Of all the world's ancient calendar systems, the Maya and other Mesoamerican systems are the most complex, intricate and accurate. Calculations of the congruence of the 260-day and the 365-day Maya cycles is almost exactly equal to the actual solar year in the tropics, with only a 19-minute margin of error.
Maya astronomer-priests looked to the heavens for guidance. They used observatories, shadow-casting devices, and observations of the horizon to trace the complex motions of the sun, the stars and planets in order to observe, calculate and record this information in their chronicles, or "codices". From these observations, the Maya developed calendars to keep track of celestial movements and the passage of time. The Maya also kept detailed records of the moon, although these do not seem to constitute a formal lunar calendar.
With the aid of a forked stick, astronomer-priests used only the naked eye to take observations that allowed them to calculate the path of Venus and other celestial bodies. From the records of their observations they could calculate with precision events such as solar eclipses.
In Maya cities, ceremonial buildings were precisely aligned with compass directions. At the spring and fall equinoxes, for example, the Sun might be made to cast its rays through small openings in a Maya observatory, lighting up the observatory's interior walls.
Other alignments might relate to the exteriors of temples and palaces.
The most famous example of this kind of alignment can be observed at Chichén
Itzá, the principal Maya city of the
Yucatán Peninsula. People
still gather there each year, as they have for
centuries, to observe the sun illuminate the stairs of a pyramid
dedicated to Quetzalcoatl, the Feathered Serpent god. At the vernal and
autumnal equinoxes, the Sun gradually illuminates the pyramid stairs and
the serpent head at its base, creating the image of a snake slithering
down the sacred mountain to Earth.
Why did the Maya go to such lengths to align their ceremonial plazas and temples with the Sun and stars? In part, it was to venerate the gods. Pacal's tomb in the Temple of the Inscriptions at Palenque, for example, is aligned with the Sun. At winter solstice, the Sun sets behind the high ridge beyond the temple, in line with the centre of the temple roof. As the Sun crosses the sky, it enters a doorway in the temple, hits the back wall and, as it heads for the horizon beyond the temple, appears to descend the temple stairway into Pacal's tomb. Pacal's death and entry into the Underworld are thus equated with the Sun's death and entry into the Underworld.
The Maya built observatories at many of their cities, and aligned important structures with the movements of celestial bodies. Some of these are temple groupings, such as a group of three at Uaxactún, which marks the Sun's rising position at summer solstice, the two equinoxes and winter solstice. Architecture such as the Caracol at Chichén Itzá was also aligned with the appearance of celestial bodies such as the Pleiades and Venus. Another temple at Uxmal contains hundreds of Venus symbols.
Astronomical metaphors and celestial events defined the ritual landscape for Maya rulers. Transfers of royal power, for example, seem to have been timed by the summer solstice at certain centres. At Palenque, an inscription notes that Pacal's son Chan-Bahlum dedicated the Cross Temple grouping on July 23, 690 - timed to coincide with the conjunction of Jupiter, Saturn, Mars and the Moon. To the Maya, this event may have represented the primordial birth of the three ancestor gods of the Palenque dynasty with the First Mother (the Moon), and would have been an appropriate moment to consecrate an accession monument.
Maya murals and carvings show rulers wearing symbols of the heavens, including a belt or sky-band made of a chain of symbols relating to the Moon, the Sun, Venus, day, night and the sky. Rulers are also depicted carrying bars decorated as sky-bands to indicate that they had the mandate of heaven. Sometimes they are seated, surrounded by a sky-band which gives the ruler a halo of celestial authority. Rulers also liked to associate themselves with auspicious gods of the sky such as the Sun God, and Maya rulers and priests in real life often "clothed themselves with the heavens" by dressing in the pelt of the jaguar, whose spots were taken to represent the stars.
The Maya believed that the gods guided the Sun and Moon across the sky. Even in the darkness of night, the Maya believed that the Sun and Moon continued to journey through the Underworld, threatened all the way by evil gods who wanted to stop their progress. For this reason, the Maya believed that the heavenly bodies needed human help, which was provided through sacred rituals such as self-mutilation, torture, and human sacrifice. To the Maya, offering this help was simply the price to be paid for the continued survival of the universe. Death from such rituals was a privilege, and conferred immortality on those who died, or who offered themselves as victims.
The repeating cycles of creation and destruction as described in Maya mythology were a reminder of the consequences if humans neglected their obligations to the gods. Humans had an inherent responsibility to the gods who made humanity's continued existence possible. According to the Maya sacred calendar, each 52-year period signalled the renewed possibility of the destruction of the world. This was seen as a frightening time when the gods and other forces of creation and chaos would do battle in the world of mortals, determining the fate of all earthly creatures.
The planet Venus was particularly significant to the Maya; the important god Quetzalcoatl, for example, is identified with Venus. The Dresden Codex, one of four surviving Maya chronicles, contains an extensive tabulation of the appearances of Venus, and was used to predict the future. The Maya also went to war by the sky, again triggered by the planet Venus. Venus war regalia is seen on stelae and other carvings, and raids and captures were timed by appearances of Venus, particularly as an evening "star". Warfare related to the movements of Venus was, in fact, well established throughout Mesoamerica.
Maya calendars, mythology and astrology were integrated into a single system of belief. The Maya observed the sky and calendars to predict solar and lunar eclipses, the cycles of the planet Venus, and the movements of the constellations. These occurrences were far more than mere mechanical movements of the heavens, and were believed to be the activities of gods replaying mythical events from the time of Creation.
Calendar priests still exist in Maya regions today, and keep the 260-day Sacred Round count for divination and other shamanistic activity. Many of the components of this belief system originated in the sky, but were manipulated on Earth by astronomer-priests who applied the sacred structure of the cosmos to affairs on Earth.