Mayan calendars were kept by specialists known as “diaries,” a cultural tradition that continues today. There is general agreement that eclipses were important to the Mayans. “They tracked them down, they had rituals around [eclipses]“And it was built into their belief system,” Lowry told Ars. “So we know that the eclipse table is part of the cultural knowledge of the time. “We were just trying to figure out how the table ended up in its current state.”
Predictive mechanism
Lowry and Justeson's analysis involved mathematical modeling of eclipse predictions in the Dresden Codex table and comparing the results to NASA's historical database. They focused on 145 solar eclipses that could be observed in the Mayan geographic region between 350 and 1150 AD.
First published in 1810 by Alexander von Humboldt, who recolored five pages for his atlas.
Credit: Public Domain
They concluded that the Codex eclipse tables were derived from a more general table of successive lunar months. The length of the 405-month lunar cycle (11,960 days) corresponded much better to the 260-day calendar (46 x 260 = 11,960) than to the cycles of solar or lunar eclipses. This suggests that the Mayan day keepers figured out that the 405 new moons almost always correspond to 46 periods of 260 days. The Mayans used this knowledge to accurately predict the dates of full moons and new moons for 405 consecutive lunar dates.
Daytime observers also realized that solar eclipses seemed to repeat on the same day or nearly the same day in their 260-day calendar, and over time figured out how to predict the days on which a solar eclipse might occur locally. “A“An eclipse only occurs at a new moon,” Lowry said. “The fact that it has to be a new moon means that if you can accurately predict a new moon, you can accurately predict the one in seven chance of an eclipse. That's why it makes sense that the Mayans would revise their moon prediction models to get an accurate eclipse, because they don't have to predict where the moon is relative to the ecliptic.”
The Mayans also realized that they had to adjust their tables from time to time to account for variations over time. “When we talk about accuracy, sometimes we think about being able to predict something down to the microsecond,” Lowry said, pointing to NASA records. “The Mayans have a very accurate calendar, but they predict to the day, not to the second.”
