Why Did the Maya Care So Much About Predicting Venus’ Location?
published during a new moon.


Global radar view of Venus (without the clouds) from Magellan between 1990 and 1994. Credit: NASA

In 1739, the director of the Dresden Royal Library came into the possession of a mysterious tome full of tables and unknown hieroglyphics. The man he bought it from was a private owner who described the artifact only as a “Mexican book.” Nobody knows for sure how this book, now recognized as one of only four surviving pre-Columbian texts from Mesoamerica, found its way to Europe, but it would play dramatic role in shaping how Western investigators built the popular view of the Maya as a numerologically obsessed culture. Now, a new reinterpretation of a single word in this text has the potential to alter that classic view.

The Dresden Codex, as scholars now refer to it, contains an enigmatic series of pages called the “Venus table”— a collection of symbols grouped into columns and rows that appear to describe when and where Venus was visible in the sky. The interpretation of this section, made long before anyone had any idea what the hieroglyphs introducing the table actually meant, had been that it was a published correction to the Maya’s 260 day-ceremonial cycle which is based on Venus (which has a problematically irregular cycle of 583.92 days). The Maya revered the planet Venus for much of their history.


The Venus table contained within the Dresden Codex.

The assumption behind this first view (which most scholars still hold as valid) was that an ancient mathematician had calculated a way to predict the future appearance of Venus using not historical observations, but instead complex numerological techniques not actually anchored to any actual event. The purpose for such an exercise, these scholars argue, was to use Venus as a correction tool to create the most accurate calendar system possible. Scholarship on the topic since then has focused on ways to recreate the elegant formulas that would have produced these predictions.

But Gerardo Aldana, an archaeologist and Mesoamerican hieroglyph expert with a background in engineering at the University of California, Santa Barbara, thinks that this interpretation isn’t entirely accurate, and is based off of early scholars’ inability to actually read the preface to the table. In a paper published recently in the Journal of Astronomy in Culture, he argues that the main objective of the table was not to develop a hyper-accurate calendar, but instead to have an historically informed method to assure that Venus would show up in the right place when their religious ceremonies were scheduled to happen.

This revelation, he said, began with his reinterpretation of one of the Mayan words which appears most frequently in the Venus table: “K’al.” Aldana told NOW.SPACE that the word has many meanings, but that one commonly used—to bind—is both imprecise and ambiguous. Instead, Aldana argues for a different definition—to enclose. This interpretation would create a linguistic connection to a specific kind of mesoamerican ritual in which priests and dignitaries physically carry representations of various celestial deities to various altars in the cardinal directions around the center of town.


“The Observatory” building in Chich’en Itza from which a Mayan astronomer would have been viewing Venus. Credit: Gerardo Aldana.

Two other independent lines of evidence seem to support Aldana’s interpretation. The first comes from historical observations of the sky. The classical view, Aldana said, is that the Venus table is not anchored to a date, but rather grounded in time only through impressive mathematical trial and error. But according to Aldana, the preface to the table includes references to a specific observation of Venus documented in an unrelated text.

The third line of evidence comes from human—not celestial—history. The time period that this specific Venus sighting lines up with matches a 25-year period when records from the Maya city of Chichen’Itza indicate that an ancient astronomer used that city’s temple, which is full of astronomical inscriptions supporting this claim, to observe Venus. In Aldana’s interpretation, the measurement recorded in the preface to the table is from that historically recorded event, followed by the math used to correct for the irregular cycle into the future. The actual Venus table (and the codex itself), he argues, were projections written 200 years later using math derived from that earlier information.

This subtle difference paints a largely different picture of early Maya scientific inquiry, Aldana said. Where before the Codex represented a collective, faceless society able to do impressive math for—essentially—math’s sake, now it’s the story of an actual person or group of people with the ability to build off prior scholarship to find a pattern that allows them to solve a specific problem. This new view provides a picture of scientists solving a problem using an approach not at all dissimilar to medieval astronomers of ‘Western’ science who looked to the writings of Ptolemy to solve problems, he added.

But, speaking to National Geographic News’ Erik Vance, Maya archaeoastronomy expert Harvey Bricker, an emeritus professor at Tulane University, said he doesn’t think that the re-translation of a single hieroglyph should force scholars to abandon the correction equations they derived during the past century of research. He says that there are plenty of historical and astronomical reasons it is the best explanation, and that Aldana’s math would change many of the dates associated with Maya events and make the Maya calendar less precise.

Aldana, for his part, feels that the prevailing understanding of the Codex as correction for raw accuracy’s sake is a fiction that stems from researchers using heavy-handed math to force large amounts of data into a hyper-accurate fit. This, he said, has resulted in the circular logic that the Maya were obsessed with accuracy in their calendars—a defining characteristic that has resulted in an inaccurate view of Maya science that places them outside the traditions of scientific history associated with other cultures.

“When we look at previous attempts to address the Venus table, they were motivated by looking for what […] is the most accurate way to interpret these numbers to match up with reality. It was more than that; it was what were the Maya doing with this accuracy,” Aldanda explained.

“[My attempt] was really just trying to show Maya astronomers at work.”