134 astronomy: The Americas 16.5 degrees clockwise from the cardinal directions, lining up with certain mountain peaks that could have been used as natural markers of sunrises and sunsets on significant dates These dates were necessary for predicting important seasonal changes and for efficiently scheduling corresponding agricultural activity For example, in the first century c.e these alignments would have recorded sunrises on February 11 and October 29 and sunsets on April 30 and August 13 The intervals from February 11 to October 29 and from August 13 THE NAZCA LINES First located in the 1920s from aerial reconnaissance, the Nazca Lines have prompted debate, speculation, and confusion over what exactly they represent Created by the Nazca culture (1–700 C.E.) across a 130square-mile swath of desert tableland on the central Peruvian coast, the lines are made by displacing dark stones from atop lighter ones Created over many hundreds of years, the more than 1,000 miles of lines consist of overlapping, radiating lines and trapezoids and immense figures of animals, humans, plants, and objects (including a monkey, a dog, a killer whale, lizards, birds, a tuber, geometric figures, and even a fantastic figure often referred to as the Martian) The span of a hummingbird image is greater than the length of five jumbo jets One line goes perfectly straight for 13 miles Theories have linked the lines to pilgrimages, water rituals, astronomical alignment, ceremonial walkways, and religious activity tied to ensuring a good harvest Modeling the lines with the aid of computerized mapping in reference to celestial positioning has shown that twice as many astronomical alignments show up than would be expected from pure chance Furthermore, prominent archaeoastronomists (scholars who combine astronomy and archaeology to study ancient civilizations) have used computer analysis to show that many lines point to the sun’s position on the horizon during the time of year when the rains begin The immensity of the lines prevents them from being viewable on the ground, automatically orienting them to the celestial world above, where a shaman, or holy man, in bird form might have been the intended audience Although their overall meaning is still debated, most theories involve the idea of repeated ritual action Where some of the rituals are tied to water and thus to agriculture and seasons, simply by raising one’s head one connects the lines at one’s feet to the horizon and eventually to the rising sun and stars to April 30 are exactly 260 days, again coinciding with the 260-day sacred calendar The 260-day period is also tied to the human gestation period, the time from the first missed menstrual flow to birth, thereby connecting the functional aspect of the calendar to the birth cycle as well as to agriculture, ritual, and urban planning The astronomical record for North and South America in the ancient period suffers from a lack of hard data Data for later periods are much more convincing Some evidence does suggest, however, that ancient North American mound builders used the star group Pleiades as a celestial template for particular clusters of conical mounds in the Midwest, such as burial mounds and earthworks at Poverty Point, Louisiana (1600–1300 b.c.e.); Adena burial mounds in Ohio, Kentucky, and West Virginia (1000 b.c.e.–200 c.e.); and Hopewell mounds in southern Ohio (200 b.c.e.–400 c.e.) The Pleiades were important, especially in northeastern North American latitudes, because their horizon cycle corresponds to the limits of the frost-free zone and thus helped define the growing season once agriculture became common The medicine wheels left by the nomadic Indians of the Great Plains are thought to have astronomical significance, though the exact use is unclear Medicine wheels are enigmatic large patterns of linear stone alignments, many of which have the appearance of a spoked wheel Often the spokes, or rays, point to the horizon and mark points of the summer solstice sunrise, the winter solstice sunrise, or the rise of the star Sirius Various examined sites, such as those at Majorville in Alberta, Canada, and Moose Mountain in Saskatchewan, show evidence of use dating back to 2500 b.c Many of the medicine wheels are thought to exist from later periods In South America a clearer data record exists for the Inca (1438–1534 c.e.) than it does for earlier cultures, such as those at Chavín de Huántar (900–200 b.c.e.), Paracas (600–175 b.c.e.), and Nazca (1–700 c.e.) The most suggestive early astronomical possibility comes from the Nazca culture, which created the Nazca Lines with some possible astronomical significance in mind Shaman imagery on textiles from the Paracas culture suggests at least an affinity for connecting the earth and the heavens through visual iconography, or symbolism Architectural remains at Chavín de Huántar show a solar east-west axis that conflates architecture, human ritual, and cosmological associations A corresponding north-south axis is suspected, thereby symbolizing all four cardinal directions More research needs to be undertaken to establish a clearer record for the relationship of astronomy to these sites See also agriculture; architecture; calendars and clocks; cities; climate and geography; death and burial practices; hunting, fishing, and gathering; inventions; literature; numbers and counting; religion and cosmology; sacred sites; science; seafaring and navigation; weights and measures; writing