Dresden Codex Maya Solar Eclipse Table May Finally Be Decoded

A medieval Maya document used to forecast solar eclipses has baffled Western scholars for centuries. Now, two researchers may have worked out how it was actually intended to function.

Indigenous societies in Mexico and Guatemala maintained calendars for over two thousand years before Europeans invaded the Americas. These systems enabled them to determine the timing of significant events in the sky and on Earth with remarkable precision.

Much of this expertise - together with the writings that recorded it - was lost during the Spanish Inquisition. Only scattered remnants remain from which these sophisticated techniques for predicting celestial events can be reconstructed.

The Dresden Codex and Maya solar eclipse prediction

Created in the 11th or 12th century, the Dresden Codex is one of just four hieroglyphic Maya codices that survived European colonisation.

This bark-paper codex consists of 78 accordion-folded pages. Every page was written and illustrated by hand in vivid colour, covering astronomy, astrology, the seasons and medical knowledge.

Forecasting solar eclipses - when the Moon blocks the Sun's light and throws a shadow across Earth's surface - was a matter of great importance in Maya society, whose organisation and activities centred on celestial events.

"If you kept accounts of what happened at the time of certain celestial events, you could be forewarned and take proper precautions when cycles repeated themselves," explained University of Texas historian Kimberley Breuer in an article for The Conversation.

For example, when the Moon concealed the Sun and darkened the daytime sky, Maya nobles performed bloodletting rituals intended to offer strength to the Sun god.

"Priests and rulers would know how to act, which rituals to perform and which sacrifices to make to the gods to guarantee that the cycles of destruction, rebirth and renewal continued," Breuer explained.

How the Maya eclipse table may have worked

One table in the Dresden Codex enabled Maya calendar experts, called "daykeepers", to anticipate eclipses across roughly 700 years. It covers 405 lunar months (11,960 days), although precisely how it was used has remained unclear - until now.

Linguist John Justeson of the University of Albany in the US and archaeologist Justin Lowry of the State University of New York at Plattsburgh set out a persuasive account of the calendar's intended operation in a new Science Advances paper.

Justeson and Lowry challenge the established idea that the table was restarted at its last position - in other words, that it was designed as a continuous cycle returning to month 1 after month 405.

The problem is that the table does not work properly when applied in this manner.

"Unanticipated eclipses could occur in the application of the next table or two if the final station of one table was used as the base for composing the next, and increasingly with each successive resetting," Juteson and Lowry write.

They instead suggest beginning a successor table in the 358th month of the existing one. Under this system, its forecasts for the alignment of both the Sun and Moon run only around 2 hours and 20 minutes early.

"This procedure would also entail that, occasionally, the first date in a successor table would be set at the 223rd month, about 10 hours and 10 min later relative to that alignment, to adjust for the gradually accumulating deviations of resettings at month 358," the authors write.

Accuracy across centuries

When the researchers compared the table against modern understanding of eclipse cycles, they found that this approach would have allowed the Maya to predict accurately every solar eclipse visible in their territory between 350 and 1150 CE. It accounts for the minor inaccuracies that build up with time.

"Such revisions would maintain the viability of the table indefinitely, with departures of under 51 min over 134 years," the authors note.

The findings offer a compelling view of the Maya daykeeper's vital role, as well as of the advanced mathematics developed to support this lost civilisation's spiritual relationship with the cosmos.

The research was published in Science Advances.