The Maya developed one of the most sophisticated astronomical systems of antiquity, without the aid of telescopes or optical instruments. Their meticulous observation of the sky over centuries allowed them to create calendars of remarkable precision and predict celestial events with impressive accuracy.
Unlike Western astronomy, which gradually separated science and religion, Mayan astronomy was inseparable from their cosmovision. The sky was not merely an object of study, but a sacred book where divine wills and life cycles were read. Each celestial body had religious, agricultural, and political significance. This holistic approach enabled them to calculate the cycles of Venus with an accuracy of 0.01 days and predict eclipses decades in advance. These predictions were based on the cyclical repetition of celestial configurations, rather than the exact geometric modeling of trajectories as in modern astronomy.
N.B.:
The Maya were a great Mesoamerican civilization between 2000 BCE and the 16th century. Organized into independent city-states, they distinguished themselves by an advanced hieroglyphic writing system, high-precision astronomy, a complex calendar, and monumental architecture based on geometric and astronomical principles.
The Mayan calendar system was based on several interlocking cycles, the two main ones being the Tzolk'in and the Haab. The Tzolk'in, a ritual calendar of 260 days, combined 13 numbers with 20 day signs. The Haab, a solar calendar of 365 days, included 18 months of 20 days plus 5 unlucky days called Wayeb.
The interweaving of the Tzolk'in and the Haab created a cycle of 52 years before the same date combinations reappeared. The Maya attributed considerable ritual value to this arithmetic cycle, seeing it as periods of cosmic transformation requiring great celebrations.
For long historical periods, the Maya used the Long Count, a base-20 numbering system (with an exception for the third level, which used 18) that allowed counting days from a mythical creation date set at August 11, 3114 BCE according to the most accepted correlation. This system used five units:
| Period | Scientific Contribution | Precision or Characteristic | Source or Site |
|---|---|---|---|
| Late Preclassic (300 BCE - 250 CE) | Development of the Tzolk'in and Haab calendars | Cycles of 260 and 365 days | Inscriptions at El Mirador, Kaminaljuyú |
| Around 36 BCE | Oldest known Long Count date | Dating system over several millennia | Stela 2 of Chiapa de Corzo |
| Around 350 CE | Invention of the mathematical zero | Represented by a shell-shaped glyph | Mayan numeral system |
| Classic (250-900 CE) | Calculation of the tropical year | 365.2420 days (error of 0.0002 days) | Observations at multiple sites |
| Classic (250-900 CE) | Measurement of the synodic cycle of Venus | 583.92 days (error of 0.01 days) | Dresden Codex, inscriptions |
| Classic (250-900 CE) | Calculation of the synodic lunar month | 29.53 days (error of 0.0006 days) | Dresden Codex |
| Around 682 CE | Astronomical observatory of El Caracol | Alignments on Venus and solar events | Chichen Itza |
| Classic (250-900 CE) | Eclipse prediction tables | Use of the Saros cycle (6,585.32 days) | Dresden Codex |
| Around 750 CE | Observatory of Group E | Markers of solstices and equinoxes | Uaxactun |
| Postclassic (900-1500 CE) | Pyramid of Kukulcan | Serpent phenomenon during equinoxes | Chichen Itza |
| 12th-13th century | Writing of the Dresden Codex | Venus tables over 104 years, eclipses over 33 years | Yucatán (probably Chichen Itza) |
Source: Foundation for the Advancement of Mesoamerican Studies and Mesoweb Resources.
Mayan astronomers had calculated the length of the solar year with remarkable precision. Their observations, recorded in various codexes, indicate that they estimated the tropical year at about 365.2420 days, a value extremely close to the modern measurement of 365.2422 days. This precision is all the more impressive as it was achieved without sophisticated measuring instruments, solely through patient observation and meticulous recording of solar positions during solstices and equinoxes.
Many Mayan sites featured architectural structures specially designed to mark these astronomical events. At Chichen Itza, the pyramid of Kukulcan creates a play of shadows and light during the equinoxes that draws a serpent descending the stairs, demonstrating the perfect integration of architecture, astronomy, and religious symbolism. At Uaxactun, the Group E complex served as a solar observatory, allowing the precise determination of the dates of solstices and equinoxes.
N.B.:
The codexes of the Mayan civilization are accordion-folded manuscripts, made from amate paper, where lunar ephemerides, synodic cycles of Venus, and tables for predicting eclipses and conjunctions are compiled. Despite massive destruction in the 16th century, a few codexes have been preserved.
The Maya had identified Venus as a planet and not a star, and they had determined its synodic cycle with astonishing precision: 583.92 days, while the modern value is 583.93 days.
The Dresden Codex, one of the few Mayan manuscripts to survive colonial destruction, contains astronomical tables of Venus spanning 104 years. Based on the synodic cycle (same Earth-Venus-Sun configuration) of 583.92 days, these tables allowed the precise prediction of Venus's appearances as the morning star and evening star, moments considered particularly auspicious or inauspicious for various activities, especially war.
The Maya had observed that 5 synodic cycles of Venus (2,920 days) corresponded almost exactly to 8 Haab years (2,920 days) and 146 Tzolk'in cycles (2,920 days). This triple correspondence demonstrated, in their cosmological vision, the deep harmony of the universe and justified the importance given to Venus in their rituals and political decisions.
Venus was associated with the god Kukulcan (the feathered serpent), and its first appearance after inferior conjunction (when it passes between Earth and the Sun) was considered a moment of danger and renewal.
N.B.:
The synodic cycle of Venus of 583.92 days corresponds to the time needed for the planet to return to the same configuration relative to Earth and the Sun. This cycle is divided into four phases: Venus appears as an evening star for about 263 days (visible after sunset), then disappears for 50 days during the superior conjunction (Venus behind the Sun), reappears as a morning star for 263 days (visible before sunrise), and disappears again for 8 days during the inferior conjunction (Venus between Earth and the Sun). The Maya attached particular importance to the first heliacal appearance of Venus as the morning star, a moment considered particularly dangerous and unfavorable for warlike undertakings.
The Maya also followed lunar cycles with great attention. They had calculated the duration of the synodic lunar month at about 29.53 days, a value very close to the modern measurement of 29.53059 days. The Dresden Codex contains eclipse tables covering 33 years, allowing the prediction of solar and lunar eclipses with remarkable precision.
To predict eclipses, Mayan astronomers used the Saros cycle (independently discovered by several civilizations), lasting 6,585.32 days (about 18 years and 11 days), a period after which the Sun-Earth-Moon configurations repeat in a similar manner. Eclipses were considered particularly alarming events. A solar eclipse was seen as a celestial jaguar devouring the Sun, while a lunar eclipse was caused by a serpent attacking the Moon.
Several Mayan sites featured structures dedicated to astronomical observation. The Caracol of Chichen Itza, whose Spanish name means "snail" due to its internal spiral staircase, is one of the best-preserved observatories. Its windows and openings are aligned with key astronomical positions, particularly the setting of Venus at its maximum elongation.
At Palenque, the Temple of the Inscriptions and other structures have architectural alignments that mark the winter and summer solstices. At Copán, Stela 12 and other monuments were positioned to observe the Sun's passage at the zenith, an event particularly significant for populations located between the Tropics of Cancer and Capricorn.
These observatories were not merely scientific tools but sacred places where priest-astronomers performed their religious and political functions. Access to this astronomical knowledge was reserved for an elite, thus reinforcing their power and authority over the population.
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