Inca astronomy
The Inca empire, the largest in the New World before the European invasions, was a powerful social structure centred on the city of Cuzco in the Peruvian Andes, although it encompassed an area of over 375,000 square miles. Its impressive legacy, including the structures at Machu Picchu tends to hide the fact that, in fact, it only lasted around one century until the Spanish conquest in the 16th century CE. Astronomy was a very important part of the culture, probably because of the importance of agriculture to the empire. In addition to its practical uses, astronomy was also the source of a number of powerful gods who, by controlling the weather, health, fertility and time itself, were believed to hold the fate of the empire in their hands.
Like ancient Egypt and India, Inca astronomy was horizon-focussed with the most important events involving certain risings and settings of the Sun, Moon and stars. The rising of Pleides signalled the start of the Inca year. The Sun was central to Inca astronomy and the basis of the Inca calendar. They built carefully positioned sets of pillars on hills overlooking Cuzco and when the Sun rose or set between certain ones at different times of the year, it was time to start planting crops at particular altitudes. Venus was regarded as a servant of the Sun, always nearby and ordered either to go ahead in the evening, or follow in the morning. The Sun was also the focus of their observatories, which captured the first and last rays through specifically designed and placed windows. The main observatory was the ‘golden enclosure’. Covered in gold, it also contained a gold sun disc which faced the rising Sun. This was one of the sites whose gold was pillaged by the Spaniards.
At Machu Picchu there is a Temple of the Sun located in the most sacred and private area of the city. Unlike the pillars overlooking Cuzco, this was small, and only open to a small number of astronomers. The shadow cast on a central rock by a plumbline marked the path of the Sun throughout the day and the year (a shadow clock), but was particularly important in marking the winter solstice, the start of the coming summer and another agricultural year.
Aztec astronomy
Like other Meso-American peoples, the Aztecs tracked the movements of the celestial bodies, work done mostly by nobles and priests. Some of the religious rituals deemed necessary to keep the Sun on its course and the Earth bountiful involved blood sacrifices. As the ancient Egyptians did independently millennia earlier, the Aztecs orientated plans for cities and important buildings along lines determined by the tracks of the Sun, Moon, planets and stars. Equinoctial lines were particularly important. In addition to regular celestial cycles, the Aztecs also observed eclipses and comets, seeing them as sources of omens. For example, the comet seen by Montezuma prior to the Spanish invasion was interpreted as a forewarning of impending crisis.
Unlike the Incas, Aztec astronomy was mostly undertaken for religious and ritual purposes, although it is likely that their 365-day solar calendar was also used for agricultural purposes. The Aztec calendar was a complex one, based on the earlier Mayan calendar. A 260-day ritual calendar counted days for religious purposes, while the 365-day calendar counted the years. The Aztec year consisted of 18 months of 20 days each, each month having a specific name. An additional 5 sacrificial days made the total of 365. The start of each of these aligned on a 52 year cycle, effectively an Aztec century, the change from one to another a time of important religious festivals.
All these cycles are included in the large, round stone Aztec Sun Calendar. Weighing 24 tones, it was 12 feet in diameter and 3 feet deep. At the centre was the face of the Aztec sun god. This was then surrounded by circles containing information including months, days etc. Each day of the 20-day month was represented by an object from nature or from everyday life eg. snake, wind, house. In a system reminiscent of the Mayans, the calendar told them that they were living in the fifth and final world. Taking 50 years to construct (from 1427 – 1479), the calendar was initially placed on top of the temple in Tenochtitlan, the Aztec capital. After the Spanish invasion, the calendar was ‘lost’ for 250 years, until it was found in 1790 by workers repairing the cathedral in Mexico City.
Sources http://en.wikipedia.org, www.starteachastronomy.com, www.spaceodyssey.dmns,org, www.wikis.lib.ncsu.edu, www.sir-ray.com, www.crystal-links.com
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