Equinoctial Sun and Astronomical Alignments in Mesoamerican Architecture: Fiction and Fact

Abstract

Archaeoastronomical studies carried out during the last decades in Mesoamerica have demonstrated that civic and ceremonial buildings were largely oriented on astronomical grounds, mostly to sunrises and sunsets on certain dates, allowing the use of observational calendars that facilitated the scheduling of agricultural and related ritual activities. One of the deeply rooted but unfounded ideas is that many alignments recorded the Sun's positions at the equinoxes. By examining such proposals and analyzing their methodological flaws, I argue that they are not based on reliable and objectively selected alignment data, but rather derive from the preconceived significance attributed to the equinoxes. The most likely targets of the near-equinoctial orientations were the so-called quarter days, which occur two days after/before the spring/fall equinox and mark mid-points in time between the solstices. Considering that the astronomical alignments dominate extensive parts of the built environment, they must have played an important role in religion, worldview, and political ideology. Therefore, only a correct identification of their celestial referents, a prerequisite for any convincing interpretation of their meaning, underlying intents, and observational practices employed, can contribute to a proper understanding of some prominent aspects of architectural and urban planning in Mesoamerica.

The archaeoastronomy of Tikal: A reanalysis

“…In conclusion, this reanalysis of the archaeoastronomy of Tikal compared, contrasted, and (using tools provided by Google Earth Pro) corroborated the field measurements of two earlier studies, those by Aveni & Hartung (1988) and Šprajc & Richter (2014). It provided a dynastic and historical context unavailable to Aveni & Hartung (1988) at their time of writing and highlighted recent insights as to the unique worldview and orientation patterning used by the Maya as demonstrated by Šprajc (2005, 2021a, 2021b). Locations for the construction of public ceremonial architecture were carefully selected and oriented in relation to astronomical and calendrical conditions by an elite group possessing a required, and quite possibly secretive, esoteric knowledge.…”

“…Our own measurements from Temple I to Temple III using Google Earth Pro yield an azimuth of 270° (Figure 6). When viewed in this direction, the declination corresponds to the positions of the setting Sun on the quarter‐days of the year which marks the temporal mid‐point between solstices (Šprajc 2021a, 2021b).…”

“…Aveni & Hartung (1988) suggested that the alignment between Temple I and Temple III pointed to the setting equinox Sun. Šprajc (2021a) notes “it can hardly be related to the equinoxes because the equinoctial sunrises or sunsets along this alignment could have been observed only on the natural horizon (with an altitude of about 0°) … due to their heights, both temples mutually block the view to the horizon”. Instead, this alignment marks the “quarter day” which is the temporal mid‐point between solstices.…”

“…The first, by Aveni & Hartung (1988), examined the spatial inter‐relationship between Temples I, II, III, and IV of Tikal's central district, and speculated upon the dynastic relationship of their patrons. These spatial relationships were remeasured and reanalyzed by Šprajc (2021a, 2021b) and Šprajc & Richter (2014) in terms of solar alignment to important day‐pair intervals of the Maya ritual calendar. In recent years, archaeoastronomers have been leveraging the power of Virtual Globe software, such as Google Earth Pro, to access the potential of measuring azimuths of ancient structures remotely (Belmonte et al, 2009; Magli 2016; Romain 2022).…”

Origins of Mesoamerican astronomy and calendar: Evidence from the Olmec and Maya regions

“…The next basic references in time computations must have been the quarter days: falling 1 or 2 days after/before the spring/fall equinox, they divide each half of the year delimited by the solstices in two equal parts. While there is no compelling evidence that the Mesoamericans were aware of the equinox as defined by modern astronomy ( 30 ), the importance of the solstices and quarter days is attested by architectural orientations throughout Mesoamerica ( 4 ).…”