A recent investigation sheds new illumination on one of the most renowned architectural marvels of antiquity. Four archaeoastronomers from premier Mexican research institutions have established that the celebrated “descent of Kukulcan” spectacle at El Castillo, the great pyramid in Chichen Itza, is not restricted to the equinoxes, as long presumed, but instead adheres to a precise, year-round solar illumination cycle that embeds the entirety of the Maya calendar within the structure’s very stonework. The findings, published in the Arqueología Mexicana journal, suggest the pyramid was conceived as a functional astronomical instrument, capable of marking every single significant solar year event.
The pyramid, also known as El Castillo or the Temple of Kukulcan, stands 30 meters high and features nine tiered bodies topped by a temple sanctuary. Its four faces each measure 55.5 meters on a side and are flanked by balustraded staircases. As the sun descends toward the western horizon, shadows cast by the pyramid’s corners fall upon the northwest ramp, creating a sequence of light triangles that cumulatively delineate the undulating form of a serpent—a hierophany recognized as the “descent of Kukulcan.”
According to the study’s authors—Orlando Casares Contreras from the INAH Center of Yucatan, Arturo Montero García from Tepeyac University, Jesús Galindo Trejo from UNAM’s Institute of Aesthetic Research, and David Wood Cano from the ENAH-UNAM Archaeoastronomy Seminar—the phenomenon commences as early as February 12th, when the first faint trace of light appears at the upper edge of the ramp. At this stage, the triangles are incomplete and last only a few moments. By March 4th, near dusk, five triangles are visible, and by March 15th, seven light triangles are projected onto the balustrade, remaining visible until sunset.
The researchers point out that the actual astronomical equinox falls precisely in the middle of this seven-triangle window, five days after the pattern first manifests and five days before the appearance of the eighth triangle on March 26th. This observation leads the team to hypothesize that the seven-triangle projection may have served as a practical means for Maya priest-astronomers to determine the equinox with startling accuracy—a conclusion that contrasts with the views of some academics who doubted whether Mesoamerican observers ever formally fixed the equinox.
The astronomical show does not conclude with the equinox. By April 9th, all nine triangles are fully formed—one corresponding to each of the pyramid’s nine terraced bodies. The triangles gradually expand over the ensuing weeks until May 24th, the date of the first solar zenith passage in Chichen Itza, at which point the entire balustrade is bathed in light. This total illumination persists through the summer solstice on June 21st and culminates with the second zenith passage on July 19th. Following this second zenith, the nine triangles begin to reconfigure, achieving their complete form again by September 2nd, before the pattern reverses as the autumnal equinox approaches. The final brief flashes of light are observed around October 29th, after which the ramp remains in shadow for exactly 52 days leading up to the winter solstice, and for another 52 days following it, until the cycle restarts on February 12th.
The significance of the number 52 in this context is deliberate. The 52-year calendrical cycle—the period whereupon the Maya’s 365-day solar calendar (Haab) and 260-day ritual calendar (Tzolk’in) realign—was one of the most sacred periods in the Mesoamerican system of timekeeping. The 52-day interval without shadows on either side of the winter solstice appears to directly encode this fundamental unit into the pyramid’s design. Thus, the archaeoastronomy embedded within El Castillo operates simultaneously across multiple calendrical strata, linking the sun’s daily movement to the deepest cycles of Maya sacred time.
The mathematical elegance of El Castillo’s design is made evident in the analysis of key numerical intervals presented in the study. The span between a solar zenith passage and the timely equinoxes is 63 days, and the interval between the timely equinox and the solstice is 28 days. Combined, these two intervals total 91 days—the exact number of steps on each of the pyramid’s four stairways. Multiplying this figure by four and adding the temple platform as the final step yields 365—the exact count of days in the solar year. The numbers 7 (the triangles marking the equinox), 9 (the pyramid’s tiered sections), and 13 (a sacred Maya number) are interconnected through the relations 63 = 7 × 9 and 91 = 7 × 13, revealing a system of extraordinary internal coherence.
The researchers conclude that El Castillo served as the Maya axis mundi, connecting the celestial realm (symbolized by the number 13) with the underworld (represented by the number 9) via the earth’s surface, where the light serpent descends to fertilize the soil. Monitoring this light regimen throughout the year by the Maya observer-priests provided not only a means to pinpoint the equinoxes but also a dependable benchmark for the agricultural and ceremonial calendar that governed Maya civilization for three millennia.
As the study authors state, “The Maya utilized their astronomical knowledge, encoded in calendrical units of measure, to achieve astonishing precision in the tracking of time.”
About the Author
