reasonably so, and beyond that the reconstruction is thin, partly because the codices were burned. Three or four survive out of what must have been a substantial library, and Diego de Landa, who burned them at Mani in 1562, also wrote the account that made much of the script decipherable four centuries later.

The atlas records the figures that are secure and does not fill the gaps. A Maya sky reconstructed to look as complete as the Greek one would be mostly invention.