In a cosmovision that is based on polar opposites – complementary opposites -- the pair day/night holds a central position. Although these depend on the alternation between the Sun and the Moon, both day and night are specific moments, each one with its own time-space, means of organization and measurement, systems of representation and, of course, characteristic inhabitants. In spite of their particular features, they communicate and change places during their transitions. The Sun and the Moon have been subjects of many symbolic representations, from myths, rituals, sculptures and the layout of cities, where fundamental spaces were designated to study the celestial sphere.
Since time immemorial, celestial observation has been a cultural and historical practice in both prehispanic and contemporary societies. The Moon, mistress of the night, rules when the sun disappears to the west, therefore bringing about primordial chaos. Knowledge of the lunar movements enabled cultures to create calendars related to the growth of vegetables and eclipses. The observers of the sky also recorded other astronomical phenomena, such as the cycles of Venus and the Pleiades. The importance of the Sun’s journey through the sky is seen in the calendar systems organized according to seasonal cycles, as well as in following the Sun’s rising and setting at key times of the year, such as the solstices and equinoxes.
In antiquity, celestial observers were able to identify the movement of certain bodies near the horizon with stationary or manual instruments made of sticks or crossed bars. Other ways to record the Sun’s passage used shadows projected onto vertical objects – like ritual stelae or columns – or in underground observatories, where calculations were made by projecting a beam of light through a vent or a hole in the ceiling, lighting up an object or the surface inside the cave. Water, pyrite and obsidian mirrors were also used to capture the light of the Sun and the Moon.