astronomy: The Americas The Latin literary tradition also includes astronomical material, with Roman writers adapting it to their own cultural and social contexts The poet Virgil (70–19 b.c.e.) bases parts of his Georgics on the Greek agricultural poem Works and Days of Hesiod (late eighth century b.c.e.), a major source for early Greek observational astronomy Political elements appear in the Georgics as well For example, Virgil suggests that the origin of the constellation Libra derives from cosmic support for the emperor Augustus Ovid, too, incorporates into his epic Metamorphoses elements from the account of the beginnings of the universe in Hesiod’s Theogony A number of tales in Ovid’s works also recount instances of catasterism, the transformation of a mortal into a star, constellation, or other celestial object This concept was not restricted to myths, for at the very end of the Metamorphoses, Ovid describes the ascent of Julius Caesar’s spirit as a comet, known as the Sidus Iulium (“Julian Star”) Ovid also wrote in praise of astronomers in his Fasti (Festivals), a poem explaining the myths associated with the traditional Roman calendar Popular handbooks of astronomy appear during the Roman period While many were in Greek, such as that of Geminus (ca 110–40 b.c.e.), the De astronomia (Concerning Astronomy) of Hyginus (early first century c.e.) was an important Latin work In addition to outlining the basics of astronomy, the author retells from Greek sources the myths related to the constellations Vitruvius (late first century b.c.e.) includes an account of the heavens in his work on architecture Another important figure was Pliny the Elder (24– 79 c.e.), whose second book of the Naturalis historia (Natural History), preserved for later ages valuable information about the scientific astronomy of the day THE AMERICAS BY J J GEORGE Most ancient American cultures paid attention to what was happening in the sky The periodic cycles of the sun, moon, stars, and planets, being reliable and predictable, allowed for the development of the calendar Broadly speaking, astronomy was one area that contributed to a greater Mesoamerican cosmology, and subsequent uses helped define and order such areas as agriculture, site orientation, astrology, myth, shamanism, divination, and even warfare Our best astronomical data come from successful early agricultural cultures in Mesoamerica—the Olmec of the Gulf Coast of Mexico (1500–400 b.c.e.), the Zapotec of the Valley of Oaxaca at Monte Albán (600 b.c.e.–900 c.e.), and the inhabitants just outside the Basin of Mexico at Teotihuacán (1 b.c.e.–650 c.e.) The Classic Period Maya (200–900 c.e.), building upon earlier Mesoamerican thought, established the clearest astronomical record Astronomy in the ancient period focused on horizon and zenith events of the rising and setting sun, moon, planet Venus, and star cluster Pleiades and on the sacred four cardinal directions 133 The beginnings of the Mesoamerican calendar signified the first concrete astronomical achievement A carved stela, or upright stone, from La Mojarra on Mexico’s Gulf Coast (150 c.e.), exhibits in hieroglyphic form the beginnings of a solar 365-day calendar When used in tandem with a unique 260-day sacred calendar (called the Tzolkin), like a system of interlocking cogwheels, this stela established everything in the Mesoamerican world, from agricultural rites to ritual and religious ceremonies to feasts and the inauguration of New Year This stela also records a hieroglyph for Venus as well as a date that correlates with a visible solar eclipse The Mayans later developed an extraordinarily accurate Venus table as well as an eclipse table that accurately predicted the occurrence of those celestial events Mesoamerican site orientation, the layout of a particular ritual site or city across the landscape, often had astronomical significance For example, a structure referred to as Building J at Monte Albán strongly suggests an astronomical relationship Building J is unique in that it is roughly pentagonal (with a “pointer” side and a stairway side) and set considerably askew (nearly 45 degrees) from the general site orientation Recent research suggests that Building J aligns with another building (Building P) to form a sightline that extends to the horizon point where the rising star Capella announces the solar zenith passage Similarly, Building J aligns with a neighboring site, Caballito Blanco, which has a similar skewed building A straight line between the two coincides with the sunset position on the horizon on the day of the solar zenith passage, when at local noon the sun is directly overhead and casts no shadow of perfectly vertical structures In the opposite direction the line marks the sunrise azimuth on the morning after the antizenith (nadir) passage, when the sun is directly below at local midnight It has been suggested that Building J was a calendar temple, a structure that embodied numerology and astronomy and permitted Mesoamericans to create their interlocking calendars By 550 c.e Teotihuacán, northeast of modern-day Mexico City, was the sixth-largest city on the planet, with an estimated population between 125,000 and 250,000 The Aztecs later called Teotihuacán the place where time began and centered their origin myths there Astronomical alignments were used at Teotihuacán for overall site orientation and to orient more specific dates related to agriculture and the sacred calendar The overall orientation of its grid pattern falls within what is often referred to as the 17-degree family of orientations, a group of orientations widely distributed throughout Mesoamerican sites with axes typically 15 to 18 degrees clockwise from the cardinal directions Punctuating the grid of Teotihuacán is a large, flat-topped pyramid called the Pyramid of the Sun (a second pyramid on the site is called the Pyramid of the Moon; both names are attributed to the later Aztec) and a ceremonial structure called the Ciudadela, both skewed approximately 15.5 degrees and